arXiv subjects

Promila Biswas

Publications and source records attributed to Promila Biswas.

10 recordsLinked to original sources

arXiv2025

Constraining Redshift Parametrization Models with Recentmost Data : Impacts on an Accretion Disc around Finslerian Kiselev Black Hole

We investigate the evolution of black hole mass within a cosmological background modeled by a Modified Chaplygin Gas (MCG) under various dark energy equation of state parametrizations, including Linear, Logarithmic, CPL, JBP models. The logarithmic mass ratio $\log_{10}[M(z)/M_0]$ is found to be highly sensitive to the redshift-dependent evolution of $\omega(z)$, with gentle slopes in Linear, Logarithmic and CPL models indicating quasi-static accretion and steep slopes in JBP corresponding to rapid late-time variations highlighting transient suppression or enhancement of accretion due to repulsive dark energy effects. Peaks, minima and amplitude offsets in the mass ratio reflect the dynamic interplay between horizon thermodynamics, the evolving pressure of the MCG and cosmic expansion, illustrating how the black hole mass growth is directly influenced by both the temporal evolution of dark energy and the effective gravitational potential of the surrounding cosmic fluid. Our results demonstrate that black hole accretion acts as a sensitive probe of the time-dependent cosmic pressure landscape and provides physical insights into the coupling between local strong gravity and global accelerated expansion.

gr-qc↗

arXiv2025

Some New Types of Well-Behaved Polynomial Redshift Parametrization of Dark Energy Equation of State

In this paper, we explore a new type of smooth and well-behaved polynomial redshift function that can avoid a future singularity. Using this function, we have proposed different redshift parametrizations of the dark energy equation of state, drawing motivation from different polynomial functions like conventional polynomial, Legendre polynomial, Laguerre polynomial, Chebyshev polynomial and Fibonacci polynomial. The main feature of these parametrizations is their well-behaved nature throughout the evolution of the universe, which was a matter of concern in most of the previous polynomial parametrizations of the dark energy equation of state (EoS). This form of parametrization may be considered as an extension of those forms with no divergence at any redshift value. A comprehensive observational data analysis is performed with the Hubble, BAO and DESI datasets to constrain the parameter space of the models. Confidence contours showing joint and marginalized posterior distribution with different combinations of datasets are generated using a Markov Chain Monte Carlo approach. We see that our improved parametrizations enable us to derive more stringent restrictions on the current dark energy EoS and its derivative, which improves performance. Finally, a machine learning analysis is performed using some suitable algorithms like ELR, PILR, ANN, SVR, ERFR and GBR to compare the models. Among all the tested polynomial bases, the Legendre basis demonstrated superior performance with the lowest test RMSE and reduced $\chi^{2}$ value under the Modified Differential Evolution theoretical model, indicating exceptional physical accuracy and numerical stability.

gr-qc↗

arXiv2025

Cosmology with Distinct Functions $f$ of the Non-metricity Scalar $Q$ : A Dynamical System Approach

Symmetric teleparallel gravity is one among the general relativistic trinity which deals with the non-metricity scalar $Q$. In the Einstein Hilbert action, a function of $Q$ is chosen to be the main contributory part of the Lagrangian and a modified theory of gravity is constructed. In literature, different structures of the function of $Q$ are found which sustain several astrophysical observations like Big Bang nucleosynthesis, late-time cosmic acceleration etc. Autonomous systems for each such models with different $f(Q)$ structures are constructed. Corresponding fixed points and their stability properties are studied. For every case, stable, unstable and saddle-type fixed points are found to exist. These points on the phase portraits are cosmologically analyzed. It is tried to justify which way the corresponding state may lead if the initial state is perturbed. A comparative study of different models is represented.

gr-qc↗

arXiv2025

Accretion of Dark Energy Candidates Following Redshift Parametrization Type Equation of State : Horava-Lifshitz Gravity

In this article, accretion of particular dark energy candidates is studied. These dark energy models possess equation of state dependent on redshift and some free parameters. Central gravitating object for this accretion model is chosen to be the Kehagias Sfetsos black hole sitting in Horava Gravity. Four special redshift parametrization models, viz. Chevallier-Polarski-Linder, Jassal-Bagala-Padmanabhan, Barboza-Alcaniz and Barboza-Alcaniz-Zhu-Silva are picked to study different accretion properties. Formation of critical point and related radial infalling speed, sonic speed, different arbitrary parameters' values etc are obtained. Mass growth curves are plotted. The rate of growth is followed to depend on the dark matter's behavior as well as the free parameters of dark energy models. Future loss in mass is noted for some of the chosen dark energy models.

gr-qc↗

arXiv2021

Viscous Dark Energy Accretion Activities : Sonic Speed, Angular Momentum and Mach Number Studies

In this present article, we study different accretion properties regarding viscous accretion of dark energy. Modified Chaplygin gas is chosen as the dark energy candidate. Viscosity is encountered with the help of Shakura-Sunyaev viscosity parameter. We study sonic speed vs radial distance curves. We compare between adiabatic and dark energy dominated cases and follow that sonic speed falls as we go nearer to the central gravitating object. As viscosity is imposed, a threshold drop in accretion sonic speed is followed. Average rate of fall in accretion sonic speed is increased with black hole's spin. This is signifying that this kind of accretion is weakening the overall matter/energy infall. Specific angular momentum to Keplerian angular momentum ratio is found to fall as we go far from the black hole. Accretion Mach number turns high as we go towards the inner region and high wind Mach number is not allowed as we are going out. Combining, we conclude that the system weakens the feeding process of accretion.

astro-ph.CO↗

arXiv2021

Accretion onto a Quintessence Contaminated Rotating Black Hole : Violating the Lower Limit for Eta over s

Viscous accretion flow around a rotating supermassive black hole sitting in a quintessence tub is studied in this article. To introduce such a dark energy contaminated black hole's gravitational force, a new pseudo-Newtonian potential is used. This pseudo-Newtonian force can be calculated if we know the distance from the black hole's center, spin of the black hole and equation of state of the quintessence inside which the black hole is considered to lie. This force helps us to avoid complicated nonlinearity of general relativistic field equations. Transonic, viscous, continuous and Keplerian flow is assumed to take place. Fluid speed, sonic speed profile and specific angular momentum to Keplerian angular momentum ratio are found out for different values of spin parameter and quintessence parameter. Density variation is built and tallied with observations. Shear viscosity to entropy density ratio is constructed for our model and a comparison with theoretical lower limit is done.

gr-qc↗

arXiv2020

Posing Constraints on the Free Parameters of a New Model of Dark Energy EoS : Responses Through Cosmological Behaviours

Since the late 1990's observations of type Ia Supernova, our universe is predicted to experience a late time cosmic acceleration. Theoretical support to this observation were intended to be built via proposition of a hypothetical fluid which staying inside the universe exerts negative pressure. Cosmologists have prescribed many candidates for this exotic fluid so far. In this alley, a popular method is to choose time dependent equation of state parameter $ω= \frac{p}ρ$ and to parametrize it as a function of redshift. Again some common families of such parametrizations are constructed among which different members justify different properties of observed universe. Mainly, these were model dependent studies which comprise free parameters to be constrained by different observations. In this present article, a new expression for redshift parametrization is considered and we have constrain its free parameters for two Hubble parameter vs redshift data sets. These data sets are obtained depending on two basic methodologies known as different ages method and baryonic acoustic oscillation method. Different confidence contours for our model are located under the constraints of said data sets. Besides, different thermodynamic parameters related to the evolution of our universe are analysed. It is notified that our model indicates towards a delayed dark matter model which mimics EoS = $-1(Λ)$ phenomena at the present epoch. Deceleration parameters behaviour's are studied. It is noticed that a possibility of future deceleration may occur for this new model. Outcomes for both the data sets are compared with each other.

gr-qc↗

arXiv2019

Barboza-Alcaniz Equation of State Parametrization : Constraining the Parameters in Different Gravity Theories

To justify the twenty years old distant Ia Supernova observations which revealed to us that our universe is experiencing a late time cosmic acceleration, propositions of existence of exotic fluids inside our universe are made. These fluids are assumed to occupy homogeneously the whole space of the universe and to exert negative pressure from inside such that the late time accelerated expansion is caused. Among the different suggested models of such exotic matters/ energy popularly coined as dark matter / dark energy, a well known and popular process is "introduction of redshift parametrization" of the equation of state parameter of these fluids. We, very particularly, take the parametrization proposed by Barboza and Alcaniz along with the cosmological constant. We use thirty nine data points for Hubble's parameter calculated for different redshifts and try to constrain the dark energy equation of state parameters for Barboza Alcaniz modelling. We then constrain the dark energy parametrization parameters in the background of Einstein's general relativity, loop quantum gravity and Horava Lifshitz gravity one after another. We find the 1$σ$, 2$σ$ and 3$σ$ confidence contours for all these cases and compare them with each other. We try to speculate which gravity is constraining the parameters most and which one is letting the parameters to stay within a larger domain. We tally our results of 557 points Union2 Sample and again compare them for different gravity theories.

physics.gen-ph↗

arXiv2019

Interacting Models of Generalised Chaplygin Gas and Modified Chaplygin Gas with Barotropic Fluid

In this letter we consider two different models of our present universe. We choose the models which are consisting different sets of two seperate fluids. The first one of each set tries to justify the late time acceleration and the second one is barotropic fluid. The former model considers our present time universe to be homogeneously filled up by Generalized Chaplygin Gas which is interacting with barotropic fluid. On the other hand, the latter model considers that the cosmic acceleration is generated by Modified Chaplygin Gas which is interacting with matter depicted by barotropic equation of state. For both the models, we consider the interaction term to vary proportionally with Hubble's parameter as well as with the exotic matter/dark energy's energy density. We find an explicit function form of the energy density of the cosmos which is found to depend on different cosmological parameters like scale factor, dark energy and barotropic fluid's EoS parameters and other constants like interacting constants etc. We draw curves of effective EoS-s, different cosmological parameters like deceleration parameter $q$, statefinder parameters $r$ and $s$ with repect to the redshift $z$ (for different values of dark energy and barotopic fluid parameters) and study them thoroughly. We compare two models as well as the nature of dependencies on these models' interaction coefficients. We point out the particular redshift for which the universe may transit from a deceleration to acceleration phase. We tally all these values with different observational data. Here we also analyse how this value of particular redshift does change for different values of interaction coefficients and different dark energy models.

physics.gen-ph↗

arXiv2018

Evolution of Universe as a Homogeneous System : Changes of Scale Factors with Different Dark Energy EoS-s

We analyse the universe homogeneously filled up by different dark energies. We calculate the relations between time and the scale factor. We thoroughly check the differences to be obtained with the changes of different parameters. $t$ vs $a(t)$ curves are studied. Physical differences between several dark energy models are studied. We conclude about the future singularities to be occurred.

gr-qc↗