Physics of the Dark Universe最新文献

{"title":"Inflating without a flat potential: Viscous inflation","authors":"Luca Visinelli","doi":"10.1016/j.dark.2025.101921","DOIUrl":"10.1016/j.dark.2025.101921","url":null,"abstract":"<div><div>We propose a novel inflationary model driven by bulk viscosity, where the negative pressure induced by the viscous term plays the role of an inflaton potential. Unlike conventional slow-roll inflation, where a nearly flat potential governs the inflaton’s dynamics, our model relies on a dissipative mechanism to sustain inflation. Since viscosity does not contribute directly to the Universe’s energy density, the Hubble rate is determined solely by the inflaton’s kinetic energy. The resulting power spectrum is nearly scale-invariant, with its spectral tilt governed by slow-roll parameters intrinsic to the model. We compare our predictions for the scalar spectral index and tensor-to-scalar ratio with the latest <em>Planck</em> 2018 measurements, demonstrating the viability of this alternative inflationary framework.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"48 ","pages":"Article 101921"},"PeriodicalIF":5.0,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834104","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":"Generalized entropic dark energy with spatial curvature","authors":"Sergei D. Odintsov ,&nbsp;Simone D’Onofrio ,&nbsp;Tanmoy Paul","doi":"10.1016/j.dark.2025.101920","DOIUrl":"10.1016/j.dark.2025.101920","url":null,"abstract":"<div><div>In the realm of thermodynamics of apparent horizon, we construct a dark energy (DE) model from 4-parameter generalized entropy of apparent horizon in a spatially non-flat universe. In particular, considering a non-zero spatial curvature of the universe, we determine the dark energy fractional density and the dark energy equation of state (EoS) parameter (corresponding to the 4-parameter generalized entropy) in closed analytic forms. It turns out that the scenario can describe the correct thermal history of the universe, with the sequence of matter and dark energy epochs. Comparing with the <span><math><mi>Λ</mi></math></span>CDM model, the proposed generalized entropic DE model provides a higher value of present Hubble parameter for certain range of entropic parameter(s) leading to a possible resolution of Hubble tension issue. This in turn leads to a positive spatial curvature of the universe. We confront the scenario with CC &amp; BAO, Pantheon+ &amp; SH0ES and joint analysis of the CC &amp; BAO &amp; Pantheon+ &amp; SH0ES datasets, which clearly depicts the phenomenological viability of the present model for some best fitted values of entropic parameter(s) that are indeed consistent with the resolution of Hubble tension.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"48 ","pages":"Article 101920"},"PeriodicalIF":5.0,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143850509","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":"Exploring non-perturbative effects on quasi-topological black hole thermodynamics","authors":"Vivek Kumar Srivastava ,&nbsp;Sudhaker Upadhyay ,&nbsp;Alok Kumar Verma ,&nbsp;Dharm Veer Singh ,&nbsp;Yerlan Myrzakulov ,&nbsp;Kairat Myrzakulov","doi":"10.1016/j.dark.2025.101915","DOIUrl":"10.1016/j.dark.2025.101915","url":null,"abstract":"<div><div>We examine the impact of non-perturbative quantum corrections on the entropy of both charged and charged rotating quasi-topological black holes, focusing on their thermodynamic properties. The negative-valued correction to the entropy for small black holes is unphysical. Furthermore, we analyze the effect of these non-perturbative corrections on other thermodynamic quantities, including internal energy, Gibbs free energy, charge density, and mass density, for both black holes. Our findings indicate that the sign of the correction parameter plays a crucial role at small horizon radii. Additionally, we assess the stability and phase transitions of these black holes in the presence of non-perturbative corrections. Below the critical point, the corrected and uncorrected specific heat per unit volume is unstable. This instability leads to a first-order phase transition, wherein the specific heat transitions from negative to positive values as the system reaches a stable state.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"48 ","pages":"Article 101915"},"PeriodicalIF":5.0,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143826181","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":"New limits on warm inflation from pulsar timing arrays","authors":"Rocco D’Agostino ,&nbsp;Matteo Califano","doi":"10.1016/j.dark.2025.101910","DOIUrl":"10.1016/j.dark.2025.101910","url":null,"abstract":"<div><div>In this paper, we investigate scalar-induced gravitational waves (GWs) generated in the post-inflationary universe to infer new limits on warm inflation. We specifically examine the evolution of primordial GWs by scalar perturbations produced during the radiation-dominated epoch. For this purpose, we assume a weak regime of warm inflation under the slow-roll approximation, with a dissipation coefficient linearly dependent on the temperature of the radiation bath. We then derive analytical expressions for the curvature power spectrum and the scalar index, in the cases of chaotic and exponential potentials of the inflationary field. Subsequently, we compare the theoretical predictions regarding the relic energy density of GWs with the stochastic GW background signal recently detected by the NANOGrav collaboration through the use of pulsar timing array measurements. In so doing, we obtain numerical constraints on the free parameters of the inflationary models under study. Finally, we conduct a model selection analysis through the Bayesian inference method to measure the statistical performance of the different theoretical scenarios.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"48 ","pages":"Article 101910"},"PeriodicalIF":5.0,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834105","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":"Universality relation and thermodynamic topology with three-parameter entropy model","authors":"Ankit Anand ,&nbsp;Saeed Noori Gashti","doi":"10.1016/j.dark.2025.101916","DOIUrl":"10.1016/j.dark.2025.101916","url":null,"abstract":"<div><div>This work investigates the extended universal relation for Reissner–Nordström–AdS (RN–AdS) black holes within the framework of a non-extensive three-parameter entropy model. This analysis provides insights into how the interplay of these parameters influences the black hole’s thermodynamic behavior and validates the universality of the relation under non-extensive entropy conditions. Then, this study delves into the topological nature of phase transitions in black hole thermodynamics. We examine the thermodynamic topology of RN–AdS black holes with parameters <span><math><mi>α</mi></math></span>, <span><math><mi>β</mi></math></span>, and <span><math><mi>γ</mi></math></span> within the Restricted Phase Space (RPS) thermodynamics and Bulk Boundary thermodynamics frameworks. Our findings show that the parameter <span><math><mi>β</mi></math></span> significantly influences the number of topological charges and the classification of black holes.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"48 ","pages":"Article 101916"},"PeriodicalIF":5.0,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834166","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":"Topological electroweak phase transition","authors":"V.K. Oikonomou","doi":"10.1016/j.dark.2025.101908","DOIUrl":"10.1016/j.dark.2025.101908","url":null,"abstract":"<div><div>In this work we shall consider the effects of a non-trivial topology on the effective potential of the Standard Model. Specifically we shall assume that the spacetime topology is <span><math><mrow><msup><mrow><mi>S</mi></mrow><mrow><mn>1</mn></mrow></msup><mo>×</mo><msup><mrow><mi>R</mi></mrow><mrow><mn>3</mn></mrow></msup></mrow></math></span> and we shall calculate the Standard Model effective potential for such a topological spacetime. As we demonstrate, for small values of the compact dimension radius, the electroweak symmetry is unbroken, but for a critical length and beyond, the electroweak symmetry is broken, since the configuration space of the Higgs field contains an additional energetically favorable minimum, compared to the minimum at the origin. The two minima are separated by a barrier, thus a phase transition can occur, via quantum tunneling, which mimics a first order phase transition. This is a non-thermal phase transition, similar possibly to quantum Hall topological phase transitions, hence in the context of this scenario, the electroweak symmetry breaking does not require a high temperature to occur. The present scenario does not rely on the occurrence of the inflationary era, only on the expansion of the Universe, however we briefly discuss the freezing of the superhorizon terms in <span><math><mrow><msup><mrow><mi>S</mi></mrow><mrow><mn>1</mn></mrow></msup><mo>×</mo><msup><mrow><mi>R</mi></mrow><mrow><mn>3</mn></mrow></msup></mrow></math></span> spacetime, if inflation occurred. We also investigate the large scale differences of the gravitational potential due to the non-trivial topology. Finally, we briefly mention the distinct inequivalent topological field configurations that can exist due to the non-trivial topology, which are classified by the first Stieffel class which in the case at hand is <span><math><mrow><msup><mrow><mi>H</mi></mrow><mrow><mn>1</mn></mrow></msup><mrow><mo>(</mo><msup><mrow><mi>S</mi></mrow><mrow><mn>1</mn></mrow></msup><msup><mrow><mo>×</mo><mi>R</mi></mrow><mrow><mn>3</mn></mrow></msup><mo>,</mo><msub><mrow><mi>Z</mi></mrow><mrow><mover><mrow><mn>2</mn></mrow><mrow><mo>˜</mo></mrow></mover></mrow></msub><mo>)</mo></mrow><mo>=</mo><msub><mrow><mi>Z</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span>, so even and odd elements can exist. We also briefly qualitatively discuss how a topologically induced electroweak phase transition can yield primordial gravitational waves.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"48 ","pages":"Article 101908"},"PeriodicalIF":5.0,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143824136","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":"Interpreting decisions of lightweight CNN for glitch classification in time frequency images: Enhancing black-hole merger detection in O1 and O2 runs","authors":"Mohan Bhandari ,&nbsp;Aakash Thapa ,&nbsp;Loknath Regmi ,&nbsp;Suman Sharma ,&nbsp;Prakash Paudel ,&nbsp;Sanjeeb Prasad Panday","doi":"10.1016/j.dark.2025.101914","DOIUrl":"10.1016/j.dark.2025.101914","url":null,"abstract":"<div><div>When two or more black holes orbit each other and eventually merge, they emit significant gravitational waves (GWs). These waves, first detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO), are recorded as time-frequency patterns in images. The classification and segmentation of these images are critical for conducting precise and thorough characterization analysis. A robust signal-versus-glitch classifier designed for automation must be capable of handling diverse background noise, new glitch sources, overlapping glitches, and gravitational wave signals. This challenge becomes increasingly complex, particularly in the context of lightweight devices. This study introduce a custom CNN architecture with 1,899,318 trainable parameters, effectively classifying 22 categories in the Gravity Spy dataset (time-frequency domain visualization of glitch behavior), even with the challenging nature of glitches, and showing strong resistance to adversarial attacks. Under 10-fold cross-validation, the proposed model achieves training, validation, and test precisions of 96.02 ± 0.2790%, 96.54 ± 0.2840%, and 97.12 ± 0.5240% respectively. Cohen’s Kappa score is 0.978 ± 0.0038, while the Mann–Whitney and Kruskal–Wallis tests yield 3214.59 ± 1.44 and 0.155 ± 0.003, respectively. The minimum AUC-ROC is 0.98 for only two categories—‘No Glitch’ and ‘None of the Above’ — whereas all other categories have higher values. To enhance interpretability, local interpretable model-agnostic explanations are generated as helping information for the decision-making process, and the model is deployed in a web environment using Flask to evaluate the performance of the CNN model when implemented on lightweight devices.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"48 ","pages":"Article 101914"},"PeriodicalIF":5.0,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143808375","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":"Tracing cosmic evolution through Weyl-Type f(Q,T) gravity model: Theoretical analysis and observational validation","authors":"Rahul Bhagat ,&nbsp;Francisco Tello-Ortiz ,&nbsp;B. Mishra","doi":"10.1016/j.dark.2025.101913","DOIUrl":"10.1016/j.dark.2025.101913","url":null,"abstract":"<div><div>We investigate the cosmic evolution of the Universe across different cosmological epochs in exponential Weyl-type <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>Q</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> gravity model. The theoretical analysis involves a detailed dynamical system approach, where we define dimensionless variables and derive a system of linear differential equations to identify critical points corresponding to the radiation, matter and de Sitter phase. The findings show the transition from deceleration to acceleration phase, with stable and unstable critical points characterizing different phases of the evolution. In the second phase, we validate the theoretical predictions by using observational data from Cosmic Chronometers (<span><math><mrow><mi>C</mi><mi>C</mi></mrow></math></span>) and Pantheon<span><math><msup><mrow></mrow><mrow><mo>+</mo></mrow></msup></math></span> datasets. We constrain the Hubble parameter and subsequently analyzed the other cosmological and geometrical parameters. In this approach also, the transition from deceleration to acceleration has been confirmed, with the equation of state (EoS) parameter approaching <span><math><mi>Λ</mi></math></span>CDM at late times. The model behavior in both the approaches show the late-time behavior of the Universe. The evolutionary behavior of both the Hubble parameter and distance modulus, reinforcing the reliability of the Weyl-type <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>Q</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> gravity model in describing the expansion history of Universe.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"48 ","pages":"Article 101913"},"PeriodicalIF":5.0,"publicationDate":"2025-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143786036","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":"New insights on a sign-switching Λ","authors":"Jorge F. Soriano ,&nbsp;Shimon Wohlberg ,&nbsp;Luis A. Anchordoqui","doi":"10.1016/j.dark.2025.101911","DOIUrl":"10.1016/j.dark.2025.101911","url":null,"abstract":"<div><div>The proposal for a sudden sign-switching cosmological constant <span><math><mi>Λ</mi></math></span> in the local universe, emulating a phase transition from anti-de Sitter (AdS) to de Sitter (dS) space, has markedly revamped the fit to observational data and lays out a propitious framework for ameliorating major cosmological tensions, such as the <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>S</mi></mrow><mrow><mn>8</mn></mrow></msub></math></span> tensions. This proposal is widely known as <span><math><msub><mrow><mi>Λ</mi></mrow><mrow><mi>s</mi></mrow></msub></math></span>CDM. We investigate the possibility that <span><math><mi>Λ</mi></math></span> does not only flip sign at the transition but has also different curvature radii in the AdS and dS phases. We show that the critical redshift of the transition <span><math><msub><mrow><mi>z</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span> is strongly correlated with the vacuum energy in the AdS phase <span><math><msub><mrow><mi>Ω</mi></mrow><mrow><msub><mrow><mi>Λ</mi></mrow><mrow><mo>−</mo></mrow></msub></mrow></msub></math></span>, and that these two variables do not correlate strongly with the other cosmological parameters. We also show that the cost of adding an additional parameter to the <span><math><msub><mrow><mi>Λ</mi></mrow><mrow><mi>s</mi></mrow></msub></math></span>CDM cosmological model does not improve the goodness of fit. Armed with our findings, we demonstrate that for a proper choice of <span><math><msub><mrow><mi>z</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span>, the vacuum energy in the dS phase may not necessarily be <span><math><mrow><mo>−</mo><msub><mrow><mi>Ω</mi></mrow><mrow><msub><mrow><mi>Λ</mi></mrow><mrow><mo>−</mo></mrow></msub></mrow></msub></mrow></math></span>, for comparable degree of conformity between the model prediction and experimental data.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"48 ","pages":"Article 101911"},"PeriodicalIF":5.0,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143786113","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":"Dynamical dark energy in the light of DESI 2024 data","authors":"Nandan Roy","doi":"10.1016/j.dark.2025.101912","DOIUrl":"10.1016/j.dark.2025.101912","url":null,"abstract":"<div><div>The latest findings from the DESI (Dark Energy Spectroscopic Instrument) data release 1 (DR1) Adame et al. (2024), combined with data from the cosmic microwave background and supernovae, suggest a preference for dynamical dark energy over the cosmological constant. This study has considered the Chevallier–Polarski–Linder (CPL) parameterization for the dark energy equation of state (EoS) and has indicated a possible phantom barrier crossing in the recent past. Despite CPL being the most commonly used parameterization, recent research has pointed out issues with its prior selection and parameter degeneracies. In this paper, we propose an alternative two-parameter parameterization of the dark energy equation of state (EoS). At higher redshifts, it behaves like the cosmological constant. At redshifts <span><math><mrow><mi>z</mi><mo>&lt;</mo><mn>1</mn></mrow></math></span>, this parameterization closely approximates the CPL form but deviates from it at lower redshifts. Our findings also indicate that the current value of the EoS of dark energy resembles quintessence, with evidence of a recent crossing of the phantom barrier, supporting the conclusions in Adame et al. (2024). Furthermore, our model significantly reduces the Hubble tension to about <span><math><mrow><mn>2</mn><mo>.</mo><mn>8</mn><mi>σ</mi></mrow></math></span> when compared to Hubble Space Telescope and SH0ES data Riess et al. (2022), and to <span><math><mrow><mn>1</mn><mo>.</mo><mn>6</mn><mi>σ</mi></mrow></math></span> with standardized TRGB and Type Ia supernova data Scolnic et al. (2023). Bayesian model selection using Bayes factors and Akaike Information Criteria (ACI), shows a strong preference for our parameterization over the <span><math><mi>Λ</mi></math></span> CDM model, aligned with the DESI2024 results and favoring dynamical dark energy.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"48 ","pages":"Article 101912"},"PeriodicalIF":5.0,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143783988","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}