Abstract
We review scenarios of baryogenesis through leptogenesis at early epochs of the universe, in string-inspired minimal extensions of the Standard Model (SM), involving heavy right-handed Majorana neutrinos. Spontaneous violation of CPT symmetry is induced by appropriate (in general, temperature-dependent) backgrounds of the Kalb–Ramond (KR) axion field, which has its origins in the (bosonic) massless string multiplet. As interesting features of the model, we also discuss two issues associated with quantum (chiral) anomalies: (i) the non-contribution of the KR axion background to the (anomalous) chiral magnetic effect, which arises in the presence of external electromagnetic fields and non-zero chiral chemical potentials of charged fermions; and (ii) the potential role of quantum fluctuations of the KR axion on the (anomalous) radiative generation of a Majorana mass for the right-handed neutrinos themselves.
Highlights
It is well known [1,2,3] that the Standard Model (SM) of particle physics cannot explain the observed matter–antimatter asymmetry in the universe [4,5], which requires ∆n( T ∼ 1 GeV) = nB − nB ∼ nB + nB s (1)for times t ∼ 10−6 s and temperatures T ∼ 1 GeV
The structure of the article is as follows: in Section 2. we review the basic features of the mechanism for the CPT violation (CPTV)-induced lepton asymmetry in a rather generic framework, without specifying the microscopic origin of the CPTV
We have reviewed our previous studies of leptogenesis induced by a Lorentz invariance violating (LV) and CPTV time-like axial background B0, which is provided by the field strength of the antisymmetric tensor KR field appearing in the massless spectrum of microscopic, ultraviolet complete, string-inspired models
Summary
It is well known [1,2,3] that the Standard Model (SM) of particle physics cannot explain the observed (primarily baryonic) matter–antimatter asymmetry in the universe [4,5], which requires. Some of the attempts mentioned above involve the elegant mechanism of baryogenesis via leptogenesis In such scenarios, a lepton asymmetry is generated first, by means of decays of right handed sterile neutrinos to SM particles, and is subsequently communicated to the baryon sector by means of sphaleron processes which violate both Baryon (B) and Lepton (L) numbers, but preserve the difference B-L [16,17,18,19,20,21,22]. Where +(−) denotes a fermionic (bosonic) particle species and a bar over a quantity associates the quantity with an antiparticle; we have for the chemical potentials μ = −μ In principle, such scenarios, in the SME context, can lead to alternative explanations for the observed matter–antimatter asymmetry, provided that detailed mechanisms for freeze-out of particle interactions are provided.
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