Physics of the Dark Universe最新文献

{"title":"Probing quantum gravity in stellar spacetimes: Phenomenological insights","authors":"Reggie C. Pantig ,&nbsp;Ali Övgün ,&nbsp;Gaetano Lambiase","doi":"10.1016/j.dark.2026.102243","DOIUrl":"10.1016/j.dark.2026.102243","url":null,"abstract":"<div><div>We explore the weak-field phenomenology of a compact star spacetime modified by quantum gravitational corrections derived from the effective field theoretical (EFT) approach by Calmet et al. [1]. These corrections, encoded in non-local curvature-squared terms, distinguish matter-supported geometries from vacuum solutions by contributing nontrivial modifications at order <em>O</em>(<em>G</em>²). Using the corrected metric, we analytically derive expressions for the deflection of light and time-like particles via the Gauss-Bonnet theorem. We further compute the perihelion advance of Mercury, Shapiro time delay, and gravitational redshift within this framework. Each classical observable acquires quantum corrections that, though exceedingly small (on the order of <span><math><msup><mn>10</mn><mrow><mo>−</mo><mn>9</mn></mrow></msup></math></span> arcsecond per century for perihelion precession and <span><math><msup><mn>10</mn><mrow><mo>−</mo><mn>18</mn></mrow></msup></math></span> arcsecond for light deflection) represent potential imprints of quantum gravity. The Shapiro delay and redshift likewise exhibit finite, source-dependent deviations from their general relativistic predictions due to the modified temporal metric component. While current observational capabilities remain insufficient to detect these minute effects, the analysis demonstrates that quantum gravitational signatures are embedded even in weak-field observables. Last, we study massless scalar perturbations in static, spherically symmetric spacetimes by analyzing their quasinormal modes (QNMs) and greybody factors using the WKB method and Pade resummation. Our findings demonstrate that increasing the coupling parameter enhances spacetime stability and significantly influences emission spectra through frequency-dependent transparency. Moreover, the results underscore that quantum-corrected star metrics yield phenomenological distinctions from classical black holes, particularly near the Planck scale, where vacuum solutions lose validity.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"52 ","pages":"Article 102243"},"PeriodicalIF":6.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146191406","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}

{"title":"Letelier black hole immersed in an electromagnetic universe","authors":"Ahmad Al-Badawi ,&nbsp;Faizuddin Ahmed ,&nbsp;İzzet Sakallı","doi":"10.1016/j.dark.2026.102245","DOIUrl":"10.1016/j.dark.2026.102245","url":null,"abstract":"<div><div>We investigate a static, spherically symmetric black hole solution surrounded by a cloud of strings and immersed in an electromagnetic universe. By deriving the event horizon from the lapse function, we demonstrate that both the string cloud parameter and the electromagnetic background parameter significantly modify the horizon radius compared to the Schwarzschild case. Consequently, thermodynamic quantities-including the Hawking temperature, Bekenstein-Hawking entropy, and heat capacity-become explicit functions of these additional parameters, with the heat capacity exhibiting divergences that signal phase transitions. We analyze the motion of massive test particles in this spacetime, deriving the effective potential and calculating the innermost stable circular orbit radius, which governs the inner edge of accretion disks and influences orbital stability. Scalar perturbations are examined through the associated effective potential, and quasinormal mode frequencies are computed using the sixth-order WKB approximation; the negative imaginary parts confirm the stability of the black hole under such perturbations. We also study the photon sphere structure, black hole shadow radius, and photon trajectories, showing how the interplay between string clouds and the electromagnetic background shapes the optical properties of this spacetime. Finally, we investigate weak gravitational lensing phenomena by deriving the deflection angle for both massive particles and photons using the Gauss-Bonnet theorem applied to the optical geometry. The results exhibit notable deviations from the Schwarzschild geometry, with the string cloud enhancing the deflection through a <span><math><msup><mrow><mo>(</mo><mn>1</mn><mo>−</mo><mi>α</mi><mo>)</mo></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span> factor while the electromagnetic parameter introduces competing corrections at second order.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"52 ","pages":"Article 102245"},"PeriodicalIF":6.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146192137","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}

{"title":"Images of black holes in the center of Moore dark matter halo","authors":"Yang Cao ,&nbsp;Benrong Mu ,&nbsp;Jun Tao ,&nbsp;Xuetao Yang","doi":"10.1016/j.dark.2026.102235","DOIUrl":"10.1016/j.dark.2026.102235","url":null,"abstract":"<div><div>This paper explores the observational appearance of black holes surrounded by the Moore dark matter halo, utilizing the celestial sphere and accretion disks as light sources. We can obtain the equations for circular orbits by employing the weak-field expansion approximation of the black hole metric within a Moore dark matter halo. The study explores the variations in the visual characteristics of black holes when observed from different observational points within the celestial sphere model. For both rotating and stationary accretion disks, we investigated the effects of the radius and characteristic density of the Moore dark matter halo on observable phenomena, while examining the angular dependence in both types of disks. Our investigation shows that in rotating accretion disks, the blue shift effect of photons becomes more prominent as the observation angle increases.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"52 ","pages":"Article 102235"},"PeriodicalIF":6.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146116670","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}

{"title":"Casimir effect and gravitational balance: A search for stable configurations","authors":"Leonardo Bellinato Giacomelli ,&nbsp;Benjamin Koch ,&nbsp;Iva Lovrekovic ,&nbsp;Ángel Rincón","doi":"10.1016/j.dark.2026.102242","DOIUrl":"10.1016/j.dark.2026.102242","url":null,"abstract":"<div><div>In this study, we examine the role of the repulsive Casimir force in counteracting the gravitational contraction of a thin, spherically symmetric shell. Our primary focus is to explore the possibility of achieving a stable, balanced configuration within the theoretically reliable weak-field limit. To this end, we consider various types of Casimir forces, including those generated by massless scalar fields, massive scalar fields, electromagnetic fields, and temperature-dependent fields.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"52 ","pages":"Article 102242"},"PeriodicalIF":6.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146191405","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}

{"title":"Observationally guided redshift function: energy conditions, stability and dark matter implications","authors":"Farook Rahaman ,&nbsp;Aritra Sanyal ,&nbsp;Bikramarka S. Choudhury ,&nbsp;Saibal Ray","doi":"10.1016/j.dark.2026.102212","DOIUrl":"10.1016/j.dark.2026.102212","url":null,"abstract":"<div><div>In this article, we present a detailed analytical as well as statistical study of a redshift function derived from a high-degree polynomial fit to the azimuthal velocity profile <em>v_ϕ</em>(<em>r</em>) of a spherically symmetric spacetime. The analysis is based on the unified Milky Way rotation curve compiled, which provides an observationally consistent description of the Galactic rotational dynamics over a wide radial range. Using a seventh-degree polynomial representation, we model the Milky Way azimuthal velocity profile and validate the fit through rigorous statistical tools including the Kolmogorov–Smirnov test, chi-square test, and the coefficient of determination (<em>R</em>²), achieving an <em>R</em>² value of 0.990. From this fit, we construct the redshift function <em>f</em>(<em>r</em>) by integrating <span><math><mrow><msup><mi>f</mi><mo>′</mo></msup><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow><mo>=</mo><msubsup><mi>v</mi><mi>ϕ</mi><mn>2</mn></msubsup><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow><mo>/</mo><mi>r</mi></mrow></math></span>, which is then used to define the spacetime metric. Employing Einstein’s field equations with an anisotropic fluid source having vanishing radial pressure, we derive explicit forms for the mass function <em>m</em>(<em>r</em>), energy density <em>ρ</em>(<em>r</em>), and tangential pressure <em>p</em>(<em>r</em>). We analyze the equation of state parameter (EOS) <span><math><mrow><mi>ω</mi><mo>(</mo><mi>r</mi><mo>)</mo><mo>=</mo><mi>p</mi><mo>(</mo><mi>r</mi><mo>)</mo><mo>/</mo><mi>ρ</mi><mo>(</mo><mi>r</mi><mo>)</mo></mrow></math></span>, the causality condition via the sound speed <span><math><mrow><msubsup><mi>v</mi><mi>s</mi><mn>2</mn></msubsup><mo>=</mo><mi>d</mi><mi>p</mi><mo>/</mo><mi>d</mi><mi>ρ</mi></mrow></math></span>, and confirm the physical viability of the solution. The stability of circular orbits is assessed through the effective potential approach, and the attractive nature of gravity is corroborated using both geodesic deviation and gravitational energy arguments. Finally, observational constraints are imposed by calculating the approximate gravitational redshift in the weak-field limit. This comprehensive study establishes a consistent and physically viable spacetime geometry guided by a statistically robust Milky Way azimuthal velocity profile.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"52 ","pages":"Article 102212"},"PeriodicalIF":6.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146191460","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}

{"title":"WIMP freeze-out dynamics under Tsallis statistics","authors":"Matias P. Gonzalez,&nbsp;Roberto A. Lineros","doi":"10.1016/j.dark.2026.102241","DOIUrl":"10.1016/j.dark.2026.102241","url":null,"abstract":"<div><div>We generalize thermal WIMP (Weakly Interacting Massive Particle) freeze-out within Tsallis nonextensive statistics. Using Curado–Tsallis <em>q</em>-distributions <em>f_q</em>(<em>E</em>; <em>μ, T</em>) we compute <em>q</em>-deformed number and energy densities, pressure, entropy density and Hubble rate, {<em>n_q, ρ_q, P_q, s_q, H_q</em>}. The Boltzmann equation is generalized accordingly to obtain the comoving abundance <em>Y</em>_{<em>χ,q</em>}(<em>x</em>) and relic density Ω_{<em>χ,q</em>}<em>h</em>² for a dark-matter candidate <em>χ</em> in a model-independent setup. The thermally averaged cross section is expanded as <span><math><mrow><msub><mrow><mo>〈</mo><mi>σ</mi><mi>v</mi><mo>〉</mo></mrow><mi>q</mi></msub><mo>≈</mo><mi>a</mi><mo>+</mo><mi>b</mi><mspace></mspace><msub><mrow><mo>〈</mo><msubsup><mi>v</mi><mrow><mrow><mi>r</mi></mrow><mi>e</mi><mi>l</mi></mrow><mn>2</mn></msubsup><mo>〉</mo></mrow><mi>q</mi></msub></mrow></math></span> up to <em>p</em>-wave. The freeze-out parameter <em>x_f</em>(<em>q</em>) is determined from Γ_{ann,<em>q</em>}(<em>T_f</em>) ≃ <em>H_q</em>(<em>T_f</em>) using a <em>q</em>-logarithmic inversion, with the expansion rate modified through ultra-relativistic rescalings <em>R_ρ</em>(<em>q</em>) of the effective relativistic degrees of freedom <em>g</em>_* and <em>g</em>_*<em>s</em>. We show that <em>x_f</em> increases with <em>q</em> and that QCD-threshold features propagate into <em>Y</em>_{<em>χ,q</em>}(<em>x</em>) and Ω_{<em>χ,q</em>}<em>h</em>². We then perform two <em>q</em>-grid scans: fixing ⟨<em>σv</em>⟩_<em>q</em> while varying the dark-matter mass <em>m_χ</em>, and fixing <em>m_χ</em> while varying the <em>s</em>-wave coefficient <em>a</em>. For an <em>s</em>-wave dominated scenario we construct <em>χ</em>² profiles in these planes by comparing Ω_{<em>χ,q</em>}<em>h</em>² with the Planck benchmark <span><math><mrow><msub><mstyle><mi>Ω</mi></mstyle><mi>c</mi></msub><msup><mi>h</mi><mn>2</mn></msup><mo>=</mo><mn>0.120</mn><mo>±</mo><mn>0.001</mn></mrow></math></span>. In both cases we find a clear degeneracy in the preferred nonextensive parameter <em>q</em>_best along valleys in parameter space. However, fixed-mass scans (varying ⟨<em>σv</em>⟩_<em>q</em>) are significantly more constraining than fixed-cross-section scans, reflecting that Ω_{<em>χ,q</em>}<em>h</em>² is mainly controlled by ⟨<em>σv</em>⟩_<em>q</em>, so that for realistic cross sections the best-fit <em>q</em>_best remains close to the extensive limit <em>q</em> → 1.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"52 ","pages":"Article 102241"},"PeriodicalIF":6.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146116716","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}

{"title":"Chaos bounds or violation? Fate of charged AdS black holes","authors":"Maryam Shahid ,&nbsp;Abdul Jawad ,&nbsp;Usman Zafar ,&nbsp;Sanjar Shaymatov ,&nbsp;Shamaila Rani ,&nbsp;Nurgissa Myrzakulov","doi":"10.1016/j.dark.2026.102239","DOIUrl":"10.1016/j.dark.2026.102239","url":null,"abstract":"<div><div>The study of chaos bounds offers significant insights regarding the thermalization process, quantum information flow, and the stability of the gravitational system. In this work, we examine the Lyapunov exponent and potential chaos bound violations in Yang-Mills AdS black holes, AdS black holes with massive gravity, and ModMax AdS black holes to uncover the association between quantum information, thermalization, and gravitational stability. We explicitly compute the Lyapunov exponent using the Jacobian matrix method, which allows us to investigate the roles of angular momentum, electric charge, and the normalization constant in determining orbital equilibrium and its stability. Our analysis reveals that chaos-bound violations are highly spacetime dependent. In the case of ModMax AdS black holes, the chaos bound remains valid throughout the full parameter ranges, highlighting the stabilizing influence of nonlinear electrodynamics. On the other hand, in AdS black holes arising in massive gravity and Yang-Mills theories, chaos-bound violation occurs primarily near the horizon within specific parameter domains, while at finite distances the bound remains satisfied. Additionally, our analysis shows a dual influence of angular momentum. These results demonstrate the model dependence of chaos bounds, with their preservation and violations serving as probes of the black holes’ microstructure and stability.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"52 ","pages":"Article 102239"},"PeriodicalIF":6.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146191404","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}

{"title":"Data-driven modeling of rotation curves with artificial neural networks","authors":"Gabriela Garcia-Arroyo ,&nbsp;Isidro Gómez-Vargas ,&nbsp;J. Alberto Vázquez","doi":"10.1016/j.dark.2026.102240","DOIUrl":"10.1016/j.dark.2026.102240","url":null,"abstract":"<div><div>Galactic rotation curves are crucial for understanding the distribution of mass in galaxies. Despite advances in precision observations, there are discrepancies between the inferred mass from luminosity and the observed rotational velocities, often attributed to dark matter. While traditional parametric models provide valuable insights, they struggle with complex galactic features like prominent bulges and non-circular motions. In this study, we apply artificial neural networks to generate robust, data-driven models, tailored to each galaxy, for the rotation curves of spiral galaxies using high-quality observational data. Our approach demonstrates that neural networks can effectively capture the intricate structure of rotation curves without relying on predefined astrophysical assumptions. By comparing the data-based models with the Navarro-Frenk-White model under two different assumptions for the stellar component, we classify galaxies based on the model that best fits their rotation curves, offering insights into the limitations and strengths of both theoretical and data-based methods. This work highlights the potential of machine learning techniques in identifying galaxies whose dynamics are not well captured by standard theoretical models, pointing to the need for more refined physical descriptions.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"52 ","pages":"Article 102240"},"PeriodicalIF":6.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146116671","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}

{"title":"Probing the perturbative reheating history of decaying oscillatory inflation with ACT constraints","authors":"Li-Yang Chen ,&nbsp;Rongrong Zhai ,&nbsp;Feng-Yi Zhang","doi":"10.1016/j.dark.2026.102247","DOIUrl":"10.1016/j.dark.2026.102247","url":null,"abstract":"<div><div>Precision measurements of the Cosmic Microwave Background (CMB) now offer a powerful probe of the unknown reheating epoch. In this work, we scrutinize a decaying oscillatory inflation model inspired by supergravity, replacing standard ad hoc reheating assumptions with a fully dynamical calculation based on perturbative inflaton decay. By numerically tracking the energy transfer and the evolution of the equation of state, we eliminate the theoretical degeneracy associated with the reheating duration, directly linking the microphysical decay rate Γ to the observable spectral index <em>n_s</em>. We confront these self-consistent predictions with the combined constraints from Planck 2018 and ACT DR6. Our analysis demonstrates that the viable parameter space is tightly bracketed: the thermalization requirement from Big Bang Nucleosynthesis imposes a strict lower bound on the coupling strength, while the latest ACT data strongly favor scenarios with efficient reheating (<em>T</em>_re ≳ 10¹⁴ GeV), effectively pushing the model towards the instantaneous reheating limit. This study highlights the capability of modern CMB data to constrain the particle physics nature of the early universe.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"52 ","pages":"Article 102247"},"PeriodicalIF":6.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146192138","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}

{"title":"Violation of Bell inequality from a squeezed coherent state of inflationary perturbations","authors":"Aurindam Mondal ,&nbsp;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}