Baryon Asymmetry, Supersymmetry and Gravitational Anomalies

The inferred values of the cosmological baryon and dark matter densities are strikingly similar, but in most theories of the early universe there is no true explanation of this fact; in particular, the baryon asymmetry and thus density depends upon unknown, and {\it a priori} unknown and possibly small, CP-violating phases which are independent of all parameters determining the dark matter density. We consider models of dark matter possessing a particle-antiparticle asymmetry...

Baryogenesis appears to require lepton number violation. This is naturally realized in extensions of the standard model containing right-handed neutrinos. We discuss the generation of a baryon asymmetry by the out-of-equilibrium decay of heavy Majorana neutrinos in these models, without and with supersymmetry. All relevant lepton number violating scattering processes which can inhibit the generation of an asymmetry are taken into account. We assume a similar pattern of mixing...

We discuss two cosmological issues in a generic gauge-mediated supersymmetry (SUSY)-breaking model, namely the Universe's baryon asymmetry and the gravitino dark-matter density. We show that both problems can be simultaneously solved if there exist extra matter multiplets of a SUSY-invariant mass of the order of the ``$\mu$-term'', as suggested in several realistic SUSY grand-unified theories. We propose an attractive scenario in which the observed baryon asymmetry is produce...

We review the current status of baryogenesis with emphasis on electroweak baryogenesis and leptogenesis. The first detailed studies were carried out for SU(5) GUT models where CP-violating decays of leptoquarks generate a baryon asymmetry. These GUT models were excluded by the discovery of B+L violating sphaleron processes at high temperatures. Yet a new possibility emerged, electroweak baryogenesis. Here sphaleron processes generate a baryon asymmetry during a strongly first...

A new scenario for baryogenesis is described. The basic idea is that theories beyond the standard model which contain a ${\rm U}(1)_{B-L}$ gauge symmetry, where $B$ and $L$ are respectively baryon and lepton numbers, predict the existence of $B-L$ cosmic strings with right-handed neutrinos trapped as transverse zero modes. Cosmic string loops loose their energy via gravitational radiation and rapidly decay releasing these right-handed neutrinos. These decay into lepton and el...

In models with the fundamental gravity scale in the TeV range, early cosmology is quite different from the standard picture, because the universe must have arisen at a much lower temperature and the electroweak symmetry was probably never restored. In this context, baryogenesis appears to be problematic: if the involved physics is essentially that of the Standard Model, ``conventional'' non-conserving baryon number processes are completely negligible at such low temperatures....

In this work we review the theories of origin of matter-antimatter asymmetry in the Universe. The general conditions for achieving baryogenesis and leptogenesis in a CPT conserving field theory have been laid down by Sakharov. In this review we discuss scenarios where a background scalar or gravitational field spontaneously breaks the CPT symmetry and splits the energy levels between particles and anti-particles. Baryon or Lepton number violating processes in proceeding at th...

The paper proposes an alternative scenario for the emergence of baryon asymmetry in the Universe. This scenario is realized in the lattice gravity model associated with the Dirac field as follows. At ultra-high temperatures of the Grand Unification order $T_c\sim10^{18}$ GeV and higher, the system is in a PT-symmetric phase. But when the temperature decreases, a phase transition to an asymmetric phase occurs, in which a non-zero tetrad appears, that is, space-time with the Mi...

We investigate whether the baryon asymmetry of the universe is explained in the framework of the supersymmetric extension of the Standard Model with R-parity violating interactions. It is shown that the Affleck-Dine mechanism naturally works via a trilinear interaction $LLE^c$, $LQD^c$, or $U^cD^cD^c$, if the magnitude of the coupling corresponding to the operator $\lambda$, $\lambda'$, or $\lambda''$ is sufficiently small. The formation of Q-balls and their subsequent evolut...

We propose a resonant leptogenesis scenario in a U(1)_{B-L} gauge extension of the standard model to generate large lepton asymmetries for cosmological baryon asymmetry and dark matter. After B-L number is spontaneously broken, inflaton can pick up a small vacuum expectation value for the mass splits of three pairs of quasi-degenerately heavy Majorana neutrinos and the masses of three sterile neutrinos. With thermal mass effects of sphalerons, the observed small baryon asymme...