Observational Tests of Antimatter Cosmologies

Steigman, Gary

doi:10.1146/annurev.aa.14.090176.002011

Cited by 341 publications

(284 citation statements)

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“…While these efforts concentrate on direct detection of antinuclei in the solar system, several limits on the existence of antimatter domains have been placed in the past. It has been known for a long time, that the presence of significant amounts of antimatter within a distance of about 20 Mpc from the solar system may be excluded on grounds of the non-observation of annihilation radiation [1]. More recent studies of the diffuse γ-ray background claim to exclude antimatter regions in today's Universe within a distance of ∼ 1000 Mpc [2], a considerable fraction of the present horizon ∼ 3000 Mpc.…”

Section: Introductionmentioning

confidence: 99%

“…Prior studies of the influence of antimatter domains on the light element abundances have only been carried out in the context of a baryo-symmetric Universe [1,12]. Of course, such models have to assume that annihilation of all cosmic baryons may be avoided by an assumed "unphysical" , and unknown rapid separation mechanism of matter from antimatter.…”

Section: Introductionmentioning

confidence: 99%

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Limits on cosmic matter-antimatter domains from big bang nucleosynthesis

Rehm

Jedamzik

2001

Phys. Rev. D

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We present detailed numerical calculations of the light element abundances synthesized in a Universe consisting of matter-and antimatter-domains, as predicted to arise in some electroweak baryogenesis scenarios. In our simulations all relevant physical effects, such as baryon-antibaryon annihilations, production of secondary particles during annihilations, baryon diffusion, and hydrodynamic processes are coupled to the nuclear reaction network. We identify two dominant effects, according to the typical spatial dimensions of the domains. Small antimatter domains are dissipated via neutron diffusion prior to 4 He synthesis at T4 He ≈ 80 keV, leading to a suppression of the primordial 4 He mass fraction. Larger domains are dissipated below T4 He via a combination of proton diffusion and hydrodynamic expansion. In this case the strongest effects on the elemental abundances are due top 4 He annihilations, leading to an overproduction of 3 He relative to 2 H and to overproduction of 6 Li via non-thermal nuclear reactions. Both effects may result in light element abundances deviating substantially from the standard Big Bang Nucleosynthesis yields and from the observationally inferred values. This allows us to derive stringent constraints on the antimatter parameters. For some combinations of the parameters, one may obtain both, low 2 H and low 4 He, at a common value of the cosmic baryon density, a result seemingly favored by current observational data. 26.35.+c,98.80Cq,25.43.+t

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Limits on cosmic matter-antimatter domains from big bang nucleosynthesis

Rehm

Jedamzik

2001

Phys. Rev. D

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“…The baryon number to entropy ratio in the observed part of the universe is estimated to be n B /s ∼ (4 − 6)10 −11 [3]. In 1967 A.D. Sakharov [4] established the three building blocks required from any candidate theory of baryogenesis:…”

Section: Introductionmentioning

confidence: 99%

Standard model CP-violation and baryon asymmetry (I). Zero temperature

Lozano²,

et al. 1994

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We consider quantum effects in a world with two coexisting symmetry phases, unbroken and spontaneously broken, as a result of a first order phase transition. The discrete symmetries of the problem are discussed in general. We compute the exact twopoint Green function for a free fermion, when a thin wall separates the two phases. The Dirac propagator displays both massive and massless poles, and new CP-even phases resulting from the fermion reflection on the wall. We discuss the possible quarkantiquark CP asymmetries produced in the Standard Model(SM) for the academic T = 0 case. General arguments indicate that an effect first appears at order α W in the reflection amplitude, as the wall acts as a source of momentum and the on-shell one-loop self-energy cannot be renormalized away. The asymmetries stem from the interference of the SM CP-odd couplings and the CP-even phases in the propagator. We perform a toy computation that indicates the type of GIM cancellations of the problem. The behaviour can be expressed in terms of two unitarity triangles.

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“…Earlier work on this problem [5] has concentrated on the presence of matter{antimatter domains in baryo-symmetric universes (i.e. Omnes-model).…”

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confidence: 99%

Big Bang Nucleosynthesis with Matter-Antimatter Domains

1998

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We i n v estigate Big Bang nucleosynthesis (hereafter, BBN) in a cosmic environment c haracterised by a distribution of small-scale matter{antimatter domains. Production of antimatter domains in a baryo-asymmetric universe is predicted in some electroweak baryogenesis scenarios. We nd that cosmic antimatter domains of size exceeding the neutron-di usion length at temperature T 1 MeV signi cantly a ect the light-element production. Annihilation of antimatter preferentially occurs on neutrons such that antimatter domains may yield a reduction of the 4 He abundance relative to a standard BBN scenario. In the limiting case, all neutrons will be removed before the onset of light-element production, and a universe with net baryon number but without production of light elements results. In general, antimatter domains spoil agreement b e t w een BBN abundance yields and observationally inferred primordial abundances limits which allows us to derive limits on their presence in the early universe. However, if only small amounts of antimatter are present, BBN with low deuterium and low 4 He, as seemingly favored by current observational data, is possible. 26.35.+c,98.80Cq,25.43.+t Big Bang Nucleosynthesis is one of the furthest back{ reaching cosmological probes available. By means of comparing the predicted and observationally inferred light element abundances the cosmic conditions as early as a few seconds after the Big Bang may be scrutinized. Nucleosynthesis has thus been used to constrain, for example, inhomogeneities in the baryon-to-photon ratio or abundances and properties of decaying particles during the BBN era (for reviews on non-standard BBN see [1]).In this Letter we examine the BBN process in a universe where matter and antimatter are segregated. A segregation of matter and antimatter may a ect BBN abundance yields even if the average segregation scale is very small in terms of characteristic astrophysical scales. Such small scales imply annihilation of antimatter well before the present epoch. We are therefore particularly interested in the case where the universe contains net baryon number, as for example, through an excess of matter domains over antimatter domains. A baryo-asymmetric universe lled with a distribution of small-scale matter{ antimatter domains may arise during an epoch of baryogenesis at the electroweak scale. It has been shown within the minimal supersymmetric standard model, and under the assumption of explicit as well as spontaneous CP violation, that during a rst-order electroweak phase transition the baryogenesis process may result in individual bubbles containing either net baryon number, or net antibaryon number [2]. Recently, it has been argued that pre-existing stochastic (hyper)magnetic elds in the early universe, in conjunction with an era of electroweak baryogenesis, may cause the production of regions containing either matter or antimatter [3]. In general, any segregation of matter and antimatter either produced on scales larger than the neutron di usion length at weak freeze...

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Observational Tests of Antimatter Cosmologies

Cited by 341 publications

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Limits on cosmic matter-antimatter domains from big bang nucleosynthesis

Limits on cosmic matter-antimatter domains from big bang nucleosynthesis

Standard model CP-violation and baryon asymmetry (I). Zero temperature

Big Bang Nucleosynthesis with Matter-Antimatter Domains

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