arXiv subjects

Baiju Dayanandan

Publications and source records attributed to Baiju Dayanandan.

8 recordsLinked to original sources

arXiv2026

Neutron Stars in Energy--Momentum Squared Gravity: Structure, Stability, and Multimessenger Constraints

We study nonrotating neutron stars in energy--momentum squared gravity (EMSG). The stellar models are obtained from the modified Tolman--Oppenheimer--Volkoff equations and four original tabulated hadronic equations of state: WFF1, SLy4, APR4, and MPA1. We use the common coupling set $α\in\{-20,-10,0,+5,+7.5\}\,\mathrm{km}^{2}$ and construct mass--radius and mass--central-density sequences. We compare these sequences with the $2\,M_\odot$ mass requirement, the NICER measurements of PSR J0030+0451 and PSR J0740+6620, and the region inferred from GW170817. Within the sampled coupling range, the computed pre-turning-point branches remain compatible with these four benchmarks. Negative values of $α$ generally shift the high-density branches toward larger masses. Positive values produce smaller shifts in the opposite direction. The microscopic sound speed becomes superluminal at high density in the WFF1 and SLy4 tables, whereas APR4 and MPA1 remain causal over their tabulated ranges. For WFF1, the causal boundary falls within a coarse table segment. Its compatibility with the $2\,M_\odot$ requirement therefore cannot be decided at the available density resolution. At $α=-20\,\mathrm{km}^{2}$, the effective-fluid sound-speed diagnostic becomes singular for WFF1, SLy4, and APR4. This singularity is absent from the explicit modified TOV system. All computed sequences remain below the standard Buchdahl reference values for compactness and surface redshift.

physics.gen-ph↗

arXiv2025

Interpretation of complexity for spherically symmetric fluid composition within the context of modified gravity theory

Regardless of the adequate descriptions of complexity in distinct alternative gravity theories, its elaboration in the framework of $f(R,\mathcal{L}_{m},\mathcal{T})$ theory remains uncertain. The orthogonal splitting of the curvature tensor yields the complexity factor as suggested by Herrera \cite {herrera2018new}. To commence our study, the inner spacetime is assumed to be spherically symmetric static composition comprised of the anisotropic fluid. In this context, we derive the modified field equations for the considered theory and take into account the established relationship between the conformal and curvature tensors to interpret the complexity. Furthermore, we determine the correspondence of the mass functions with the complexity factor, represented by a specific scalar $Y_{TF}$. Certain solutions complying with the precedent of diminishing $Y_{TF}$ are also evaluated. It is noted that celestial formations having anisotropic and non-uniform compositions of matter assert the utmost complexity. Nevertheless, the spherically symmetric matter distribution may not exhibit complexity in the scenario of vanishing impacts of non-homogenous energy density and anisotropic pressure due to the presence of dark source terms associated with this extended gravity theory.

gr-qc↗

arXiv2025

Impact of Non-metricity and Matter Source on the Geometry of Anisotropic Spheres

This paper delves into the impact of extended symmetric teleparallel theory on anisotropic compact stellar structures. The explicit field equations were formulated by considering a minimum model of this extended gravity. Basically, the Darmois junction conditions are used to determine the unknown constants of metric coefficients. We explore some significant properties of the compact stars under consideration to check their viable existence in this modified framework. The Tolman-Oppenheimer-Volkoff equation assess the equilibrium state of the compact stars. Moreover, the stability analysis is defined by using methods based on sound speed (related to how disturbances propagate in the star) and adiabatic index (related to the thermodynamic behavior of the star). We find that the proposed compact stars in the $f(\mathbb{Q}, \mathbb{T})$ gravity are physically viable and stable.

gr-qc↗

arXiv2025

Comprehensive Study of Generalized Ghost Dark Energy in $f(\textsl{Q}, \textsl{L}_{m})$ Gravity: New Insights into Cosmic Dynamics

This paper explores the generalized ghost dark energy model in the framework of $f(\textsl{Q}, \textsl{L}_{m})$ gravity, where $\textsl{Q}$ represents the non-metricity scalar and $\textsl{L}_{m}$ denotes the matter-Lagrangian density. We take the homogeneous and isotropic universe with an ideal matter distribution and examine a scenario with interacting dark energy and dark matter. We then reconstruct $f(\textsl{Q}, \textsl{L}_{m})$ model to examine the effects of this extended gravitational framework on the cosmic evolution. The behavior of numerous cosmic parameters are explored corresponding to distinct parametric values. The stability is evaluated by the squared sound speed method. The statefinder $(r,s)$ and standard diagnostic pairs $(ω_D-ω'_{D})$ are used to study the various cosmic eras. Our results align with recent observational evidence, indicating that the $f(\textsl{Q}, \textsl{L}_{m})$ model effectively characterizes dark energy and cosmic evolution.

gr-qc↗

arXiv2017

Modeling of charged anisotropic compact stars in general relativity

A charged compact star models have been determined for anisotropic fluid distribution. We have solved the Einstein's- Maxwell field equations to construct the charged compact star models by using radial pressure, metric function $e^λ$ and electric charge function. The generic charged anisotropic solution is verified by exploring different physical conditions like, causality condition, mass-radius relation and stability of the solution (via. adiabatic index, TOV equations and Herrera cracking concept). It is observed that the present charged anisotropic compact star is compatible with the star PSR 1937+21. However we also presented the EOS $ρ=f(p)$ for present charged compact star model.

gr-qc↗

arXiv2016

A new model for spherically symmetric anisotropic compact star

In this article we obtain a new anisotropic solution for Einstein's field equation of embedding class one metric. The solution is representing the realistic objects such as $Her~X-1$ and $RXJ~1856-37$. We perform detailed investigation of both objects by solving numerically the Einstein field equations under with anisotropic pressure. The physical features of the parameters depend on the anisotropic factor i.e. if anisotropy is zero everywhere inside the star then the density and pressures will become zero and metric turns out to be flat. We report our results and compare with the above mentioned two compact objects on a number of key aspects: the central density, the surface density onset and the critical scaling behavior, the effective mass and radius ratio, the anisotropization with isotropic initial conditions, adiabatic index and red shift. Along with this we have also made a comparison between the classical limit and theoretical model treatment of the compact objects. Finally we discuss the implications of our findings for the stability condition in relativistic compact star.

physics.gen-ph↗

arXiv2015

Generalized relativistic anisotropic models for compact stars

We present new anisotropic generalization of Buchdahl [1] type perfect fluid solution by using the method of earlier work [2]. In similar approach we have constructed the new pressure anisotropy factor $Δ$ by the help both the metric potential $e^λ$ and $e^ν$. The metric potential $e^λ$ same as Buchdahl [1] and $e^ν$ is monotonic increasing function as suggested by Lake [3]. After that we obtain new well behaved general solution for anisotropic fluid distribution. We calculated the physical quantities like energy density, radial and tangential pressures, velocity of sound and red-shift etc. We observe that these quantities are positive and finite inside the compact star. Also note that mass and radius of our models can represent the structure of realistic astrophysical objects such as like Her X-1 and RXJ1856-37.

gr-qc↗

arXiv2015

Anisotropic models for compact stars

In the present paper we obtain an anisotropic analogue of Durgapal-Fuloria (1985) perfect fluid solution. The methodology consists of contraction of anisotropic factor $Δ$ by the help of both metric potentials $e^ν$ and $e^λ$. Here we consider $e^λ$ same as Durgapal-Fuloria (1985) whereas $e^ν$ is that given by Lake (2003). The field equations are solved by the change of dependent variable method. The solutions set mathematically thus obtained are compared with the physical properties of some of the compact stars, strange star as well as white dwarf. It is observed that all the expected physical features are available related to stellar fluid distribution which clearly indicate validity of the model.

gr-qc↗