General Relativity and Gravitation最新文献

{"title":"Constraining the f-mode oscillations frequency in neutron stars through universal relations in the realm of energy-momentum squared gravity","authors":"Sayantan Ghosh","doi":"10.1007/s10714-025-03405-1","DOIUrl":"10.1007/s10714-025-03405-1","url":null,"abstract":"<div><p>Neutron stars (NSs), superdense objects with exceptionally strong gravitational fields, provide an ideal laboratory for probing general relativity (GR) in the high-curvature regime. They also present an exciting opportunity to explore new gravitational physics beyond the traditional framework of GR. Thus, investigating modified theories of gravity in the context of superdense stars is intriguing and essential for advancing our understanding of gravitational phenomena in extreme environments. energy-momentum squared gravity (EMSG) is a modified theory of gravity that extends GR by including nonlinear terms involving the energy-momentum tensor <span>(T_{mu nu })</span>. EMSG and GR are indistinguishable in local tests like Solar System experiments, as both yield identical gravitational potentials, parametrized post-Newtonian (PPN) parameters, and geodesic motion in the weak-field regime. Therefore, detecting EMSG effects requires alternative approaches, such as NS observations in strong-field gravity. In this study, we examine the effects of EMSG on the properties and behaviour of NSs by varying the free parameter <span>(alpha )</span>. The hydrostatic equilibrium equations in the EMSG framework are derived and solved numerically to obtain mass-radius relations for soft, stiff, and intermediate equations of state (EOS). Observational measurements of NS masses and radii are used to constrain the fundamental-mode (<i>f</i>-mode) oscillation frequency through its universal relation with the tidal Love number and compactness. Results indicate that the stiff EOS undergoes a phase transition at the highest energy densities and pressures, followed by the intermediate and soft EOSs, highlighting the distinctive characteristics of these models. We also study the impact of EOS choice on the sound speed profile of NSs, reaffirming the physical validity of the models across the different <span>(alpha )</span> values.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 4","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143835743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Analysis of the cosmological evolution parameters, energy conditions, and linear matter perturbations of an exponential-type model in f(Q) gravity","authors":"Ivan R. Vasquez,&nbsp;A. Oliveros","doi":"10.1007/s10714-025-03403-3","DOIUrl":"10.1007/s10714-025-03403-3","url":null,"abstract":"<div><p>We analytically study cosmological evolution in a flat FLRW spacetime in the context of modified STEGR gravity or <i>f</i>(<i>Q</i>), using an exponential two-parameter model which represents a smooth perturbative expansion around the <span>(Lambda )</span>CDM model. The cosmological analysis is carried out by calculating the Hubble parameter as a function of redshift, for selected values of the parameters. The Hubble parameter is obtained analytically by means of several approximations good enough to deviate slightly from the numerical solution. Several late-time cosmological parameters are computed, such as dark energy state parameter, deceleration parameter, and statefinder parameters. Additionally, we analyzed the behavior of the classical energy conditions WEC, SEC, NEC, and DEC for both the combination of matter and geometrical contribution and the geometrical contribution alone. Beyond the background level, linear matter perturbations are studied by calculating parameters relevant to structure growth and formation. The overall results indicate that the model may exhibit quintessence-like and phantom-like behavior and it also impacts the growth of structures in the universe by means late-time contributions to clustering.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 4","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143818260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Agegraphic dark energy with fractional entropy: Implications for cosmological evolution","authors":"Muhammad Naeem,&nbsp;Aysha Bibi","doi":"10.1007/s10714-025-03401-5","DOIUrl":"10.1007/s10714-025-03401-5","url":null,"abstract":"<div><p>This work revisits the agegraphic dark energy (ADE) model by associating fractional entropy with the apparent horizon. This reveals the extent to which quantum-gravitational effects deform the horizon. The thermodynamic-gravity conjecture modifies the entropy expression, leading to changes in the energy density of ADE and the Friedmann equations. Based on this relationship, we have utilized modified fractional cosmology to investigate the cosmological implications of ADE and demonstrate how the exponent <span>(delta )</span> affects the evolution of cosmic parameters. Depending on the value of <span>(delta )</span>, the equation of state (EoS) parameter <span>(omega _{text {DE}})</span> make transition from the quintessence range (<span>(-1&lt; omega _{text {DE}} &lt; -1/3)</span>) to the phantom regime <span>((omega _{text {DE}} &lt; -1))</span>, resulting in a shift from early deceleration to late time acceleration. Furthermore, the stability, theoretical and observational analyses of both the old and the new ADE models are discussed. All ADE results are reproduced in standard cosmology when <span>(delta = 2)</span>.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 4","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143822016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"On the detectability of gravitational waves emitted from head-on collisions of (ell )-boson stars","authors":"Mariana Lira,&nbsp;Laura O. Villegas,&nbsp;Javier M. Antelis,&nbsp;Víctor Jaramillo,&nbsp;Claudia Moreno,&nbsp;Darío Núñez","doi":"10.1007/s10714-025-03397-y","DOIUrl":"10.1007/s10714-025-03397-y","url":null,"abstract":"<div><p>In this work, we examine head-on collisions, produced by other work, of <span>(ell )</span>-boson stars, potential candidates for dark matter compact objects. We begin with a review of the general properties and features of these stars, leveraging results from prior studies to analyze the gravitational wave signals generated by such collisions. Considering a maximum distance of 100 Mpc for potential events, we identify the range of scalar field masses and frequencies for these stars that would render the gravitational waves detectable by current gravitational wave observatories. The ranges obtained for the scalar field masses are <span>(m_phi ,c^2 in [10^{-15}, 10^{-10}])</span> eV. Additionally, we process the resulting signals to generate simulated observatory images, highlighting their similarities and differences compared to those produced by black hole collisions.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 4","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10714-025-03397-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143819089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

{"title":"Primordial black holes from inflation","authors":"Misao Sasaki","doi":"10.1007/s10714-025-03400-6","DOIUrl":"10.1007/s10714-025-03400-6","url":null,"abstract":"<div><p>It has now been widely accepted that many inflation models can account for the formation of primordial black holes (PBHs). In particular, it has been fully realized that the PBH formation depends crucially on the tails of the probability distribution function of the curvature perturbation. I will review some models of inflation that give rise to the PBH formation, and their observational implications, in particular, for the blossoming field of gravitational-wave cosmology.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 4","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10714-025-03400-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809337","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

{"title":"One-loop corrections in Maxwell-metric-affine bumblebee gravity","authors":"A. C. Lehum,&nbsp;J. R. Nascimento,&nbsp;A. Yu. Petrov,&nbsp;P. J. Porfírio","doi":"10.1007/s10714-025-03402-4","DOIUrl":"10.1007/s10714-025-03402-4","url":null,"abstract":"<div><p>In this paper, we consider the coupling of the metric-affine bumblebee gravity to the Abelian gauge field and obtain the effective model corresponding to the weak gravity limit of this theory. The effective bumblebee theory displays new unconventional couplings between the bumblebee field and its field strength, and the <i>U</i>(1) gauge field along with its respective field strength, as a result of the non-metricity effects. Thus, being a new gauge-bumblebee theory, it represents an example of vector-vector couplings which are very rarely considered, if not entirely overlooked, in the Abelian case. For this theory, we calculate the lower perturbative corrections. We close the paper with discussions of other possible vector-vector couplings.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 4","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"A numerical framework for studying asymptotic quantities","authors":"Breanna Camden,&nbsp;Jörg Frauendiener,&nbsp;Joseph Galinski,&nbsp;Kaushal Pillay,&nbsp;Chris Stevens,&nbsp;Sebenele Thwala","doi":"10.1007/s10714-025-03399-w","DOIUrl":"10.1007/s10714-025-03399-w","url":null,"abstract":"<div><p>In this contribution we present an overview of our work on the numerical simulation of the perturbation of a black hole space-time by incoming gravitational waves. The formulation we use is based on Friedrich’s general conformal equations which have the unique property that they allow access to the asymptotic region of an asymptotically regular space-time. In our approach we set up an initial boundary value problem on a finite boundary, which cleanly separates the initial conditions, a static black hole, from the perturbation, an incoming gravitational wave specified by a spin-2 function on the time-like boundary. The main advantage of this approach is that the finite boundary expands fast enough to reach null-infinity where the asymptotic properties can be studied. This provides, for the first time, a direct relationship between finite initial and boundary data and asymptotic quantities within one simulation. We discuss the possibilities and limitations of this approach.\u0000</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 4","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10714-025-03399-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143778006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

{"title":"Gyroscopic precession in Reissner–Nordström spacetime","authors":"Paulami Majumder,&nbsp;K. Rajesh Nayak","doi":"10.1007/s10714-025-03395-0","DOIUrl":"10.1007/s10714-025-03395-0","url":null,"abstract":"<div><p>In this work, we investigate a static spherically symmetric Reissner–Nordström event horizon and a naked singularity by analyzing the behavior of a gyroscope transported along a timelike curve. We find that the precession frequency remains finite for both the black hole and the naked singularity as long as the trajectory is timelike. Our objective is to quantify the differences in the gyroscope’s precession behavior when approaching an event horizon versus a naked singularity. Additionally, we explore the potential for distinguishing between an event horizon and a naked singularity by examining the reversal of the precession frequency.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 4","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143740627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"A healthier stochastic semiclassical gravity: world without Schrödinger cats","authors":"Lajos Diósi","doi":"10.1007/s10714-025-03396-z","DOIUrl":"10.1007/s10714-025-03396-z","url":null,"abstract":"<div><p>Semiclassical gravity couples classical gravity to the quantized matter in meanfield approximation. The meanfield coupling is problematic for two reasons. First, it ignores the quantum fluctuation of matter distribution. Second, it violates the linearity of the quantum dynamics. The first problem can be be mitigated by allowing stochastic fluctuations of the geometry but the second problem lies deep in quantum foundations. Restoration of quantum linearity requires a conceptual approach to hybrid classical-quantum coupling. Studies of the measurement problem and the quantum-classical transition point the way to a solution. It is based on a postulated mechanism of spontaneous quantum monitoring plus feedback. This approach eliminates Schrödinger cat states, takes quantum fluctuations into the account, and restores the linearity of quantum dynamics. Such conceptionally ’healthier’ semiclassical theory is captivating, exists in the Newtonian limit, but its relativistic covariance hits a wall. Here we will briefly recapitulate the concept and its realization in the nonrelativistic limit. We emphasize that the long-known obstacles to the relativistic extension lie in quantum foundations.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 4","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10714-025-03396-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143740628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

{"title":"Cooling and heating regions of Joule-Thomson expansion for AdS black holes: Einstein-Maxwell-power-Yang-Mills and Kerr Sen black holes","authors":"Mohammad Reza Alipour,&nbsp;Saeed Noori Gashti,&nbsp;Mohammad Ali S. Afshar,&nbsp;Jafar Sadeghi","doi":"10.1007/s10714-025-03393-2","DOIUrl":"10.1007/s10714-025-03393-2","url":null,"abstract":"<div><p>In this paper, we study the Joule-Thomson Expansion process for two types of black holes: AdS-Einstein-Maxwell-power-Yang-Mills (AEMPYM) and AdS-Kerr-Sen (AKS). Our study focuses on understanding how various parameters influence the Joule-Thomson Coefficient, the inversion curve, and the ratio of minimum inversion temperature to critical temperature. For the AKS black hole, we observe that the isenthalpic curves can exhibit either cooling or heating behavior. This behavior is determined by the inversion curve, which is affected by the black hole’s mass and specific parameters such as <i>b</i> (parameter signifies the ionic charge of the black hole) and <i>a</i> (rotation parameter). In the case of the AEMPYM black hole, our findings reveal that the ratio of minimum inversion temperature to critical temperature approaches a specific value as Maxwell’s charge increases. This ratio remains constant for certain parameter values, while it varies for others. Specifically, when the parameter <span>(q)</span> (real positive parameter of AEMPYM black hole) is greater than 1, the ratio is almost equal to 1/2 as Maxwell’s charge <span>(C)</span> increases. When q equals 1/2, the ratio is exactly 1/2 for all values of <span>(C)</span>. For values of <span>(q)</span> between 1/2 and 1, the ratio is close to 1/2, and for values of <span>(q)</span> between 0 and 1/2, the ratio decreases, moving away from 1/2. For the AKS black hole, we find that specific parameter values, such as <span>(a = 0.00951)</span> and <span>(b = 0.00475)</span>, yield a ratio of minimum inversion temperature to a critical temperature that is approximately 1/2. This consistency across different parameter values highlights the robustness of our findings. Finally, we compare our results with those reported in the existing literature, providing a comprehensive summary in detailed tables. This comparison not only validates our findings but also situates them within the broader context of black hole thermodynamics and the Joule-Thomson effect.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 3","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10714-025-03393-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143707175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}