arXiv subjects

Anirudh Pradhan

Publications and source records attributed to Anirudh Pradhan.

At least 37 records · Page 2Linked to original sources

arXiv2026

Alleviating the Hubble Tension with Logarithmic Dark Energy: Constraints on the $w_{log}$CDM Model

Observational constraints are considered on a $w_{log}$CDM model of the dark energy equation of state, $w_{d}(z) = w_{0} + w_{a}\left( \frac{\ln(2+z)}{1+z} - \ln 2 \right)$, using the most recent cosmological datasets including DESI Baryon Acoustic Oscillation (BAO) measurements, Big Bang Nucleosynthesis (BBN) priors, Cosmic Chronometer (CC) observations, and Pantheon Plus (PPS) Type Ia supernovae. From the combined DESI BAO+BBN+CC+PPS dataset, we obtain $H_0 = 71.02 \pm 0.66~\text{kms}^{-1}\text{Mpc}^{-1}$, $Ω_m = 0.2863 \pm 0.0080,$ $w_0 = -0.875 \pm 0.066,$ $w_a = -0.69^{+0.37}_{-0.32},$ at the 68\% and 95\% confidence levels, indicating a preference for phantom dark energy with mild evidence for temporal evolution. The Hubble constant obtained from our model is closer to the local SH0ES measurement than the standard $Λ$CDM prediction, partially easing the Hubble tension. We perform extensive parameter-space exploration revealing correlations between $w_0$, $w_a$, and $H_0$, showing that dynamical dark energy models can fit higher values of the Hubble constant. The reconstructed deceleration parameter $q(z)$ shows the transition from deceleration to acceleration at $z \sim 0.6$--$0.7$, while the equation-of-state reconstruction remains consistent with a cosmological constant across the observed redshift range. A model comparison using information criteria indicates that the $w_{log}$CDM model remains statistically competitive with $Λ$CDM.

physics.gen-ph↗

arXiv2026

Observational Constraints and Geometric Diagnostics of Barboza-Alcaniz and Logarithmic Dark Energy Parametrizations

This study investigates and compares two prominent two-dimensional dark energy (DE) parameterizations: Barboza-Alcaniz (BA) and Logarithmic forms by comparing them with a comprehensive set of observational data comprising Type Ia Supernovae (SNe Ia) from the Pantheon compilation, Baryon Acoustic Oscillations (DESI BAO), and Cosmic Chronometers (CC). The primary objective was to explore the constraining power and cosmological implications of each parameterization in light of the current data. After formulating the theoretical framework and background equations governing cosmic expansion, we employ Markov Chain Monte Carlo (MCMC) techniques using the emcee Python package to constrain the free parameters of each model. The best-fit values for parameters $ω_0$, $ω_a$, and $H_0$ were extracted for each model using individual and combined datasets. The results include confidence contours at the levels $1σ$ and $2σ$. Our findings demonstrate that both parameterizations are consistent with observational data, with logarithmic parameterization showing slightly better constraints in terms of parameter evolution. Furthermore, we employed a statefinder diagnostic to analyze the geometric behavior of the models, providing an effective distinction between the two DE scenarios. This study contributes to a deeper understanding of DE evolution and its constraints in light of current cosmological data.

physics.gen-ph↗

arXiv2026

Dynamical Dark Energy Signatures from a New Transition $Om(z)$ Parametrization in Flat FLRW Cosmology

We investigate a cosmic scenario using a new transition parameterization of the $Om(z)$ diagnostic, $Om(z) = \frac{z^l}{(1+z)^m}$, in the spatially flat Friedmann Lemaître Robertson-Walker (FLRW) framework. Using observational datasets such as Observational Hubble Data (OHD), Pantheon Plus (PP), and SH0ES, we analyze the evolution of the $Om(z)$ function to probe deviations from the standard $Λ$CDM model and constrain free parameter space {$H_0$, l, m } using Markov Chain Monte Carlo (MCMC) analysis with the emcee sampler. Our analysis reveals a clear transition in the slope of $Om(z)$ from negative to positive at transition redshift values $z_t \approx 1.41$, $0.65$, and $0.33$ for the OHD, OHD+PP, and OHD+PP$\&$SH0ES datasets, respectively. This behavior suggests a dynamical evolution of dark energy, indicating a transition from a quintessence-like phase to a phantom regime. From the combined OHD+PP$\&$SH0ES dataset, we obtain a best-fit value of the Hubble constant $ H_0 = 73.01 \pm 0.36 \, \mathrm{km\,s^{-1}\,Mpc^{-1}} $, which is consistent with the SH0ES calibration and supports the viability of our model. Additionally, our analysis indicates that the current age of the Universe is approximately $13 \sim 14$ Gyr from all available combinations of datasets, which is consistent with observational expectations. Further, we find that the deceleration-to-acceleration transition, which marks the beginning of cosmic acceleration, is inferred to occur within the redshift interval $z_t \in [0.5, 0.8]$, highlighting the emergence of dark energy as the dominant component in the Universe's recent expansion history. Our transition $Om(z)$ parameterization captured progressive cosmological changes and enabled seamless interpolation over cosmic epochs.

gr-qc↗

arXiv2026

Constraining a $f(R, L_m)$ Gravity Cosmological Model with Observational Data

We investigate a spatially flat FLRW cosmological model in the framework of modified gravity described by the function $ f(R, L_m) = αR + L_m^β+ γ$, where $ L_m $ is the matter Lagrangian density. The modified Friedmann equations yield the Hubble parameter as $ H(z) = H_0 \sqrt{(1 - λ) + λ(1 + z)^{3(1 + w)}},$ with the parameters $ λ= \fracγ{6αH_0^2} + 1 $ and $ w = \frac{β(n - 2) + 1}{2β- 1} $. Using a Bayesian Markov Chain Monte Carlo (MCMC) approach, we constrain the model parameters with recent observational data, including cosmic chronometers, the Pantheon+ Supernovae dataset, Baryon Acoustic Oscillations (BAO), and Cosmic Microwave Background (CMB) shift parameters. The best-fit values are found to be $ H_0 = 72.773^{+0.148}_{-0.152} $ km/s/Mpc, $ λ= 0.289^{+0.007}_{-0.007} $, and $ w = -0.002^{+0.002}_{-0.002} $, all quoted at the 1$σ$ confidence level.This model predicts a transition redshift of $ z_t \approx 0.76 $ for the onset of cosmic acceleration and an estimated universe age of 13.21 Gyr. The higher inferred value of $ H_0 $ compared to the Planck 2018 result offers a potential resolution to the Hubble tension. Additionally, using $ ρ_0 = 0.534 \times 10^{-30} \, \text{g/cm}^3 $ and assuming $ n = 1 $, we derive the model constants as $ β= 1.00201 $, $ α= 512247 $, and $ γ= -1.215 \times 10^{-29} $. We also evaluate the Bayesian Information Criterion (BIC) to compare the model's performance with that of the standard $Λ$CDM model. The small BIC difference ($ Δ\text{BIC} = 0.16 $) indicates comparable statistical support for both models. Thus, the $ f(R, L_m) $ gravity scenario serves as a consistent and viable alternative to $Λ$CDM, potentially addressing open questions in late-time cosmology.

gr-qc↗

arXiv2026

Dynamical Oscillations in Dark Energy: Joint Constraints on the $w_{sin}$CDM Model from DESI, OHD, and Supernova Samples

In this study, we investigate the oscillatory dark energy model $w_{\sin}\mathrm{CDM}$ based on the DESI BAO data together with OHD, Pantheon Plus, and SH0ES measurements. We examine how the DESI data influence the dark energy equation-of-state plane $(w_0, w_a)$ within cosmological models that are free from Hubble tension and employ a Monte Carlo Markov Chain (MCMC) approach. Our findings indicate that although the parameter space still favors $w_a < 0$ and $w_0 > -1$ , the cosmological constant remains consistent with the DESI+OHD+PP combination at the $2σ$ level. We also observe that the best-fit Hubble constant $H_0$ is higher for the DESI+OHD+PP+SH0ES data combination, leading to a residual Hubble tension of less than $1σ$ to remain consistent with the SH0ES measurement. These results suggest that attempts to address the Hubble tension tend to reduce indication of DESI for the oscillatory dark energy model. Therefore, claims that the cosmological constant should be approached with greater caution, considering both the latest observational datasets and the existing cosmological tensions. We also obtained the present deceleration parameter and the effective equation-of-state value as $q_0 = -0.36$ and $w_{\mathrm{eff}} = -0.57$, respectively, for the DESI+OHD+PP+SH0ES dataset combination. Further analysis indicated a strong departure of $w_0$ from $w=-1$ at the $4σ$ level for the DR2+OHD+DES-5yr data combination. The inferred $Ω_{m}$ tended to shift toward higher values when supernova samples were included, indicating a systematic preference for larger $Ω_{m}$ in combinations involving supernova data.

physics.gen-ph↗

arXiv2026

Dark Energy Behavior from Static Equation of State in Non-Minimally Coupled Gravity with Scalar Deformation

In this study, we explore the cosmological implications of a modified gravity theory characterized by the function $ f(R, Σ, T) $, where $ R $ is the Ricci scalar, $ Σ$ represents a geometric deformation term, and $ T $ denotes the trace of the energy-momentum tensor. The model is reconstructed under the framework of three fundamental energy conditions: Null Energy Condition (NEC), Dominant Energy Condition (DEC), and Strong Energy Condition (SEC). We derive the corresponding Hubble parameter $ H(z) $ for each case and constrain the free parameters $ H_0 $, $ α$, and $ β$ using the latest Cosmic Chronometer (CC) and Pantheon+ Type Ia Supernova datasets. A thorough analysis of physical quantities such as pressure, energy density, and the equation of state parameter is carried out. Furthermore, diagnostic tools including the deceleration parameter $ q(z) $, statefinder parameters $ \{r, s\} $, and the $O_m(z)$ diagnostic are employed to assess the models viability. Our findings suggest that the model can consistently describe late-time cosmic acceleration and offers distinct behavior under different energy conditions, all while aligning with current observational data.

gr-qc↗

arXiv2025

Constraints on Spatial Curvature and Dark Energy Dynamics in the $w$CDM Model from DESI DR1 and DR2

In this study, we investigate the $w$CDM dynamical dark energy model with spatial curvature utilizing the recently released DESI Collaboration data (DR1 and DR2) in conjunction with other observational probes such as BBN, Observational Hubble Data (OHD), and Pantheon Plus (PP). Our investigation attempts to discover which DESI dataset gives a better match to the $w$CDM framework and assess the impact of spatial curvature on cosmological constraints. We find that the cosmic curvature parameter, $Ω_k$, disfavors the cosmological constant for the DR2+BBN and DR2+BBN+OHD data combinations. However, the deviation from the cosmological constant remains below the $1σ$ level, indicating a mild preference for a open universe. In contrast, when using the DR1 based combinations namely DR1+BBN and DR1+BBN+OHD-the deviation from the cosmological constant increases to approximately $1.2σ$, suggesting a slightly stronger indication of a open geometry. Also, the best-fit values of the Hubble constant ($H_0$) obtained from the DR1+BBN+OHD+PP and DR2+BBN+OHD+PP combinations within the dynamical dark energy model are consistent with the results reported by the Planck Collaboration. Our findings provide constraints on the dark energy EoS parameter $ w_{\mathrm{}0}$, reveal a mild but notable deviation from the vacuum energy ($w = -1$) scenario at a significance level $1.8σ$ from DR2+BBN+OHD+PP and $0.5σ$ from DR1+BBN+OHD+PP, both favoring the quintessence region of dark energy. Furthermore, the key physical distance measures $D_H$, $D_V$, and $D_M$ show better consistency with our model when analyzed with the DR2 data.

astro-ph.CO↗

arXiv2025

Dark-Energy Anisotropic Compact Configurations in 4D Einstein-Gauss-Bonnet Gravity: From Structure to Observational Viability

We address the equilibrium configurations and stability properties of anisotropic compact stars whose interior is described by a modified Chaplygin gas (MCG) equation of state in the framework of the regularized four-dimensional Einstein-Gauss-Bonnet (4DEGB) theory. Applying a quasi-local prescription for the pressure anisotropy, we derive the modified Tolman-Oppenheimer-Volkoff (TOV) equations and integrate them numerically over a large parameter space in the Gauss-Bonnet coupling $α$ and the degree of anisotropy $β$. We provide mass-radius sequences, mass-compactness, energy density, and pressure profiles, and perform a full stability analysis based on the turning-point criterion, the radial adiabatic index $γ_r$, and the radial and transverse sound speeds $v_r^2$ and $v_t^2$. Our results show that positive $α$ and positive anisotropy $(β> 0)$ systematically increase the maximum mass and radius, enabling then configurations that exceed $2\,M_\odot$ while still obeying causality and the modified Buchdahl bound in 4DEGB gravity. A comparison with the latest astrophysical constraints (NICER, GW170817, GW190814, and massive-pulsar measurements) identifies regions of the $(α,β)$ parameter space that are observationally allowable. In conclusion, anisotropic dark-energy stars in 4DEGB gravity provide viable, observationally testable ultra-compact alternatives to normal neutron stars and black holes, and also potentially open rich avenues for further multi-messenger searches for higher-curvature effects.

gr-qc↗

arXiv2025

Beyond $Λ$CDM: Exploring a Dynamical Cosmological Constant Framework Consistent with Late-Time Observations

In this work, we investigate a cosmological scenario with a time-dependent cosmological constant $Λ$(t) within the spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) framework. Here we study a power-law $Λ(t)$CDM model characterized by a dynamic cosmological constant expressed as a function of the Hubble parameter and its derivative $Λ(t)$ $=α(\dot H+H^{2})+λH^2+4πGρη.$ Using recent observational datasets (DESI BAO, OHD, and PP\&SH0ES), we constrain the model's free parameters $(H_{0},α,λ,η)$ and analyze their impact on key cosmological quantities. A Markov chain Monte Carlo (MCMC) analysis of the best-fit value of $H_{0}=71.9\pm 0.23$ km/s/Mpc from PP\&SH0ES analysis only, which substantially alleviates the existing tension between early and late-time determinations of the Hubble constant, reducing it to $\sim1.5σ$. The reconstructed $Om$ diagnostic exhibits a negative slope, indicating a dynamic dark energy behavior with quintessence-like characteristics ($ω>-1$). These results suggest that the proposed $Λ(t)$ model provides a viable alternative to the standard $Λ$CDM paradigm to explain the late-time acceleration of the universe. Our findings show that this model alleviates the Hubble tension more effectively than the standard $Λ$CDM . The model also demonstrates compatibility with late-time Hubble parameter observations and offers a compelling framework to address the limitations of $Λ$CDM.

gr-qc↗

arXiv2025

Cosmological Evolution of Viscous Dark Energy in f(Q,C) Gravity: Two-Fluid Approach

In this paper, we study the cosmological evolution of a viscous dark energy model within the framework of $f(Q, C)$ gravity, utilizing a two-fluid approach. The model incorporates non-metricity and boundary contributions to the total action, represented by the scalar quantities $Q$ and $C$. The viscosity in the dark energy fluid is modeled to understand the impact of bulk viscosity on cosmic expansion and the late-time acceleration of the universe. We derive the field equations using the modified FLRW metric and analyze the behavior of key cosmological parameters, including the energy density, pressure, and the equation of state (EoS) parameter. The effective EoS parameter is also studied in the context of cosmic evolution. We impose observational constraints on the Hubble parameter $H(z)$ using recent datasets from DESI-Y1, SDSS-IV, Pantheon+ (without SHOES calibration), and cosmic chronometer measurements. The analysis shows that the model effectively describes the universe's expansion history and predicts a transition from deceleration to acceleration, consistent with observational data. This model also provides an alternative explanation for cosmic acceleration without the need for a cosmological constant.

gr-qc↗

arXiv2025

Investigating the $w$CDM Model with Latest DESI BAO Observations

In this study, we explore the impact of various combinations of CMB-independent datasets, including the recent DESI BAO measurements, on the equation of state (EoS) of dark energy and other cosmological parameters within the framework of the dynamical dark energy model ($w$CDM). Assuming a constant EoS parameter for dark energy, we derive constraints on the free parameters of the model using observational datasets such as DESI BAO, BBN, Observational Hubble Data (OHD), and Pantheon Plus (SN$^+$) $\&$ SH0ES. Our analysis examines the deviations of the $w$CDM model from the standard $Λ$CDM scenario and assesses its implications for cosmological tensions, particularly the $H_0$ tension [$\text{km} \text{s}^{-1} \text{Mpc}^{-1}$]. We find that the combination of DESI BAO + BBN + OHD + SN$^+$ (DESI BAO + BBN + OHD + SN$^+$ \&SH0ES) datasets provides constraints on $w_{\mathrm{de}0}$, suggesting a possible deviation from the cosmological constant scenario at a significance level of $1.6σ$ ($1.4σ$), respectively. Furthermore, we observe an inverse correlation between $w_{\text{de0}}$ and $H_0$, which highlights the role of dark energy dynamics in resolving the tension $H_0$ by approximately $2.1σ(0.8σ)$ from DESI BAO + BBN + OHD (DESI BAO + BBN + OHD + SN$^+$ \&SH0ES) datasets, respectively. Our findings offer valuable insights into the nature of dark energy and its influence on the cosmic expansion history, with implications for future observational efforts. We utilize the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) to evaluate our model's performance. The results indicate that the $w$CDM model demonstrates superior effectiveness.

astro-ph.CO↗

arXiv2025

Empirical Validation: Investigating the $Λ_s $CDM Model with new DESI BAO Observations

The $Λ$CDM model has long served as the cornerstone of modern cosmology, offering an elegant and successful framework for interpreting a wide range of cosmological observations. However, the rise of high-precision datasets has revealed statistically significant tensions, most notably the Hubble tension and the $S_8$ discrepancy, which challenge the completeness of this standard model. In this context, we explore the $Λ_{\rm s}$CDM model-an extension of $Λ$CDM featuring a single additional parameter, $z_\dagger$, corresponding to a sign-switching cosmological constant. This minimal modification aims to alleviate key observational tensions without compromising the model's overall coherence. Recent findings present in the literature indicate that the $Λ_{\rm s}$CDM model not only provides a better fit to Lyman-$α$ forest data for $z_\dagger < 2.3$, but also accommodates both the SH0ES measurement of $H_0$ and the angular diameter distance to the last scattering surface when 2D BAO data are included. We present a comprehensive analysis combining the full Planck 2018 CMB data, the Pantheon Type Ia Supernovae sample, and the recently released Baryon Acoustic Oscillation (BAO) measurements from the Dark Energy Spectroscopic Instrument (DESI). Our finding reveal that the Preliminary DESI results, a possible $3.9σ$ deviation from $Λ$CDM expectations, reinforce the importance of exploring such dynamic dark energy frameworks. In sum, our study underscores the potential of $Λ_{\rm s}$CDM to reconcile multiple cosmological tensions and sheds light on the role of upcoming high-precision observations in reshaping our understanding of the universe's expansion history and the nature of dark energy.

astro-ph.CO↗

arXiv2025

Cosmological Implications of a New Creation Field in Hoyle-Narlikar Gravity with Bulk Viscous Fluid

In this study, we present a comprehensive investigation of the Narlikar gravity model with bulk viscous fluid by the new foam of creation field $C(t) = t + \int α(1 - a)dt + c_1$, based on the Hoyle-Narlikar's creation-field theory, using a joint analysis of Observational Hubble Data (OHD) and the Pantheon supernova (PP) compilation. Our analysis reveals that the creation field coupling constant $(f)$ is always positive within the Narlikar gravity model from OHD+PP data sets. The best-fit estimates yield $ H_0 = 71.2 \pm 2.1 \text{km s}^{-1}\text{Mpc}^{-1}$ and $ξ_0 = 0.23$, quoted at the $1 σ$ level. The Narlikar gravity model predicts a transition redshift of $z_t \approx 0.63$ marking the onset of late-time cosmic acceleration, with the corresponding age of the Universe estimated as $13.50\pm1.80 Gyr$. Interestingly, the inferred higher value of $H_0$, relative to SH0ES determinations, suggests a possible alleviation of the $\sim 4.1σ$ Hubble tension. Furthermore, we assess the stability of the model and demonstrate that the late-time acceleration can be consistently explained through the energy conditions. This model retains dynamical flexibility while ensuring analytical tractability and provides a promising framework to investigate the cosmological implications of Hoyle-Narlikar gravity, particularly regarding late-time acceleration and the evolution of dark energy.

gr-qc↗

arXiv2025

Testing $f(T)$ Gravity with Cosmological Observations: Confronting the Hubble Tension and Implications for the Late-Time Universe

In recent years, modifications to General Relativity (GR) have been explored to address cosmological observations, particularly in the context of late-time cosmic acceleration. Among these, modifications based on the Teleparallel Equivalent of General Relativity (TEGR), particularly $f(T)$ gravity, have gained significant attention. In this work, we investigate the scalar perturbations in $f(T)$ gravity, focusing on how these perturbations modify the Poisson and lensing equations and how they impact cosmological observables. By incorporating observational data from cosmic chromatometers, Big Bang nucleosynthesis, the DESI BAO survey, and Type Ia Supernovae (SNe Ia), we derive constraints on the parameters of the $f(T)$ power-law model. Our results suggest that $f(T)$ gravity can effectively alleviate some of the tensions observed in the standard $Λ$CDM model, including the Hubble constant ($H_0$) discrepancy. Furthermore, the evolution of the supernova luminosity and its dependence on the gravitational constant are considered to refine the measurement of cosmological parameters. The model's ability to address the $H_0$ tension is critically examined, and we find that $f(T)$ gravity offers a viable alternative to the standard model. The work concludes by comparing the fits of the $f(T)$ gravity model to the $Λ$CDM model using various information criteria, revealing key insights into the viability of modified gravity in contemporary cosmology.

astro-ph.CO↗

arXiv2025

A novel cosmic framework of interdependent dark matter and Holographic Dark Energy within the Bianchi type-V universe

We study the anisotropic and homogeneous Bianchi type-V Universe with holographic dark energy (HDE) and interacting dark matter (DM). The solution for the field equations have been obtained for a certain form of the deceleration parameter. As for $Λ$CDM, we show that the coincidence problem disappears for a specific choice of the dark matter-holographic dark energy interaction. In this study, the observational data combination of OHD and JLA (Yu et al., Astrophys. J. 856 (2018) 3), where $q_0$ = $-0.52$ and $H_0$ = $69.2$, have been taken into consideration. We also found that the anisotropy of the expansion achieves isotropy after some finite time. We have also explained the physical and geometrical aspects of the model. The physical acceptability and stability of the model have been examined.

gr-qc↗

arXiv2025

Exploring the dynamics of coincident f(Q) gravity in the presence of DBI-essence scalar field

In theoretical cosmology, symmetric teleparallel gravity or $f(Q)$ gravity based on nonmetricity tensor Q has become an interesting alternative to General relativity in recent years. The present research paper contains a rigorous dynamical system analysis of coincident f (Q) gravity in the presence of a generalized DBI essence scalar field. We have considered two different models of coincident f(Q) gravity, such as power law model $f(Q) = Q + nQ^m$ and exponential model $f(Q) = Q e^{\frac{βQ_0}{Q}}$ respectively, where n, m, \b{eta} are constant parameter and Q is the nonmetricity component. In this study, the generalized DBI essence scalar field acts as an additional dark energy component. After obtaining the field equation for the corresponding cosmological model, we employed several dynamical variables to form the dynamical system. The critical points of these dynamical systems are influenced by cosmological parameters and associated with particular epochs in the cosmological timeline. For different combinations of cosmological parameters, the critical points exhibit different cosmological eras, starting from the accelerated stiff matter era to late-time acceleration phenomena. The stability criteria of each critical point are studied by using linear stability theory, and the physical constraints on the cosmological parameters are also considered during this analysis. Furthermore, the current values of energy densities, deceleration parameters, and equation of state parameters obtained from the evolution diagram are compatible with observational data.

gr-qc↗

arXiv2025

Cosmological Analysis of $f(R, Σ, T)$ Gravity with EoS Parameterization

In this paper, we present a comprehensive cosmological analysis within the framework of $f(R, Σ, T)$ gravity, a modified theory that incorporates nonlinear matter-geometry coupling via the inclusion of both the trace of the energy-momentum tensor $T$ and the scalar $Σ= T_{μν}T^{μν}$. We consider a spatially flat Friedmann-Robertson-Walker (FRW) universe and introduce a linear parameterization for the equation of state (EoS) parameter based on the Chevallier-Polarski-Linder (CPL) form, which allows us to explore the dynamical evolution of dark energy without imposing restrictive assumptions. To confront the theoretical model with observations, we utilize the latest Hubble parameter measurements from cosmic chronometers. The model parameters are constrained using Markov Chain Monte Carlo (MCMC) simulations with the \texttt{emcee} package, leading to tight bounds on the parameters. The analysis reveals that the model remains consistent with the $Λ$CDM scenario while allowing mild deviations consistent with observational data. Furthermore, we examine the physical and kinematical features of the model by studying the behavior of the physical parameters. Finally, the calculated age of the universe within this framework is found to be in excellent agreement with Planck 2018 results, highlighting the and viability of $f(R, Σ, T)$ gravity as a candidate for explaining late-time cosmic acceleration.

gr-qc↗

arXiv2025

Dark matter admixed relativistic stars: Structural properties and tidal Love numbers

We study the impact of bosonic, self-interacting dark matter on structural properties and tidal deformabilities of compact stars. As far as the gravitational theory is concerned, we assume Einstein's gravity in four dimensions with a vanishing cosmological constant. Regarding matter content, we consider a state-of-matter to a linear form of equation-of-state (EoS), while for dark matter we assume a quartic scalar potential, which implies a certain non-linear EoS obtained long time ago. Adopting the two-fluid formalism we integrate the structure equations as well as the Riccati equation for the metric even perturbations imposing appropriate initial conditions at the center of the stars and matching conditions at their surface. We compute the stellar mass and radius, factor of compactness and dimensionless deformability varying several free parameters of the model studied here. Tidal deformability and the corresponding tidal Love number determine the imprint of the underlying EoS within the signals emitted during binary coalescences, and it is expected to be altered due to the presence of dark matter inside the objects. We find that in all cases considered here, the dimensionless deformability of the canonical stellar mass remains lower than the upper bound, $Λ_{1.4} < 800$. We also look at the stability of these stars based on the Harrison-Zeldovich-Novikov criterion under various conditions. It is observed that the presence of dark matter implies significantly lower highest stellar mass, and also smaller and more compact stars for a given stellar mass.

gr-qc↗