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Sayantan Choudhury

Publications and source records attributed to Sayantan Choudhury.

At least 109 records · Page 6Linked to original sources
arXiv2015

Constraining brane inflationary magnetic field from cosmoparticle physics after Planck

In this article, I have studied the cosmological and particle physics constraints on a generic class of large field ($|Δϕ|>M_{p}$) and small field ($|Δϕ<M_{p}$) models of brane inflationary magnetic field from: (1) tensor-to-scalar ratio ($r$), (2) reheating, (3) leptogenesis and (4) baryogenesis in case of Randall-Sundrum single braneworld gravity (RSII) framework. I also establish a direct connection between the magnetic field at the present epoch ($B_{0}$) and primordial gravity waves ($r$), which give a precise estimate of non-vanishing CP asymmetry ($ε_{CP}$) in leptogenesis and baryon asymmetry ($η_{B}$) in baryogenesis scenario respectively. Further assuming the conformal invariance to be restored after inflation in the framework of RSII, I have explicitly shown that the requirement of the sub-dominant feature of large scale coherent magnetic field after inflation gives two fold non-trivial characteristic constraints- on equation of state parameter ($w$) and the corresponding energy scale during reheating ($ρ^{1/4}_{rh}$) epoch. Hence giving the proposal for avoiding the contribution of back-reaction from the magnetic field I have established a bound on the generic reheating characteristic parameter ($R_{rh}$) and its rescaled version ($R_{sc}$), to achieve large scale magnetic field within the prescribed setup and further apply the CMB constraints as obtained from recently observed Planck 2015 data and Planck+BICEP2+Keck Array joint constraints. Using all these derived results I have shown that it is possible to put further stringent constraints on various classes of large and small field inflationary models to break the degeneracy between various cosmological parameters within the framework of RSII. Finally, I have studied the consequences from two specific models of brane inflation- monomial and hilltop.

astro-ph.CO↗
arXiv2015

Priomordial non-Gaussian features from DBI Galileon inflation

We have studied primordial non-Gaussian features from a model of potential driven single field DBI Galileon inflation. We have computed the bispectrum from the three point correlation function considering all possible cross correlation between scalar and tensor modes from the proposed setup. Further, we have computed the trispectrum from four point correlation function considering the contribution from contact interaction, scalar and graviton exchange diagrams in the in-in picture. Finally we have obtained the non-Gaussian consistency conditions from the four point correlator, which results in partial violation of the Suyama-Yamaguchi four-point consistency relation. This further leads to the conclusion that sufficient primordial non-Gaussianities can be obtained from DBI Galileon inflation.

hep-th↗
arXiv2015

Can Effective Field Theory of inflation generate large tensor-to-scalar ratio within Randall Sundrum single braneworld?

In this paper my prime objective is to explain the generation of large tensor-to-scalar ratio from the single field sub-Planckian inflationary paradigm within Randall Sundrum (RS) single braneworld scenario in a model independent fashion. By explicit computation I have shown that the effective field theory prescription of brane inflation within RS single brane setup is consistent with sub- Planckian excursion of the inflaton field, which will further generate large value of tensor-to-scalar ratio, provided the energy density for inflaton degrees of freedom is high enough compared to the brane tension in high energy regime. Finally, I have mentioned the stringent theoretical constraint on positive brane tension, cut-off of the quantum gravity scale and bulk cosmological constant to get sub-Planckian field excursion along with large tensor-to-scalar ratio as recently observed by BICEP2 or at least generates the tensor-to-scalar ratio consistent with the upper bound of Planck (2013 and 2015) data and Planck+BICEP2+Keck Array joint constraint.

hep-th↗
arXiv2014

A step towards exploring the features of Gravidilaton sector in Randall-Sundrum scenario via lightest Kaluza-Klein graviton mass

In this paper we study the role of the 5D Gauss-Bonnet corrections and two loop higher genus contribution to the gravity action in type IIB string theory inspired low energy supergravity theory in the light of gravidilatonic interactions on the lightest Kaluza-Klein graviton mass spectrum. From the latest constraints on the lightest Kaluza-Klein graviton mass as obtained from the ATLAS dilepton search in 7 TeV proton-proton collision, we have shown that due to the presence of Gauss-Bonnet and string loop corrections, the warping solution in an ${\bf AdS_{5}}$ bulk is quite distinct from Randall-Sundrum scenario. We discuss the constraints on the model parameters to fit with present ATLAS data.

hep-ph↗
arXiv2014

Modulus stabilization in higher curvature dilaton gravity

We propose a framework of modulus stabilization in two brane warped geometry scenario in presence of higher curvature gravity and dilaton in bulk space-time. In the prescribed setup we study various features of the stabilized potential for the modulus field, generated by a bulk scalar degrees of freedom with quartic interactions localized on the two 3-branes placed at the orbifold fixed points. We determine the parameter space for the gravidilaton and Gauss-Bonnet required to stabilize the modulus in such higher curvature dilaton gravity setup.

hep-th↗
arXiv2014

Inflamagnetogenesis redux: Unzipping sub-Planckian inflation via various cosmoparticle probes

In this paper I introduce a precise constraint on primordial magnetogenesis, for a generic class of single-field inflationary model followed by small field excursion below the Planck scale. I also establish a connection between the magnetic field at the present epoch and primordial gravity waves ($r$) via non-vanishing CP asymmetry parameter ($ε_{\bf CP}$), which triggers the leptogenesis scenario. Finally, I explore various hidden cosmophenomenological features of theoretical CMB B-mode polarization spectra, which can be treated as a significant probe to put further stringent constraint on low and high scale small field inflationary models after releasing the Planck B-mode polarization data.

hep-th↗
arXiv2014

Primordial blackholes and gravitational waves for an inflection-point model of inflation

In this article we provide a new closed relationship between cosmic abundance of primordial gravitational waves and primordial blackholes originated from initial inflationary perturbations for inflection-point models of inflation where inflation occurs below the Planck scale. The current Planck constraint on tensor-to-scalar ratio, running of the spectral tilt, and from the abundance of dark matter content in the universe, we can deduce a strict bound on the current abundance of primordial blackholes to be within a range, $9.99712\times 10^{-3}<Ω_{PBH}h^{2}<9.99736\times 10^{-3}$.

astro-ph.CO↗
arXiv2014

Reconstructing inflationary potential from BICEP2 and running of tensor modes

In this paper we will analyse the constraints on a sub-Planckian excursion of a single inflaton field, which would yield a large tensor to scalar ratio, while explaining the temperature anisotropy of the cosmic microwave background (CMB) radiation. In particular, our attempt will be to reconstruct the inflationary potential by constraining, $V(ϕ_0), V^{\prime}(ϕ_0), V^{\prime\prime}(ϕ_0), V^{\prime\prime\prime}(ϕ_0)$ and $V^{\prime\prime\prime\prime}(ϕ_0)$, in the vicinity of the field, $ϕ_0\ll M_p$, and the field displacement, $Δϕ\ll M_p$, where $M_p$ is the reduced Planck mass. We will provide, for the first time, a set of new {\it consistency} relationships for sub-Planckian excursion of the inflaton field, which would help us to differentiate sub-versus-super Planckian models of inflation. For a generic single field inflationary potential, we will be able to put a stringent bound on the potential energy density: $2.07\times10^{16} {\rm GeV}\leq\sqrt[4]{V_{\star}}\leq 2.40\times 10^{16} {\rm GeV}$, where inflation can occur on the flat potential within, $0.066 \leq\frac{\left |Δϕ\right|}{M_p}\,\leq 0.092$, for the following observational constraints: (Planck+WMAP-9+high L+BICEP2). We then provide a prediction for the spectral tilt ($n_{T}$), running ($α_{T}$) and running of running ($κ_{T}$) of the tensor modes within the window, $-0.019<n_{T}<-0.033$, $-2.97\times 10^{-4}<α_{T}(=dn_{T}/d\ln k)<2.86\times 10^{-5}$,and $-0.11\times 10^{-4}<κ_{T}(=d^{2}n_{T}/d\ln k^{2})<-3.58\times 10^{-4}$, in a model independent way. We also provide a simple example of an {\it inflection-point} model of inflation and reconstruct the potential in a model independent way to match the current observations.

hep-th↗
arXiv2014

Constraining ${\cal N}=1$ supergravity inflationary framework with non-minimal Kähler operators

In this paper we will illustrate how to constrain unavoidable Kähler corrections for ${\cal N}=1$ supergravity (SUGRA) inflation from the recent Planck data. We will show that the non-renormalizable Kähler operators will induce in general non-minimal kinetic term for the inflaton field, and two types of SUGRA corrections in the potential - the Hubble-induced mass ($c_{H}$), and the Hubble-induced A-term ($a_{H}$) correction. The entire SUGRA inflationary framework can now be constrained from (i) the speed of sound, $c_s$, and (ii) from the upper bound on the tensor to scalar ratio, $r_{\star}$. We will illustrate this by considering a heavy scalar degree of freedom at a scale, $M_s$, and a light inflationary field which is responsible for a slow-roll inflation. We will compute the corrections to the kinetic term and the potential for the light field explicitly. As an example, we will consider a visible sector inflationary model of inflation where inflation occurs at the point of inflection, which can match the density perturbations for the cosmic microwave background radiation, and also explain why the universe is filled with the Standard Model degrees of freedom. We will scan the parameter space of the non-renormalizable Kähler operators, which we find them to be order ${\cal O}(1)$, consistent with physical arguments. While the scale of heavy physics is found to be bounded by the tensor-to scalar ratio, and the speed of sound, $ {\cal O}(10^{11}\leq M_s\leq 10^{16}) $GeV, for $0.02\leq c_s\leq 1$ and $10^{-22}\leq r_\star \leq 0.12$.

hep-th↗
arXiv2014

Constraining ${\cal N}=1$ supergravity inflation with non-minimal Kähler operators using $δN$ formalism

In this paper I provide a general framework based on $δN$ formalism to study the features of unavoidable higher dimensional non-renormalizable Kähler operators for ${\cal N}=1$ supergravity (SUGRA) during primordial inflation from the combined constraint on non-Gaussianity, sound speed and CMB dipolar asymmetry as obtained from the recent Planck data. In particular I study the nonlinear evolution of cosmological perturbations on large scales which enables us to compute the curvature perturbation, $ζ$, without solving the exact perturbed field equations. Further I compute the non-Gaussian parameters $f_{NL}$, $τ_{NL}$ and $g_{NL}$ for local type of non-Gaussianities and CMB dipolar asymmetry parameter, $ A_{CMB}$, using the $δN$ formalism for a generic class of sub-Planckian models induced by the Hubble-induced corrections for a minimal supersymmetric D-flat direction where inflation occurs at the point of inflection within the visible sector. Hence by using multi parameter scan I constrain the non-minimal couplings appearing in non-renormalizable Kähler operators within, ${\cal O}(1)$, for the speed of sound, $0.02\leq c_s\leq 1$, and tensor to scalar, $10^{-22} \leq r_{\star} \leq 0.12$. Finally applying all of these constraints I will fix the lower as well as the upper bound of the non-Gaussian parameters within, ${\cal O}(1-5)\leq f_{NL}\leq 8.5$, ${\cal O}(75-150)\leqτ_{NL}\leq 2800$ and ${\cal O}(17.4-34.7)\leq g_{NL}\leq 648.2$, and CMB dipolar asymmetry parameter within the range, $0.05\leq A_{CMB}\leq 0.09$.

hep-th↗
arXiv2014

An accurate bound on tensor-to-scalar ratio and the scale of inflation

In this paper we provide an accurate bound on primordial gravitational waves, i.e. tensor-to-scalar ratio $(r)$ for a general class of single-field models of inflation where inflation occurs always below the Planck scale, and the field displacement during inflation remains sub-Planckian. If inflation has to make connection with the real particle physics framework then it must be explained within an effective field theory description where it can be trustable below the UV cut-off of the scale of gravity. We provide an analytical estimation and estimate the largest possible $r$, i.e. $r\leq 0.12$, for the field displacement less than the Planck cut-off.

hep-ph↗
arXiv2014

Galileogenesis: A new cosmophenomenological zip code for reheating through R-parity violating coupling

In this paper we introduce an idea of leptogenesis scenario in higher derivative gravity induced DBI Galileon framework {\it aka Galileogenesis} in presence of one-loop R-parity violating couplings in the background of a low energy effective supergravity setup. We have studied extensively the detailed feature of reheating constraints and the cosmophenomenological consequences of thermal gravitino dark matter in light of PLANCK and PDG data. Finally we have also established a direct cosmological connection among dark matter relic abundance, reheating temperature and tensor-to-scalar ratio in the context of DBI Galileon inflation.

hep-ph↗
arXiv2014

Higgs inflation from new Kähler potential

We introduce a new class of models of Higgs inflation using the superconformal approach to supergravity by modifying the K$\ddot{a}$hler geometry. Using such a mechanism, we construct a phenomenological functional form of a new K$\ddot{a}$hler potential. From this we construct various types of models which are characterized by a superconformal symmetry breaking parameter $χ$, and depending on the numerical values of $χ$ we classify all of the proposed models into three categories. Models with minimal coupling are identified by $χ=\pm\frac{2}{3}$ branch which are made up of shift symmetry preserving flat directions. We also propose various other models by introducing a non-minimal coupling of the inflaton field to gravity described by $χ\neq\frac{2}{3}$ branch. We employ all these proposed models to study the inflationary paradigm by estimating the major cosmological observables and confront them with recent observational data from WMAP9 along with other complementary data sets, as well as independently with PLANCK. We also mention an allowed range of non-minimal couplings and the {\it Yukawa} type of couplings appearing in the proposed models used for cosmological parameter estimation.

hep-th↗
arXiv2013

Collider constraints on Gauss-Bonnet coupling in warped geometry model

In this paper the requirement of a warp solution in an Einstein-Gauss-Bonnet 5D warped geometry is shown to fix the signature of Gauss-Bonnet coupling ($α_{5}$). Further, imposing the phenomenological constraints, obtained from the recently observed Higgs like scalar mass as well as $μ$ parameter of the decay channels ${H}_{0}\rightarrowγγ,τ{\bar τ}$ explored in ATLAS and CMS detectors, we obtain a stringent bound on $α_{5}$ within $(4.8 - 5.1)\times 10^{-7}$.

hep-ph↗
arXiv2013

Low & High scale MSSM inflation, gravitational waves and constraints from Planck

In this paper we will analyze generic predictions of an inflection-point model of inflation with Hubble-induced corrections and study them in light of the Planck data. Typically inflection-point models of inflation can be embedded within Minimal Supersymmetric Standard Model (MSSM) where inflation can occur below the Planck scale. The flexibility of the potential allows us to match the observed amplitude of the TT-power spectrum of the cosmic microwave background radiation with low and high multipoles, spectral tilt, and virtually mild running of the spectral tilt, which can put a bound on an upper limit on the tensor-to-scalar ratio, $r \leq 0.12$. Since the inflaton within MSSM carries the Standard Model charges, therefore it is the minimal model of inflation beyond the Standard Model which can reheat the universe with the right thermal degrees of freedom without any dark-radiation.

hep-ph↗
arXiv2013

Features of warped geometry in presence of Gauss-Bonnet coupling

We study the role of the Gauss-Bonnet corrections and two loop higher genus contribution to the gravity action on the Kaluza-Klien modes and their interactions for different bulk fields which enable one to study various phenomenological implications of string loop corrected Gauss-Bonnet modified warped geometry model in one canvas. We have explicitly derived a phenomenological bound on the Gauss-Bonnet parameter so that the required Planck to TeV scale hierarchy can be achieved through the warp factor in the light of recently discovered Higgs like boson at 125 GeV. Moreover due to the presence of small perturbative Gauss-Bonnet as well as string loop corrections we have shown that the warping solution can be obtained for both de-Sitter and anti-de-Sitter bulk which is quite distinct from Randall-Sundrum scenario. Finally we have evaluated various interactions among these bulk fields and determined the coupling parameters and the Kaluza- Klien mode masses which is crucial to understand the phenomenology of a string two loop corrected Einstein-Gauss-Bonnet warp geometry.

hep-th↗
arXiv2013

Thermodynamics of Charged Kalb Ramond AdS black hole in presence of Gauss-Bonnet coupling

We study the role of the Gauss-Bonnet corrections to the gravity action on the charged AdS black hole in presence of rank 3 antisymmetric Kalb Ramond tensor field strength. Analyzing the branch singularity and the killing horizon, we explicitly derive various thermodynamic parameters and study their behaviour in presence of five dimensional Gauss-Bonnet coupling in AdS space-time. The possibility of a second order phase transition is explored in the light of AdS/CMT correspondence and various critical exponents associated with the discontinuities of the various thermodynamic parameters are determined. We further comment on the universality of the well known Rushbrooke Josephson scaling law and derive a relation between the degree of homogeneity appearing in various free energies and the critical exponents by homogeneous hypothesis test. By making use of the constraints appearing from Hawking temperature and Gauss-Bonnet extended gravity version of Kubo formula we introduce a bound on the five dimensional Gauss-Bonnet coupling and the viscosity entropy ratio in the four dimensional holographic Conformal Field Theory (CFT) dual. This yields a fractional deviation in viscosity entropy ratio from the result obtained from Einstein gravity.

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