Biomedical subjects

Anupam Mazumdar

Publications and source records attributed to Anupam Mazumdar.

7 recordsLinked to original sources

PubMed2005

Non-Gaussianity from preheating.

We consider a two-field model for inflation where the second order metric perturbations can be amplified by a parametric resonance during preheating. We demonstrate that there can arise a considerable enhancement of non-Gaussianity sourced by the local terms generated through the coupled perturbations. We argue that the non-Gaussianity parameter could be as large as f(NL) approximately 50. Our results may provide a useful test of preheating in future cosmic microwave background experiments.

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PubMed2004

Minimal supersymmetric Higgs bosons with extra dimensions as the source of reheating and all matter.

We consider the possibility that the dark energy responsible for inflation is deposited into extra dimensions outside of our observable Universe. Reheating and all matter can then be obtained from the minimal supersymmetric standard model flat direction condensate involving the Higgs bosons Hu and Hd, which acquires large amplitude by virtue of quantum fluctuations during inflation. The reheat temperature is TRH < or = 10(9) GeV so that there is no gravitino problem. We find a spectral index ns 1 with a very weak dependence on the Higgs potential.

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PubMed2004

Sneutrino condensate source for density perturbations, leptogenesis, and low reheat temperature.

We bring together some known ingredients beyond the standard model physics that can explain the hot big bang model with the observed baryon asymmetry and also the fluctuations in the cosmic microwave background radiation with a minimal set of assumptions. We propose an interesting scenario where the inflaton energy density is dumped into an infinitely large extra dimension. Instead of the inflaton it is the right handed sneutrino condensate, which is acquiring a nonzero vacuum expectation value during inflation, whose fluctuations are responsible for the density perturbations seen in the cosmic microwave background radiation with a spectral index n(s) approximately 1. The decay of the condensate is explaining the reheating of the Universe with a temperature, T(rh)< or =10(9) GeV, and the baryon asymmetry of order one part in 10(10) with no baryon-isocurvature fluctuations.

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PubMed2004

Model for fluctuating inflaton coupling: sneutrino induced adiabatic perturbations and nonthermal leptogenesis.

We discuss a unique possibility of generating adiabatic density perturbations and leptogenesis from the spatial fluctuations of the inflaton decay rate. The key assumption is that the initial isocurvature perturbations are created in the right-handed sneutrino sector during inflation which is then converted into adiabatic perturbations when the inflaton decays. We discuss distinct imprints on the cosmic microwave background radiation, which can distinguish nonthermal versus thermal leptogenesis.

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PubMed2003

Ultrahigh energy cosmic rays, cosmological constant, and theta vacua.

We propose that the origin of ultrahigh energy cosmic rays beyond the Greisen-Zatsepin-Kuzmin cutoff and the origin of small cosmological constant can both be explained by vacuum tunneling effects in a theory with degenerate vacua and fermionic doublets. By considering the possibility of tunneling from a particular winding number state, accompanied by violation of some global quantum number of fermions, the small value of the vacuum dark energy and the production of high energy cosmic rays are shown to be related. We predict that the energy of such cosmic rays should be at least 5x10(14) GeV.

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PubMed2003

Adiabatic density perturbations and matter generation from the minimal supersymmetric standard model.

We propose that the inflaton is coupled to ordinary matter only gravitationally and that it decays into a completely hidden sector. In this scenario both baryonic and dark matter originate from the decay of a flat direction of the minimal supersymmetric standard model, which is shown to generate the desired adiabatic perturbation spectrum via the curvaton mechanism. The requirement that the energy density along the flat direction dominates over the inflaton decay products fixes the flat direction almost uniquely. The present residual energy density in the hidden sector is typically shown to be small.

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PubMed2002

Reheating as a surface effect.

We describe a new mechanism for reheating the Universe through evaporation of a surface charge of a fragmented inflaton condensate. We show that for a range of Yukawa coupling of the inflaton to the matter sector evaporation gives rise to a much smaller reheat temperature compared to the standard perturbative decay. As a consequence, reheating through a surface effect could solve the gravitino and moduli overproduction problem in inflationary models without fine tuning the Yukawa sector.

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