arXiv subjects

Koushik Ballav Goswami

Publications and source records attributed to Koushik Ballav Goswami.

4 recordsLinked to original sources

arXiv2026

Hybrid compact stars with finite strange quark mass and dark energy: implications for astrophysical observations

In this work, we present a detailed investigation of compact stars composed of deconfined quark matter, with finite strange quark mass ($m_s\neq0$), admixed with dark energy. The quark sector is described using the MIT bag model equation of state, while the dark energy component is assumed to satisfy a linear equation of state of the form $p^{de}=ωρ^{de}$, where $ω$ lies in the range $-1\leqω\leq-\frac{1}{3}$. The stellar configuration is studied within the Finch-Skea ansatz for the $g_{rr}$ metric potential. A coupling between the two components is introduced through the relation $ρ^{de}=βρ^Q$, where $β$ denotes the dark energy coupling parameter. From causality arguments, the admissible range of $β$ is constrained as $0<β<-\frac{1}{3ω}$. The structural properties of such compact stars are then analysed by varying $β$ within this range. Solution of the Tolman-Oppenheimer-Volkoff equations yields a maximum mass of $2.012~ M_{\odot}$ with a corresponding radius of $\approx 11$ km. Notably, for a fixed $ω$, both the stellar mass and radius are found to decrease with increasing $β$. The model is further examined through causality, energy, and stability conditions, all of which are satisfied, thereby ensuring physical viability. Finally, the framework is applied to estimate radii of several compact star candidates identified as strange quark stars admixed with dark energy, with predictions showing close agreement with recent observational results.

gr-qc↗

arXiv2025

Exploring density dependent B as a suitable parameter in higher dimensional approach with a non-linear equation of state

In this investigation, we present a singularity free interior solution of the Einstein field equation for a class of anisotropic compact objects in dimensions $D\geq4$. In accordance with the concept of Vaidya and Tikekar, the geometry of the physical $(D-1)$-space of a star corresponding to $t=constant$ hypersurface is assumed to be of a $(D-1)$ spheroid. For the fulfilment of causality condition, a limit of the spheroidal parameter ($λ$) is noted depending on the values of amount of anisotropy ($α$) and space-time dimensions ($D$). We note that by switching off the extra parameters ($α$ and $D$), previously obtained limit of $λ$ can be generated. To validate our findings, we compare the results obtained from our model with observational data of PSR J1614-2230 (mass=$1.908^{+0.016}_{-0.016}M_{\odot}$, radius=$11.93^{+0.50}_{-0.50}km$). It is noted that the best fit equation of state corresponds to polynomial equation of state of the order of five. We use this finding to develop a density dependent MIT bag model which seems to be useful for the correct description of compact object in our model. The mass radius relation shows that our model mimics a wide range of recently observed pulsars in four and higher dimensions. Furthermore, we also found that our model exhibits stability according to Generalised TOV equation, Herrera cracking condition, and the adiabatic index.

gr-qc↗

arXiv2025

Influence of density-dependent bag function $B(n)$ on strange stars for non-zero strange quark mass ($m_s\neq0$) in $f(R,T)$ gravity consistent with observational validation

In this work, a new class of solution of the Einstein field equation for an isotropic strange star using the modified Mak-Harko type density profile along with the equation of state as proposed in the MIT bag model and considering finite mass of the strange quark ($m_s$) is presented in the framework of $f(R,T)$ gravity with $f(R,T)=R+2ζT$, where, $ζ$ is the coupling parameter. To incorporate the quark matter hypothesis with a physically viable stellar framework, a baryon number density ($n$) dependent bag function $B(n)$ is analysed, using exponential type parametrisation. The energy per baryon ($E_B$) has been investigated to restrict $B(n)$ and corresponding $n$ within a stable window, specifically satisfying the condition $E_B\leq 930.4~MeV$, which corresponds to the binding energy of $\isotope[56]{Fe}$. We note a lower limit of $n$ below which $E_B>930.4~MeV$ as $E_B$ increases with the decrease of $n$. This value, however, depends on $m_s$. Additionally, $n$ has a maximum value of $0.36~fm^{-3}$ irrespective of $m_s$ depending on the range of bag function. All the essential characteristics are satisfactorily fulfilled within the stellar interior for the selected set of parameter space. In this model, the maximum mass and radius are found by solving the TOV equations numerically which yields $M=2.03~M_{\odot}$ with a radius of $11.49~km$ for $m_s=0~MeV$ and $n=0.36~fm^{-3}$ and $ζ=-0.1$. It is also noted that the maximum mass and the corresponding radius are the function of $m_s$, $ζ$ and $n$. The proposed model has been shown to comply with the required energy conditions and satisfies the criterion for dynamical stability, thereby confirming its physical plausibility as a physically consistent stellar model within the parameter space used.

gr-qc↗

arXiv2025

Interacting quark matter and $f(Q)$ gravity: A new paradigm in exploring the properties of quark stars

Perturbative Quantum Chromodynamics corrections and the colour superconductivity indicate that strongly interacting matter can manifest unique physical behaviours under extreme conditions. Motivated by this notion, we investigate the interior structure and properties of quark stars composed of interacting quark matter, which provides a comprehensive avenue to explore the strong interaction effects, within the framework of $f(Q)$ gravity. A unified equation of state is formulated to describe various phases of quark matter, including up-down quark matter $(2SC)$, strange quark matter $(2SC+s)$, and the Colour-Flavor Locked $(CFL)$ phase. By employing a systematic reparametrisation and rescaling, the number of degrees of freedom in the equation of state is significantly reduced. Utilising the Buchdahl-I metric ansatz and a linear $f(Q)$ functional form, $f(Q)=α_{0}+α_{1}Q$, we derive the exact solutions of the Einstein field equations in presence of the unified interacting quark matter equation of state. For the $2SC$ phase, we examine the properties of quark stars composed of up-down quark matter. For the $(2SC+s)$and $CFL$ phases, we incorporate the effects of a finite strange quark mass $(m_{s}\neq0)$. The Tolman-Oppenheimer-Volkoff equations are numerically solved to determine the maximum mass-radius relations for each phase. Our results indicate that the model satisfies key physical criteria, including causality, energy conditions, and stability requirements, ensuring the viability of the configurations. Furthermore, the predicted radii for certain compact star candidates align well with observational data. The study highlights that quark stars composed of interacting quark matter within the $f(Q)$ gravity framework provide a robust and physically consistent stellar model across all considered phases.

gr-qc↗