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Barun Kumar Pal

Publications and source records attributed to Barun Kumar Pal.

15 recordsLinked to original sources
arXiv2025

Mutated Hilltop Inflation in the Era of Present and Future CMB Experiments

In this article we confront both large-field and small-field sectors of mutated hilltop inflation model with the recent observational results. We begin with confrontation of predictions from mutated hilltop inflation with the joint analysis of Planck-2018 and BICEP/Keck-2018 data. Subsequently, we extend our analysis by incorporating the ACT-DR6 data in combination with Planck-2018, BICEP/Keck-2018, and DESI-Y1 observations. In both cases, the predictions of mutated hilltop inflation show good consistency with the observational constraints. We have also forecasted the constraints on mutated hilltop inflation model from upcoming CMB experiments, LiteBIRD and Simons Observatory along with their combinations. Here also we find that the prediction from mutated hilltop inflation are in tune with those upcoming CMB experiments. The small-field sector of mutated hilltop inflation, in principle, can probe up to $r\sim \mathcal{O}(10^{-4})$, resulting in a tensor amplitude consistent with current bounds and potentially detectable by next-generation CMB missions. However, accommodating the high observational value of the scalar spectral index may demand relatively higher e-foldings in mutated hilltop inflation. A key appealing feature of the mutated hilltop inflation model turns out to be its ability to remain consistent with a potential non-detection of primordial gravitational waves by LiteBIRD and/or Simons Observatory.

astro-ph.CO↗
arXiv2025

Confronting Mukhanov Parametrization of Inflationary Equation-of-State with ACT-DR6

We provide a simple yet effective semi-analytical approach to confront Mukhanov Parametrization of inflationary equation-of-state, $1+\omega =\frac{\beta}{({N}+1)^\alpha}$, with the latest ACT-DR6 data employing Hamilton-Jacobi formulation. We find that equation-of-state formalism comes up with excellent fit to the latest data. In the process we are also able to put stringent constraint on the two model parameters. In order to get the bounds of $\alpha$ and $\beta$ we have also made use of the recent finding $r<0.032$. We have further utilized results from the joint analysis of ACT-DR6, Planck-2018 and DESI-Y1 data to find the observationally viable region for $\alpha$ and $\beta$. We have also employed the predictions on primordial gravity waves from forthcoming CMB missions in the likes of CMB-S4 and LiteBIRD along with results from the combination of ACT-DR6, Planck-2018 and DESI-Y1 data to further restrict the model parameters. We find that detection of gravity waves would help us narrow the viable parameter space for Mukhanov parametrization. But in the absence of detection of primordial gravity waves signal by those CMB missions parameter space is reduced significantly for $\beta$, while the range for $\alpha$ is slightly increased. In addition we observe that, $\alpha$ is primarily dependent on the observationally viable range for scalar spectral index while other model parameter $\beta$ is resting heavily on the restriction upon the amplitude of primordial gravity waves. We find that equation-of-state formalism has a wide range of parameter values consistent with recent observational data set along with futuristic CMB missions in the likes of CMB-S4 and LiteBIRD.

astro-ph.CO↗
arXiv2025

The fate of Quasi-Exponential inflation in the light of ACT-DR6

We have revisited quasi-exponential model of inflation in the light of recent ACT-DR6 and Planck data along with latest constraint on the amplitude of primordial gravitational waves. For our analysis we have followed Mukhanov approach for inflationary equation-of-state employing Hamilton-Jacobi formulation. We find that the model is capable of mimicking latest Planck results by providing excellent fit to scalar spectral index and its running. Not only that, amount of primordial gravitational waves is also within the present observational bound, $r<0.032$. In addition to that, when the combination of ACT-DR6 and Planck joint with BICEP/Keck 2018 data is taken into account inflationary predictions from quasi-exponential model are in excellent agreement. The model also yields sublime fit to the result of joint analysis of ACT-DR6, Planck joint with BICEP/Keck 2018 and DESI-Y1 data. The futuristic CMB missions LiteBIRD, Simons Observatory and CMB-S4 are promising to detect primordial gravitational waves if $r\geq0.003$. We have also forecasted inflationary predictions from quasi-exponential model of inflation assuming the sensitivities of LiteBIRD, Simons Observatory and CMB-S4 along with combination of LiteBIRD and CMB-S4. We found that in each case quasi-exponential inflation may render excellent fit provided $r\geq10^{-2}$. However, non-detection of primordial gravitational waves by LiteBIRD, Simons Observatory and CMB-S4 will potentially rule out quasi-exponential model.

astro-ph.CO↗
arXiv2024

Returning Back to Mukhanov Parametrization of Inflationary Equation of State

We have re-examined Mukhanov parametrization for inflationary equation of state, $1+\omega=\frac{\beta}{({N}+1)^\alpha}$, in the light of Planck 2018 results and latest bound of tensor-to-scalar ratio employing Hamilton-Jacobi formalism. We have found that the current observational values of scalar spectral index and tensor-to-scalar ratio can be used efficiently to constrain the model parameters. The recent bound of $r<0.032$ has been used to put an upper bound on one of the model parameter. Whereas 1-$\sigma$ bound of the scalar spectral index $0.9607\leq n_{_S}\leq 0.9691$ along with the upper bound of tensor-to-scalar ratio provided restriction on the other model parameter $1.50<\alpha\leq2.20$. These bounds however depend on the number of e-foldings still left before the end of inflation and whenever $1.50<\alpha\leq2.20$ we can find appropriate values of the other model parameter $\beta$ so that the observational predictions are in tune with the latest available inflationary observables. We have further utilized the predictions from forthcoming CMB missions in the likes of CMB-S4 and LiteBIRD in order to obtain bounds on the model parameters. We find that detection of gravity waves would help us constrain the model parameters further. But in the absence of detection of primordial gravity wave signal by these CMB missions may rule out Mukhanov parametrization.

gr-qc↗
arXiv2022

An Inflationary Equation of State

We have studied inflationary paradigm through an inflationary equation of state. With a single parameter equation of state as a function of the scalar field responsible for accelerated expansion, we find an observationally viable model satisfying all the constraints as laid down by the recent observations. The resulting model can efficiently cover a wide range of tensor-to-scalar ratio ranging from $r\sim\mathcal{O}(10^{-1})$ to $\mathcal{O}(10^{-6})$, other inflationary observables being consistent with the latest data. Nowadays ultimate eliminator between inflationary models is the tensor-to-scalar ratio, the model presented here is capable of keeping up with the future probes of tensor-to-scalar ratio at the same time having good agreement with other inflationary observables.

gr-qc↗
arXiv2019

Reconstruction of Convergence power spectrum from SNLS weak lensing data

We estimate the lensing convergence power spectrum from supernovae magnification data using real space correlation function technique. For our analysis we have utilized 296 supernovae from 5-year Supernovae Legacy Survey in the weak lensing limit. The data we used consists of measurements from four different patches, each of them covers almost 1 square degree of the sky, merged together. We demonstrate that it is quite possible to have a good estimate of the convergence power spectrum from this data. Our primary intention is to extract meaningful informations from SNLS weak lensing data and to demonstrate how the power spectrum for convergence can be reconstructed therefrom, without going into the nitty-gritty of errors, although we have done some error analysis in the process.

astro-ph.CO↗
arXiv2018

Mutated hilltop inflation revisited

In this work we re-investigate pros and cons of mutated hilltop inflation. Applying Hamilton-Jacobi formalism we solve inflationary dynamics and find that inflation goes on along the ${\cal W}_{-1}$ branch of the Lambert function. Depending on the model parameter mutated hilltop model renders two types of inflationary solutions: one corresponds to small inflaton excursion during observable inflation and the other describes large field inflation. The inflationary observables from curvature perturbation are in tune with the current data for a wide range of the model parameter. The small field branch predicts negligible amount of tensor to scalar ratio $r\sim \mathcal{O}(10^{-4})$, while the large field sector is capable of generating high amplitude for tensor perturbations, $r\sim \mathcal{O}(10^{-1})$. Also, the spectral index is almost independent of the model parameter along with a very small negative amount of scalar running. Finally we find that the mutated hilltop inflation closely resembles the $α$-attractor class of inflationary models in the limit of $αϕ\gg 1$.

gr-qc↗
arXiv2018

Gravitationally influenced particle creation models and late-time cosmic acceleration

In this work we focus on the gravitationally influenced adiabatic particle creation process, a mechanism that does not need any dark energy or modified gravity models to explain the current accelerating phase of the universe. Introducing some particle creation models that generalize some previous models in the literature, we constrain the cosmological scenarios using the latest compilation of the Type Ia Supernovae data only, the first indicator of the accelerating universe. Aside from the observational constraints on the models, we examine the models using two model independent diagnoses, namely the cosmography and $Om$. Further, we establish the general conditions to test the thermodynamic viabilities of any particle creation model. Our analysis shows that at late-time, the models have close resemblance to that of the $Λ$CDM cosmology, and the models always satisfy the generalized second law of thermodynamics under certain conditions.

gr-qc↗
arXiv2015

Quantum Gravity Effect in Torsion Driven Inflation and CP violation

We have derived an effective potential for inflationary scenario from torsion and quantum gravity correction in terms of the scalar field hidden in torsion. A strict bound on the CP violating $θ$ parameter, ${\cal O}(10^{-10})<θ<{\cal O}(10^{-9})$ has been obtained, using {\tt Planck+WMAP9} best fit cosmological parameters.

hep-th↗
arXiv2014

Towards reconstruction of unlensed, intrinsic CMB power spectra from lensed map

We propose a method to extract the unlensed, intrinsic CMB temperature and polarization power spectra from the observed (i.e., lensed) spectra. Using a matrix inversion technique, we demonstrate how one can reconstruct the intrinsic CMB power spectra directly from lensed data for both flat sky and full sky analyses. The delensed spectra obtained by the technique are calibrated against the Code for Anisotropies in the Microwave Background (CAMB) using WMAP 7-year best-fit data and applied to WMAP 9-year unbinned data as well. In principle, our methodology may help in subtracting out the E-mode lensing contribution in order to obtain the intrinsic B-mode power.

astro-ph.CO↗
arXiv2013

The Berry phase in inflationary cosmology

We derive an analogue of the Berry phase associated with inflationary cosmological perturbations of quantum mechanical origin by obtaining the corresponding wavefunction. We have further shown that cosmological Berry phase can be completely envisioned through the observable parameters, viz. spectral indices. Finally, physical significance of this phase is discussed from the point of view of theoretical and observational aspects with some possible consequences of this quantity in inflationary cosmology.

astro-ph.CO↗
arXiv2012

Confronting quasi-exponential inflation with WMAP seven

We confront quasi-exponential models of inflation with WMAP seven years dataset using Hamilton Jacobi formalism. With a phenomenological Hubble parameter, representing quasi exponential inflation, we develop the formalism and subject the analysis to confrontation with WMAP seven using the publicly available code CAMB. The observable parameters are found to fair extremely well with WMAP seven. We also obtain a ratio of tensor to scalar amplitudes which may be detectable in PLANCK.

astro-ph.CO↗
arXiv2012

A semi-analytical approach to perturbations in mutated hilltop inflation

We study cosmological perturbations and observational aspects for mutated hilltop model of inflation. Employing mostly analytical treatment, we evaluate observable parameters during inflation as well as post-inflationary perturbations. This further leads to exploring observational aspects related to Cosmic Microwave Background (CMB) radiation. This semi-analytical treatment reduces complications related to numerical computation to some extent for studying the different phenomena related to CMB angular power spectrum for mutated hilltop inflation.

astro-ph.CO↗
arXiv2010

Mutated Hilltop Inflation : A Natural Choice for Early Universe

We propose a model of inflation with a suitable potential for a single scalar field which falls in the wide class of hilltop inflation. We derive the analytical expressions for most of the physical quantities related to inflation and show that all of them represent the true behavior as required from a model of inflation. We further subject the results to observational verification by formulating the theory of perturbations based on our model followed by an estimation for the values of those observable parameters. Our model is found to be in excellent agreement with observational data. Thus, the features related to the model leads us to infer that this type of hilltop inflation may be a natural choice for explaining the early universe.

hep-th↗