Pub Date : 2025-12-25DOI: 10.1016/j.dark.2025.102201
Cemsinan Deliduman , Furkan Şakir Dilsiz , Selinay Sude Binici
To better distinguish the nature of H0 and S8 tensions, it is necessary to separate the effects of expansion and the growth of structure. The growth index γ was identified as the most important parameter that characterizes the growth of density fluctuations independently of the effects of cosmic expansion. In the ΛCDM model, analyses performed with various cosmological datasets indicate that the growth index has to be larger than its theoretically predicted value. Cosmological models based on f(R) gravity theories have scale-dependent growth indices, whose values are even more at odds with the growth rate data. In this work, we evaluate the growth index in the γδCDM model both theoretically and numerically. Although based on f(R) gravity theory, we show through several analyses with different combinations of datasets that the growth index in the γδCDM model is very close in value to the ΛCDM and the ωCDM models. The growth of structure is suppressed in the γδCDM model, which is formulated with the extended gravitational growth framework. Upon analyzing cosmological data, we ascertain that the γδCDM model is equally competitive as the ΛCDM and the ωCDM models.
{"title":"Growth index in the γδCDM model","authors":"Cemsinan Deliduman , Furkan Şakir Dilsiz , Selinay Sude Binici","doi":"10.1016/j.dark.2025.102201","DOIUrl":"10.1016/j.dark.2025.102201","url":null,"abstract":"<div><div>To better distinguish the nature of <em>H</em><sub>0</sub> and <em>S</em><sub>8</sub> tensions, it is necessary to separate the effects of expansion and the growth of structure. The growth index <em>γ</em> was identified as the most important parameter that characterizes the growth of density fluctuations independently of the effects of cosmic expansion. In the ΛCDM model, analyses performed with various cosmological datasets indicate that the growth index has to be larger than its theoretically predicted value. Cosmological models based on <em>f</em>(<em>R</em>) gravity theories have scale-dependent growth indices, whose values are even more at odds with the growth rate data. In this work, we evaluate the growth index in the <em>γδ</em>CDM model both theoretically and numerically. Although based on <em>f</em>(<em>R</em>) gravity theory, we show through several analyses with different combinations of datasets that the growth index in the <em>γδ</em>CDM model is very close in value to the ΛCDM and the <em>ω</em>CDM models. The growth of structure is suppressed in the <em>γδ</em>CDM model, which is formulated with the extended gravitational growth framework. Upon analyzing cosmological data, we ascertain that the <em>γδ</em>CDM model is equally competitive as the ΛCDM and the <em>ω</em>CDM models.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102201"},"PeriodicalIF":6.4,"publicationDate":"2025-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145883992","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}
The modeling of astrophysical compact objects has recently attracted significant interest of the research community to understand their stable internal structures. In particular, the addition of dark energy as another source of matter configuration in the interiors of such stars has elevated the focus on their theoretical development. In this study, we present a ne model of static, spherically symmetric, and anisotropic compact stars within the framework of f(R) modified theories. The stellar structure is described by a two-fluid system consisting of ordinary matter and dark energy. We develop the analytical solutions to the governing modified field equations using the well-known Finch-Skea ansatz for the metric potentials, coupled with a linear equation of state for the dark energy component. The model parameters, including the metric ansatz, are determined via smooth matching conditions at the boundary between the interior and exterior spacetime regions. To demonstrate the physical viability of the model, we apply our formulation to the compact star 4U 1538-52, utilizing the stable and widely studied gravity model. We analyze an extensive investigation of the physical features, including the behavior of metric equations, matter variables, energy conditions, and stability criteria. In addition, we evaluate the evolution of the mass function, surface redshift, and compactness factor of the considered compact star candidates. The results confirm the stability, feasibility, and physical impact of the constructed solutions along with presenting additional insight into the interplay between dark energy structures and modified gravity within astrophysical circumstances. Graphical representations of key parameters enhance the clarity of our findings. The results demonstrate that our model is physically acceptable and stable in f(R) gravity.
{"title":"Interior structure and physical features of dark energy relativistic stars in power law gravity model","authors":"M.R. Shahzad , Wajiha Habib , Asifa Ashraf , Muneerah Alomar , Awatef Abidi , Maryam Al Huwayz","doi":"10.1016/j.dark.2025.102198","DOIUrl":"10.1016/j.dark.2025.102198","url":null,"abstract":"<div><div>The modeling of astrophysical compact objects has recently attracted significant interest of the research community to understand their stable internal structures. In particular, the addition of dark energy as another source of matter configuration in the interiors of such stars has elevated the focus on their theoretical development. In this study, we present a ne model of static, spherically symmetric, and anisotropic compact stars within the framework of <em>f</em>(<em>R</em>) modified theories. The stellar structure is described by a two-fluid system consisting of ordinary matter and dark energy. We develop the analytical solutions to the governing modified field equations using the well-known Finch-Skea ansatz for the metric potentials, coupled with a linear equation of state for the dark energy component. The model parameters, including the metric ansatz, are determined via smooth matching conditions at the boundary between the interior and exterior spacetime regions. To demonstrate the physical viability of the model, we apply our formulation to the compact star 4U 1538-52, utilizing the stable and widely studied <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>)</mo></mrow><mo>=</mo><mi>R</mi><mo>+</mo><mn>2</mn><mi>χ</mi><msup><mi>R</mi><mn>2</mn></msup></mrow></math></span> gravity model. We analyze an extensive investigation of the physical features, including the behavior of metric equations, matter variables, energy conditions, and stability criteria. In addition, we evaluate the evolution of the mass function, surface redshift, and compactness factor of the considered compact star candidates. The results confirm the stability, feasibility, and physical impact of the constructed solutions along with presenting additional insight into the interplay between dark energy structures and modified gravity within astrophysical circumstances. Graphical representations of key parameters enhance the clarity of our findings. The results demonstrate that our model is physically acceptable and stable in <em>f</em>(<em>R</em>) gravity.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102198"},"PeriodicalIF":6.4,"publicationDate":"2025-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145977319","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 : 2025-12-24DOI: 10.1016/j.dark.2025.102202
Erdem Sucu, İzzet Sakallı
We investigate quantum corrections to the thermodynamics of charged, rotating BTZ black holes in AdS spacetime using both Generalized Uncertainty Principle (GUP) and exponential entropy corrections. The Hamilton–Jacobi tunneling method yields the Hawking temperature and its GUP-modified form, revealing how Planck-scale effects suppress thermal radiation. Exponential corrections to the Bekenstein-Hawking entropy lead to modified expressions for internal energy, Helmholtz and Gibbs free energies, pressure, enthalpy, and heat capacity. The AdS radius ℓ emerges as a critical parameter: smaller values enhance gravitational confinement and thermodynamic stability, while larger values weaken these effects. The heat capacity remains positive across parameter space, ruling out second-order phase transitions. However, the JT coefficient exhibits remarkable oscillatory behavior near rh ≈ 1.05, alternating between heating and cooling phases during isenthalpic expansion. These oscillations intensify with increasing ℓ, indicating reduced stability in weakly curved AdS backgrounds. Gravitational redshift calculations in the weak-field limit show that the logarithmic charge coupling produces unbounded growth at large distances, with strong ℓ-dependence providing observational signatures. Our results demonstrate that (2+1)-dimensional black holes possess richer thermodynamic structure than their higher-dimensional counterparts, with quantum corrections introducing novel critical phenomena while preserving overall stability. These findings connect microscopic quantum gravity effects to macroscopic thermodynamic behavior, offering new perspectives on black hole physics in lower dimensions.
{"title":"Quantum corrections and exotic criticality in charged rotating BTZ black holes","authors":"Erdem Sucu, İzzet Sakallı","doi":"10.1016/j.dark.2025.102202","DOIUrl":"10.1016/j.dark.2025.102202","url":null,"abstract":"<div><div>We investigate quantum corrections to the thermodynamics of charged, rotating BTZ black holes in AdS spacetime using both Generalized Uncertainty Principle (GUP) and exponential entropy corrections. The Hamilton–Jacobi tunneling method yields the Hawking temperature and its GUP-modified form, revealing how Planck-scale effects suppress thermal radiation. Exponential corrections to the Bekenstein-Hawking entropy lead to modified expressions for internal energy, Helmholtz and Gibbs free energies, pressure, enthalpy, and heat capacity. The AdS radius ℓ emerges as a critical parameter: smaller values enhance gravitational confinement and thermodynamic stability, while larger values weaken these effects. The heat capacity remains positive across parameter space, ruling out second-order phase transitions. However, the JT coefficient exhibits remarkable oscillatory behavior near <em>r<sub>h</sub></em> ≈ 1.05, alternating between heating and cooling phases during isenthalpic expansion. These oscillations intensify with increasing ℓ, indicating reduced stability in weakly curved AdS backgrounds. Gravitational redshift calculations in the weak-field limit show that the logarithmic charge coupling produces unbounded growth at large distances, with strong ℓ-dependence providing observational signatures. Our results demonstrate that (2+1)-dimensional black holes possess richer thermodynamic structure than their higher-dimensional counterparts, with quantum corrections introducing novel critical phenomena while preserving overall stability. These findings connect microscopic quantum gravity effects to macroscopic thermodynamic behavior, offering new perspectives on black hole physics in lower dimensions.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102202"},"PeriodicalIF":6.4,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145884622","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 investigate the motion of test particles around a black hole (BH) characterized by spontaneous Lorentz symmetry breaking, parameterized by α. We begin by outlining the theoretical framework underlying such BH geometries and subsequently analyze the corresponding dynamics of massive test particles. By applying the effective potential, we determine the exact conditions for circular trajectories and analyze the properties of the innermost stable circular orbits (ISCOs) parameters. In addition, the effective force acting on particles is studied, which gives further insight into orbital stability. Also, we are testing the BH shadow with M87* and Sgr A* under the influence of BH parameters.. Furthermore, we explore oscillatory phenomena associated with small perturbations around circular orbits, calculating the frequencies as measured by both local and distant observers, as well as the periastron precession. In this context, these results shed light on possible observational signatures of Lorentz-symmetry breaking in strong gravitational regimes and contribute to the understanding of modified BH physics.
{"title":"Stability analysis and oscillatory behavior of orbits around Lorentz-violating black holes","authors":"Rana Muhammad Zulqarnain , Abdelmalek Bouzenada , Farruh Atamurotov , Ikhtiyor Saidov , A.S. Alqahtani , Phongpichit Channuie","doi":"10.1016/j.dark.2025.102200","DOIUrl":"10.1016/j.dark.2025.102200","url":null,"abstract":"<div><div>In this paper, we investigate the motion of test particles around a black hole (BH) characterized by spontaneous Lorentz symmetry breaking, parameterized by <em>α</em>. We begin by outlining the theoretical framework underlying such BH geometries and subsequently analyze the corresponding dynamics of massive test particles. By applying the effective potential, we determine the exact conditions for circular trajectories and analyze the properties of the innermost stable circular orbits (ISCOs) parameters. In addition, the effective force acting on particles is studied, which gives further insight into orbital stability. Also, we are testing the BH shadow with M87* and Sgr A* under the influence of BH parameters.. Furthermore, we explore oscillatory phenomena associated with small perturbations around circular orbits, calculating the frequencies as measured by both local and distant observers, as well as the periastron precession. In this context, these results shed light on possible observational signatures of Lorentz-symmetry breaking in strong gravitational regimes and contribute to the understanding of modified BH physics.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102200"},"PeriodicalIF":6.4,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926343","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 : 2025-12-21DOI: 10.1016/j.dark.2025.102195
Oem Trivedi , Abraham Loeb
Primordial Black Holes (PBHs) represent one of the more interesting ways to address dark matter, at the interface of both cosmology and quantum gravity. It is no surprise then that testing PBHs is a venue of active interest, with several cosmological and astrophysical probes constraining different mass ranges. In this work, we propose novel Solar System scale searches for PBHs, motivated by the unique precision and coverage of local observables. We show that asteroid to dwarf planet mass PBHs can induce measurable dipolar timing signatures in pulsar timing arrays, while planetary mass PBHs can generate detectable ADAF accretion flares through interactions with Kuiper Belt bodies. Together, these complementary approaches open a new observational frontier for probing PBHs across mass ranges that remain unconstrained by conventional cosmological methods.
{"title":"Novel solar system probes for primordial black holes","authors":"Oem Trivedi , Abraham Loeb","doi":"10.1016/j.dark.2025.102195","DOIUrl":"10.1016/j.dark.2025.102195","url":null,"abstract":"<div><div>Primordial Black Holes (PBHs) represent one of the more interesting ways to address dark matter, at the interface of both cosmology and quantum gravity. It is no surprise then that testing PBHs is a venue of active interest, with several cosmological and astrophysical probes constraining different mass ranges. In this work, we propose novel Solar System scale searches for PBHs, motivated by the unique precision and coverage of local observables. We show that asteroid to dwarf planet mass PBHs can induce measurable dipolar timing signatures in pulsar timing arrays, while planetary mass PBHs can generate detectable ADAF accretion flares through interactions with Kuiper Belt bodies. Together, these complementary approaches open a new observational frontier for probing PBHs across mass ranges that remain unconstrained by conventional cosmological methods.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102195"},"PeriodicalIF":6.4,"publicationDate":"2025-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145883991","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 : 2025-12-20DOI: 10.1016/j.dark.2025.102192
Hyerim Noh , Jai-chan Hwang
We study a massive-photon electrodynamics and magnetohydrodynamics (MHD) in the curved spacetime of Einstein’s gravity. We consider a Proca-type photon mass and present equations in terms of electric and magnetic (EM) fields and the vector potential. We present the electrodynamics and MHD in the covariant and ADM formulations valid in general spacetime and in linearly perturbed cosmological spacetime. We present wave equations assuming the metric variations are negligible compared with the field variations. Equations are derived without fixing the temporal gauge condition and the gauge transformation properties of the EM fields and the vector potential are presented. Using the post-Newtonian approximation we show the dark Proca field behaves as dust in the non-relativistic limit under the Klein transformation.
{"title":"Massive-photon electrodynamics and MHD in curved spacetime and cosmology","authors":"Hyerim Noh , Jai-chan Hwang","doi":"10.1016/j.dark.2025.102192","DOIUrl":"10.1016/j.dark.2025.102192","url":null,"abstract":"<div><div>We study a massive-photon electrodynamics and magnetohydrodynamics (MHD) in the curved spacetime of Einstein’s gravity. We consider a Proca-type photon mass and present equations in terms of electric and magnetic (EM) fields and the vector potential. We present the electrodynamics and MHD in the covariant and ADM formulations valid in general spacetime and in linearly perturbed cosmological spacetime. We present wave equations assuming the metric variations are negligible compared with the field variations. Equations are derived without fixing the temporal gauge condition and the gauge transformation properties of the EM fields and the vector potential are presented. Using the post-Newtonian approximation we show the dark Proca field behaves as dust in the non-relativistic limit under the Klein transformation.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102192"},"PeriodicalIF":6.4,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840514","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}
We investigate the thermodynamic extremality, topological charge structure, and thermodynamic curvature of non-Abelian dilaton black holes. The dilaton coupling significantly alters thermodynamic properties, enabling the verification of extremality conditions. By analyzing normalized thermodynamic vector fields, we classify topological charges through the identification of critical zero points, with their stability confirmed via winding number analysis. These topological sectors vary distinctly with the dilaton parameter. The free energy landscape is interpreted as a scalar field over parameter space, with its extrema corresponding to topological phases. This allows consistent charge assignments aligned with known solutions, such as the AdS Reissner-Nordström black hole. We further explore the topology of photon spheres and demonstrate their crucial role in black hole stability, establishing a strong link between thermodynamic topology and spacetime geometry. Finally, thermodynamic curvature is used to probe microscopic interactions, revealing predominantly attractive behavior with possible repulsive transitions near criticality. Our results indicate a rich phase structure and a non-trivial microstructure shaped by the interplay of dilaton and non-Abelian gauge fields.
{"title":"Thermodynamic signatures of non-Abelian dilaton black holes","authors":"Ankit Anand , Aditya Singh , Saeed Noori Gashti , Behnam Pourhassan","doi":"10.1016/j.dark.2025.102197","DOIUrl":"10.1016/j.dark.2025.102197","url":null,"abstract":"<div><div>We investigate the thermodynamic extremality, topological charge structure, and thermodynamic curvature of non-Abelian dilaton black holes. The dilaton coupling significantly alters thermodynamic properties, enabling the verification of extremality conditions. By analyzing normalized thermodynamic vector fields, we classify topological charges through the identification of critical zero points, with their stability confirmed via winding number analysis. These topological sectors vary distinctly with the dilaton parameter. The free energy landscape is interpreted as a scalar field over parameter space, with its extrema corresponding to topological phases. This allows consistent charge assignments aligned with known solutions, such as the AdS Reissner-Nordström black hole. We further explore the topology of photon spheres and demonstrate their crucial role in black hole stability, establishing a strong link between thermodynamic topology and spacetime geometry. Finally, thermodynamic curvature is used to probe microscopic interactions, revealing predominantly attractive behavior with possible repulsive transitions near criticality. Our results indicate a rich phase structure and a non-trivial microstructure shaped by the interplay of dilaton and non-Abelian gauge fields.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102197"},"PeriodicalIF":6.4,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926346","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 : 2025-12-20DOI: 10.1016/j.dark.2025.102196
Salvatore Capozziello , Himanshu Chaudhary , Tiberiu Harko , G. Mustafa
We investigate whether the recent DESI DR2 measurements provide or not evidences for dynamical dark energy by exploring the ω0ωaCDM model and its extensions with free ∑mν and Neff. Using a comprehensive MCMC analysis with a wide range of cosmological datasets including DESI DR2 BAO and Lyα data, CMB compressed likelihoods, BBN, cosmic chronometers, and multiple Type Ia supernova compilations we assess the statistical preference for departures from ΛCDM. We find that neither ΛCDM nor ω0ωaCDM reduces the sound horizon by the ∼ 7 % required to alleviate the Hubble tension. DESI DR2 consistently favors the quadrant and ωa < 0, indicating a preference for dynamical dark energy of the Quintom-B type at the ≲ 3σ level for most dataset combinations, rising to ∼ 3.8σ only when the DES-SN5Y supernova sample is included. Allowing ∑mν and Neff to vary does not alter this preference and yields neutrino mass constraints consistent with ∑mν ≲ 0.1 eV, with nonzero masses detected up to the level. The systematics diagnosis shows that the preference for dynamical dark energy is biased by the low-z (z < 0.1) DES-SN5Y SNe Ia sample from the CfA/CSP sample. When these low-z SNe Ia are excluded, our analysis no longer requires a dynamical dark energy and fully restores the ΛCDM model. The reconstructed evolution of ω(z) and fDE(z) shows a transition from the phantom to the quintessence regime by crossing the phantom divide. Overall, DESI DR2 provides valuable new insights into dark energy but does not yet challenge the ΛCDM paradigm. Forthcoming Stage IV surveys including DESI DR3, Rubin Observatory, Euclid, Roman Space Telescope, and the Simons Observatory will be crucial for determining whether these hints of dynamical dark energy persist or are due to statistical fluctuations or residual systematics in low-redshift supernova samples.
{"title":"Is dark energy dynamical in the DESI era? A critical review","authors":"Salvatore Capozziello , Himanshu Chaudhary , Tiberiu Harko , G. Mustafa","doi":"10.1016/j.dark.2025.102196","DOIUrl":"10.1016/j.dark.2025.102196","url":null,"abstract":"<div><div>We investigate whether the recent DESI DR2 measurements provide or not evidences for dynamical dark energy by exploring the <em>ω</em><sub>0</sub><em>ω<sub>a</sub></em>CDM model and its extensions with free ∑<em>m<sub>ν</sub></em> and <em>N</em><sub>eff</sub>. Using a comprehensive MCMC analysis with a wide range of cosmological datasets including DESI DR2 BAO and Ly<em>α</em> data, CMB compressed likelihoods, BBN, cosmic chronometers, and multiple Type Ia supernova compilations we assess the statistical preference for departures from ΛCDM. We find that neither ΛCDM nor <em>ω</em><sub>0</sub><em>ω<sub>a</sub></em>CDM reduces the sound horizon by the ∼ 7 % required to alleviate the Hubble tension. DESI DR2 consistently favors the quadrant <span><math><mrow><msub><mi>ω</mi><mn>0</mn></msub><mo>></mo><mo>−</mo><mn>1</mn></mrow></math></span> and <em>ω<sub>a</sub></em> < 0, indicating a preference for dynamical dark energy of the Quintom-B type at the ≲ 3<em>σ</em> level for most dataset combinations, rising to ∼ 3.8<em>σ</em> only when the DES-SN5Y supernova sample is included. Allowing ∑<em>m<sub>ν</sub></em> and <em>N</em><sub>eff</sub> to vary does not alter this preference and yields neutrino mass constraints consistent with ∑<em>m<sub>ν</sub></em> ≲ 0.1 eV, with nonzero masses detected up to the <span><math><mrow><mo>∼</mo><mn>1.5</mn><mi>σ</mi><mspace></mspace><mo>+</mo></mrow></math></span> level. The systematics diagnosis shows that the preference for dynamical dark energy is biased by the low-<em>z</em> (<em>z</em> < 0.1) DES-SN5Y SNe Ia sample from the CfA/CSP sample. When these low-<em>z</em> SNe Ia are excluded, our analysis no longer requires a dynamical dark energy and fully restores the ΛCDM model. The reconstructed evolution of <em>ω</em>(<em>z</em>) and <em>f</em><sub>DE</sub>(<em>z</em>) shows a transition from the phantom to the quintessence regime by crossing the phantom divide. Overall, DESI DR2 provides valuable new insights into dark energy but does not yet challenge the ΛCDM paradigm. Forthcoming Stage IV surveys including DESI DR3, Rubin Observatory, Euclid, Roman Space Telescope, and the Simons Observatory will be crucial for determining whether these hints of dynamical dark energy persist or are due to statistical fluctuations or residual systematics in low-redshift supernova samples.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102196"},"PeriodicalIF":6.4,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840512","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 : 2025-12-19DOI: 10.1016/j.dark.2025.102193
Debadri Bhattacharjee, Pradip Kumar Chattopadhyay
Present study explores the gravastars in the framework of modified theory of gravity, proposed by P. Rastall, in generalised cylindrically symmetric space-time. Following the Mazur-Mottola hypothesis, gravastars are classified as one of the most unique and exotic kind of compact objects, presenting themselves as a plausible alternative to black holes. In this study, we build upon the Mazur-Mottola framework of Gravitational Bose-Einstein Condensate (GBEC) stars by generalising it to a cylindrically symmetric spacetime within the framework of Rastall gravity to present a novel approach for estimating the mass limit of the thin shell of isotropic gravastars. We have ensured singularity-free solutions for the interior de-Sitter core, non-vanishing solutions for the thin shell and flat vacuum solution of the exterior region, within this parameter space. Under the framework of Rastall gravity and cylindrically symmetric spacetime, the Lanczos equations at the hypersurface junction undergo significant modifications, leading to a revised form of the Darmois-Israel junction conditions. These modified junction conditions are utilised to investigate the influence of the Rastall parameter (ξ) on the mass of the thin shell and key characteristics of gravastars, including the shell’s proper length, energy, and entropy. Additionally, we propose a novel method for estimating the mass of the thin shell using the concept of surface redshift (Zs). By adhering to the Buchdahl upper limit, Zs < 2 for isotropic configuration, we have determined the mass bounds of the thin shell for various characteristic radii and values of the Rastall parameter (ξ).
{"title":"Investigating the gross properties of gravastars in generalised cylindrically symmetric space-time within the framework of Rastall theory of gravity","authors":"Debadri Bhattacharjee, Pradip Kumar Chattopadhyay","doi":"10.1016/j.dark.2025.102193","DOIUrl":"10.1016/j.dark.2025.102193","url":null,"abstract":"<div><div>Present study explores the gravastars in the framework of modified theory of gravity, proposed by P. Rastall, in generalised cylindrically symmetric space-time. Following the Mazur-Mottola hypothesis, gravastars are classified as one of the most unique and exotic kind of compact objects, presenting themselves as a plausible alternative to black holes. In this study, we build upon the Mazur-Mottola framework of Gravitational Bose-Einstein Condensate (GBEC) stars by generalising it to a cylindrically symmetric spacetime within the framework of Rastall gravity to present a novel approach for estimating the mass limit of the thin shell of isotropic gravastars. We have ensured singularity-free solutions for the interior de-Sitter core, non-vanishing solutions for the thin shell and flat vacuum solution of the exterior region, within this parameter space. Under the framework of Rastall gravity and cylindrically symmetric spacetime, the Lanczos equations at the hypersurface junction <span><math><mrow><mo>(</mo><mi>r</mi><mo>=</mo><mi>R</mi><mo>)</mo></mrow></math></span> undergo significant modifications, leading to a revised form of the Darmois-Israel junction conditions. These modified junction conditions are utilised to investigate the influence of the Rastall parameter (<em>ξ</em>) on the mass of the thin shell and key characteristics of gravastars, including the shell’s proper length, energy, and entropy. Additionally, we propose a novel method for estimating the mass of the thin shell using the concept of surface redshift (<em>Z<sub>s</sub></em>). By adhering to the Buchdahl upper limit, <em>Z<sub>s</sub></em> < 2 for isotropic configuration, we have determined the mass bounds of the thin shell for various characteristic radii and values of the Rastall parameter (<em>ξ</em>).</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102193"},"PeriodicalIF":6.4,"publicationDate":"2025-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840513","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}
The detailed study of the strong gravitational lensing of a Kerr black hole within quantum Einstein gravity (QEG) is performed. We calculate the photon sphere, the deflection angle of light, and observables on the equatorial plane under the strong deflection limit in a vacuum. The presence of quantum effects reduces the radius of the photon sphere, the light deflection angle, the ratio of magnification, the positions of relativistic images, and the time delays on the same side of the lens. However, it increases the separations, and the time delays on the opposite side of the lens. By modeling M87* and Sgr A* as the Kerr black hole within QEG, we find that the time delays are more significant in M87*, while other observables are more pronounced in Sgr A*. Furthermore, we consider the influence of plasma on the gravitational lensing effect. Plasma causes an additional deflection of light, increasing the ratio of magnification, image positions and the time delays, but decreasing the separations. More importantly, we calculate the time delays under the strong deflection limit in the presence of plasma and find that they increase with higher plasma concentrations. Finally, we calculate the weak deflection angle in the weak deflection limit. Our research may be helpful for evaluating the observational imprints of quantum effects on light propagation, as well as the influence of plasma around black holes on gravitational lensing.
{"title":"Gravitational lensing in a Kerr black hole within quantum Einstein gravity","authors":"Chen-Hao Xie, Yu Zhang, Bo-Li Liu, Peng-Fei Duan, Yu-Li Lou","doi":"10.1016/j.dark.2025.102191","DOIUrl":"10.1016/j.dark.2025.102191","url":null,"abstract":"<div><div>The detailed study of the strong gravitational lensing of a Kerr black hole within quantum Einstein gravity (QEG) is performed. We calculate the photon sphere, the deflection angle of light, and observables on the equatorial plane under the strong deflection limit in a vacuum. The presence of quantum effects reduces the radius of the photon sphere, the light deflection angle, the ratio of magnification, the positions of relativistic images, and the time delays on the same side of the lens. However, it increases the separations, and the time delays on the opposite side of the lens. By modeling M87* and Sgr A* as the Kerr black hole within QEG, we find that the time delays are more significant in M87*, while other observables are more pronounced in Sgr A*. Furthermore, we consider the influence of plasma on the gravitational lensing effect. Plasma causes an additional deflection of light, increasing the ratio of magnification, image positions and the time delays, but decreasing the separations. More importantly, we calculate the time delays under the strong deflection limit in the presence of plasma and find that they increase with higher plasma concentrations. Finally, we calculate the weak deflection angle in the weak deflection limit. Our research may be helpful for evaluating the observational imprints of quantum effects on light propagation, as well as the influence of plasma around black holes on gravitational lensing.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102191"},"PeriodicalIF":6.4,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790922","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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