Pub Date : 2026-02-01Epub Date: 2025-11-23DOI: 10.1016/j.dark.2025.102182
Dong-Hoon Kim
We consider a situation in which light emitted from the neighborhood of a binary interacts with gravitational waves from the binary (e.g., a supermassive black hole binary in a quasar, a binary pulsar, etc.). The effect is cumulative over the long path lengths of light propagation and might be appreciable if the interaction initially takes place close to the source of gravitational waves, where the strain amplitude can be large. This situation can be modeled effectively using spherical gravitational waves (i.e., transverse-traceless radially propagating waves), with the strain amplitude varying with the distance from the source to a field point where the two wavefronts of light and gravitational waves meet each other. Our analysis employs geometrical-optics methods in curved spacetime, where the curvature is due to gravitational waves propagating in a flat spacetime background. We place a particular focus on the effect of gravitational Faraday rotation (or Skrotskii/Rytov effect) resulting from the interaction between light and gravitational waves from binaries.
{"title":"Geometrical-optics analysis of the interaction between light and gravitational waves from binaries","authors":"Dong-Hoon Kim","doi":"10.1016/j.dark.2025.102182","DOIUrl":"10.1016/j.dark.2025.102182","url":null,"abstract":"<div><div>We consider a situation in which light emitted from the neighborhood of a binary interacts with gravitational waves from the binary (e.g., a supermassive black hole binary in a quasar, a binary pulsar, etc.). The effect is cumulative over the long path lengths of light propagation and might be appreciable if the interaction initially takes place close to the source of gravitational waves, where the strain amplitude can be large. This situation can be modeled effectively using spherical gravitational waves (i.e., transverse-traceless radially propagating waves), with the strain amplitude varying with the distance from the source to a field point where the two wavefronts of light and gravitational waves meet each other. Our analysis employs geometrical-optics methods in curved spacetime, where the curvature is due to gravitational waves propagating in a flat spacetime background. We place a particular focus on the effect of gravitational Faraday rotation (or Skrotskii/Rytov effect) resulting from the interaction between light and gravitational waves from binaries.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102182"},"PeriodicalIF":6.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145665511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2026-01-18DOI: 10.1016/j.dark.2026.102218
Aurindam Mondal , Rathul Nath Raveendran
We investigate the quantum nature of primordial perturbations by studying the violation of Bell inequality when the initial state is taken to be a coherent state rather than the usual Bunch-Davies vacuum. As inflation progresses, the coherent state evolves into a squeezed coherent state, and we derive an analytical expression for the expectation value of the Bell operator constructed from pseudo-spin operators. Our analysis shows that although the expectation value of the Bell operator initially deviates from the vacuum case, it asymptotically saturates to the same value. Notably, this saturation occurs more rapidly for non-zero coherent state parameters, indicating that a larger one-point correlation function accelerates the approach to maximal Bell inequality violation.
{"title":"Violation of Bell inequality from a squeezed coherent state of inflationary perturbations","authors":"Aurindam Mondal , Rathul Nath Raveendran","doi":"10.1016/j.dark.2026.102218","DOIUrl":"10.1016/j.dark.2026.102218","url":null,"abstract":"<div><div>We investigate the quantum nature of primordial perturbations by studying the violation of Bell inequality when the initial state is taken to be a coherent state rather than the usual Bunch-Davies vacuum. As inflation progresses, the coherent state evolves into a squeezed coherent state, and we derive an analytical expression for the expectation value of the Bell operator constructed from pseudo-spin operators. Our analysis shows that although the expectation value of the Bell operator initially deviates from the vacuum case, it asymptotically saturates to the same value. Notably, this saturation occurs more rapidly for non-zero coherent state parameters, indicating that a larger one-point correlation function accelerates the approach to maximal Bell inequality violation.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102218"},"PeriodicalIF":6.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146077975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2025-11-29DOI: 10.1016/j.dark.2025.102183
Abdulmohsen Daham Alruwaili , Abdul Jawad , Ruqia Arif
This paper explores the stability analysis of Friedmann-like spacetimes using dynamical system methods. In this context, we begin by considering a modified cosmological scenario based on Tsallis entropy corrections. These entropic formulations modify the cosmological field equations that govern the universes dynamics. To analyze the dynamics of the adjusted Friedmann equations, we first transform them into an autonomous system of first-order differential equations. This formulation allows us to locate and examine the critical points, which represent the system’s equilibrium states. We consider the various linear and non-linear forms of interaction between cosmological fluids. For each model, we calculate the critical points and discuss their behavior associated with eigenvalues. We investigate the different stages in the universe’s evolution including dust and radiation dominated era of the universe as well as quintessence, ΛCDM and phantom regimes. In addition, we develop the phase space portraits of all the interaction models revealing the stable, unstable and saddle behavior of critical points. In most of the cases, the system supports stable critical points.
{"title":"Testing cosmic stability phenomenon of Tsallis entropy corrected universe","authors":"Abdulmohsen Daham Alruwaili , Abdul Jawad , Ruqia Arif","doi":"10.1016/j.dark.2025.102183","DOIUrl":"10.1016/j.dark.2025.102183","url":null,"abstract":"<div><div>This paper explores the stability analysis of Friedmann-like spacetimes using dynamical system methods. In this context, we begin by considering a modified cosmological scenario based on Tsallis entropy corrections. These entropic formulations modify the cosmological field equations that govern the universes dynamics. To analyze the dynamics of the adjusted Friedmann equations, we first transform them into an autonomous system of first-order differential equations. This formulation allows us to locate and examine the critical points, which represent the system’s equilibrium states. We consider the various linear and non-linear forms of interaction between cosmological fluids. For each model, we calculate the critical points and discuss their behavior associated with eigenvalues. We investigate the different stages in the universe’s evolution including dust and radiation dominated era of the universe as well as quintessence, ΛCDM and phantom regimes. In addition, we develop the phase space portraits of all the interaction models revealing the stable, unstable and saddle behavior of critical points. In most of the cases, the system supports stable critical points.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102183"},"PeriodicalIF":6.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145738732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2026-01-12DOI: 10.1016/j.dark.2026.102219
Mohammad Alshammari , M. Rizwan , Othman Abdullah Almatroud , M.Z. Bhatti , Saleh Alshammari , Z. Yousaf
In this paper, we construct and examine a new type of static, spherically symmetric wormhole geometries within the context of the minimal geometric deformation (MGD) formalism of gravitational decoupling. The seed solution is warped through an auxiliary source, with its temporal component described by holographic dark energy, thus including a phenomenologically driven dark sector. We study the resulting spacetime using several diagnostic tools: the embedding diagram is used to plot the wormhole throat and flare–out structure; the mass function is calculated to examine gravitational energy distribution; the volume integral quantifier is evaluated to determine the total amount of exotic matter needed; and the exoticity parameter is examined to describe the violation of energy conditions. Additionally, the singularity structure is analyzed to validate the regularity of spacetime, while the anisotropy factor is investigated to analyze pressure distributions between tangential and radial directions. Total effective energy–momentum tensor conservation equation is considered with emphasis on the interaction between the seed geometry and the θ-sector. Last, we analyze complexity factors to determine matter–energy content structural organization. We find that the addition of holographic dark energy in the time component of the θ-sector permits traversable, asymptotically flat wormhole solutions with regulated exotic matter and smooth geometric structures.
{"title":"Imprints of holographic dark energy and minimally deformed wormholes in general relativity","authors":"Mohammad Alshammari , M. Rizwan , Othman Abdullah Almatroud , M.Z. Bhatti , Saleh Alshammari , Z. Yousaf","doi":"10.1016/j.dark.2026.102219","DOIUrl":"10.1016/j.dark.2026.102219","url":null,"abstract":"<div><div>In this paper, we construct and examine a new type of static, spherically symmetric wormhole geometries within the context of the minimal geometric deformation (MGD) formalism of gravitational decoupling. The seed solution is warped through an auxiliary source, <span><math><msub><mover><mi>T</mi><mi>θ</mi></mover><mrow><mi>κ</mi><mi>μ</mi></mrow></msub></math></span> with its temporal component described by holographic dark energy, thus including a phenomenologically driven dark sector. We study the resulting spacetime using several diagnostic tools: the embedding diagram is used to plot the wormhole throat and flare–out structure; the mass function is calculated to examine gravitational energy distribution; the volume integral quantifier is evaluated to determine the total amount of exotic matter needed; and the exoticity parameter is examined to describe the violation of energy conditions. Additionally, the singularity structure is analyzed to validate the regularity of spacetime, while the anisotropy factor is investigated to analyze pressure distributions between tangential and radial directions. Total effective energy–momentum tensor conservation equation is considered with emphasis on the interaction between the seed geometry and the <em>θ</em>-sector. Last, we analyze complexity factors to determine matter–energy content structural organization. We find that the addition of holographic dark energy in the time component of the <em>θ</em>-sector permits traversable, asymptotically flat wormhole solutions with regulated exotic matter and smooth geometric structures.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102219"},"PeriodicalIF":6.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145977316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2026-01-05DOI: 10.1016/j.dark.2025.102205
Anna Chiara Alfano , Orlando Luongo
The cosmic distance duality relates angular-diameter and luminosity distances ensuring the cosmological principle, null geodesic motion of photons, and photon number conservation. Hence, any violations would challenge any metric theory of gravity. On the other hand, although independent from the specific cosmological model, it is particularly relevant to revisit the cosmic distance duality in view of recent DESI results, favoring dynamical dark energy over a cosmological constant standard paradigm. To do so, we take into account possible violations by considering four different parameterizations, namely: a Taylor expansion around z ≃ 0, a slightly-departing logarithmic correction, a (1;2) Padé rational series to heal the convergence problem and a Chebyshev polynomial expansion, reducing de facto the systematic errors associated with the analysis. We test each of them in a model-independent (-dependent) way, by working out Monte-Carlo Markov chain analyses, employing the Bézier interpolation of the Hubble rate H(z) for the model-independent approach while assuming the flat (non-flat) ΛCDM and ω0ω1CDM models, motivating the latter paradigm in view of the DESI findings. Subsequently, we explore two analyses, employing observational Hubble data, galaxy clusters from the Sunyaev-Zeldovich effect and type Ia supernovae, investigating the impact of the DESI data catalog, first including then excluding the entire data set. Afterwards, we adopt statistical model selection criteria to assess the statistically favored cosmological model. Our results suggest no violation of the cosmic distance duality as the contour plots suggest, where the parameter used to address a possible violation is independent of the background cosmological models adopted. Moreover, from our analyses we conclude that the Taylor parametrization is the worst performing and that the largest deviations from 0 at z ≈ 2 are found when the DESI sample is removed. In particular, for the flat case the cosmic distance duality is less than 2.1% (Bézier), 1.7% (ΛCDM) and 2.1% (ω0ω1CDM) with DESI versus 5.1% (Bézier), 3.3% (ΛCDM) and 7.0% (ω0ω1CDM) without DESI. This is even more accentuated when the curvature is accounted for, when we consider DESI the cosmic distance duality is less 4.0%, 1.2% and 2.1% while without the BAO it is less than 22.0%, 2.2% and 11.0% for Bézier, the concordance and ω0ω1CDM scenario, respectively. Finally, while a slight spatial curvature cannot be entirely excluded, the preferred cosmological model remains the flat ΛCDM background, even when incorporating DESI data.
{"title":"Cosmic distance duality after DESI 2024 data release and dark energy evolution","authors":"Anna Chiara Alfano , Orlando Luongo","doi":"10.1016/j.dark.2025.102205","DOIUrl":"10.1016/j.dark.2025.102205","url":null,"abstract":"<div><div>The cosmic distance duality relates angular-diameter and luminosity distances ensuring the cosmological principle, null geodesic motion of photons, and photon number conservation. Hence, any violations would challenge any metric theory of gravity. On the other hand, although independent from the specific cosmological model, it is particularly relevant to revisit the cosmic distance duality in view of recent DESI results, favoring dynamical dark energy over a cosmological constant standard paradigm. To do so, we take into account possible violations by considering four different parameterizations, namely: a Taylor expansion around <em>z</em> ≃ 0, a slightly-departing logarithmic correction, a (1;2) Padé rational series to heal the convergence problem and a Chebyshev polynomial expansion, reducing <em>de facto</em> the systematic errors associated with the analysis. We test each of them in a model-independent (-dependent) way, by working out Monte-Carlo Markov chain analyses, employing the Bézier interpolation of the Hubble rate <em>H</em>(<em>z</em>) for the model-independent approach while assuming the flat (non-flat) ΛCDM and <em>ω</em><sub>0</sub><em>ω</em><sub>1</sub>CDM models, motivating the latter paradigm in view of the DESI findings. Subsequently, we explore two analyses, employing observational Hubble data, galaxy clusters from the Sunyaev-Zeldovich effect and type Ia supernovae, investigating the impact of the DESI data catalog, first including then excluding the entire data set. Afterwards, we adopt statistical model selection criteria to assess the statistically favored cosmological model. Our results suggest <em>no violation</em> of the cosmic distance duality as the contour plots suggest, where the parameter used to address a possible violation is independent of the background cosmological models adopted. Moreover, from our analyses we conclude that the Taylor parametrization is the worst performing and that the largest deviations from 0 at <em>z</em> ≈ 2 are found when the DESI sample is removed. In particular, for the flat case the cosmic distance duality is less than 2.1% (Bézier), 1.7% (ΛCDM) and 2.1% (<em>ω</em><sub>0</sub><em>ω</em><sub>1</sub>CDM) with DESI versus 5.1% (Bézier), 3.3% (ΛCDM) and 7.0% (<em>ω</em><sub>0</sub><em>ω</em><sub>1</sub>CDM) without DESI. This is even more accentuated when the curvature is accounted for, when we consider DESI the cosmic distance duality is less 4.0%, 1.2% and 2.1% while without the BAO it is less than 22.0%, 2.2% and 11.0% for Bézier, the concordance and <em>ω</em><sub>0</sub><em>ω</em><sub>1</sub>CDM scenario, respectively. Finally, while a slight spatial curvature cannot be entirely excluded, the preferred cosmological model remains the flat ΛCDM background, even when incorporating DESI data.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102205"},"PeriodicalIF":6.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2026-01-24DOI: 10.1016/j.dark.2026.102233
Ghulam Fatima , Abdelmalek Bouzenada , Orhan Donmez , Allah Ditta , G. Mustafa , Farruh Atamurotov
In this study, we examine the accretion of perfect and polytropic fluids onto Barrow’s nonlinear charged black hole models, described by a static spherically symmetric spacetime with a metric function X(r) explicitly dependent on the Yang-Mills coupling parameter α, magnetic charge Q, and black hole mass M. We employ two equations of state: (i) , which incorporates a reference density ρ0 to account for a nonzero rest energy baseline, and (ii) , representing a conventional linear equations of state. Applying the steady-state approximation, we derive the conservation equations for mass, momentum, and energy, which allow analytical determination of the critical (sonic) points and the mass accretion rate. In this case, the analysis reveals that increasing either α or Q reduces the fluid inflow velocity and local sound speed while simultaneously enhancing the accretion rate near the event horizon. Also, both equations of state models exhibit smooth, continuous transitions through the sonic points, and numerical evaluations demonstrate pronounced effects of α and Q on the horizon geometry, location of critical points, fluid density, and sound speed, quantitatively illustrating the influence of nonlinear electrodynamics and Barrow deformation on relativistic accretion dynamics.
{"title":"Exact and numerical analysis of accretion dynamics with perfect and polytropic fluids around nonlinear charged black holes","authors":"Ghulam Fatima , Abdelmalek Bouzenada , Orhan Donmez , Allah Ditta , G. Mustafa , Farruh Atamurotov","doi":"10.1016/j.dark.2026.102233","DOIUrl":"10.1016/j.dark.2026.102233","url":null,"abstract":"<div><div>In this study, we examine the accretion of perfect and polytropic fluids onto Barrow’s nonlinear charged black hole models, described by a static spherically symmetric spacetime with a metric function <em>X</em>(<em>r</em>) explicitly dependent on the Yang-Mills coupling parameter <em>α</em>, magnetic charge <em>Q</em>, and black hole mass <em>M</em>. We employ two equations of state: <strong>(i)</strong> <span><math><mrow><mi>p</mi><mo>=</mo><mi>ω</mi><mo>(</mo><mi>ρ</mi><mo>−</mo><msub><mi>ρ</mi><mn>0</mn></msub><mo>)</mo></mrow></math></span>, which incorporates a reference density <em>ρ</em><sub>0</sub> to account for a nonzero rest energy baseline, and <strong>(ii)</strong> <span><math><mrow><mi>p</mi><mo>=</mo><mi>κ</mi><mi>ρ</mi></mrow></math></span>, representing a conventional linear equations of state. Applying the steady-state approximation, we derive the conservation equations for mass, momentum, and energy, which allow analytical determination of the critical (sonic) points and the mass accretion rate. In this case, the analysis reveals that increasing either <em>α</em> or <em>Q</em> reduces the fluid inflow velocity and local sound speed while simultaneously enhancing the accretion rate near the event horizon. Also, both equations of state models exhibit smooth, continuous transitions through the sonic points, and numerical evaluations demonstrate pronounced effects of <em>α</em> and <em>Q</em> on the horizon geometry, location of critical points, fluid density, and sound speed, quantitatively illustrating the influence of nonlinear electrodynamics and Barrow deformation on relativistic accretion dynamics.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102233"},"PeriodicalIF":6.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146077914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we focus on the influence of effective quantum gravity corrections on neutrino oscillations around static black holes. Following a covariant Hamiltonian, which maintains diffeomorphism invariance, we consider a black hole metric from semiclassical quantum gravity and look at how the parameter ξ/M, which describes the deviation from the Schwarzschild solution affects the neutrino flavor transitions. The analysis includes both radial and non-radial propagation of neutrinos with emphasis on their gravitational lensing. The analysis is performed with two- and three-flavor oscillation models with normal and inverted mass hierarchy configurations and varying effective neutrino mass values. The calculation of the energy deposition rate due to neutrino annihilation is also presented.
{"title":"Gravitational lensing effects on neutrino oscillations around static black hole in effective quantum gravity","authors":"Sojida Mannobova , Bakhtiyor Narzilloev , Farruh Atamurotov , Ahmadjon Abdujabbarov , Ibrar Hussain , Bobomurat Ahmedov","doi":"10.1016/j.dark.2025.102194","DOIUrl":"10.1016/j.dark.2025.102194","url":null,"abstract":"<div><div>In this paper, we focus on the influence of effective quantum gravity corrections on neutrino oscillations around static black holes. Following a covariant Hamiltonian, which maintains diffeomorphism invariance, we consider a black hole metric from semiclassical quantum gravity and look at how the parameter <em>ξ</em>/<em>M</em>, which describes the deviation from the Schwarzschild solution affects the neutrino flavor transitions. The analysis includes both radial and non-radial propagation of neutrinos with emphasis on their gravitational lensing. The analysis is performed with two- and three-flavor oscillation models with normal and inverted mass hierarchy configurations and varying effective neutrino mass values. The calculation of the energy deposition rate due to neutrino annihilation is also presented.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102194"},"PeriodicalIF":6.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145883993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2025-11-27DOI: 10.1016/j.dark.2025.102178
Iqra Ibrar , Eman M. Moneer , M. Sharif , Euaggelos E. Zotos
This paper investigates a new model that describes the structure of spherically symmetric anisotropic compact stars in the framework of f(Q, T) gravity, where Q represents non-metricity and T is the trace of the energy-momentum tensor. We use the Tolman-Durgapal-V metric as the seed solution and apply the MIT bag model equation of state to obtain a closed form solution. To test the physical validity of our model, we apply it to two well-known compact star candidates: SAX J 178.9-2021 and 4U 1538-52. Using graphical features, we analyze key physical properties such as matter density, pressure profiles, anisotropy, equation of state parameters, energy conditions, mass function and important stability parameters including compactness, gravitational redshift, causality, Herrera’s cracking condition and the adiabatic index. The results demonstrate that our model is free from singularities and accurately describes a variety of observed compact stars.
{"title":"Imprints of the MIT bag equation of state on the compact stars in the framework of f(Q, T) gravity","authors":"Iqra Ibrar , Eman M. Moneer , M. Sharif , Euaggelos E. Zotos","doi":"10.1016/j.dark.2025.102178","DOIUrl":"10.1016/j.dark.2025.102178","url":null,"abstract":"<div><div>This paper investigates a new model that describes the structure of spherically symmetric anisotropic compact stars in the framework of <em>f</em>(<em>Q, T</em>) gravity, where <em>Q</em> represents non-metricity and <em>T</em> is the trace of the energy-momentum tensor. We use the <em>Tolman-Durgapal-V</em> metric as the seed solution and apply the <em>MIT bag</em> model equation of state to obtain a closed form solution. To test the physical validity of our model, we apply it to two well-known compact star candidates: SAX J 178.9-2021 and 4U 1538-52. Using graphical features, we analyze key physical properties such as matter density, pressure profiles, anisotropy, equation of state parameters, energy conditions, mass function and important stability parameters including compactness, gravitational redshift, causality, Herrera’s cracking condition and the adiabatic index. The results demonstrate that our model is free from singularities and accurately describes a variety of observed compact stars.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102178"},"PeriodicalIF":6.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work studies the construction of anisotropic self-gravitating star models influenced by a surrounding quintessence field described by a parameter ωq with , under the theoretical requirement of a vanishing gravitational complexity factor. The complexity-free constraint, originally proposed as a measure of the structural inhomogeneity and pressure anisotropy of relativistic stellar fluids, is employed to obtain astrophysically relevant solutions of general relativistic field equations. By considering a suitable metric potential, we derive exact expressions for the matter density, principal stresses, and anisotropy factor. The influence of the quintessence field on stellar structure is analyzed in detail, highlighting its role in tuning the pressure anisotropy and energy distribution within the stellar distribution. To ensure realistic stellar modeling, we examine central regularity, positivity of density and principal stresses, energy conditions, causality, and stability requirements. Furthermore, matching conditions with the exterior spacetime are imposed to determine the unknown constants. The resulting stellar configurations are shown to be consistent with observational data of compact stars, thereby demonstrating that the combined effects of the quintessence field and the vanishing complexity condition provide an elegant framework for modeling anisotropic relativistic configuration.
{"title":"Anisotropic compact stars under quintessence field with vanishing gravitational complexity factor","authors":"S. Khan , Javlon Rayimbaev , Sarvar Iskandarov , Aybek Seytov , Inomjon Ibragimov , Sokhibjan Muminov","doi":"10.1016/j.dark.2026.102220","DOIUrl":"10.1016/j.dark.2026.102220","url":null,"abstract":"<div><div>This work studies the construction of anisotropic self-gravitating star models influenced by a surrounding quintessence field described by a parameter <em>ω<sub>q</sub></em> with <span><math><mrow><mo>−</mo><mn>1</mn><mo><</mo><msub><mi>ω</mi><mi>q</mi></msub><mo><</mo><mo>−</mo><mfrac><mn>1</mn><mn>3</mn></mfrac></mrow></math></span>, under the theoretical requirement of a vanishing gravitational complexity factor. The complexity-free constraint, originally proposed as a measure of the structural inhomogeneity and pressure anisotropy of relativistic stellar fluids, is employed to obtain astrophysically relevant solutions of general relativistic field equations. By considering a suitable metric potential, we derive exact expressions for the matter density, principal stresses, and anisotropy factor. The influence of the quintessence field on stellar structure is analyzed in detail, highlighting its role in tuning the pressure anisotropy and energy distribution within the stellar distribution. To ensure realistic stellar modeling, we examine central regularity, positivity of density and principal stresses, energy conditions, causality, and stability requirements. Furthermore, matching conditions with the exterior spacetime are imposed to determine the unknown constants. The resulting stellar configurations are shown to be consistent with observational data of compact stars, thereby demonstrating that the combined effects of the quintessence field and the vanishing complexity condition provide an elegant framework for modeling anisotropic relativistic configuration.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102220"},"PeriodicalIF":6.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146077979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2026-01-21DOI: 10.1016/j.dark.2026.102231
Aylin Çalışkan
<div><div>We study the late-time cosmological implications of Weyl-type <em>f</em>(<em>Q, T</em>) modified gravity in a spatially flat FLRW background. Working in Weyl geometry, where non-metricity is sourced by a gauge field <em>w<sub>μ</sub></em>, we enforce the vanishing Weyl scalar condition <span><math><mrow><mover><mi>R</mi><mo>¯</mo></mover><mo>=</mo><mn>0</mn></mrow></math></span> through a Lagrange multiplier, which yields modified field equations containing both a Proca-like vector contribution and a matter-geometry coupling via <em>f</em>(<em>Q, T</em>). By adopting the linear ansatz <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>Q</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow><mo>=</mo><mi>α</mi><mi>Q</mi><mo>+</mo><mfrac><mi>β</mi><mrow><mn>6</mn><msup><mi>κ</mi><mn>2</mn></msup></mrow></mfrac><mi>T</mi><mo>+</mo><mi>γ</mi></mrow></math></span> and a homogeneous Weyl vector <span><math><mrow><msub><mi>w</mi><mi>μ</mi></msub><mo>=</mo><mrow><mo>(</mo><mi>ψ</mi><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo>,</mo><mn>0</mn><mo>,</mo><mn>0</mn><mo>,</mo><mn>0</mn><mo>)</mo></mrow></mrow></math></span> (so that <span><math><mrow><mi>Q</mi><mo>=</mo><mn>6</mn><msup><mi>ψ</mi><mn>2</mn></msup></mrow></math></span>), we derive the generalized Friedmann equations and close the system under the approximation <em>λ</em> ≃ <em>κ</em><sup>2</sup>. The Weyl constraint admits the branch <span><math><mrow><mi>ψ</mi><mo>=</mo><mi>H</mi></mrow></math></span>, and consistency with the generalized Proca equation selects the massless effective mode <span><math><mrow><msubsup><mi>m</mi><mrow><mrow><mi>e</mi></mrow><mi>f</mi><mi>f</mi></mrow><mn>2</mn></msubsup><mo>=</mo><mn>0</mn></mrow></math></span>, fixing <em>α</em> and leaving (<em>β, γ</em>) as the relevant phenomenological parameters. For a dust sector (<span><math><mrow><mi>p</mi><mo>=</mo><mn>0</mn></mrow></math></span>), the dynamics reduces to a Riccati-type equation that can be integrated analytically, leading to a closed-form expression for the Hubble function <em>H</em>(<em>z</em>) and well-defined viability conditions (notably <span><math><mrow><mi>β</mi><mo>≠</mo><mo>−</mo><mn>2</mn></mrow></math></span> and <em>H</em><sup>2</sup>(<em>z</em>) ≥ 0). We then confront the model with current late-time data using an affine-invariant MCMC analysis with cosmic chronometer <em>H</em>(<em>z</em>) measurements, Pantheon+ SNe Ia, and DESI BAO. The combined dataset yields <span><math><mrow><msub><mi>H</mi><mn>0</mn></msub><mo>=</mo><mn>67.86</mn><mo>±</mo><mn>0.37</mn></mrow></math></span>, <span><math><mrow><mi>β</mi><mo>=</mo><mn>0</mn><mo>.</mo><msubsup><mn>27</mn><mrow><mo>−</mo><mn>0.13</mn></mrow><mrow><mo>+</mo><mn>0.11</mn></mrow></msubsup></mrow></math></span>, and <span><math><mrow><mi>γ</mi><mo>=</mo><mo>−</mo><mn>1.8</mn><mo>×</mo><msup><mn>10</mn><mn>4</mn></msup><mo>±</mo><mn>1.0</mn></mrow></math></span>, with a goodness of fit comparable to ΛCDM (<span><math><mrow><msubsup><mi>χ</mi><mrow
{"title":"Late-time cosmology in Weyl-type f(Q, T) modified gravity: Analytic background solutions and observational constraints from H(z), Pantheon+, and DESI","authors":"Aylin Çalışkan","doi":"10.1016/j.dark.2026.102231","DOIUrl":"10.1016/j.dark.2026.102231","url":null,"abstract":"<div><div>We study the late-time cosmological implications of Weyl-type <em>f</em>(<em>Q, T</em>) modified gravity in a spatially flat FLRW background. Working in Weyl geometry, where non-metricity is sourced by a gauge field <em>w<sub>μ</sub></em>, we enforce the vanishing Weyl scalar condition <span><math><mrow><mover><mi>R</mi><mo>¯</mo></mover><mo>=</mo><mn>0</mn></mrow></math></span> through a Lagrange multiplier, which yields modified field equations containing both a Proca-like vector contribution and a matter-geometry coupling via <em>f</em>(<em>Q, T</em>). By adopting the linear ansatz <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>Q</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow><mo>=</mo><mi>α</mi><mi>Q</mi><mo>+</mo><mfrac><mi>β</mi><mrow><mn>6</mn><msup><mi>κ</mi><mn>2</mn></msup></mrow></mfrac><mi>T</mi><mo>+</mo><mi>γ</mi></mrow></math></span> and a homogeneous Weyl vector <span><math><mrow><msub><mi>w</mi><mi>μ</mi></msub><mo>=</mo><mrow><mo>(</mo><mi>ψ</mi><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo>,</mo><mn>0</mn><mo>,</mo><mn>0</mn><mo>,</mo><mn>0</mn><mo>)</mo></mrow></mrow></math></span> (so that <span><math><mrow><mi>Q</mi><mo>=</mo><mn>6</mn><msup><mi>ψ</mi><mn>2</mn></msup></mrow></math></span>), we derive the generalized Friedmann equations and close the system under the approximation <em>λ</em> ≃ <em>κ</em><sup>2</sup>. The Weyl constraint admits the branch <span><math><mrow><mi>ψ</mi><mo>=</mo><mi>H</mi></mrow></math></span>, and consistency with the generalized Proca equation selects the massless effective mode <span><math><mrow><msubsup><mi>m</mi><mrow><mrow><mi>e</mi></mrow><mi>f</mi><mi>f</mi></mrow><mn>2</mn></msubsup><mo>=</mo><mn>0</mn></mrow></math></span>, fixing <em>α</em> and leaving (<em>β, γ</em>) as the relevant phenomenological parameters. For a dust sector (<span><math><mrow><mi>p</mi><mo>=</mo><mn>0</mn></mrow></math></span>), the dynamics reduces to a Riccati-type equation that can be integrated analytically, leading to a closed-form expression for the Hubble function <em>H</em>(<em>z</em>) and well-defined viability conditions (notably <span><math><mrow><mi>β</mi><mo>≠</mo><mo>−</mo><mn>2</mn></mrow></math></span> and <em>H</em><sup>2</sup>(<em>z</em>) ≥ 0). We then confront the model with current late-time data using an affine-invariant MCMC analysis with cosmic chronometer <em>H</em>(<em>z</em>) measurements, Pantheon+ SNe Ia, and DESI BAO. The combined dataset yields <span><math><mrow><msub><mi>H</mi><mn>0</mn></msub><mo>=</mo><mn>67.86</mn><mo>±</mo><mn>0.37</mn></mrow></math></span>, <span><math><mrow><mi>β</mi><mo>=</mo><mn>0</mn><mo>.</mo><msubsup><mn>27</mn><mrow><mo>−</mo><mn>0.13</mn></mrow><mrow><mo>+</mo><mn>0.11</mn></mrow></msubsup></mrow></math></span>, and <span><math><mrow><mi>γ</mi><mo>=</mo><mo>−</mo><mn>1.8</mn><mo>×</mo><msup><mn>10</mn><mn>4</mn></msup><mo>±</mo><mn>1.0</mn></mrow></math></span>, with a goodness of fit comparable to ΛCDM (<span><math><mrow><msubsup><mi>χ</mi><mrow","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102231"},"PeriodicalIF":6.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146077976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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