{"title":"White Dwarf envelops and temperature corrections in exponential f(T) gravity","authors":"Gabriel Farrugia, Carlos Gafa’, Jackson Levi Said","doi":"10.1007/s10714-024-03341-6","DOIUrl":"https://doi.org/10.1007/s10714-024-03341-6","url":null,"abstract":"<p>Compact stars have long served as a test bed of gravitational models and their coupling with stellar matter. In this work, we explore the behavior of an exponential model in <i>f</i>(<i>T</i>) gravity through the Tolman-Oppenheimer-Volkoff equation. This is performed for different envelope thicknesses. Finally, constraints on the models parameters are obtained, which are comparable to the results obtained using cosmological survey data. This consistency across the strong astrophysical and weak cosmological scales shows reasonable viability of the underlying model.</p>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"292 1","pages":""},"PeriodicalIF":2.8,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142879882","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}
J. Ríos–Padilla, O. Obregón, J. C. López–Domínguez
{"title":"Towards the entanglement entropy of two quantum black holes","authors":"J. Ríos–Padilla, O. Obregón, J. C. López–Domínguez","doi":"10.1007/s10714-024-03334-5","DOIUrl":"10.1007/s10714-024-03334-5","url":null,"abstract":"<div><p>Starting from a Wheeler–DeWitt type equation for an uncharged black hole <span>(Q=0)</span>, and by choosing the order parameter <span>((s=2))</span> and running the gravitational degrees of freedom it is possible to reduce the Wheeler–DeWitt equation to the canonical form of a quantum harmonic oscillator. In this direction, a natural frequency of oscillation is identified for the black hole. The entanglement entropy of a pair of interacting quantum black holes of mass <i>M</i> is obtained and analyzed. Here we consider as a starting model a pair of identical oscillators of frequency <span>(omega )</span> coupled by a quadratic potential and with interaction constant given by <span>(omega _{c})</span>. Given the relation between the oscillation frequency <span>(omega )</span> of an isolated quantum black hole and its mass, the entanglement entropy of this system is obtained by analogy with a pair of quantum oscillators coupled by a quadratic interaction potential of frequency <span>(omega _{c})</span>. The analysis of the entanglement entropy is performed by introducing the reduced variables <span>({widetilde{omega }})</span> and <span>({widetilde{A}})</span>. An interesting result arises when we consider <span>({widetilde{A}}gg 1)</span> and the interaction parameter is set <span>({widetilde{omega }}=1)</span>. In this case, the entanglement entropy can be replaced by its asymptotic expansion, where the dominant term is of logarithmic character in the reduced area. Another case of analysis emerges when the reduced area <span>({widetilde{A}}=1)</span> and <span>({widetilde{omega }})</span> varies. In this case, the entanglement entropy depends uniquely on the interaction parameter between the two black holes.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142870464","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":"How the black hole puzzles are resolved in string theory","authors":"Samir D. Mathur","doi":"10.1007/s10714-024-03336-3","DOIUrl":"10.1007/s10714-024-03336-3","url":null,"abstract":"<div><p>String theory has provided a resolution of the puzzles that arise in the quantum theory of black holes. The emerging picture of the hole, encoded in the ‘fuzzball paradigm’, offers deep lessons about the role of quantum gravity on macroscopic length scales. In this article we list these puzzles and explain how they get resolved. We extract the lessons of this resolution in a form that does not involve the technical details of string theory; it is hoped that this form will allow the lessons to be absorbed into other approaches to quantum gravity.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142848901","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}
Jibril Ben Achour, Dario Benedetti, Martin Bojowald, Robert Brandenberger, Salvatore Butera, Renata Ferrero, Flaminia Giacomini, Kristina Giesel, Christophe Goeller, Tobias Haas, Philipp A. Höhn, Joshua Kirklin, Luca Marchetti, Daniele Oriti, Roberto Percacci, Antonio D. Pereira, Andreas G. A. Pithis, Mairi Sakellariadou, Sebastian Steinhaus, Johannes Thürigen
{"title":"Quantum gravity, hydrodynamics and emergent cosmology: a collection of perspectives","authors":"Jibril Ben Achour, Dario Benedetti, Martin Bojowald, Robert Brandenberger, Salvatore Butera, Renata Ferrero, Flaminia Giacomini, Kristina Giesel, Christophe Goeller, Tobias Haas, Philipp A. Höhn, Joshua Kirklin, Luca Marchetti, Daniele Oriti, Roberto Percacci, Antonio D. Pereira, Andreas G. A. Pithis, Mairi Sakellariadou, Sebastian Steinhaus, Johannes Thürigen","doi":"10.1007/s10714-024-03335-4","DOIUrl":"10.1007/s10714-024-03335-4","url":null,"abstract":"<div><p>This collection of perspective pieces captures recent advancements and reflections from a dynamic research community dedicated to bridging quantum gravity, hydrodynamics, and emergent cosmology. It explores four key research areas: (a) the interplay between hydrodynamics and cosmology, including analog gravity systems; (b) phase transitions, continuum limits and emergent geometry in quantum gravity; (c) relational perspectives in gravity and quantum gravity; and (d) the emergence of cosmological models rooted in quantum gravity frameworks. Each contribution presents the distinct perspectives of its respective authors. Additionally, the introduction by the editors proposes an integrative view, suggesting how these thematic units could serve as foundational pillars for a novel theoretical cosmology framework termed “hydrodynamics on superspace”.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142844833","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":"Inhomogeneous brane models","authors":"Pantelis S. Apostolopoulos, Noeleen Naidoo","doi":"10.1007/s10714-024-03337-2","DOIUrl":"10.1007/s10714-024-03337-2","url":null,"abstract":"<div><p>The existence of a set of 10 Intrinsic Conformal Symmetries, which acts on three-dimensional hypersurfaces (spacelike or timelike), leads to the existence of two distinct families of 5D geometries. These models represent the general solutions of the bulk field equations where their energy-momentum tensor, includes only two components: a negative cosmological constant and a parallel pressure <span>(p_{parallel })</span> aligned with the extra spatial dimension. Significantly, these models offer a novel perspective for investigating the impacts of spatial inhomogeneity and anisotropy on the cosmological evolution of the Universe, particularly within the context of the braneworld scenarios. It is shown that one of these families reduces to a <i>fully inhomogeneous, anisotropic and conformally flat brane model</i> with a <i>perfect fluid equation of state</i> and corresponds to the Stephani Universe (i.e. a Stephani brane) which implies that our model can be matched smoothly with the standard FRW model. We provide the generalized Friedmann and Raychaudhuri equations and we present how the additional quantities could affect the cosmological evolution. In particular we show that the new constituents are the terms <span>(p_{parallel })</span>, <span>(sigma ^{2})</span> and the four acceleration of the brane observers that could affect the observational measurement of the Hubble parameter depending on which term dominates therefore provide us a potential answer to the Hubble tension and cosmic acceleration problems due to local inhomogeneities and anisotropies.\u0000</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142826424","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":"Tests of general relativity with future detectors","authors":"Emanuele Berti","doi":"10.1007/s10714-024-03332-7","DOIUrl":"10.1007/s10714-024-03332-7","url":null,"abstract":"<div><p>This \"vision document\" is about what the future has in store for tests of general relativity with gravitational wave detectors. I will make an honest attempt to answer this question by addressing the role of inspiral-based and ringdown-based tests; recent progress on quasinormal modes in modified theories of gravity; the complementarity between light ring tests and ringdown tests; and the interesting possibility of observing some of the nonlinear effects predicted by general relativity. I may well prove to be wrong. To quote Yogi Berra: \"It’s hard to make predictions, especially about the future\".\u0000</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"56 12","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142809460","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":"Black holes, Cauchy horizons, and mass inflation","authors":"Matt Visser","doi":"10.1007/s10714-024-03330-9","DOIUrl":"10.1007/s10714-024-03330-9","url":null,"abstract":"<div><p>Event horizons and Cauchy horizons are highly idealized mathematical constructions that do not fully capture the key physics of either Hawking radiation or mass inflation. Indeed, because they are teleological, both event horizons and Cauchy horizons are (in a precise technical sense) not physically observable. In contrast, by inspecting the quasi-local behaviour of null geodesics, long-lived apparent horizons (or more generally long-lived quasi-local horizons) are in principle physically observable, and are “good enough\" for then pragmatically redefining a black hole, and “good enough” for generating Hawking radiation. Furthermore it is now also clear that long lived apparent horizons (quasi-local horizons) are also “good enough\" for generating mass inflation. These observations suggest that one should be somewhat careful when trying to extrapolate rigorous mathematical theorems, which often embody mathematical idealizations that do not necessarily correspond to what a finite resource astronomer can actually measure, into the astrophysical realm.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"56 12","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142809431","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":"Low-temperature holographic screens correspond to einstein-rosen bridges","authors":"Marco Alberto Javarone","doi":"10.1007/s10714-024-03328-3","DOIUrl":"10.1007/s10714-024-03328-3","url":null,"abstract":"<div><p>Recent conjectures on the complexity of black holes suggest that their evolution manifests in the structural properties of Einstein-Rosen bridges, like the length and volume. The complexity of black holes relates to the computational complexity of their dual, namely holographic, quantum systems identified via the Gauge/Gravity duality framework. Interestingly, the latter allows us to study the evolution of a black hole as the transformation of a qubit collection performed through a quantum circuit. In this work, we focus on the complexity of Einstein-Rosen bridges. More in detail, we start with a preliminary discussion about their computational properties, and then we aim to assess whether an Ising-like model could represent their holographic dual. In this regard, we recall that the Ising model captures essential aspects of complex phenomena such as phase transitions and, in general, is deeply related to information processing systems. To perform this assessment, which relies on a heuristic model, we attempt to describe the dynamics of information relating to an Einstein-Rosen bridge encoded in a holographic screen in terms of dynamics occurring in a spin lattice at low temperatures. We conclude by discussing our observations and related implications.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"56 12","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142790437","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":"Hawking radiation with pure states","authors":"K. Sravan Kumar, João Marto","doi":"10.1007/s10714-024-03329-2","DOIUrl":"10.1007/s10714-024-03329-2","url":null,"abstract":"<div><p>Hawking’s seminal work on black hole radiation highlights a critical issue in our understanding of quantum field theory in curved spacetime (QFTCS), specifically the problem of unitarity loss (where pure states evolve into mixed states). In this paper, we examine a recent proposal for a direct-sum QFTCS, which maintains unitarity through a novel quantization method that employs geometric superselection rules based on discrete spacetime transformations. This approach describes a quantum state in terms of components that evolve within geometric superselection sectors of the complete Hilbert space, adhering to the discrete symmetries of a Schwarzschild black hole. Consequently, it represents a maximally entangled pure state as a direct-sum of two components in the interior and exterior regions of the black hole, thereby preserving the unitarity of Hawking radiation by keeping it in the form of pure states.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"56 12","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10714-024-03329-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142789943","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}
A. Bazrafshan, M. Ghanaatian, S. Rezaei, Gh. Forozani
{"title":"Quasitopological Lifshitz dilaton black brane","authors":"A. Bazrafshan, M. Ghanaatian, S. Rezaei, Gh. Forozani","doi":"10.1007/s10714-024-03331-8","DOIUrl":"10.1007/s10714-024-03331-8","url":null,"abstract":"<div><p>We construct a new class of <span>((n+1))</span>-dimensional Lifshitz dilaton black brane solutions in the presence of the cubic quasitopological gravity for a flat boundary. The related action supports asymptotically Lifshitz solutions by applying some conditions which are used throughout the paper. We have to add a new boundary term and some new counterterms to the bulk action to have finite solutions. Then we define a finite stress tensor complex by which we can calculate the energy density of the quasitopological Lifshitz dilaton black brane. It is not possible to obtain analytical solutions, and so we use some expansions to probe -the behaviors of the functions, both near the horizon and, at the infinity. Combining the equations, we can attain a total constant along the coordinate <i>r</i>. At the horizon, this constant is proportional to the product of the temperature and the entropy and at the infinity, the total constant shows the energydensity of the quasitopological Lifshitz dilaton black brane. Therefore, we can reach a relation between the conserved quantities temperature, entropy and the energy density and get a smarr-type formula. Using the first law of thermodynamics, we can find a relation between the entropy and the temperature and then obtain the heat capacity. Our results show that the quasitopological Lifshitz dilaton black brane solutions are thermally stable for each positive value of the dynamical critiacl exponent, <i>z</i>.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"56 12","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142788721","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}
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