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Safia Ahmad

Publications and source records attributed to Safia Ahmad.

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Baryogenesis in the paradigm of quintessential inflation

We explore the possibility of baryogenesis in the framework of quintessential inflation. We focus on the model independent features of the underlying paradigm and demonstrate that the required baryon asymmetry can successfully be generated in this scenario. To this effect, we use the effective field theory framework with desired terms in the Lagrangian necessary to mimic baryon number violation \textit{à la} spontaneous baryogenesis which can successfully evade Sakharov's requirement allowing us to generate the observed baryon asymmetry in the equilibrium process. Our estimates are independent of the underlying physical process responsible for baryon number violation. The underlying framework of quintessential inflation essentially includes the presence of kinetic regime after inflation which gives rise to blue spectrum of gravitational wave background at high frequencies. In addition to baryogenesis, we discuss the prospects of detection of relic gravitational wave background, in the future proposed missions, sticking to model independent treatment.

gr-qc

Relic gravitational waves from Quintessential Inflation

We study relic gravitational waves in the paradigm of quintessential inflation. In this framework, irrespective of the underlying model, inflation is followed by the kinetic regime. Thereafter, the field energy density remains sub-dominant before the onset of acceleration. We carry out model independent analysis to obtain the temperature at the end of inflation and the estimate for upper bound on the Hubble parameter to circumvent the problem due to relic gravitational waves. In this process, we used Planck 2015 data to constrain the inflationary phase. We demonstrate that the required temperature can be produced by the mechanism of instant preheating. The generic feature of the scenario includes the presence of kinetic regime after inflation which results into blue spectrum of gravitational wave background at high frequencies. We discuss the prospects of detection of relic gravitational wave background in the advanced LIGO and LISA space-born gravitational wave missions. Finally we consider a concrete model to realize the paradigm of quintessential inflation and show that inflationary as well as post-inflationary evolution can successfully be described by the inflaton potential, $V(ϕ) \propto Exp(-λϕ^n/\Mpl^n)(n>1)$, by suitably constraining the parameters of the model.

gr-qc

Tachyon field non-minimally coupled to massive neutrino matter

In this paper, we consider rolling tachyon, with steep run-away type of potentials non-minimally coupled to massive neutrino matter. The coupling dynamically builds up at late times as neutrino matter turns non-relativistic. In case of scaling and string inspired potentials, we have shown that non-minimal coupling leads to minimum in the field potential. Given a suitable choice of model parameters, it is shown to give rise to late-time acceleration with the desired equation of state.

gr-qc