arXiv subjects

Bikash R. Dinda

Publications and source records attributed to Bikash R. Dinda.

32 records · Page 2Linked to original sources

arXiv2023

Model independent bounds on Type Ia supernova absolute peak magnitude

We put constraints on the peak absolute magnitude, $M_B$ of type Ia supernova using the Pantheon sample for type Ia supernova observations and the cosmic chronometers data for the Hubble parameter by a model independent and non-parametric approach. Our analysis is based on the Gaussian process regression. We find percent level bounds on the peak absolute magnitude given as $M_B=-19.384\pm0.052$. For completeness and to check the consistency of the results, we also include the Baryon acoustic oscillation data and the prior of the comoving sound horizon from Planck 2018 cosmic microwave background observations. The inclusion of these two data gives tighter constraints on $M_B$ at the sub-percent level. We obtain constraints on $M_B$ from the combination of pantheon compilation of type Ia supernova observations and baryon acoustic oscillation observations given as $M_B=-19.396\pm0.016$. When adding the cosmic chronometer observations with these observations, we find $M_B=-19.395\pm0.015$. The mean values of peak absolute magnitude from all these data are consistent with each other and the values are approximately equal to $-19.4$.

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arXiv2022

21 cm power spectrum in interacting cubic Galileon model

We show the detectability of interacting and non-interacting cubic Galileon models from the $Λ$CDM model through the 21 cm power spectrum. We show that the interferometric observations like the upcoming SKA1-mid can detect both the interacting and the non-interacting cubic Galileon model from the $Λ$CDM model depending on the parameter values.

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arXiv2022

Cosmic expansion parametrization: Implication for curvature and $\text{H}_{0}$ tension

We propose an analytical parametrization of the comoving distance and Hubble parameter to study the cosmic expansion history beyond the vanilla $Λ$CDM model. The parametrization is generalized enough to include the contribution of spatial curvature and to capture the higher redshift behaviors. With this parameterization, we study the late time cosmic behavior and put constraints on the cosmological parameters like present values of Hubble parameter ($H_{0}$), matter energy density parameter ($Ω_{m0}$), spatial curvature energy density parameter ($Ω_{k0}$) and baryonic matter energy density parameter ($Ω_{b0}$) using different combinations data like CMB (Cosmic microwave background), BAO (baryon acoustic oscillation), and SN (Pantheon sample for type Ia supernovae). We also rigorously study the Hubble tension in the framework of late time modification from the standard $Λ$CDM model. We find that the late time modification of the cosmic expansion can solve the Hubble tension between CMB $\&$ SHOES (local distance ladder observation for $H_{0}$), between CMB+BAO $\&$ SHOES and between CMB+SN $\&$ SHOES, but the late time modification can not solve the Hubble tension between CMB+BAO+SN and SHOES. That means CMB, BAO, and SN data combined put strong enough constraints on $H_{0}$ (even with varying $Ω_{k0}$) and on other background cosmological parameters so that the addition of $H_{0}$ prior from SHOES (or from similar other local distance observations) can not significantly pull the $H_{0}$ value towards the corresponding SHOES value.

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arXiv2021

Probing Compensated Isocurvature with the 21-cm Signal during Cosmic Dawn

Upcoming measurements of the 21-cm line of neutral hydrogen will open a new observational window into the early stages of structure growth, providing a unique opportunity for probing large-scale cosmological signatures using the small-scale signals from the first stars. In this paper we evaluate the detection significance of compensated isocurvature perturbations (CIPs) from observations of the 21-cm hydrogen-line during the cosmic-dawn era. CIPs are modulations of the relative baryon and dark-matter density that leave the total matter density unchanged. We find that, under different assumptions for feedback and foregrounds, the ongoing HERA and upcoming SKA1-low experiments will provide constraints on uncorrelated CIPs at the level of $σ(A_{\rm CIP})= 10^{-3}-10^{-4}$, comparable to the sensitivity of upcoming CMB experiments, and potentially exceeding the constraints from cosmic-variance limited BAO surveys.

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arXiv2020

A study on Cubic Galileon Gravity Using N-body Simulations

We use N-body simulation to study the structure formation in the Cubic Galileon Gravity model where along with the usual kinetic and potential term we also have a higher derivative self-interaction term. We find that the large scale structure provides a unique constraining power for this model. The matter power spectrum, halo mass function, galaxy-galaxy weak lensing signal, marked density power spectrum as well as count in cell are measured. The simulations show that there are less massive halos in the Cubic Galileon Gravity model than corresponding $Λ$CDM model and the marked density power spectrum in these two models are different by more than $10\%$. Furthermore, the Cubic Galileon model shows significant differences in voids compared to $Λ$CDM. The number of low density cells is far higher in the Cubic Galileon model than that in the $Λ$CDM model. Therefore, it would be interesting to put constraints on this model using future large scale structure observations, especially in void regions.

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arXiv2019

A model independent parametrization of the late time cosmic acceleration: constraints on the parameters from recent observations

In this work, we have considered a model independent approach to study the nature of the late time cosmic acceleration. We have used the Pade approximation to parametrize the comoving distance. Consequently, from this comoving distance, we derive a parameterization for the Hubble parameter. Our parametrization is completely analytic and valid for late-time and matter dominated eras only. This parametrization possesses sub-percentage accuracy compared to any arbitrary cosmological model or parametrization up to matter dominated era. Using this parametrization, we put constraints on the parameters from recent low redshift cosmological observations including Planck 2018 distance priors. Our results show that the $Λ$CDM model is 1$σ$ to 2$σ$ away for lower redshifts. We find that the phantom crossing is allowed by all the combinations of dataset considered. We also find that the dynamical dark energy models are preferable at lower redshifts. Our study also shows that, at lower redshifts ($z<0.5$), phantom models are allowed at almost 1$σ$ confidence level.

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arXiv2019

Nonlinear power spectrum in clustering and smooth dark energy models beyond the BAO scale

We study the nonlinear effects of the clustering and smooth quintessence. We present numerical and also approximate semi-analytical expressions of nonlinear power spectrum both for clustering and smooth dark energy models beyond the Baryon Acoustic Oscillations (BAO) scale. This approximation is motivated by the extension of the resummation method of Anselmi $\&$ Pietroni (J Cosmol Astro-Part Phys 12:13, 2012. \url{arXiv:1205.2235}) for the dark energy models with evolving equation of state. The results of this scheme allow us for the prediction of the nonlinear power spectrum in the mildly nonlinear regime up to few percentage accuracies compared to the other available tools to compute the nonlinear power spectrum for the evolving dark energy models.

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arXiv2018

Weak lensing probe of cubic Galileon model

The cubic Galileon model containing the lowest non-trivial order action of the full Galileon action can produce the stable late-time cosmic acceleration. This model can have a significant role in the growth of structures. The signatures of the cubic Galileon model in the structure formation can be probed by the weak lensing statistics. Weak lensing convergence statistics is one of the strongest probes to the structure formation and hence it can probe the dark energy or modified theories of gravity models. In this work, we investigate the detectability of the cubic Galileon model from the $ Λ$CDM model or from the canonical quintessence model through the convergence power spectrum and bi-spectrum.

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arXiv2018

Dark energy constraints from the 21~cm intensity mapping surveys with SKA1

Understanding the nature of dark energy is one of the most outstanding problems in cosmology at present. In last twenty years, cosmological observations related to SNIa, Cosmic Microwave Background Radiation, Baryon Acoustic Oscillations etc, have put stringent constraints on the the dark energy evolution, still there is enough uncertainty in our knowledge about dark energy that demands new generation of cosmological observations. Post-reionization neutral hydrogen 21 cm intensity mapping surveys are one of the most promising future cosmological observations that have the potential to map the cosmological evolution from dark ages till present time with unprecedented accuracy and Square Kilometer Array (SKA) is one of the most sensitive instruments to measure the post-reionization 21 cm signal. In this work, we study the future dark energy constraints using post-reionization 21 cm intensity mapping power spectra with SKA1-mid specifications. We use three different parametrizations for dark energy equation of state (EoS) including the widely used CPL one. To generate simulated data, we use to two fiducial models: the concordance $Λ$CDM and the best fit CPL model for Planck+SNIa+BAO+HST. Our study shows that SKA1-mid alone has the potential to reach the present accuracy for combined Planck+SNIa+BAO+HST to constrain the dark energy behaviour. Whether dark energy is phantom or non-phantom or whether it exhibits phantom crossing, we may potentially address such questions with SKA1-mid. We also show that it is crucial to choose the correct parametrization for dark energy equation of state as some parametrizations are better than others to constrain the dark energy behaviour. Specifically, as observed in this study, the widely used CPL parametrization may not give the best constraint for dark energy behaviour.

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arXiv2017

Bayesian Evidences for Dark Energy models in light of current obsevational data

We do a comprehensive study of the Bayesian evidences for a large number of dark energy models using a combination of latest cosmological data from SNIa, CMB, BAO, Strong lensing time delay, Growth measurements, measurements of Hubble parameter at different redshifts and measurements of angular diameter distance by Megamaser Cosmology Project . We consider a variety of scalar field models with different potentials as well as different parametrisations for the dark energy equation of state. Among 21 models that we consider in our study, we do not find strong evidences in favour of any evolving dark energy model compared to $Λ$CDM. For the evolving dark energy models, we show that purely non-phantom models have much better evidences compared to those models that allow both phantom and non-phantom behaviours. Canonical scalar field with exponential and tachyon field with square potential have highest evidences among all the models considered in this work. We also show that a combination of low redshift measurements decisively favours an accelerating $Λ$CDM model compared to a non-accelerating power law model.

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arXiv2017

Imprint of thawing scalar fields on large scale galaxy overdensity

We investigate the observed galaxy power spectrum for the thawing class of scalar field models taking into account various general relativistic corrections that occur on very large scales. We consider the full general relativistic perturbation equations for the matter as well as the dark energy fluid. We form a single autonomous system of equations containing both the background and perturbed equations of motion which we subsequently solve for different scalar field potentials. First we study the percentage deviation from $Λ$CDM model for different cosmological parameters as well as in the observed galaxy power spectra on different scales in scalar field models for various choices of scalar field potentials. Interestingly the difference in background expansion results enhancement of power from $Λ$CDM on small scales whereas the inclusion of GR corrections results the suppression of power from $Λ$CDM on large scales. This can be useful to distinguish scalar field models from $Λ$CDM with future optical/radio surveys. We also compare the observed galaxy power spectra for tracking and thawing types of scalar field using some particular choices for the scalar field potentials. We show that thawing and tracking models can have large differences in observed galaxy power spectra on large scales and for smaller redshifts due to different GR effects. But on smaller scales and for larger redshifts, the difference is small and is mainly due to difference in background expansion.

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arXiv2017

Probing dark energy using convergence power spectrum and bi-spectrum

Weak lensing convergence statistics is a powerful tool to probe dark energy. Dark energy plays an important role to the structure formation and the effects can be detected through the convergence power spectrum, bi-spectrum etc. One of the most promising and simplest dark energy model is the $ Λ$CDM. However, it is worth investigating different dark energy models with evolving equation of state of the dark energy. In this work, detectability of different dark energy models from $ Λ$CDM model has been explored through convergence power spectrum and bi-spectrum.

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arXiv2017

Observed galaxy power spectrum in cubic Galileon model

In this paper, we study the effects of general relativistic corrections on the observed galaxy power spectrum in thawing class of cubic Galileon model with linear potential that preserves the shift symmetry. In this scenario, the observed galaxy power spectrum differs from the standard matter power spectrum mainly due to redshift space distortion (RSD) factor and relativistic effects. The RSD term enhances the matter power spectrum both at larger and smaller scales whereas the relativistic terms further enhance the matter power spectrum only at larger scales. In comparison with $Λ$CDM, the observed galaxy power spectrum is always suppressed at large scales in this scenario although this suppression is always small compared to the canonical quintessence scenario.

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arXiv2015

Prospect of probing dark energy using stochastic gravitational waves

We study the possibility of probing dark energy behaviour using gravitational wave experiments like LISA and Advanced LIGO. Using two popular parameterizations for dark energy equation of state, we show that with current sensitivities of LISA and Advanced LIGO to detect the stochastic gravitational waves, it is possible to probe a large section of parameter space for the dark energy equation of state which is allowed by present cosmological observations.

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