Pub Date : 2025-11-05DOI: 10.1016/j.dark.2025.102158
Tayyab Naseer , M. Sharif , M. Afaq , Omer A. Magzoub , M. Abdalla
In this study, we explore traversable wormhole solutions in the framework of modified torsion-based gravity theory. In this context, the anisotropic field equations corresponding to a given linear model of the modified theory are constructed using the Morris–Thorne metric. Four distinct shape functions are constructed using several equations of state with varying parameters, and their validity is verified by confirming that they satisfy fundamental physical requirements. Furthermore, we analyze the profile of null energy conditions for each model to ascertain if exotic matter is necessary to claim these solutions viable. We also explore the behavior of active gravitational mass alongside embedding diagrams, establishing that the former parameter becomes increasing as one moves away from the throat. Afterwards, we evaluate three essential aspects: volume integral quantifier, force’s equilibrium, and anisotropic pressure distribution. The results of our investigation demonstrate that all the derived wormhole solutions satisfy viability criteria within this torsion-based gravity framework, eliminating the necessity for exotic matter to hold them.
{"title":"Traversable wormholes admitting non-exotic fluid: Implications of different equations of state in torsion-based gravity","authors":"Tayyab Naseer , M. Sharif , M. Afaq , Omer A. Magzoub , M. Abdalla","doi":"10.1016/j.dark.2025.102158","DOIUrl":"10.1016/j.dark.2025.102158","url":null,"abstract":"<div><div>In this study, we explore traversable wormhole solutions in the framework of modified torsion-based gravity theory. In this context, the anisotropic field equations corresponding to a given linear model of the modified theory are constructed using the Morris–Thorne metric. Four distinct shape functions are constructed using several equations of state with varying parameters, and their validity is verified by confirming that they satisfy fundamental physical requirements. Furthermore, we analyze the profile of null energy conditions for each model to ascertain if exotic matter is necessary to claim these solutions viable. We also explore the behavior of active gravitational mass alongside embedding diagrams, establishing that the former parameter becomes increasing as one moves away from the throat. Afterwards, we evaluate three essential aspects: volume integral quantifier, force’s equilibrium, and anisotropic pressure distribution. The results of our investigation demonstrate that all the derived wormhole solutions satisfy viability criteria within this torsion-based gravity framework, eliminating the necessity for exotic matter to hold them.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"50 ","pages":"Article 102158"},"PeriodicalIF":6.4,"publicationDate":"2025-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145465749","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 : 2025-11-04DOI: 10.1016/j.dark.2025.102140
Asma Alaei, Vahid Kamali, Zahra Shamloui
Our present research delves into the intricacies of the intermediate-warm little inflation (WLI) model. Our focus centers on examining a dissipation parameter characterized by the expression , where the dissipation coefficient is directly proportional to the temperature, denoted by . Notably, our calculations are exclusively conducted within the high dissipative regime of intermediate warm inflation, allowing for a more detailed exploration of this specific parameter range. Our investigative approach involves constraining our model by utilizing observational data from Planck 2018. Our results highlight warm little inflation as a compelling alternative to standard cold inflation, and we outline future directions where full statistical analyses can further clarify its relation to CDM and other cosmological models.
{"title":"Warm little inflation in high dissipative regime in the light of Planck 2018","authors":"Asma Alaei, Vahid Kamali, Zahra Shamloui","doi":"10.1016/j.dark.2025.102140","DOIUrl":"10.1016/j.dark.2025.102140","url":null,"abstract":"<div><div>Our present research delves into the intricacies of the intermediate-warm little inflation (WLI) model. Our focus centers on examining a dissipation parameter characterized by the expression <span><math><mrow><mi>Υ</mi><mo>=</mo><msub><mrow><mi>C</mi></mrow><mrow><mi>T</mi></mrow></msub><mi>T</mi></mrow></math></span>, where the dissipation coefficient is directly proportional to the temperature, denoted by <span><math><mi>T</mi></math></span>. Notably, our calculations are exclusively conducted within the high dissipative regime of intermediate warm inflation, allowing for a more detailed exploration of this specific parameter range. Our investigative approach involves constraining our model by utilizing observational data from Planck 2018. Our results highlight warm little inflation as a compelling alternative to standard cold inflation, and we outline future directions where full statistical analyses can further clarify its relation to <span><math><mi>Λ</mi></math></span>CDM and other cosmological models.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"50 ","pages":"Article 102140"},"PeriodicalIF":6.4,"publicationDate":"2025-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145465751","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 : 2025-11-01DOI: 10.1016/j.dark.2025.102156
Gonzalo Herrera
NGC 1068 is the brightest extragalactic source in high-energy neutrinos as seen by IceCube, yet the accompanying gamma-ray flux is orders of magnitude weaker. It has been argued that this indicates that the bulk of neutrinos and gamma rays are emitted in the innermost vicinity of the central supermassive black hole, which is transparent to neutrinos, but opaque to gamma rays. Even in such extreme scenarios for the acceleration of cosmic rays, astrophysical models typically overestimate the low-energy gamma-ray flux and/or require some fine-tuning in the physical parameters. Here we suggest instead that the dark matter surrounding the supermassive black hole may absorb the gamma rays, inducing the observed deficit. We show that for a dark matter–photon scattering cross section in the range cm/GeV, Fermi-LAT measurements can be well reconciled with IceCube data. We also present some simple particle physics examples that achieve the correct spectral energy dependence while respecting complementary constraints.
NGC 1068是冰立方观测到的最亮的星系外高能中微子源，但伴随的伽马射线通量要弱几个数量级。有人认为，这表明大部分中微子和伽马射线是在中央超大质量黑洞的最内层附近发射的，那里对中微子是透明的，但对伽马射线是不透明的。即使在宇宙射线加速的这种极端情况下，天体物理模型通常也会高估低能伽马射线通量和/或需要对物理参数进行一些微调。在这里，我们认为围绕在超大质量黑洞周围的暗物质可能会吸收伽马射线，从而导致观测到的缺陷。研究结果表明，在σDM−γ/mDM≃10−28−10−30 cm2/GeV范围内，Fermi-LAT测量值与冰立方数据可以很好地协调。我们还提出了一些简单的粒子物理例子，在尊重互补约束的同时实现了正确的光谱能量依赖。
{"title":"Plausible indication of gamma-ray absorption by dark matter in NGC 1068","authors":"Gonzalo Herrera","doi":"10.1016/j.dark.2025.102156","DOIUrl":"10.1016/j.dark.2025.102156","url":null,"abstract":"<div><div>NGC 1068 is the brightest extragalactic source in high-energy neutrinos as seen by IceCube, yet the accompanying gamma-ray flux is orders of magnitude weaker. It has been argued that this indicates that the bulk of neutrinos and gamma rays are emitted in the innermost vicinity of the central supermassive black hole, which is transparent to neutrinos, but opaque to gamma rays. Even in such extreme scenarios for the acceleration of cosmic rays, astrophysical models typically overestimate the low-energy gamma-ray flux and/or require some fine-tuning in the physical parameters. Here we suggest instead that the dark matter surrounding the supermassive black hole may absorb the gamma rays, inducing the observed deficit. We show that for a dark matter–photon scattering cross section in the range <span><math><mrow><msub><mrow><mi>σ</mi></mrow><mrow><mi>DM−γ</mi></mrow></msub><mo>/</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>DM</mi></mrow></msub><mo>≃</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>28</mn></mrow></msup><mo>−</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>30</mn></mrow></msup></mrow></math></span> cm<span><math><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup></math></span>/GeV, Fermi-LAT measurements can be well reconciled with IceCube data. We also present some simple particle physics examples that achieve the correct spectral energy dependence while respecting complementary constraints.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"50 ","pages":"Article 102156"},"PeriodicalIF":6.4,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145465210","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 : 2025-10-31DOI: 10.1016/j.dark.2025.102153
Allan R.P Moreira , Faizuddin Ahmed , Abdelmalek Bouzenada
In this work, we investigate a novel class of static, spherically symmetric black hole (BH) solutions that incorporate several fundamental physical features: electric charge, Lorentz symmetry violation, a surrounding cloud of strings, and an external quintessence-like field. The proposed metric generalizes earlier configurations by including a Lorentz-violating deformation inspired by the Kalb-Ramond field vacuum expectation value. We analyze the dynamics of null geodesics and characterize the effective potential, photon trajectories, and the conditions for circular orbits, photon sphere, and shadow formation. We further study the scalar perturbations by solving the Klein–Gordon equation in the BH background, revealing how various geometric and physical parameters influence the scalar potential. Additionally, we examine the thermodynamic behavior of the solution, computing key quantities such as the mass, Hawking temperature, heat capacity, and Gibbs free energy.
{"title":"Geometric properties, scalar perturbations and thermodynamics of a charged Lorentz-violating hairy black hole with quintessence-like field","authors":"Allan R.P Moreira , Faizuddin Ahmed , Abdelmalek Bouzenada","doi":"10.1016/j.dark.2025.102153","DOIUrl":"10.1016/j.dark.2025.102153","url":null,"abstract":"<div><div>In this work, we investigate a novel class of static, spherically symmetric black hole (BH) solutions that incorporate several fundamental physical features: electric charge, Lorentz symmetry violation, a surrounding cloud of strings, and an external quintessence-like field. The proposed metric generalizes earlier configurations by including a Lorentz-violating deformation inspired by the Kalb-Ramond field vacuum expectation value. We analyze the dynamics of null geodesics and characterize the effective potential, photon trajectories, and the conditions for circular orbits, photon sphere, and shadow formation. We further study the scalar perturbations by solving the Klein–Gordon equation in the BH background, revealing how various geometric and physical parameters influence the scalar potential. Additionally, we examine the thermodynamic behavior of the solution, computing key quantities such as the mass, Hawking temperature, heat capacity, and Gibbs free energy.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"50 ","pages":"Article 102153"},"PeriodicalIF":6.4,"publicationDate":"2025-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145465214","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 : 2025-10-31DOI: 10.1016/j.dark.2025.102155
Fabiola Arevalo , Luis Firinguetti , Marcos Peña
The assumption of Gaussian distribution in Type Ia supernova data underlies most cosmological parameter estimates and led to the discovery of late acceleration. In this work, we assess the validity of this assumption using the Pantheon+ dataset and analyze its impact on parameter estimation for dark energy cosmological models.
We perform a comprehensive statistical, analysis including the Lilliefors and Jarque–Bera tests, to assess the normality of both the data and model residuals. We find that the Gaussianity assumption is untenable and that the redshift distribution is more accurately described by a t-distribution, as indicated by the Kolmogorov Smirnov test.
These statistical findings are explored within the framework of a nonlinear cosmological interaction for the dark sector. Free parameters are estimated using multiple methods, and bootstrap confidence intervals are constructed for them. Our results suggest that standard Gaussian assumptions may underestimate uncertainties in cosmological inference, and we advocate for incorporating more flexible statistical models in future analyses.
{"title":"On the Gaussian assumption in the estimation of parameters for dark energy models","authors":"Fabiola Arevalo , Luis Firinguetti , Marcos Peña","doi":"10.1016/j.dark.2025.102155","DOIUrl":"10.1016/j.dark.2025.102155","url":null,"abstract":"<div><div>The assumption of Gaussian distribution in Type Ia supernova data underlies most cosmological parameter estimates and led to the discovery of late acceleration. In this work, we assess the validity of this assumption using the Pantheon+ dataset and analyze its impact on parameter estimation for dark energy cosmological models.</div><div>We perform a comprehensive statistical, analysis including the Lilliefors and Jarque–Bera tests, to assess the normality of both the data and model residuals. We find that the Gaussianity assumption is untenable and that the redshift distribution is more accurately described by a t-distribution, as indicated by the Kolmogorov Smirnov test.</div><div>These statistical findings are explored within the framework of a nonlinear cosmological interaction for the dark sector. Free parameters are estimated using multiple methods, and bootstrap confidence intervals are constructed for them. Our results suggest that standard Gaussian assumptions may underestimate uncertainties in cosmological inference, and we advocate for incorporating more flexible statistical models in future analyses.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"50 ","pages":"Article 102155"},"PeriodicalIF":6.4,"publicationDate":"2025-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145465753","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 : 2025-10-31DOI: 10.1016/j.dark.2025.102151
Luis M. Nieto , Farokhnaz Hosseinifar , Kuantay Boshkayev , Soroush Zare , Hassan Hassanabadi
In this work, we analyze some characteristics and gravitational signatures of the Schwarzschild black hole immersed in a Hernquist dark matter halo. We determine the black hole’s remnant radius and mass, which provide useful residual information at the end of its evaporation, and we then explore the luminosity of the accretion disk for the model under study. In this way, we determine the key orbital parameters of the test particles within the accretion disk, such as angular velocity, angular momentum, energy, and the radius of the innermost stable circular orbit, based on the dark matter model parameters. We also numerically estimate the accretion disk’s efficiency in converting matter into radiation. We also demonstrate that dark matter, which significantly alters the geometry surrounding a Schwarzschild black hole, influences the accretion disk’s radiative flux, temperature, differential luminosity, and spectral luminosity. The stability of a black hole spacetime is determined in the eikonal regime. The Lyapunov exponent is also analyzed to quantify the stability of the particle regime and to demonstrate the infall into or escape from the black hole to infinity, as well as the quasi-normal modes. Finally, some properties of black holes are studied from a topological perspective.
{"title":"Accretion disk luminosity and topological characteristics for a Schwarzschild black hole surrounded by a Hernquist dark matter halo","authors":"Luis M. Nieto , Farokhnaz Hosseinifar , Kuantay Boshkayev , Soroush Zare , Hassan Hassanabadi","doi":"10.1016/j.dark.2025.102151","DOIUrl":"10.1016/j.dark.2025.102151","url":null,"abstract":"<div><div>In this work, we analyze some characteristics and gravitational signatures of the Schwarzschild black hole immersed in a Hernquist dark matter halo. We determine the black hole’s remnant radius and mass, which provide useful residual information at the end of its evaporation, and we then explore the luminosity of the accretion disk for the model under study. In this way, we determine the key orbital parameters of the test particles within the accretion disk, such as angular velocity, angular momentum, energy, and the radius of the innermost stable circular orbit, based on the dark matter model parameters. We also numerically estimate the accretion disk’s efficiency in converting matter into radiation. We also demonstrate that dark matter, which significantly alters the geometry surrounding a Schwarzschild black hole, influences the accretion disk’s radiative flux, temperature, differential luminosity, and spectral luminosity. The stability of a black hole spacetime is determined in the eikonal regime. The Lyapunov exponent is also analyzed to quantify the stability of the particle regime and to demonstrate the infall into or escape from the black hole to infinity, as well as the quasi-normal modes. Finally, some properties of black holes are studied from a topological perspective.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"50 ","pages":"Article 102151"},"PeriodicalIF":6.4,"publicationDate":"2025-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145415954","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 : 2025-10-30DOI: 10.1016/j.dark.2025.102148
Yuxuan Kang, Mingzhe Li, Yeheng Tong
Recently the modified teleparallel gravity models attracted a lot of interests. In this paper we consider more extensions to the New General Relativity (NGR) model with parity violations. This extended NGR model differs from the normal NGR model by the inclusion of additional parity-odd term that is quadratic in the torsion tensor. By investigating its cosmological perturbations of this model, we find that this model can avoid ghost instabilities in certain regions of the parameter space, where the coefficient of the parity-odd term does not vanish.
{"title":"Cosmological perturbations of extended NGR model with parity violation","authors":"Yuxuan Kang, Mingzhe Li, Yeheng Tong","doi":"10.1016/j.dark.2025.102148","DOIUrl":"10.1016/j.dark.2025.102148","url":null,"abstract":"<div><div>Recently the modified teleparallel gravity models attracted a lot of interests. In this paper we consider more extensions to the New General Relativity (NGR) model with parity violations. This extended NGR model differs from the normal NGR model by the inclusion of additional parity-odd term that is quadratic in the torsion tensor. By investigating its cosmological perturbations of this model, we find that this model can avoid ghost instabilities in certain regions of the parameter space, where the coefficient of the parity-odd term does not vanish.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"50 ","pages":"Article 102148"},"PeriodicalIF":6.4,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145415951","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 : 2025-10-29DOI: 10.1016/j.dark.2025.102154
Giacomo D’Amico , Michele Doro , Michela De Caria
We present a novel method for both forecasting and recasting upper limits (ULs) on dark matter (DM) annihilation cross sections, , or decay lifetime . The forecasting method relies solely on the instrument response functions (IRFs) to predict ULs for a given observational setup, without the need for full analysis pipelines. The recasting procedure uses published ULs to reinterpret constraints for alternative DM models or channels. We demonstrate its utility across a range of canonical annihilation channels, including , , , and , and apply it to several major gamma-ray experiments, including MAGIC, Fermi-LAT, and CTAO. Notably, we develop a recasting approach that remains effective even when the IRF is unavailable by extracting generalized IRF-dependent coefficients from benchmark channels. We apply this method to reinterpret ULs derived from standard spectra (e.g., PPPC4DMID) in terms of more recent DM scenarios, including a Higgsino-like model with mixed final states and spectra generated with the CosmiXs model. Extensive Monte Carlo simulations and direct comparison with published results confirm the robustness and accuracy of our method, with discrepancies remaining within statistical uncertainties. The algorithm is generally applicable to any scenario where the expected signal model is parametric, offering a powerful tool for reinterpreting existing gamma-ray limits and efficiently exploring the DM parameter space in current and future indirect detection experiments.
{"title":"Recasting and forecasting dark matter limits without raw data: A generalized algorithm for gamma-ray telescopes","authors":"Giacomo D’Amico , Michele Doro , Michela De Caria","doi":"10.1016/j.dark.2025.102154","DOIUrl":"10.1016/j.dark.2025.102154","url":null,"abstract":"<div><div>We present a novel method for both forecasting and recasting upper limits (ULs) on dark matter (DM) annihilation cross sections, <span><math><msup><mrow><mfenced><mrow><mi>σ</mi><mi>v</mi></mrow></mfenced></mrow><mrow><mi>U</mi><mi>L</mi></mrow></msup></math></span>, or decay lifetime <span><math><msup><mrow><mi>τ</mi></mrow><mrow><mi>L</mi><mi>L</mi></mrow></msup></math></span> . The forecasting method relies solely on the instrument response functions (IRFs) to predict ULs for a given observational setup, without the need for full analysis pipelines. The recasting procedure uses published ULs to reinterpret constraints for alternative DM models or channels. We demonstrate its utility across a range of canonical annihilation channels, including <span><math><mrow><mi>b</mi><mover><mrow><mi>b</mi></mrow><mrow><mo>̄</mo></mrow></mover></mrow></math></span>, <span><math><mrow><msup><mrow><mi>W</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>W</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math></span>, <span><math><mrow><msup><mrow><mi>τ</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>τ</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math></span>, and <span><math><mrow><msup><mrow><mi>μ</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math></span>, and apply it to several major gamma-ray experiments, including MAGIC, <em>Fermi</em>-LAT, and CTAO. Notably, we develop a recasting approach that remains effective even when the IRF is unavailable by extracting generalized IRF-dependent coefficients from benchmark channels. We apply this method to reinterpret ULs derived from standard spectra (e.g., PPPC4DMID) in terms of more recent DM scenarios, including a Higgsino-like model with mixed final states and spectra generated with the CosmiXs model. Extensive Monte Carlo simulations and direct comparison with published results confirm the robustness and accuracy of our method, with discrepancies remaining within statistical uncertainties. The algorithm is generally applicable to any scenario where the expected signal model is parametric, offering a powerful tool for reinterpreting existing gamma-ray limits and efficiently exploring the DM parameter space in current and future indirect detection experiments.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"50 ","pages":"Article 102154"},"PeriodicalIF":6.4,"publicationDate":"2025-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145415955","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 weak gravitational lensing around black holes surrounded by perfect fluid dark matter (PFDM) in the framework of Kalb–Ramond (KR) gravity, incorporating the influence of plasma environments. Starting from the static, spherically symmetric KR–PFDM solution, we derive the null geodesic equations and formulate lensing relations in the weak deflection limit. Both homogeneous and singular isothermal sphere (SIS) plasma distributions are analyzed to assess their role in modifying the trajectory of photons due to the shift of light rays from null-geodesics. Our results demonstrate that PFDM tends to enhance the bending angle, increase the angular size of Einstein rings, and amplify image magnification, thereby strengthening the observable lensing signal. In contrast, the KR parameter suppresses these effects, reflecting the role of Lorentz-violating contributions in reducing the deflection and ring size. Plasma effects are shown to be significant and highly dependent on the adopted distribution model: uniform plasma produces the strongest deviations, whereas the SIS profile leads to more moderate corrections. The interplay between PFDM, KR gravity, and plasma introduces a degree of degeneracy, as both PFDM and plasma contribute similarly to enhancing lensing, while KR corrections diminish the overall signal. This indicates that neglecting plasma may bias interpretations of astrophysical data. By applying the theoretical framework to galactic-scale strong lensing systems, we obtain preliminary bounds on the KR and PFDM parameters. The findings highlight that weak lensing observations, particularly Einstein rings and magnification measurements, can provide a valuable means to test modified gravity theories and constrain dark matter models beyond general relativity.
{"title":"Gravitational lensing by black holes surrounded by PFDM in Kalb-Ramond gravity in plasma medium","authors":"Bekzod Rahmatov , Islom Egamberdiev , Sardor Murodov , Javlon Rayimbaev , Inomjon Ibragimov , Erkaboy Davletov , Sherzod Djumanov","doi":"10.1016/j.dark.2025.102152","DOIUrl":"10.1016/j.dark.2025.102152","url":null,"abstract":"<div><div>We investigate weak gravitational lensing around black holes surrounded by perfect fluid dark matter (PFDM) in the framework of Kalb–Ramond (KR) gravity, incorporating the influence of plasma environments. Starting from the static, spherically symmetric KR–PFDM solution, we derive the null geodesic equations and formulate lensing relations in the weak deflection limit. Both homogeneous and singular isothermal sphere (SIS) plasma distributions are analyzed to assess their role in modifying the trajectory of photons due to the shift of light rays from null-geodesics. Our results demonstrate that PFDM tends to enhance the bending angle, increase the angular size of Einstein rings, and amplify image magnification, thereby strengthening the observable lensing signal. In contrast, the KR parameter suppresses these effects, reflecting the role of Lorentz-violating contributions in reducing the deflection and ring size. Plasma effects are shown to be significant and highly dependent on the adopted distribution model: uniform plasma produces the strongest deviations, whereas the SIS profile leads to more moderate corrections. The interplay between PFDM, KR gravity, and plasma introduces a degree of degeneracy, as both PFDM and plasma contribute similarly to enhancing lensing, while KR corrections diminish the overall signal. This indicates that neglecting plasma may bias interpretations of astrophysical data. By applying the theoretical framework to galactic-scale strong lensing systems, we obtain preliminary bounds on the KR and PFDM parameters. The findings highlight that weak lensing observations, particularly Einstein rings and magnification measurements, can provide a valuable means to test modified gravity theories and constrain dark matter models beyond general relativity.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"50 ","pages":"Article 102152"},"PeriodicalIF":6.4,"publicationDate":"2025-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145415950","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 : 2025-10-27DOI: 10.1016/j.dark.2025.102150
Saeed Noori Gashti , Yassine Sekhmani , Mohammad Ali S. Afshar , Mohammad Reza Alipour , Abdul Jawad , İzzet Sakallı , B. Pourhassan , Sanjar Shaymatov , J. Sadeghi , J. Rayimbaev
This work examines the thermodynamic topology of Frolov–AdS black holes with a surrounding string fluid, highlighting the role of topological charges in determining stability. By analyzing vector fields constructed from the free energy, we identify zero points corresponding to distinct topological charges, which vary with entropy-related parameters. Our findings demonstrate that the system exhibits topological charges of 1, 0, or 1, serving as a robust criterion for black hole stability classification. Furthermore, we examine photon sphere (PS) configurations, revealing that their associated (PS = 1) reflect underlying geometric and thermodynamic structures of black hole. This study establishes connections between winding numbers and black hole phase transitions. Comparative analyses with classical black holes support the universality of the topological framework. Complementarily, the analysis of quasi-periodic oscillations elucidates the intricate interplay of electric charge, spin, cosmological constant, and string-fluid background on epicyclic and precessional motions around charged AdS black holes. Electric charge diminishes gravitational binding, shifting characteristic frequencies outward, while spin-induced frame dragging enhances orbital stability and periapsis advance. The AdS curvature associated with a negative cosmological constant universally suppresses oscillatory frequencies and modifies periastron dynamics, whereas the string-fluid parameter governs asymptotic decay rates and far-field behavior. These combined effects yield comprehensive predictions for quasinormal mode spectra and potential astrophysical signatures.
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