Anupam Mazumdar

Assisted inflation via tachyon condensation.

In this paper we propose a new mechanism of inflating the Universe with non-BPS D4-branes which decay into stable D3-branes via tachyon condensation. In a single brane scenario the tachyon potential is very steep and unable to support inflation. However, if the universe lives in a stack of branes produced by a set of noninteracting unstable -branes, then the associated set of tachyons may drive inflation along our 3 spatial dimensions. After tachyon condensation the Universe is imagined to be filled with a set of parallel stable D3-branes. We study the scalar density perturbations and reheating within this setup.

Cosmological consequences of MSSM flat directions

We review the cosmological implications of the flat directions of the minimally supersymmetric standard model (MSSM). We describe how field condensates are created along the flat directions because of inflationary fluctuations. The post-inflationary dynamical evolution of the field condensate can charge up the condensate with B or L in a process known as Affleck–Dine baryogenesis. Condensate fluctuations can give rise to both adiabatic and isocurvature density perturbations and could be observable in future cosmic microwave experiments. In many cases the condensate is however not the state of lowest energy but fragments, with many interesting cosmological consequences. Fragmentation is triggered by inflation-induced perturbations and the condensate lumps will eventually form non-topological solitons, known as Q-balls. Their properties depend on how supersymmetry breaking is transmitted to the MSSM; if by gravity, then the Q-balls are semi-stable but long-lived and can be the source of all the baryons and LSP dark matter; if by gauge interactions, the Q-balls can be absolutely stable and form dark matter that can be searched for directly. We also discuss some cosmological applications of generic flat directions and Q-balls in the context of self-interacting dark matter, inflatonic solitons and extra dimensions.

Baryogenesis in theories with large extra spatial dimensions

We describe a simple and predictive scenario for baryogenesis in theories with large extra dimensions which resembles Affleck-Dine baryogenesis. The Affleck-Dine field is a complex scalar field carrying a

A dynamical stabilization of the radion potential

U(1)_{\chi}

Dynamics of coupled bosonic systems with applications to preheating

charge which is dynamically broken after the end of inflation. This generates an excess of

Final reheating temperature on a single brane

\chi

Affleck-Dine leptogenesis via right-handed sneutrino fields in a supersymmetric hybrid inflation model

over

Towards a successful reheating within supersymmetry

\bar \chi

Quasi-thermal Universe: from cosmology to colliders

, which then decays into Standard Model fermions to produce an excess of baryons over anti-baryons. Our model is very constrained because the Affleck-Dine field has to be sufficiently flat during inflation. It is also a source for density fluctuations which can be tested in the coming satellite and balloon experiments.

Inflatonic Q-ball evaporation: A new paradigm for reheating the Universe

Abstract Large extra-dimensional theories attempt to solve the hierarchy problem by assuming that the fundamental scale of the theory is at the electroweak scale. This requires the size of the extra dimensions to be stabilized at a scale which is determined by the effective four-dimensional Planck mass and the number of extra dimensions. In this Letter we concentrate upon the dynamical reasons to stabilize them by providing a running mass to the radion field. We show that it is possible to maintain the size of the extra dimensions once it is stabilized throughout the dynamics of inflation.