arXiv subjects

Abdulla Al Mamon

Publications and source records attributed to Abdulla Al Mamon.

At least 19 recordsLinked to original sources

arXiv2026

Observational constraints on Barrow holographic dark energy coupled with a non-cold dark matter component from DESI DR2

We investigate the cosmological viability of Barrow holographic dark energy in a spatially flat Friedmann--Lema\^ıtre--Robertson--Walker universe in which the dark matter component is allowed to have a non-zero pressure, characterized by a constant equation-of-state parameter $w_{m}$. By considering the future event horizon as the infrared cutoff, we derive the master equation, which describes the cosmological dynamics for the background space. We constrain the model against late-time data, combining the baryon acoustic oscillation from DESI DR2 with three different catalogues for the Type Ia Supernova measurements and the Cosmic Chronometers. The dark matter equation of state is constrained to $w_{m}=0.033_{-0.030}^{+0.045}$, $0.009_{-0.041}^{+0.047}$, and $0.033_{-0.029}^{+0.042}$, for the PantheonPlus, the Union3.0 and the DES-Dovekie supernova datasets respectively. Therefore, the pressureless limit is recovered within the $2σ$ regime. On the other hand, the Barrow exponent is weakly constrained, due to the $Δ-w_{m}$ degeneracy. The dark energy equation of state remains above the phantom divide throughout the redshift range probed. Finally, in the comparison of the statistical parameters with that of $Λ$CDM, it follows $Δ\mathrm{AIC}=+2.23$, $+0.75$, and $+1.38$, $\ $while for the Bayesian evidence we find $Δ\ln Z=-0.63$, $+0.47$, and $-0.13$, which suggest that the datasets considered in this analysis do not have a preferred model. Finally the relation with the corresponding Tsalis holographic dark energy model is discussed.

physics.gen-ph↗

arXiv2026

The Lambert $W$ equation of state in light of DESI BAO

We investigate a unified dark-fluid model whose effective equation of state (EoS) is described by logarithmic and power-law terms involving the Lambert $W$ function. The model parameters are constrained using BAO data, including DESI measurements, together with Pantheon+ Type Ia supernova observations and direct Hubble parameter measurements. The analysis yields $θ_{1}=0.087\pm 0.011$, $θ_{2}=-3.35\pm 0.13$, $r_d = 146\pm 2.5$~Mpc, and $H_0 = 67.4 \pm 1.2~\text{km\,s}^{-1}\text{Mpc}^{-1}$. The inferred Hubble constant, $H_{0}$, is consistent with the Planck 2018 measurement and remains in tension with local determinations, thereby reflecting the Hubble tension. We further examine the evolution of deceleration, effective EoS, and jerk parameters, complemented by the $Om(z)$ diagnostic. Our analysis reveals that the model provides a consistent description of late-time cosmic acceleration. Finally, the observational viability of the model is assessed using Akaike and Bayesian information criteria and compared with that of the standard $Λ$CDM model.

astro-ph.CO↗

arXiv2026

Unifying the Dark Sector with the New Generalized Chaplygin Gas: Observational Constraints

In light of recent cosmological observations, we examine a generalized Chaplygin gas model with a redshift-dependent exponent as a framework for describing the dark energy and dark matter content of the Universe. Specifically, we treat this fluid as a single unified component and test it against late-time background observational data. We employ Type Ia supernova data, cosmic chronometers, and baryon acoustic oscillations from the second data release of the Dark Energy Spectroscopic Instrument. We perform a Bayesian analysis for parameter estimation and compare the model with $Λ$CDM. We find that the generalized Chaplygin gas provides systematically higher values of the combined likelihood; nevertheless, once the larger number of free parameters is taken into account, both the Bayesian evidence and the Akaike Information Criterion suggest that the model is statistically indistinguishable from $Λ$CDM.

astro-ph.CO↗

arXiv2026

Viaggiu holographic dark energy in light of DESI DR2

We test the cosmological viability of the Viaggiu holographic dark energy (VHDE) model by using late-time observational data. In particular, we place constraints on the free parameters of the model using Type Ia supernovae from the PantheonPlus, Union3.0, and DES-Dovekie catalogues, the Cosmic Chronometers, and the Baryon Acoustic Oscillations from the DESI DR2. Our analysis suggests that the VHDE model fits the observational data better or similar to the $Λ$CDM for all dataset combinations considered. The value obtained for $H_0$ is similar to the $Λ$CDM, while the current matter density parameter is constrained around $Ω_{m0}\simeq 0.24$, smaller to that obtained by the $Λ$CDM. Moreover, the parameter introduced by the VHDE is found to have a mean value within the range $\fracπ{3} δ^2 \sim 0.27-0.33$. Finally, we used Akaike's Information Criterion (AIC) and Bayesian evidence to test the VHDE model against the $Λ$CDM scenario. The AIC demonstrates that the two models are statistically indistinguishable, while Bayesian evidence reveals that the data have a mild preference for the $Λ$CDM model for most of the dataset combinations considered. Nevertheless, the VHDE model remains consistent with current late-time cosmological observations and offers a feasible mechanism for describing the late-time accelerating scenario.

gr-qc↗

arXiv2025

Interacting tachyon with varying mass dark matter

This paper presents an investigation of cosmological dynamics of tachyon fluid coupled to varyingmass dark matter particles in the background of spatially flat FLRW universe. The mechanism of varying mass particles scenario assumes the mass of the dark matter depends on time t through the scalar field $ϕ$ in the sense that the decaying of dark matter reproduces the scalar field. First, we analyze the model from dynamical systems perspective by converting the cosmological evolution equations into an autonomous system of ordinary differential equations with a suitable transformation of variables. We choose the mass of dark matter as exponential function of scalar field and the exponential potential of the tachyon field is undertaken in such a way that the autonomous system is reduced in three dimensional form. The critical points obtained from the system are non-hyperbolic in nature. The center manifold theory is employed to discuss the nature of the critical points. Numerical investigation also carried out for some critical points. From this analysis, we obtain dust dominated decelerated transient phase of the universe followed by dark energy dominated scaling attractor alleviating the coincidence problem. Next, we perform the statefinder diagnostic approach to compare our model to $Λ$CDM and finally we study the evolution of the Hubble parameter and the distance modulus and compare this with observational data.

gr-qc↗

arXiv2025

Evolution of primordial black holes in an adiabatic FLRW universe with gravitational particle creation

We study the evolution of primordial black holes (PBHs) in an adiabatic FLRW universe with dissipation due to bulk viscosity which is considered to be in the form of gravitational particle creation. Assuming that the process of evaporation is quite suppressed during the radiation era, we obtain an analytic solution for the evolution of PBH mass by accretion during this era, subject to an initial condition. We also obtain an upper bound on the accretion efficiency $ε$ for $a \sim a_r$, where $a_r$ is the point of transition from the early de Sitter era to the radiation era. Furthermore, we obtain numerical solutions for the mass of a hypothetical PBH with initial mass 100 g assumed to be formed at an epoch when the value of the Hubble parameter was, say, 1 km/s/Mpc. We consider three values of the accretion efficiency, $ε=0.23,0.5$, and $0.89$ for our study. The analysis reveals that the mass of the PBH increases rapidly due to the accretion of radiation in the early stages of its evolution. The accretion continues but its rate decreases gradually with the evolution of the Universe. Finally, Hawking radiation comes into play and the rate of evaporation surpasses the accretion rate so that the PBH mass starts to decrease. As the Universe grows, evaporation becomes the dominant phenomenon, and the mass of the PBH decreases at a faster rate. As argued by Debnath and Paul, the evaporated mass of the PBHs might contribute towards the dark energy budget of the late Universe.

gr-qc↗

arXiv2023

Dynamical systems analysis of an interacting scalar field model in an anisotropic universe

In this paper, we investigate a non-canonical scalar field model in the background dynamics of anisotropic Locally Rotationally Symmetric (LRS) Bianchi type I universe where gravity is coupled minimally to scalar field which is taken as dark energy and pressureless dust as dark matter are the main matter content of the universe. We perform dynamical system analysis to characterize the cosmological evolution of the model with and without interaction in the dark sector separately. First, we convert the evolution equation into an autonomous system of ordinary differential equations by using a suitable choice of dimensionless variables, which are normalized over the Hubble scale. We choose scalar field coupling and potential in such a way that the autonomous system converted to a 2D system. Linear stability theory is employed to the extracted critical points to find the nature. From the analysis, we find some interesting cosmological scenarios, such as late-time scalar-field dominated solutions, which evolve in the quintessence era, cannot solve the coincidence problem. Accelerated scaling attractors are also obtained that correspond to the late phase evolution in agreement with present observational data, and these solutions also provide possible mechanisms to alleviate the coincidence problem. A complete cosmic evolution is obtained from early inflation to a late-time dark energy-dominated phase, connecting through a matter-dominated transient phase of the universe. Furthermore, we find that for different values of the interaction parameter $α$, the evolutionary trajectories of the Hubble parameter, and the distance modulus forecasted by the model are in quite well agreement with observational datasets.

gr-qc↗

arXiv2022

An extended analysis for a generalized Chaplygin gas model

In this work, we have extended the analysis on the generalized Chaplygin gas (GCG) model as the unification of dark energy and dark matter. Specifically, we have shown that the model of our consideration known as the new generalized Chaplygin gas (NGCG) model, admits a scalar field description, which means that there exist a minimally coupled scalar field for a given scalar field potential where the equation of state is that of the NGCG. With the use of the later property we can construct the slow-roll parameters and derive the corresponding values for the spectral indices for the tensor to scalar perturbation and for the density perturbations. We have also studied the growth rate of matter perturbations in the NGCG scenario. Finally, we have studied the viability of the generalized second law of thermodynamics by assuming that the dynamical apparent horizon in a NGCG universe is endowed with Hawking temperature and Bekenstein entropy.

gr-qc↗

arXiv2022

Dynamical system analysis of logotropic dark fluid with a power law in the rest-mass energy density

We consider a spatially flat FLRW universe. We assume that it is filled with dark energy in the form of logotropic dark fluid coupled with dark matter in the form of a perfect fluid having a barotropic equation of state. We employ dynamical system tools to obtain a complete qualitative idea of the evolution of such a universe. It is interesting to note that we ought to consider an approximation for the pressure of the logotropic dark fluid in the form of an infinite series so as to be able to construct the autonomous system required for a dynamical system study. This series form provides us with a power law in the rest-mass energy density of the logotropic dark fluid. We compute the critical points of the autonomous system and analyze these critical points by applying linear stability theory. Our analysis reveal a scenario of late-time accelerated universe dominated by the logotropic fluid which behaves as cosmological constant, preceded by an intermediate phase of the Universe dominated by logotropic fluid which behaves as dark matter in the form of perfect fluid. Moreover, it also crosses the phantom divide line.

gr-qc↗

arXiv2021

Dynamics of an Interacting Barrow Holographic Dark Energy Model and its Thermodynamic Implications

In this paper, using Barrow entropy, we propose an interacting model of Barrow holographic dark energy (BHDE). In particular, we study the evolution of a spatially flat FLRW universe composed of pressureless dark matter and BHDE that interact with each other through a well-motivated interaction term. Considering the Hubble horizon as the IR cut-off, we then study the evolutionary history of important cosmological parameters, particularly, the density parameter, the equation of state parameter, and the deceleration parameter in the BHDE model and find satisfactory behaviors in the model. We perform a detailed study on the dynamics of the field equations by studying the asymptotic behavior of the field equations, while we write the analytic expression for the scale factor with the use of Laurent series. Finally, we study the implications of gravitational thermodynamics in the interacting BHDE model with the dynamical apparent horizon as the cosmological boundary. In particular, we study the viability of the generalized second law by assuming that the apparent horizon is endowed with Hawking temperature and Barrow entropy.

gr-qc↗

arXiv2021

Testing Lambert$W$ equation of state with observational Hubble parameter data

In this paper, we investigate the possibility that the Universe is driven by a single dark fluid described by a Lambert $W$ equation of state parameter, $w_{eff}$, which is essentially dependent on two parameters $\vartheta_{1}$ and $\vartheta_{2}$ which need to be fixed from observations. We obtain the constraints on these parameters using the latest 51 data points of $H(z)$ measurements, spanning the redshift range $0.07\leq z \leq 2.36$. The present study shows that the Universe is indeed undergoing an accelerated expansion phase following the decelerated one at the transition redshift, $z_{t}=0.77\pm0.03$ ($1σ$) and is well consistent with the recent observations. We also find that at low redshifts, $w_{eff}$ evolves only in the quintessence regime ($-1<w_{eff}<-\frac{1}{3}$) within $1σ$ confidence level. Its present value is found to be $-0.96\pm0.02$ ($1σ$). The fact that the present value of $w_{eff}$ is very close to the Cosmological Constant $Λ$ implies that our proposed equation of state parameter might serve as a unification of dark matter and dark energy. Furthermore, we compare the evolution of $H(z)$ for the model under consideration with that of the $Λ$CDM model. Finally, we observe that for the best-fit case, the differences between the two models are negligible at $z\sim 0.67$.

gr-qc↗

arXiv2020

Growth of Perturbations using Lambert$W$ Equation of State

Recently, a novel equation of state (EoS) parameter for dark energy has been introduced which deals with a special mathematical function, known as the Lambert$W$ function. In this paper, we study the effect on the growth of perturbations for the Lambert$W$ dark energy model. We perform the analysis for two different approaches. In the first case we consider the universe to be filled with two different fluid components, namely, the baryonic matter component and the Lambert$W$ dark energy component, while in the second case we consider that there is a single fluid component in the universe whose equation of state parameter is described by the Lambert$W$ function. We then compare the growth rates of Lambert$W$ model with that for a standard $Λ$CDM model as well as the CPL model. Our results indicate that the presence of Lambert$W$ dynamical dark energy sector changes the growth rate and affects the matter fluctuations in the universe to a great extent.

gr-qc↗

arXiv2020

A Generalized Interacting Tsallis Holographic Dark Energy Model and its thermodynamic implications

The paper deals with a theoretical model for interacting Tsallis holographic dark energy (THDE) whose infrared (IR) cut-off scale is set by the Hubble length. The interaction $Q$ between the dark sectors (dark energy and pressureless dark matter) of the universe has been assumed to be non-gravitational in nature. The functional form of $Q$ is chosen in such a way that it reproduces well known and most used interactions as special cases. We then study the nature of the THDE density parameter, the equation of state parameter, the deceleration parameter and the jerk parameter for this interacting THDE model. Our study shows that the universe exhibits the usual thermal history, namely the successive sequence of radiation, dark matter and dark energy epochs, before resulting in a complete dark energy domination in the far future. It is shown the evolution of the Hubble parameter for our model and compared that with the latest Hubble parameter data. Finally, we also investigate both the stability and thermodynamic nature of this model in the present context.

gr-qc↗

arXiv2020

The Logotropic Dark Fluid: Observational and Thermodynamic Constraints

We have considered a spatially flat, homogeneous and isotropic FLRW Universe filled with a single fluid, known as logotropic dark fluid (LDF), whose pressure evolves through a logarithmic equation of state. We use the recent Pantheon SNIa and cosmic chronometer datasets to constrain the parameters of this model, the present fraction of dark matter $Ω_{m0}$ and the Hubble constant $H_0$. We find that the mean values of these parameters are $Ω_{m0}=0.288\pm 0.012$ and $H_{0}=69.652\pm 1.698~{\rm km/s/Mpc}$ at the $1σ$ CL. We also find that the LDF model shows a smooth transition from the deceleration phase to acceleration phase of the universe in the recent past. We notice that the redshift of this transition $z_{t}=0.706\pm 0.048$ ($1σ$ error) and is well consistent with the present observations. Interestingly, we find that the Universe will settle down to a $Λ$CDM model in future and there will not be any future singularity in the LDF model. Furthermore, we notice that there is no significant difference between the LDF and $Λ$CDM models at the present epoch, but the difference (at the percent level) between these models is found as the redshift increases. We have also studied the generalized second law of thermodynamics at the dynamical apparent horizon for the LDF model with the Bekenstein and Viaggiu entropies.

gr-qc↗

arXiv2020

Study of Tsallis holographic dark energy model in the framework of Fractal cosmology

In this work, we study the evolution of a fractal universe composed of Tsallis holographic dark energy (THDE) and a pressureless dark matter that interact with each other through a mutual interaction. We then reconstruct the interaction term of this model by considering the Hubble length as the IR cut-off scale. We also study the behavior of different cosmological parameters during the cosmic evolution from the early matter-dominated era until the late-time acceleration. The present study shows that the universe undergoes a smooth transition from a decelerated to an accelerated phase of expansion in the recent past. Moreover, we also shown the evolution of the normalized Hubble parameter for our model and compared that with the latest cosmic chronometer data. Finally, we test the viability of the model by exploring its stability against small perturbation by using the squared of the sound speed.

gr-qc↗

arXiv2018

Does fractal Universe describe a complete cosmic scenario?

The present work deals with evolution of the fractal model of the Universe in the background of homogeneous and isotropic FLRW space--time geometry. The cosmic substrum is taken as perfect fluid with barotropic equation of state. A general prescription for the deceleration parameter is determined and it is examined whether the deceleration parameter may have more than one transition during the evolution of the fractal Universe for monomial form of the fractal function as a function of the scale factor. Finally, the model has been examined by making comparison with the observed data.

physics.gen-ph↗

arXiv2018

Observational constraints on the jerk parameter with the data of the Hubble parameter

We study the accelerated expansion phase of the universe by using the {\textit{kinematic approach}}. In particular, the deceleration parameter $q$ is parametrized in a model-independent way. Considering a generalized parametrization for $q$, we first obtain the jerk parameter $j$ (a dimensionless third time derivative of the scale factor) and then confront it with cosmic observations. We use the latest observational dataset of the Hubble parameter $H(z)$ consisting of 41 data points in the redshift range of $0.07 \leq z \leq 2.36$, larger than the redshift range that covered by the Type Ia supernova. We also acquire the current values of the deceleration parameter $q_0$, jerk parameter $j_0$ and transition redshift $z_t$ (at which the expansion of the universe switches from being decelerated to accelerated) with $1σ$ errors ($68.3\%$ confidence level). As a result, it is demonstrate that the universe is indeed undergoing an accelerated expansion phase following the decelerated one. This is consistent with the present observations. Moreover, we find the departure for the present model from the standard $Λ$CDM model according to the evolution of $j$. Furthermore, the evolution of the normalized Hubble parameter is shown for the present model and it is compared with the dataset of $H(z)$.

gr-qc↗

arXiv2018

A new parametrization for dark energy density and future deceleration

In this work, we have proposed a general dark energy density parametrization to study the evolution of the universe. We have also constrained the model parameters using the combination of Type Ia supernova (SNIa), baryonic acoustic oscillations (BAO), cosmic microwave background radiation (CMB) and observational $H(z)$ datasets. For the $H(z)$ dataset, we have used the direct observations of the Hubble rate, from the radial BAO size and the cosmic chronometer methods. Our result indicates that the SNIa+$H(z)$+BAO/CMB dataset does not favour the $Λ$CDM model at more than $2σ$ confidence level. Furthermore, we have also measured the percentage deviation in the evolution of the normalized Hubble parameter for the present model compared to a $Λ$CDM model, and the corresponding deviation is found to be $4-5\%$ at low redshifts ($z\sim 0.5$). Finally, we have also investigated whether the deceleration parameter $q$ may have more than one transition during the evolution of the universe. The present model shows a transient accelerating phase, in which the universe was decelerated in the past and is presently accelerating, but will return to a decelerating phase in the near future. This result is in great contrast to the $Λ$CDM scenario, which predicts that the cosmic acceleration must remain forever.

gr-qc↗