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Atri Deshamukhya

Publications and source records attributed to Atri Deshamukhya.

25 records · Page 2Linked to original sources
arXiv2015

A note on Low Energy Effective Theory of Chromo Natural Inflation in the light of BICEP2 results

Recent result of BICEP2, revealing a larger value of tensor to scalar ratio (r), has opened up new investigations of the in ationary models to fit the experimental data. The experiment needs to reconfirm the results, specifically the consistency between Planck and BICEP2. On the other hand, the combined analysis of Planck and BICEP2 B, including the dust polarization uncertainty, brings down the upper limit on r. In this note, we reexamine the low energy effective theory of Chromo Natural In ation model and its generalization in view of such observational data. We find that the parameter space of the model admits a large value of r as well as other cosmological observables consistent with data.

astro-ph.CO↗
arXiv2014

Warming up D3 brane motion in the background of D5 brane and Inflation

The position of a mobile D-3 brane moving towards a stack of localized D-5 branes has been studied as a candidate driving inflation in the warm inflationary scenario. We compare the results obtained by considering the dissipation parameter $Γ$ as an arbitrary function of only the inflaton field and a particular form derived by Bastro-Gil et al \cite{Berera8}. We find that the observables remain well within the recent observational constraint for a wide range of model parameters for the first case whereas the spectral index in the later case is always predicted blue, other cosmological observables remaining well within bound for a wider range of parameters though. We also discuss the non-gaussianity generated during inflation in this model.

hep-th↗
arXiv2014

Geometric Tachyon and Warm Inflation

The inflationary models developed in presence of a background radiation can be a solution to the reheating problem faced by common cold (isentropic) inflationary scenario. A D-brane system comprising of k Neuvo-Schwarz(NS) 5-branes with a transverse circle and BPS D3-branes with world volume parallel to the NS 5-branes, placed at a point on the transverse circle diametrically opposite to the NS 5-branes has a point of unstable equilibrium and the D3 brane has a geometric tachyonic mode associated with displacement of the brane along the circle. Cold inflationary scenario has been studied in connection with this geometric tachyon \cite{PA1} where it was found that one needs a background of minimum $10^4$ branes to realize a viable inflationary model. In this piece of work, we have tried to study a model of inflation driven by this geometric tachoyn in presence of radiation. We have found that compared to the isentropic scenario, to satisfy the observational bounds, the number of background branes required in this case reduces drastically and a viable model can be obtained with even six to seven NS 5-branes in the background.In this context, we have also analyzed the non-gaussianity associated with the model and observed that the concerned parameter lies well within the observation limit.

astro-ph.CO↗
arXiv2011

Inflation with improved D3-brane potential and the fine tunings associated with the model

We investigate brane-antibrane inflation in a warped deformed conifold background that includes contributions to the potential arising from imaginary anti-self-dual (IASD) fluxes including the term with irrational scaling dimension discovered recently. We find that the model can give rise to required number of e-foldings; observational constraint on COBE normalization is easily satisfied and low value of the tensor to scalar ratio of perturbations is achieved. We observe that these corrections to the effective potential help in relaxing the severe fine tunings associated with the earlier analysis.

hep-th↗
arXiv2009

Warm tachyonic inflation in warped background

We analyze warm tachyonic inflation, proposed in the literature, but from the viewpoint of four dimensional effective action for tachyon field on a non-BPS D3-brane. We find that consistency with observational data on density perturbation and validity of effective action requires warped compactification. The number of background branes which source the flux is found to be of the order of 10 in contrast to the order of $10^{14}$ in the standard cold inflationary scenario.

hep-th↗
arXiv2004

Non-minimally Coupled Tachyonic Inflation in Warped String Background

We show that the non-minimal coupling of tachyon field to the scalar curvature, as proposed by Piao et al, with the chosen coupling parameter does not produce the effective potential where the tachyon field can roll down from T=0 to large $T$ along the slope of the potential. We find a correct choice of the parameters which ensures this requirement and support slow-roll inflation. However, we find that the cosmological parameter found from the analysis of the theory are not in the range obtained from observations. We then invoke warped compactification and varying dilaton field over the compact manifold, as proposed by Raeymaekers, to show that in such a setup the observed parameter space can be ensured.

hep-th↗