Affleck-Dine Baryogenesis Research Articles

Cosmology of supersymmetric models with low-energy gauge mediation

We study the cosmology of supersymmetric models in which the supersymmetry breaking effects are mediated by gauge interactions at about the 10^5 GeV scale. We first point out that the gravitino is likely to overclose the Universe in this class of models. This requires an entropy production, which prefers a baryogenesis mechanism at a relatively low temperature. The Affleck-Dine mechanism for baryogenesis is one of the possibilities to generate enough baryon asymmetry, but the analysis is non-trivial since the shape of the potential for the flat direction differs substantially from the conventional hidden sector case. To see this, we first perform a 2-loop calculation to determine the shape of the potential. By combining the potential with the supergravity contribution, we then find that the Affleck-Dine baryogenesis works efficiently to generate sufficient baryon asymmetry. On the other hand, we also point out that string moduli fields, if present, are stable and their coherent oscillations overclose the Universe by more than 15 orders of magnitude. One needs a very late inflationary period with an e-folding of N \gtrsim 5 and an energy density of \lesssim (10^7 GeV)^4. A thermal inflation is enough for this purpose. Fortunately, the Affleck-Dine baryogenesis is so efficient that enough baryon asymmetry can survive the late inflation.

Ucdcdc-based Affleck-Dine baryogenesis

We consider the possibility of a successful Affleck-Dine mechanism along the ${u}^{c}{d}^{c}{d}^{c}$ direction in R-parity symmetric extensions of the minimal supersymmetric standard model (MSSM) which contain a gauge singlet superfield \ensuremath{\varphi}. Such gauge singlets commonly occur in extensions of the MSSM, for example, in models which seek to account for neutrino masses. We consider a two scalar Affleck-Dine mechanism, with the flat direction stabilized by a nonrenormalizible superpotential term of the form $(\ensuremath{\lambda}/M)\ensuremath{\varphi}{u}^{c}{d}^{c}{d}^{c}\ensuremath{\sim}(\ensuremath{\lambda}/M)\ensuremath{\varphi}{\ensuremath{\psi}}^{3}$, where \ensuremath{\psi} corresponds to the gauge nonsinglet flat direction. We give approximate solutions of the scalar field equations of motion which describe the evolution of the condensates and show that the final baryon asymmetry in this case is suppressed relative to that expected from the conventional single scalar Affleck-Dine mechanism, based on a superpotential term of the form $(\ensuremath{\lambda}/4M){\ensuremath{\psi}}^{4}$, by a factor $[{m}_{s}{/(m}_{\ensuremath{\varphi}}{+m}_{s}){]}^{1/2}$, where ${m}_{s}$ is the soft supersymmetry-breaking scalar mass and ${\mathit{m}}_{\mathrm{\ensuremath{\varphi}}}$ is the supersymmetric \ensuremath{\varphi} mass. It is possible for the model to generate a baryon asymmetry even in the limit of unbroken B-L, so long as the gauge singlet condensate does not decay until after anomalous electroweak B+L violation is out of equilibrium following the electroweak phase transition. This condition is generally satisfied if all Dirac neutrino masses are less than around 10 keV. This class of Affleck-Dine models can, in principle, be experimentally ruled out, for example, by the observation of a Dirac mass for the \ensuremath{\mu} or \ensuremath{\tau} neutrino significantly larger than around 10 keV together with a mostly Higgsino LSP.

Natural inflation in SUSY and gauge-mediated curvature of the flat directions

Supersymmetric theories often include the non-compact directions in the field space along which the tree level potential grows only up to a certain limited value (determined by the mass scale of the theory) and then stays constant for the arbitrarily large expectation value of the field parametrizing the direction. Above the critical value, the tree-level curvature is large and positive in the other directions. Such plateaux are natural candidates for the hybrid inflaton. The non-zero F-term density along the plateau spontaneously breaks SUSY and induces the one-loop logarithmic slope for the inflaton potential. The coupling of the inflaton to the Higgs fields in the complex representations of the gauge group, may result in a radiatively induced Fayet-Illiopoulos D-term during inflation, which destabilizes some of the squark and slepton flat directions. Corresponding soft masses can be larger than the Hubble parameter and thus, play a crucial role for the Affleck-Dine baryogenesis.

BARYON NUMBER NONCONSERVATION IN A HIGH-DENSE POST-INFLATIONARY UNIVERSE

We found the temperature at which the electroweak baryon-number nonconserving processes are frozen, as a function of the fermion number density of the universe, which results in the increase of the freezing temperature with the growth of the fermion number density combination [Formula: see text]. We combine this result with the Affleck-Dine baryogenesis mechanism to suggest a possible scenario for the evolution of the post-inflationary universe, according to which the universe could have passed through a hot stage with large baryon and lepton asymmetries [Formula: see text], that are later erased at relatively low temperatures, the correct observational baryon asymmetry nB/nγ ~ 10−9 being finally produced.