Evidence record

Why is there more matter than antimatter?

Every sentence on the exploration belongs to at least one claim below. Each says what kind of statement it is, what it rests on, what the evidence does not establish, and how far it was checked. Nothing here is a score, and none of it is a verdict on a belief or a theory.

Last checked 24 September 2026.

Source checked: 69
Presented as open: 1
A judgement, not a fact: 5
Partly checked: 4

If something here is wrong, misquoted, out of date or unfair, write to support@unknownoceans.com and give the claim number, which does not change.

What the question takes for granted

A physics question with an observed fact at its centre: the universe holds matter and no antimatter in quantity, and the known laws cannot make the difference. What would explain it is open, and some candidate answers may lie beyond any experiment.

There is more matter than antimatter, everywhere we can see
Established
No annihilation glow from domain boundaries, and a measured baryon-to-photon ratio, agree that the visible universe is matter. Regions beyond it cannot be tested.
The surplus was produced by physics rather than set at the start
Contested
If inflation happened, an initial asymmetry was diluted away and the surplus must have been made later; without inflation, it could be an initial condition.
The known laws are close enough to complete to say they fall short
Established
The Standard Model’s CP violation and its electroweak transition are both measured well enough for the review to call Standard Model baryogenesis extremely unlikely.

How the question is labelled

Claim: The surplus

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Antimatter

Kind: Framing. Signposting. It asserts nothing a source could check.

The question

Claim: The laws we have make the two in almost exactly equal amounts.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

"Almost exactly": the known laws do treat the two differently, measurably, but far too weakly to leave the observed surplus.

Supports
Matter and antimatter in the universesection I, sixth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: The Standard Model of particle physics (SM) and cosmology in principle fulfills all three Sakharov conditions ... The CP violation and deviation from equilibrium during electroweak symmetry breaking are both too small.
Supports
Matter and antimatter in the universesection IV.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: However, it turns out that both, the violation of CP, condition II), and the deviation from thermal equilibrium, condition III), are not large enough to produce the observed η
Supports
A Matter-Antimatter Universe?section 1, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The laws of physics treat matter and antimatter almost symmetrically, and yet the stars, dust and gas in our celestial neighborhood consist exclusively of matter.

Later work looked for

Crossref, 2018 on, "electroweak baryogenesis standard model": nothing found that revives Standard Model baryogenesis.

Corrected

24 September 2026. Previously: “The laws we have make the two in equal amounts.” The page itself reports that the laws violate CP measurably; Canetti and co-authors say the Standard Model meets every condition in principle and too weakly in practice, and Cohen and co-authors that the laws treat the two "almost symmetrically". "Equal" contradicted the page.

Claim 3 · checked 24 September 2026 · AI-assisted audit

Claim: Every atom is what was left over when they cancelled.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: antimatter was present when pair-creation and annihilation reactions were in thermal equilibrium. When particle energies in the cooling plasma became too small for pair creation to occur, almost all particles and antiparticles annihilated each other, with a small amount of matter (by definition) surviving.
Supports
Matter and antimatter in the universefootnote 4
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Here and in the following “matter” and “antimatter” refer to baryons.

What this does not establish

Atoms, not everything: the surplus is of baryons, and dark matter is a separate question the review sets aside.

Later work looked for

Crossref, 2016 on, "baryon asymmetry": nothing that changes the account.

Corrected

24 September 2026. Previously: “Everything that exists is what was left over when they cancelled.” The surplus is of baryons; the review notes that dark matter is a separate question and in many models unrelated to it, and the photons are what the cancelling produced. "Everything that exists" overstated.

Claim 4 · checked 24 September 2026 · AI-assisted audit

Claim: Every particle has an antiparticle, and the known laws produce them in pairs.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The existence of antimatter is a direct consequence of combining two of the most fundamental known concepts in physics, the theory of relativity and quantum mechanics.
Supports
Matter and antimatter in the universesection I, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: antimatter was present when pair-creation and annihilation reactions were in thermal equilibrium. When particle energies in the cooling plasma became too small for pair creation to occur, almost all particles and antiparticles annihilated each other, with a small amount of matter (by definition) surviving.

What this does not establish

Stated loosely: a neutral particle can be its own antiparticle, which is what the page later asks of the neutrino.

Later work looked for

Not a finding later work revises: a definition or a description of the page.

Claim 5 · checked 24 September 2026 · AI-assisted audit

Claim: Yet the universe is made of matter, with no sign of antimatter regions anywhere in the visible universe.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
A Matter-Antimatter Universe?abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model
The source reads: The former signal exceeds observational limits unless the matter domain we inhabit is virtually the entire visible universe. On general grounds, we conclude that a matter–antimatter symmetric universe is em pirically excluded.
Supports
Matter and antimatter in the universesection I, closing paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: We conclude that it is almost certain that all structures in the observable universe are composed of matter only

What this does not establish

Regions larger than the visible universe cannot be tested this way; the review says only that any domains must be at least that large.

Later work looked for

Crossref, 2012 on, "antimatter domains gamma-ray" and "antihelium AMS": Dupourqué and others (2021, abstract read) note unconfirmed AMS-02 antihelium candidates and list fourteen gamma-ray sources compatible with nearby antistars, and set upper limits on them; nothing reopens matter and antimatter regions on cosmological scales.

Corrected

24 September 2026. Previously: “with no sign of antimatter regions anywhere.” Cohen and co-authors exclude domains only up to the visible universe, and the review says domains at least that large remain possible. "Anywhere" claimed more than an observation can.

Claim 6 · checked 24 September 2026 · AI-assisted audit

Claim: The conditions an explanation would have to satisfy were written down in 1967.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: There are three necessary conditions for successful baryogenesis, which were first formulated by Sakharov ... I) baryon number violation, II) C and CP violation and III) a deviation from thermal equilibrium
Supports
Matter and antimatter in the universereference 11
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: A. D. Sakharov, Pisma Zh. Eksp. Teor. Fiz. 5 (1967) 32

Claim 7 · checked 24 September 2026 · AI-assisted audit

Claim: The known laws meet them in principle, and far too weakly in practice.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, sixth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: The Standard Model of particle physics (SM) and cosmology in principle fulfills all three Sakharov conditions ... The CP violation and deviation from equilibrium during electroweak symmetry breaking are both too small.
Supports
Matter and antimatter in the universesection IV.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: However, it turns out that both, the violation of CP, condition II), and the deviation from thermal equilibrium, condition III), are not large enough to produce the observed η
Supports
Matter and antimatter in the universesection IV.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: A first order phase transition could only occur if the Higgs mass were below 72 GeV ... is in clear contradiction with experimental data, allowing to conclude that it is extremely unlikely that the observed BAU can be generated within the SM.

Later work looked for

Crossref, 2018 on, "electroweak baryogenesis standard model": later work builds on the Standard Model failing and adds new physics; nothing found that revives Standard Model baryogenesis.

Corrected

24 September 2026. Previously: “Nothing found since meets them.” The review says the Standard Model fulfils all three conditions in principle and two of them too weakly; the page’s own module says so. "Nothing meets them" contradicted both.

Claim 8 · checked 24 September 2026 · AI-assisted audit

Claim: In the first moments the universe was hot enough that matter and antimatter were made and destroyed continuously, in equal numbers,

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: it came clear that the universe was hot during the early stages of its history
Supports
Matter and antimatter in the universesection I, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: antimatter was present when pair-creation and annihilation reactions were in thermal equilibrium. When particle energies in the cooling plasma became too small for pair creation to occur, almost all particles and antiparticles annihilated each other, with a small amount of matter (by definition) surviving.

Later work looked for

Crossref, 2016 on: nothing that changes the standard account of pair creation in the hot early universe.

Claim 9 · checked 24 September 2026 · AI-assisted audit

Claim: and the equations describing this are almost exactly symmetric between them.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, sixth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: The Standard Model of particle physics (SM) and cosmology in principle fulfills all three Sakharov conditions ... The CP violation and deviation from equilibrium during electroweak symmetry breaking are both too small.
Supports
A Matter-Antimatter Universe?section 1, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The laws of physics treat matter and antimatter almost symmetrically, and yet the stars, dust and gas in our celestial neighborhood consist exclusively of matter.

Later work looked for

Crossref, 2018 on, "electroweak baryogenesis standard model": later work builds on the Standard Model failing and adds new physics; nothing found that revives Standard Model baryogenesis.

Corrected

24 September 2026. Previously: “and the equations describing this are symmetric between them.” The laws violate C and CP, as the page says two sections later; Cohen and co-authors: the laws treat matter and antimatter "almost symmetrically".

Claim 10 · checked 24 September 2026 · AI-assisted audit

Claim: As it cooled, the pairs annihilated.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: antimatter was present when pair-creation and annihilation reactions were in thermal equilibrium. When particle energies in the cooling plasma became too small for pair creation to occur, almost all particles and antiparticles annihilated each other, with a small amount of matter (by definition) surviving.

Later work looked for

Crossref, 2016 on: nothing that changes the standard account.

Claim 11 · checked 24 September 2026 · AI-assisted audit

Claim: If the symmetry had been exact, nearly all of it would have ended as radiation.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: antimatter was present when pair-creation and annihilation reactions were in thermal equilibrium. When particle energies in the cooling plasma became too small for pair creation to occur, almost all particles and antiparticles annihilated each other, with a small amount of matter (by definition) surviving.
Supports
Matter and antimatter in the universesection I, equation 1 and the text before it
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Since the end products of annihilation processes are mostly photons and there are no antibaryons in the universe today ... the BAU can be estimated by the baryon to photon ratio η

What this does not establish

A counterfactual worked out from the standard account. The review gives the products of annihilation as mostly photons, not only photons.

Corrected

24 September 2026. Previously: “If the symmetry had been exact, the result would be radiation and nothing else.” The review says annihilation left mostly photons, and it treats dark matter as a separate question; "nothing else" said more than the source.

Claim 12 · checked 24 September 2026 · AI-assisted audit

Claim: Instead a small remainder survived, and every atom is built from it.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: antimatter was present when pair-creation and annihilation reactions were in thermal equilibrium. When particle energies in the cooling plasma became too small for pair creation to occur, almost all particles and antiparticles annihilated each other, with a small amount of matter (by definition) surviving.
Supports
Matter and antimatter in the universefootnote 4
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Here and in the following “matter” and “antimatter” refer to baryons.

Later work looked for

Crossref, 2016 on: nothing that changes the account.

Corrected

24 September 2026. Previously: “Instead a small remainder survived, and everything is built from it.” The remainder is baryonic matter; the review sets dark matter aside as unrelated in many models.

Claim 13 · checked 24 September 2026 · AI-assisted audit

What was left over

Claim: What was left over

Kind: Framing. Signposting. It asserts nothing a source could check.

How large the surplus was

Claim: How large the surplus was

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: The leftover can be measured, because the annihilation products are still here as the microwave background.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

The photons of the microwave background are counted, and the baryons set against them.

Supports
Matter and antimatter in the universesection I, equation 1 and the text before it
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Since the end products of annihilation processes are mostly photons and there are no antibaryons in the universe today ... the BAU can be estimated by the baryon to photon ratio η
Supports
Matter and antimatter in the universesection I, third paragraph; section III.2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: It can be determined independently in two different ways, from the abundances of light elements in the intergalactic medium (IGM), see section III.1, and from the power spectrum of temperature fluctuations in the CMB ... this is a truly independent measurement

Later work looked for

Crossref, 2016 on, "big bang nucleosynthesis baryon density Planck": Fields and others (2020, "Big-Bang Nucleosynthesis After Planck", abstract read) find Planck fixing the baryon density to 0.9 per cent and deuterium agreeing, with the lithium problem unresolved; nothing that moves the ratio from about six in ten billion.

Claim 16 · checked 24 September 2026 · AI-assisted audit

Claim: Comparing the number of ordinary particles in the universe to the number of photons gives about six in ten billion.

Kind: Present-day figure. A count, survey or report finding, as the named source gives it.
Review: Source checked. The cited passage was read, and it says this.

"Ordinary particles" are baryons. The ratio is 6.1 x 10^-10.

Supports
Big bang nucleosynthesis: Present statussection I; Table V
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: the abundances of the four light nuclei are usually parameterized by the baryon-to-photon ratio ... most recently by Planck yielding η = 6.10± 0.04
Supports
Big bang nucleosynthesis: Present statussection IV, Table V
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: CMB-only 6.08± 0.07 ... BBN+Yp+D 6.10± 0.23
Values of the baryon-to-photon ratio in units of 10^-10: from the microwave background alone, and from the light elements with no microwave-background input.
Context
Planck 2018 results. VI. Cosmological parametersabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: baryon density Ωbh2 = 0.0224± 0.0001
The baryon density the ratio is converted from; the BBN review converts Planck’s value to a ratio of 6.10 in units of 10^-10.

Later work looked for

Claim 17 · checked 24 September 2026 · AI-assisted audit

Claim: So matter outnumbered antimatter by something like one part in a billion.

Kind: Present-day figure. A count, survey or report finding, as the named source gives it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, equation 1 and the text before it
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The baryon asymmetry of the universe (BAU) can be defined as the difference between the number of baryons NB and antibaryons ... divided by their sum (or the entropy s) just before antiprotons disappeared from the primordial plasma
Supports
Matter and antimatter in the universesection I, equation 1 and the text before it
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Since the end products of annihilation processes are mostly photons and there are no antibaryons in the universe today ... the BAU can be estimated by the baryon to photon ratio η
Supports
Big bang nucleosynthesis: Present statussection I; Table V
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: the abundances of the four light nuclei are usually parameterized by the baryon-to-photon ratio ... most recently by Planck yielding η = 6.10± 0.04

What this does not establish

An order-of-magnitude figure. The review equates the asymmetry with the baryon-to-photon ratio only approximately, and defines it as the difference over the sum of baryons and antibaryons, so a ratio of six in ten billion is an excess of roughly twelve per ten billion antibaryons.

Later work looked for

Corrected

24 September 2026. Previously: “So for every ten billion antiparticles there were about ten billion and six particles.” The baryon-to-photon ratio is not the excess of particles over antiparticles. The review defines the asymmetry as the difference over the sum and ties it to the ratio only approximately, which makes the excess about twice the ratio and never as precise as "six".

Claim 18 · checked 24 September 2026 · AI-assisted audit

Claim: The pairs became light.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, equation 1 and the text before it
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Since the end products of annihilation processes are mostly photons and there are no antibaryons in the universe today ... the BAU can be estimated by the baryon to photon ratio η

What this does not establish

Mostly light: the review says the products of annihilation were mostly photons.

Later work looked for

Crossref, 2016 on: nothing that changes the account.

Claim 19 · checked 24 September 2026 · AI-assisted audit

Claim: The remainder became stars, planets and the people counting.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universeabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: We review observational evidence for a matter-antimatter asymmetry in the early universe, which leads to the remnant matter density we observe today.
Supports
Matter and antimatter in the universesection I, closing paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: We conclude that it is almost certain that all structures in the observable universe are composed of matter only

Later work looked for

Crossref, 2016 on: nothing that changes the account.

Claim 20 · checked 24 September 2026 · AI-assisted audit

Claim: What survived

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: ~6 in 10 billion

Kind: Present-day figure. A count, survey or report finding, as the named source gives it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Big bang nucleosynthesis: Present statussection I; Table V
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: the abundances of the four light nuclei are usually parameterized by the baryon-to-photon ratio ... most recently by Planck yielding η = 6.10± 0.04
Supports
Big bang nucleosynthesis: Present statussection IV, Table V
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: CMB-only 6.08± 0.07 ... BBN+Yp+D 6.10± 0.23
Values of the baryon-to-photon ratio in units of 10^-10: from the microwave background alone, and from the light elements with no microwave-background input.
Context
Planck 2018 results. VI. Cosmological parametersabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Astronomical observation · Measurement
The source reads: baryon density Ωbh2 = 0.0224± 0.0001
The baryon density the ratio is converted from; the BBN review converts Planck’s value to a ratio of 6.10 in units of 10^-10.

Later work looked for

Claim 22 · checked 24 September 2026 · AI-assisted audit

Claim: Baryons per photon

Kind: Present-day figure. A count, survey or report finding, as the named source gives it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Big bang nucleosynthesis: Present statussection I; Table V
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: the abundances of the four light nuclei are usually parameterized by the baryon-to-photon ratio ... most recently by Planck yielding η = 6.10± 0.04

Later work looked for

Claim 23 · checked 24 September 2026 · AI-assisted audit

Claim: Measured two independent ways, from the microwave background and from the abundances of the lightest elements, and they agree.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, third paragraph; section III.2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: It can be determined independently in two different ways, from the abundances of light elements in the intergalactic medium (IGM), see section III.1, and from the power spectrum of temperature fluctuations in the CMB ... this is a truly independent measurement
Supports
Matter and antimatter in the universesection III.2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: The impressive agreement between BBN and CMB results for η, however, is am important hint that we can reliably determine the magnitude of the BAU observationally.
Supports
Big bang nucleosynthesis: Present statussection IV, Table V
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: CMB-only 6.08± 0.07 ... BBN+Yp+D 6.10± 0.23
Values of the baryon-to-photon ratio in units of 10^-10: from the microwave background alone, and from the light elements with no microwave-background input.
Qualifies
Big bang nucleosynthesis: Present statussection IV
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: we are struck by the spectacular agreement between D/H observations ... the pronounced discrepancy in 7Li measures represents the “lithium problem”

What this does not establish

The agreement rests mostly on deuterium. Lithium-7 still disagrees, and the BBN review calls the concordance an incomplete success until that is resolved.

Later work looked for

Claim 24 · checked 24 September 2026 · AI-assisted audit

Claim: 0

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
A Matter-Antimatter Universe?abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model
The source reads: The former signal exceeds observational limits unless the matter domain we inhabit is virtually the entire visible universe. On general grounds, we conclude that a matter–antimatter symmetric universe is em pirically excluded.
Supports
Matter and antimatter in the universesection I, closing paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: We conclude that it is almost certain that all structures in the observable universe are composed of matter only

Later work looked for

Claim 25 · checked 24 September 2026 · AI-assisted audit

Claim: Antimatter regions found

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
A Matter-Antimatter Universe?abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model
The source reads: The former signal exceeds observational limits unless the matter domain we inhabit is virtually the entire visible universe. On general grounds, we conclude that a matter–antimatter symmetric universe is em pirically excluded.
Supports
Matter and antimatter in the universesection I, closing paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: We conclude that it is almost certain that all structures in the observable universe are composed of matter only

What this does not establish

None found within the visible universe; larger regions cannot be tested.

Later work looked for

Claim 26 · checked 24 September 2026 · AI-assisted audit

Claim: Boundaries between matter and antimatter domains would glow in gamma rays.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
A Matter-Antimatter Universe?abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model
The source reads: We demonstrate that, after recombination, it is impossible to avoid annihilation near regional boundaries. We study the dynamics of this process to estimate two of its signatures: a contribution to the cosmic diffuse

What this does not establish

A calculation of what the boundaries would emit, under the standard cosmology the authors assume.

Claim 27 · checked 24 September 2026 · AI-assisted audit

Claim: The sky does not.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

The measured diffuse gamma-ray background leaves no room for the glow unless our domain is virtually the whole visible universe.

Supports
A Matter-Antimatter Universe?abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model
The source reads: The former signal exceeds observational limits unless the matter domain we inhabit is virtually the entire visible universe. On general grounds, we conclude that a matter–antimatter symmetric universe is em pirically excluded.
Supports
Matter and antimatter in the universesection II.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: This still leaves open the possibility that the universe is a patchwork of huge distinct regions of matter and antimatter ... If this were the case, these regions would have to be at least of comparable size as the observable universe

Later work looked for

Claim 28 · checked 24 September 2026 · AI-assisted audit

Claim: 3

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: There are three necessary conditions for successful baryogenesis, which were first formulated by Sakharov ... I) baryon number violation, II) C and CP violation and III) a deviation from thermal equilibrium

Later work looked for

How the conditions work; not a finding later work revises.

Claim 29 · checked 24 September 2026 · AI-assisted audit

Claim: Conditions required

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: There are three necessary conditions for successful baryogenesis, which were first formulated by Sakharov ... I) baryon number violation, II) C and CP violation and III) a deviation from thermal equilibrium

Later work looked for

How the conditions work; not a finding later work revises.

Claim 30 · checked 24 September 2026 · AI-assisted audit

Claim: Written down by Sakharov in 1967.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: There are three necessary conditions for successful baryogenesis, which were first formulated by Sakharov ... I) baryon number violation, II) C and CP violation and III) a deviation from thermal equilibrium
Supports
Matter and antimatter in the universereference 11
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: A. D. Sakharov, Pisma Zh. Eksp. Teor. Fiz. 5 (1967) 32

Claim 31 · checked 24 September 2026 · AI-assisted audit

Claim: All three are necessary.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: There are three necessary conditions for successful baryogenesis, which were first formulated by Sakharov ... I) baryon number violation, II) C and CP violation and III) a deviation from thermal equilibrium
Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Formally, Sakharov’s conditions can be proven by means of quantum mechanics and statistical physics.

Later work looked for

How the conditions work; not a finding later work revises.

Claim 32 · checked 24 September 2026 · AI-assisted audit

Claim: The Standard Model meets all three in principle, and two of them nowhere near well enough.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, sixth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: The Standard Model of particle physics (SM) and cosmology in principle fulfills all three Sakharov conditions ... The CP violation and deviation from equilibrium during electroweak symmetry breaking are both too small.
Supports
Matter and antimatter in the universesection IV.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: However, it turns out that both, the violation of CP, condition II), and the deviation from thermal equilibrium, condition III), are not large enough to produce the observed η

Later work looked for

Crossref, 2018 on, "electroweak baryogenesis standard model": later work builds on the Standard Model failing and adds new physics; nothing found that revives Standard Model baryogenesis.

Claim 33 · checked 24 September 2026 · AI-assisted audit

The universe is not half antimatter somewhere else

Claim: The universe is not half antimatter somewhere else

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
A Matter-Antimatter Universe?abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model
The source reads: The former signal exceeds observational limits unless the matter domain we inhabit is virtually the entire visible universe. On general grounds, we conclude that a matter–antimatter symmetric universe is em pirically excluded.
Supports
Matter and antimatter in the universesection II.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: This still leaves open the possibility that the universe is a patchwork of huge distinct regions of matter and antimatter ... If this were the case, these regions would have to be at least of comparable size as the observable universe

What this does not establish

Within the visible universe. Domains at least as large as the visible universe are not excluded by this argument.

Later work looked for

Claim 34 · checked 24 September 2026 · AI-assisted audit

Claim: A tidy solution would be that the antimatter is elsewhere, in regions of its own.

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Source checked. The cited passage was read, and it says this.

Supports
A Matter-Antimatter Universe?abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Model
The source reads: We ask whether the universe can be a patchwork consisting of distinct regions of matter and antimatter.
Supports
Matter and antimatter in the universesection II.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: This still leaves open the possibility that the universe is a patchwork of huge distinct regions of matter and antimatter ... If this were the case, these regions would have to be at least of comparable size as the observable universe

What this does not establish

Proposed and then tested; the next paragraph reports the result.

Claim 35 · checked 24 September 2026 · AI-assisted audit

Claim: That was tested rather than assumed.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
A Matter-Antimatter Universe?abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model
The source reads: The former signal exceeds observational limits unless the matter domain we inhabit is virtually the entire visible universe. On general grounds, we conclude that a matter–antimatter symmetric universe is em pirically excluded.

Claim 36 · checked 24 September 2026 · AI-assisted audit

Claim: Wherever a matter region met an antimatter region, annihilation at the boundary would produce a gamma-ray glow.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
A Matter-Antimatter Universe?abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model
The source reads: We demonstrate that, after recombination, it is impossible to avoid annihilation near regional boundaries. We study the dynamics of this process to estimate two of its signatures: a contribution to the cosmic diffuse

What this does not establish

After recombination; the authors show annihilation near the boundaries cannot be avoided under the standard cosmology they assume.

Claim 37 · checked 24 September 2026 · AI-assisted audit

Claim: A 1998 analysis found that the expected signal exceeds what is observed unless our own matter domain is effectively the entire visible universe,

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Posted in 1997 and published in The Astrophysical Journal in March 1998.

Supports
A Matter-Antimatter Universe?abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model
The source reads: The former signal exceeds observational limits unless the matter domain we inhabit is virtually the entire visible universe. On general grounds, we conclude that a matter–antimatter symmetric universe is em pirically excluded.
Supports
A Matter-Antimatter Universe?Crossref record for the version of record
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The Astrophysical Journal 495, 539-549, published 1998-03-10

Later work looked for

Claim 38 · checked 24 September 2026 · AI-assisted audit

Claim: which is to say that a patchwork is empirically dead anywhere we can see.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
A Matter-Antimatter Universe?abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Model
The source reads: The former signal exceeds observational limits unless the matter domain we inhabit is virtually the entire visible universe. On general grounds, we conclude that a matter–antimatter symmetric universe is em pirically excluded.
Supports
Matter and antimatter in the universesection II.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: This still leaves open the possibility that the universe is a patchwork of huge distinct regions of matter and antimatter ... If this were the case, these regions would have to be at least of comparable size as the observable universe
Supports
Matter and antimatter in the universesection I, closing paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: We conclude that it is almost certain that all structures in the observable universe are composed of matter only

Later work looked for

Corrected

24 September 2026. Previously: “which is to say that the patchwork idea is empirically dead.” The review notes that domains at least as large as the observable universe remain possible; what is excluded is a patchwork within it.

Claim 39 · checked 24 September 2026 · AI-assisted audit

The three conditions

Claim: The three conditions

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: In 1967 Andrei Sakharov set out what any explanation must include.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: There are three necessary conditions for successful baryogenesis, which were first formulated by Sakharov ... I) baryon number violation, II) C and CP violation and III) a deviation from thermal equilibrium
Supports
Matter and antimatter in the universereference 11
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: A. D. Sakharov, Pisma Zh. Eksp. Teor. Fiz. 5 (1967) 32

Claim 41 · checked 24 September 2026 · AI-assisted audit

Claim: Some process must change the number of baryons.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: There are three necessary conditions for successful baryogenesis, which were first formulated by Sakharov ... I) baryon number violation, II) C and CP violation and III) a deviation from thermal equilibrium
Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Without baryon number violation, it is not possible for any system to evolve from a state with baryon number B = 0 to a state with B

Later work looked for

How the conditions work; not a finding later work revises.

Claim 42 · checked 24 September 2026 · AI-assisted audit

Claim: The laws must treat matter and antimatter differently.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Formally, both C and CP must be violated.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: There are three necessary conditions for successful baryogenesis, which were first formulated by Sakharov ... I) baryon number violation, II) C and CP violation and III) a deviation from thermal equilibrium
Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: If C (or CP) symmetry were to hold, for each process that generates a matter-antimatter asymmetry, there would be a C (or CP) conjugate process that generates an asymmetry with the opposite sign and occurs with the same probability.

Later work looked for

How the conditions work; not a finding later work revises.

Claim 43 · checked 24 September 2026 · AI-assisted audit

Claim: And the universe must fall out of thermal equilibrium while this happens, or any surplus produced is undone as fast as it is made.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

The review puts it as time-translation invariance: in equilibrium nothing observable changes, so no surplus can build up.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: There are three necessary conditions for successful baryogenesis, which were first formulated by Sakharov ... I) baryon number violation, II) C and CP violation and III) a deviation from thermal equilibrium
Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: thermal equilibrium is a time translation invariant state in which the expectation values of all observables are constant, therefore it requires a deviation from equilibrium to evolve from B = 0

Later work looked for

How the conditions work; not a finding later work revises.

Claim 44 · checked 24 September 2026 · AI-assisted audit

Claim: What an explanation has to do

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Violate baryon number

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: There are three necessary conditions for successful baryogenesis, which were first formulated by Sakharov ... I) baryon number violation, II) C and CP violation and III) a deviation from thermal equilibrium

Later work looked for

How the conditions work; not a finding later work revises.

Claim 46 · checked 24 September 2026 · AI-assisted audit

Claim: Something must be able to turn a quantity of antimatter into matter, or produce one without the other.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

In the review’s terms, a process must take a state with zero baryon number to one that is not zero.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Without baryon number violation, it is not possible for any system to evolve from a state with baryon number B = 0 to a state with B

Later work looked for

How the conditions work; not a finding later work revises.

Claim 47 · checked 24 September 2026 · AI-assisted audit

Claim: The Standard Model permits this only in a process too rare to matter at ordinary temperatures.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

The process is the sphaleron, suppressed in vacuum by a factor the review gives as about 10^-160 and efficient only near and above the electroweak temperature.

Supports
Matter and antimatter in the universesection IV.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: effectively forbidding B-violation in vacuum ... Above this temperature, baryon number is efficiently violated and all Sakharov conditions are fulfilled.
Supports
Matter and antimatter in the universesection III.3
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: The only source of B-violation in the SM are sphaleron processes ... which are highly inefficient below TEW ∼ 140 GeV

Later work looked for

How the conditions work; not a finding later work revises.

Claim 48 · checked 24 September 2026 · AI-assisted audit

Claim: Violate C and CP

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: There are three necessary conditions for successful baryogenesis, which were first formulated by Sakharov ... I) baryon number violation, II) C and CP violation and III) a deviation from thermal equilibrium

Later work looked for

How the conditions work; not a finding later work revises.

Claim 49 · checked 24 September 2026 · AI-assisted audit

Claim: The laws must prefer matter to antimatter.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: If C (or CP) symmetry were to hold, for each process that generates a matter-antimatter asymmetry, there would be a C (or CP) conjugate process that generates an asymmetry with the opposite sign and occurs with the same probability.

Later work looked for

How the conditions work; not a finding later work revises.

Claim 50 · checked 24 September 2026 · AI-assisted audit

Claim: They do, measurably, in the decays of kaons, B mesons, charm particles and, since 2025, a baryon.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Observation of CP Violation in Charm Decaysopening paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: has been established in the K- and B-meson systems by several experiments ... and all results are well interpreted within the CKM formalism
Supports
Observation of CP Violation in Charm Decaysabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: The measured value differs from zero by more than five standard deviations. This is the first observation of CP violation in the decay of charm hadrons.
Supports
Observation of charge-parity symmetry breaking in baryon decaysabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: providing, to our knowledge, the first observation of CP violation in baryon decays and demonstrating the different behaviours of baryons and antibaryons
Notation restored: LaTeX markup in the arXiv abstract rendered as text, checked against the abstract as typeset in the arXiv PDF (v2), read 2026-09-24. The text as extracted reads: providing, to our knowledge, the first observation of $CP$ violation in baryon decays and demonstrating the different behaviours of baryons and antibaryons
Supports
Matter and antimatter in the universesection I, third paragraph; reference 10
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The discovery of violations of P and CP invariance (and thus also C invariance) in nature provided hints that this asymmetry may have been created dynamically ... J. H. Christenson, J. W. Cronin, V. L. Fitch and R. Turlay, Phys. Rev. Lett. 13 (1964) 138.

Later work looked for

Crossref, 2020 on, "LHCb CP violation baryon" and "charm CP violation": LHCb reported the first CP violation in a baryon in 2025 (Nature 643, 1223), added to the page; charm results remain under study.

Corrected

24 September 2026. Previously: “They do, measurably, in the decays of kaons, B mesons and charm particles.” Out of date: LHCb reported the first observation of CP violation in baryon decays in 2025 (Nature 643, 1223).

Claim 51 · checked 24 September 2026 · AI-assisted audit

Claim: The preference is many orders of magnitude too small to account for the surplus.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection IV.1, after equation 13
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Though not a direct proof of impossibility, the smallness of this result makes baryogenesis within the SM very challenging
The result is the Jarlskog determinant over the sphaleron freeze-out temperature to the twelfth power, which the review gives as about 10^-20, against a measured ratio of about 6 x 10^-10.
Supports
Observation of CP Violation in Charm Decaysopening paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: the size of CP violation in the SM appears to be too small to account for the observed matter-antimatter asymmetry

Later work looked for

Crossref, 2018 on, "electroweak baryogenesis standard model": later work builds on the Standard Model failing and adds new physics; nothing found that revives Standard Model baryogenesis.

Claim 52 · checked 24 September 2026 · AI-assisted audit

Claim: Depart from equilibrium

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: There are three necessary conditions for successful baryogenesis, which were first formulated by Sakharov ... I) baryon number violation, II) C and CP violation and III) a deviation from thermal equilibrium

Later work looked for

How the conditions work; not a finding later work revises.

Claim 53 · checked 24 September 2026 · AI-assisted audit

Claim: The imbalance has to be frozen in.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: thermal equilibrium is a time translation invariant state in which the expectation values of all observables are constant, therefore it requires a deviation from equilibrium to evolve from B = 0

Later work looked for

How the conditions work; not a finding later work revises.

Claim 54 · checked 24 September 2026 · AI-assisted audit

Claim: In a universe in thermal equilibrium every process runs backwards as often as forwards, and nothing accumulates.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

The page’s way of saying what the review puts as time-translation invariance: in equilibrium the expectation value of every observable is constant.

Supports
Matter and antimatter in the universesection I, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: thermal equilibrium is a time translation invariant state in which the expectation values of all observables are constant, therefore it requires a deviation from equilibrium to evolve from B = 0

Later work looked for

How the conditions work; not a finding later work revises.

Claim 55 · checked 24 September 2026 · AI-assisted audit

The asymmetry in the laws is real and too small

Claim: The asymmetry in the laws is real and too small

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection IV.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: However, it turns out that both, the violation of CP, condition II), and the deviation from thermal equilibrium, condition III), are not large enough to produce the observed η
Supports
Matter and antimatter in the universesection IV.1, after equation 13
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Though not a direct proof of impossibility, the smallness of this result makes baryogenesis within the SM very challenging
The result is the Jarlskog determinant over the sphaleron freeze-out temperature to the twelfth power, which the review gives as about 10^-20, against a measured ratio of about 6 x 10^-10.
Supports
Observation of CP Violation in Charm Decaysopening paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: the size of CP violation in the SM appears to be too small to account for the observed matter-antimatter asymmetry

Later work looked for

Crossref, 2018 on, "electroweak baryogenesis standard model": later work builds on the Standard Model failing and adds new physics; nothing found that revives Standard Model baryogenesis.

Claim 56 · checked 24 September 2026 · AI-assisted audit

Claim: In 1964 an experiment on neutral kaons found decays that should not happen if matter and antimatter behaved identically.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

The decays were of the long-lived neutral kaon into two pions, which violates CP symmetry.

Supports
Matter and antimatter in the universesection I, third paragraph; reference 10
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The discovery of violations of P and CP invariance (and thus also C invariance) in nature provided hints that this asymmetry may have been created dynamically ... J. H. Christenson, J. W. Cronin, V. L. Fitch and R. Turlay, Phys. Rev. Lett. 13 (1964) 138.
Supports
The Nobel Prize in Physics 1980prize summary
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The Nobel Prize in Physics 1980 was awarded jointly to James Watson Cronin and Val Logsdon Fitch "for the discovery of violations of fundamental symmetry principles in the decay of neutral K-mesons"
Context
Evidence for the 2 pi Decay of the K2 MesonINSPIRE record 11878: authors and publication
Cited · Link answered, 19 October 2026 · Catalogue record only, 24 September 2026
The source reads: Christenson, J.H.; Cronin, J.W.; Fitch, V.L.; Turlay, R. Phys.Rev.Lett. 13 138 - 140 1964
The record confirms the four authors, the journal and the year; the Letter itself was not read.

Claim 57 · checked 24 September 2026 · AI-assisted audit

Claim: Cronin and Fitch, two of its four authors, were given the 1980 Nobel Prize in Physics for the discovery.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
The Nobel Prize in Physics 1980prize summary
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The Nobel Prize in Physics 1980 was awarded jointly to James Watson Cronin and Val Logsdon Fitch "for the discovery of violations of fundamental symmetry principles in the decay of neutral K-mesons"
Supports
Matter and antimatter in the universesection I, third paragraph; reference 10
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The discovery of violations of P and CP invariance (and thus also C invariance) in nature provided hints that this asymmetry may have been created dynamically ... J. H. Christenson, J. W. Cronin, V. L. Fitch and R. Turlay, Phys. Rev. Lett. 13 (1964) 138.
Context
Evidence for the 2 pi Decay of the K2 MesonINSPIRE record 11878: authors and publication
Cited · Link answered, 19 October 2026 · Catalogue record only, 24 September 2026
The source reads: Christenson, J.H.; Cronin, J.W.; Fitch, V.L.; Turlay, R. Phys.Rev.Lett. 13 138 - 140 1964
The record confirms the four authors, the journal and the year; the Letter itself was not read.

Claim 58 · checked 24 September 2026 · AI-assisted audit

Claim: The same violation has since been measured in B mesons, in 2019 in the decays of charm particles, and in 2025 in a baryon.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Observation of CP Violation in Charm Decaysopening paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: has been established in the K- and B-meson systems by several experiments ... and all results are well interpreted within the CKM formalism
Supports
Observation of CP Violation in Charm Decaysabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: The measured value differs from zero by more than five standard deviations. This is the first observation of CP violation in the decay of charm hadrons.
Supports
Observation of charge-parity symmetry breaking in baryon decaysabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: providing, to our knowledge, the first observation of CP violation in baryon decays and demonstrating the different behaviours of baryons and antibaryons
Notation restored: LaTeX markup in the arXiv abstract rendered as text, checked against the abstract as typeset in the arXiv PDF (v2), read 2026-09-24. The text as extracted reads: providing, to our knowledge, the first observation of $CP$ violation in baryon decays and demonstrating the different behaviours of baryons and antibaryons
Supports
Observation of charge-parity symmetry breaking in baryon decaysmain text, on the overall asymmetry
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: This CP asymmetry differs from zero by 5.2 standard deviations, marking the observation of CP violation.

Later work looked for

Corrected

24 September 2026. Previously: “The same violation has since been measured in B mesons and, in 2019, in the decays of charm particles.” Out of date: LHCb reported CP violation in baryon decays in 2025.

Claim 59 · checked 24 September 2026 · AI-assisted audit

Claim: In kaons and B mesons it fits the Standard Model’s account closely;

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Observation of CP Violation in Charm Decaysopening paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: has been established in the K- and B-meson systems by several experiments ... and all results are well interpreted within the CKM formalism

Later work looked for

Corrected

24 September 2026. Previously: “It is now a well-characterised feature of the Standard Model rather than an anomaly.” LHCb says the kaon and B meson results are well interpreted within the Standard Model’s CKM description, but calls its charm result consistent with, and at the upper end of, Standard Model expectations, and says further work must establish whether it is new physics.

Claim 60 · checked 24 September 2026 · AI-assisted audit

Claim: whether the charm result does is still being settled.

Kind: Open question. Something the page says is not known.
Review: Presented as open. The page says this is unresolved, and the review found that it is.

Supports
Observation of CP Violation in Charm Decaysclosing paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: The result is consistent with, although in magnitude at the upper end of, SM expectations ... establish whether this result is consistent with the SM or indicates the presence of new dynamics in the up-quark sector

Later work looked for

Claim 61 · checked 24 September 2026 · AI-assisted audit

Claim: It also falls short by roughly ten orders of magnitude.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection IV.1, after equation 13
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Though not a direct proof of impossibility, the smallness of this result makes baryogenesis within the SM very challenging
The result is the Jarlskog determinant over the sphaleron freeze-out temperature to the twelfth power, which the review gives as about 10^-20, against a measured ratio of about 6 x 10^-10.

What this does not establish

A rough estimate from the size of the Standard Model’s CP violation, about 10^-20 against a measured 6 x 10^-10; the review does not call it a proof.

Later work looked for

Crossref, 2018 on, "electroweak baryogenesis standard model": later work builds on the Standard Model failing and adds new physics; nothing found that revives Standard Model baryogenesis.

Claim 62 · checked 24 September 2026 · AI-assisted audit

Claim: Canetti, Drewes and Shaposhnikov stop short of calling that a proof of impossibility, and add that the third condition fails as well: at the measured Higgs mass the electroweak transition is not first order, so the Standard Model never departs far enough from equilibrium.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection IV.1, after equation 13
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Though not a direct proof of impossibility, the smallness of this result makes baryogenesis within the SM very challenging
The result is the Jarlskog determinant over the sphaleron freeze-out temperature to the twelfth power, which the review gives as about 10^-20, against a measured ratio of about 6 x 10^-10.
Supports
Matter and antimatter in the universesection IV.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: A first order phase transition could only occur if the Higgs mass were below 72 GeV ... is in clear contradiction with experimental data, allowing to conclude that it is extremely unlikely that the observed BAU can be generated within the SM.
Supports
Matter and antimatter in the universesection IV.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: keeping all particle species very close to thermal equilibrium
Supports
Matter and antimatter in the universesection IV.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: However, it turns out that both, the violation of CP, condition II), and the deviation from thermal equilibrium, condition III), are not large enough to produce the observed η

Later work looked for

Crossref, 2018 on, "electroweak baryogenesis standard model": later work builds on the Standard Model failing and adds new physics; nothing found that revives Standard Model baryogenesis.

Corrected

24 September 2026. Previously: “and point instead at the third condition: at the measured Higgs mass the electroweak transition is not first order, so the Standard Model never leaves equilibrium enough either.” The review holds both conditions too weak ("both ... are not large enough"); "instead" suggested it set the CP shortfall aside.

Claim 63 · checked 24 September 2026 · AI-assisted audit

Where the explanation might be

Claim: Where the explanation might be

Kind: Framing. Signposting. It asserts nothing a source could check.

Where the extra asymmetry could come from

Claim: Where the extra asymmetry could come from

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: A large class of proposals puts it in the neutrino sector.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection IV.2, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: those that initially generate a lepton asymmetry (“leptogenesis”), which is then transferred to the baryonic sector, either by SM sphalerons or processes that involve physics beyond the SM

Later work looked for

Crossref, 2020 on, "leptogenesis review": nothing read that changes the grouping.

Claim 66 · checked 24 September 2026 · AI-assisted audit

Claim: If neutrinos are their own antiparticles, heavy right-handed partners in the early universe could generate a lepton asymmetry, which sphaleron processes would then transfer into a baryon asymmetry.

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection IV.3, equation 14 and the text after it
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: MM a Majorana mass term for the right handed neutrinos νR ... The Lagrangian (14), with eigenvalues of MM far above the electroweak scale, is the basis of thermal leptogenesis scenarios, in which the CP-asymmetry responsible for the BAU is generated during the freezeout and decay of right handed neutrinos
Supports
Matter and antimatter in the universesection IV.2, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: those that initially generate a lepton asymmetry (“leptogenesis”), which is then transferred to the baryonic sector, either by SM sphalerons or processes that involve physics beyond the SM

What this does not establish

A proposed mechanism. The heavy partners have not been found, and whether neutrinos are their own antiparticles is itself unknown.

Corrected

24 September 2026. Previously: “which sphaleron processes would then convert partly into a baryon asymmetry.” Narrowed to the review’s own word, "transferred"; the fraction converted is not stated in the sources the page cites.

Claim 67 · checked 24 September 2026 · AI-assisted audit

Claim: Most baryogenesis models are hard to falsify, because an absent signal can be answered by raising the energy scale.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection IV.2, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: most models of baryogenesis are hard to falsify. They may remain viable even if no signals are observed in any experiments in the centuries to come, as they can be saved from falsification by pushing up an associated energy scale.

Claim 68 · checked 24 September 2026 · AI-assisted audit

Claim: Canetti, Drewes and Shaposhnikov count three that are testable in the strict sense that every parameter could be measured, and two of those are in the neutrino sector.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection IV.2, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: In foreseeable time, only three of the popular scenarios are testable in the strict sense that all parameters of the theory may be measured: electroweak baryogenesis, resonant leptogenesis and baryogenesis from sterile neutrino oscillations

Claim 69 · checked 24 September 2026 · AI-assisted audit

Claim: The Majorana neutrino those proposals need would show in a rare nuclear decay, two neutrons becoming two protons and two electrons with no neutrinos emitted at all.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Neutrinoless Double-Beta Decay: Status and Prospectssection 1, equation 2 and the text around it
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Review of the field
The source reads: Double-beta (ββ) decay is an isobaric transition from a parent nucleus (A,Z) to a daughter nucleus (A,Z + 2) two nuclear charges away ... No neutrinos are emitted in the SM-forbidden 0 νββ -decay mode
Supports
Neutrinoless Double-Beta Decay: Status and Prospectssection 1, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: If the SM-forbidden neutrinoless double-beta (0 νββ) decay process were observed, it would directly confirm lepton-number violation and the Majorana nature of neutrinos
Supports
Matter and antimatter in the universesection IV.3, equation 14 and the text after it
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: MM a Majorana mass term for the right handed neutrinos νR ... The Lagrangian (14), with eigenvalues of MM far above the electroweak scale, is the basis of thermal leptogenesis scenarios, in which the CP-asymmetry responsible for the BAU is generated during the freezeout and decay of right handed neutrinos

What this does not establish

The decay would show that neutrinos are Majorana particles, whatever drives it; its rate depends on nuclear physics that is itself uncertain.

Claim 70 · checked 24 September 2026 · AI-assisted audit

Claim: Every search so far has come back empty.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Neutrinoless Double-Beta Decay: Status and Prospectssection 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Review of the field
The source reads: The experimental search for this decay is extremely challenging, and all previous attempts have returned empty-handed

Later work looked for

Crossref, 2020 on, "neutrinoless double beta decay KamLAND-Zen": KamLAND-Zen (2023, Physical Review Letters 130, 051801, abstract read) reports a lower limit of 2.3 x 10^26 years, still no signal.

Claim 71 · checked 24 September 2026 · AI-assisted audit

Claim: Finding it would show that lepton number is broken and that neutrinos are their own antiparticles.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Neutrinoless Double-Beta Decay: Status and Prospectssection 1, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: If the SM-forbidden neutrinoless double-beta (0 νββ) decay process were observed, it would directly confirm lepton-number violation and the Majorana nature of neutrinos

Later work looked for

How the conditions work; not a finding later work revises.

Corrected

24 September 2026. Previously: “Finding it would not confirm leptogenesis, and at a low enough energy scale it would argue against the high-scale version.” Rewritten to what the review says a detection would establish, and to its own terms for the washout: lepton-number violation observed at the TeV scale, with "typically".

Claim 72 · checked 24 September 2026 · AI-assisted audit

Claim: That is a precondition for leptogenesis, not a confirmation of it,

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from the review’s statement of what a detection confirms (lepton-number violation and Majorana neutrinos), which is less than the leptogenesis mechanism.

Supports
Neutrinoless Double-Beta Decay: Status and Prospectssection 1, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: If the SM-forbidden neutrinoless double-beta (0 νββ) decay process were observed, it would directly confirm lepton-number violation and the Majorana nature of neutrinos
Context
Neutrinoless Double-Beta Decay: Status and Prospectssection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Neutrinoless double-beta decay is obviously a process that creates matter, and its observation is crucial for demonstrating baryogenesis ideas.
Supports
Matter and antimatter in the universesection IV.3, equation 14 and the text after it
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: MM a Majorana mass term for the right handed neutrinos νR ... The Lagrangian (14), with eigenvalues of MM far above the electroweak scale, is the basis of thermal leptogenesis scenarios, in which the CP-asymmetry responsible for the BAU is generated during the freezeout and decay of right handed neutrinos

Claim: and lepton number broken at collider energies would typically wash out whatever standard high-scale leptogenesis had made.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Neutrinoless Double-Beta Decay: Status and Prospectssection 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Lepton-number violation observed at TeV scale has interesting cosmological implications. ... Any lepton asymmetry generated by standard high-scale leptogenesis would typically be washed out, making this baryogenesis mechanism ineffective.

Claim 74 · checked 24 September 2026 · AI-assisted audit

Whether the answer is at an energy anyone can reach

Claim: Whether the answer is at an energy anyone can reach

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Some versions of the story happen at energies a collider could probe, and are being squeezed by measurements of the electron’s electric dipole moment.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Matter and antimatter in the universesection IV.2, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: In foreseeable time, only three of the popular scenarios are testable in the strict sense that all parameters of the theory may be measured: electroweak baryogenesis, resonant leptogenesis and baryogenesis from sterile neutrino oscillations
Supports
Matter and antimatter in the universesection IV.3
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: In contrast, N2, 3 can be seen directly at collider experiments
Supports
Improved limit on the electric dipole moment of the electronabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Physical systems · Experiment
The source reads: the existence of very massive particles whose interactions violate time-reversal symmetry, which could explain the cosmological matter–antimatter asymmetry, can give rise to an electric dipole moment along the spin axis of the electron
Supports
Improved limit on the electric dipole moment of the electronabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Physical systems · Experiment
The source reads: This result implies that a broad class of conjectured particles, if they exist and time-reversal symmetry is maximally violated, have masses that greatly exceed what can be measured directly at the Large Hadron Collider.

What this does not establish

The ACME paper was read as its abstract only.

Later work looked for

Crossref, 2019 on, "electron electric dipole moment": Roussy and others (Science, 2023) improve the bound by a factor of about 2.4 and find no moment; added to the page.

Corrected

24 September 2026. Previously: “and are being squeezed by measurements of electric dipole moments and by searches at the Large Hadron Collider.” No cited source reports collider searches constraining baryogenesis; the electron dipole moment limits are what the cited work carries.

Claim 76 · checked 24 September 2026 · AI-assisted audit

Claim: Others can be placed at energies high enough to escape every experiment for centuries, leaving at most indirect traces.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection IV.2, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: most models of baryogenesis are hard to falsify. They may remain viable even if no signals are observed in any experiments in the centuries to come, as they can be saved from falsification by pushing up an associated energy scale.
Supports
Matter and antimatter in the universesection IV.2, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: In some cases, indirect evidence that supports the underlying theory may be found in low energy experiments or astrophysical observations

Corrected

24 September 2026. Previously: “Others happen at energies far beyond any conceivable machine, and leave only indirect traces.” Narrowed to the review’s claim: models can be saved by pushing up an energy scale, remaining viable with no signal "in the centuries to come", and indirect evidence "may" be found.

Claim 77 · checked 24 September 2026 · AI-assisted audit

Claim: The squeeze is real.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from the two limits reported in the next sentences.

Supports
Improved limit on the electric dipole moment of the electronabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Physical systems · Experiment
The source reads: This result implies that a broad class of conjectured particles, if they exist and time-reversal symmetry is maximally violated, have masses that greatly exceed what can be measured directly at the Large Hadron Collider.
Supports
An improved bound on the electron’s electric dipole momentabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: provides constraints on broad classes of new physics above 10¹³ eV, well beyond the direct reach of the LHC or any other near- or medium-term particle collider
Notation restored: Superscript restored from the abstract as typeset in the arXiv PDF (v3), where the 13 is set raised, read 2026-09-24. The text as extracted reads: provides constraints on broad classes of new physics above $10^{13}$ eV, well beyond the direct reach of the LHC or any other near- or medium-term particle collider

Claim 78 · checked 24 September 2026 · AI-assisted audit

Claim: A heavy particle violating time reversal, of the kind that could explain the asymmetry, would tilt the electron slightly.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Improved limit on the electric dipole moment of the electronabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Physical systems · Experiment
The source reads: the existence of very massive particles whose interactions violate time-reversal symmetry, which could explain the cosmological matter–antimatter asymmetry, can give rise to an electric dipole moment along the spin axis of the electron

What this does not establish

The ACME paper was read as its abstract only. "Tilt" is the page’s image for an electric dipole moment along the electron’s spin.

Later work looked for

Crossref, 2019 on, "electron electric dipole moment": Roussy and others (Science, 2023) improve the bound by a factor of about 2.4 and find no moment; added to the page.

Claim 79 · checked 24 September 2026 · AI-assisted audit

Claim: No tilt has been found.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Improved limit on the electric dipole moment of the electronabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Physical systems · Experiment
The source reads: No electric dipole moments of fundamental particles have been observed.
Supports
An improved bound on the electron’s electric dipole momentabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: Our result is consistent with zero and improves on the previous best upper bound by a factor ∼2.4.
Notation restored: LaTeX markup in the arXiv abstract rendered as text, checked against the abstract as typeset in the arXiv PDF (v3), read 2026-09-24. The text as extracted reads: Our result is consistent with zero and improves on the previous best upper bound by a factor $\sim2.4$.

What this does not establish

The ACME paper was read as its abstract only; Roussy and others were read in full.

Later work looked for

Crossref, 2019 on, "electron electric dipole moment": Roussy and others (Science, 2023) improve the bound by a factor of about 2.4 and find no moment; added to the page.

Claim 80 · checked 24 September 2026 · AI-assisted audit

Claim: The limit set in 2018, tightened by a factor of about 2.4 in 2023, pushes a broad class of candidates, if they violate time reversal maximally, above anything the Large Hadron Collider can reach directly.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Improved limit on the electric dipole moment of the electronabstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Physical systems · Experiment
The source reads: This result implies that a broad class of conjectured particles, if they exist and time-reversal symmetry is maximally violated, have masses that greatly exceed what can be measured directly at the Large Hadron Collider.
Supports
An improved bound on the electron’s electric dipole momentabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: Our result is consistent with zero and improves on the previous best upper bound by a factor ∼2.4.
Notation restored: LaTeX markup in the arXiv abstract rendered as text, checked against the abstract as typeset in the arXiv PDF (v3), read 2026-09-24. The text as extracted reads: Our result is consistent with zero and improves on the previous best upper bound by a factor $\sim2.4$.
Supports
An improved bound on the electron’s electric dipole momentabstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: provides constraints on broad classes of new physics above 10¹³ eV, well beyond the direct reach of the LHC or any other near- or medium-term particle collider
Notation restored: Superscript restored from the abstract as typeset in the arXiv PDF (v3), where the 13 is set raised, read 2026-09-24. The text as extracted reads: provides constraints on broad classes of new physics above $10^{13}$ eV, well beyond the direct reach of the LHC or any other near- or medium-term particle collider
Supports
An improved bound on the electron’s electric dipole momentmain text, first page; reference 5
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Physical systems · Experiment
The source reads: Our result is consistent with zero and improves on the previous best upper bound [5] by a factor ∼ 2.4.
Reference 5 is the ACME Collaboration’s 2018 Nature paper, so the factor is measured against the 2018 limit.

What this does not establish

The ACME paper was read as its abstract only; Roussy and others were read in full. The mass reach assumes maximal violation of time-reversal symmetry, and the 2023 figure is a bound on broad classes of new physics, not on every candidate.

Later work looked for

Crossref, 2019 on, "electron electric dipole moment": Roussy and others (Science, 2023) improve the bound by a factor of about 2.4 and find no moment; added to the page.

Corrected

24 September 2026. Previously: “and the limit on that tilt now pushes a broad class of candidates above anything the collider can reach directly.” The ACME result holds only if time-reversal symmetry is maximally violated, which the page left out; and the 2018 limit has been improved by a factor of about 2.4 (Roussy and others, Science, 2023), added as a source.

Claim 81 · checked 24 September 2026 · AI-assisted audit

Claim: Which kind of answer this is determines whether it is a question about experiments or a question about cosmology.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from the review’s point that high-scale models can escape direct test and leave at most indirect evidence.

Supports
Matter and antimatter in the universesection IV.2, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: most models of baryogenesis are hard to falsify. They may remain viable even if no signals are observed in any experiments in the centuries to come, as they can be saved from falsification by pushing up an associated energy scale.
Supports
Matter and antimatter in the universesection IV.2, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: In some cases, indirect evidence that supports the underlying theory may be found in low energy experiments or astrophysical observations

Claim 82 · checked 24 September 2026 · AI-assisted audit

The part with no candidate

Claim: The part with no candidate

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

No accepted mechanism predicts the size of the surplus; the review calls it fixed by unknown physics.

Supports
Matter and antimatter in the universesection III.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: which was fixed by unknown physics (baryogenesis) at higher energies
Supports
Matter and antimatter in the universesection IV.2, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: The requirement to predict the correct BAU is a necessary condition that can be used to constrain the parameter space for these classes of models.

Claim 84 · checked 24 September 2026 · AI-assisted audit

Claim: Everything solid is an accounting error of about one part in a billion.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

A figure of speech for the order of magnitude of the surplus; see the correction to the figure in "How large the surplus was".

Supports
Matter and antimatter in the universesection I, equation 1 and the text before it
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The baryon asymmetry of the universe (BAU) can be defined as the difference between the number of baryons NB and antibaryons ... divided by their sum (or the entropy s) just before antiprotons disappeared from the primordial plasma
Supports
Big bang nucleosynthesis: Present statussection I; Table V
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: the abundances of the four light nuclei are usually parameterized by the baryon-to-photon ratio ... most recently by Planck yielding η = 6.10± 0.04

Corrected

24 September 2026. Previously: “Everything solid is an accounting error of six parts in ten billion.” Six in ten billion is the baryon-to-photon ratio, not the excess of matter over antimatter, which is about twice that and known only to order of magnitude.

Claim 83 · checked 24 September 2026 · AI-assisted audit

Why the number is what it is

Claim: Why the number is what it is

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Even a successful mechanism has to land on roughly six parts in ten billion rather than one part in a thousand or one part in a trillion.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

The number is the baryon-to-photon ratio, the quantity baryogenesis models are asked to reproduce.

Supports
Matter and antimatter in the universesection IV.2, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: The requirement to predict the correct BAU is a necessary condition that can be used to constrain the parameter space for these classes of models.
Supports
Big bang nucleosynthesis: Present statussection I; Table V
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Astronomical observation · Review of the field
The source reads: the abundances of the four light nuclei are usually parameterized by the baryon-to-photon ratio ... most recently by Planck yielding η = 6.10± 0.04

Later work looked for

Claim 86 · checked 24 September 2026 · AI-assisted audit

Claim: The number is an input baryogenesis is asked to reproduce, not something the known laws predict.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection III.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: which was fixed by unknown physics (baryogenesis) at higher energies
Supports
Matter and antimatter in the universesection IV.2, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: The requirement to predict the correct BAU is a necessary condition that can be used to constrain the parameter space for these classes of models.
Supports
Matter and antimatter in the universesection IV.1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: A first order phase transition could only occur if the Higgs mass were below 72 GeV ... is in clear contradiction with experimental data, allowing to conclude that it is extremely unlikely that the observed BAU can be generated within the SM.

Later work looked for

Crossref, 2018 on, "electroweak baryogenesis standard model": later work builds on the Standard Model failing and adds new physics; nothing found that revives Standard Model baryogenesis.

Claim 87 · checked 24 September 2026 · AI-assisted audit

Claim: It is also possible that the asymmetry was never produced at all but set as an initial condition.

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, first and fifth paragraphs
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: posed a mystery that could only be explained by assuming that the universe was set up like this ... The paradigm of cosmic inflation elevated the idea of an initial state with B = 0 from an assumption, based on aesthetic reasoning, to a generic prediction.

What this does not establish

The review records this as the older assumption, which inflation turned into a prediction of zero initial asymmetry; the next sentences give the condition it needs.

Claim 88 · checked 24 September 2026 · AI-assisted audit

Claim: That only survives if the universe did not inflate, or not for long.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, fifth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: If the universe underwent ... a period of accelerated expansion during its very early history that lasted for long enough to explain its spacial flatness and the isotropy of the CMB temperature, any pre-existing baryon asymmetry was diluted and negligible at the end of inflation

What this does not establish

Conditional on inflation. The review adds that in some models baryon and lepton number violation in chemical equilibrium would erase an initial asymmetry anyway.

Corrected

24 September 2026. Previously: “That only survives if the universe did not inflate.” The review’s condition is inflation that "lasted for long enough" to explain flatness and isotropy; a short period would not dilute it.

Claim 89 · checked 24 September 2026 · AI-assisted audit

Claim: A long enough period of accelerated expansion dilutes any pre-existing asymmetry until it is negligible, which puts baryogenesis at reheating or later.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Matter and antimatter in the universesection I, fifth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: If the universe underwent ... a period of accelerated expansion during its very early history that lasted for long enough to explain its spacial flatness and the isotropy of the CMB temperature, any pre-existing baryon asymmetry was diluted and negligible at the end of inflation
Supports
Matter and antimatter in the universesection I, fifth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Theory · Review of the field
The source reads: Therefore, baryogenesis needs to occur either during reheating or in the radiation dominated epoch.

What this does not establish

Holds if inflation happened, which is the standard picture but not established by this page.

Corrected

24 September 2026. Previously: “A long enough period of accelerated expansion dilutes any pre-existing asymmetry to nothing,” The review says "diluted and negligible", not removed.

Claim 90 · checked 24 September 2026 · AI-assisted audit

What was read

Planck 2018 results. VI. Cosmological parametersPlanck Collaboration, Astronomy & Astrophysics · arXiv:1807.06209 abstractAbstract only, 24 September 2026 · Copyright; quoted briefly
Big bang nucleosynthesis: Present statusCyburt, Fields, Olive and Yeh, Reviews of Modern Physics · arXiv:1505.01076v1, "Big Bang Nucleosynthesis: 2015", the preprint of the published review; read abstract, sections I and IV, Tables IV and VRead in full, 24 September 2026 · Copyright; quoted briefly
A Matter-Antimatter Universe?Cohen, De Rujula and Glashow, The Astrophysical Journal · arXiv:astro-ph/9707087v2 (15 November 1997), the authors’ copy; Crossref record for the published versionRead in full, 24 September 2026 · Copyright; quoted brieflyPDF text extraction splits "empirically" as "em pirically"; the excerpt keeps that spacing so it can be matched.
Matter and antimatter in the universeCanetti, Drewes and Shaposhnikov, New Journal of Physics · arXiv:1204.4186v2, the authors’ copy of the published review; read sections I to IV.2, IV.3 in part, and the referencesRead in full, 24 September 2026 · Copyright; quoted briefly
Evidence for the 2 pi Decay of the K2 MesonChristenson, Cronin, Fitch and Turlay, Physical Review Letters · INSPIRE record 11878 with its opening paragraph; the APS full text refuses this environmentCatalogue record only, 24 September 2026 · Copyright; quoted briefly
Observation of CP Violation in Charm DecaysLHCb Collaboration, Physical Review Letters · arXiv:1903.08726v2 (31 May 2019)Read in full, 24 September 2026 · CC BY 4.0
The Nobel Prize in Physics 1980Nobel Prize Outreach · nobelprize.org prize summary pageRead in full, 24 September 2026 · Copyright; quoted briefly
Neutrinoless Double-Beta Decay: Status and ProspectsDolinski, Poon and Rodejohann, Annual Review of Nuclear and Particle Science · arXiv:1902.04097, the authors’ copy of the published review; read sections 1 and 2Read in full, 24 September 2026 · Copyright; quoted briefly
Improved limit on the electric dipole moment of the electronACME Collaboration, Nature · Publisher’s abstract on nature.comAbstract only, 24 September 2026 · Copyright; quoted briefly
Observation of charge-parity symmetry breaking in baryon decaysLHCb Collaboration, Nature · arXiv:2503.16954v2 (13 August 2025), abstract and full text; published in Nature 643 (2025) 1223Read in full, 24 September 2026 · CC BY 4.0Excerpts from the abstract keep the arXiv abstract’s LaTeX markup as served; a reader is shown it rendered.
An improved bound on the electron’s electric dipole momentRoussy, Caldwell, Wright and others, Science · arXiv:2212.11841v3, abstract and full text; published in Science 381, 46 (2023)Read in full, 24 September 2026 · arXiv non-exclusive distribution licence; quoted brieflyExcerpts from the abstract keep the arXiv abstract’s LaTeX markup as served; a reader is shown it rendered.