{"title":"Quantum theory of the Lemaître model for gravitational collapse","authors":"Claus Kiefer, Hamid Mohaddes","doi":"10.1007/s10714-025-03349-6","DOIUrl":"10.1007/s10714-025-03349-6","url":null,"abstract":"<div><p>We investigate the quantum fate of the classical singularities that occur by gravitational collapse of a dust cloud. For this purpose, we address the quantization of a model first proposed by Georges Lemaître in 1933. We find that the singularities can generically be avoided. This is a consequence of unitary evolution in the quantum theory, whereby the quantum dust cloud collapses, bounces at a minimal radius and re-expands.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 2","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10714-025-03349-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143050012","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":"Quantum black holes: from regularization to information paradoxes","authors":"Niayesh Afshordi, Stefano Liberati","doi":"10.1007/s10714-025-03356-7","DOIUrl":"10.1007/s10714-025-03356-7","url":null,"abstract":"<div><p>Quantum black holes, a broad class of objects that refine the solutions of general relativity by incorporating semiclassical and/or quantum gravitational effects, have recently attracted renewed attention within the scientific community. This resurgence of interest is largely driven by advances in gravitational wave astronomy, which have opened the possibility of testing some of these models in the near future. In this essay, we provide a concise overview of the key discussions that emerged during the “Black Hole Inside/Out\" meeting, held in August 2024 in Copenhagen. We report these ideas, their connections to the information paradox, and the potential use of analogue gravity as a test bed for these concepts.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143026537","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":"Non-commutative classical and quantum fractionary cosmology: anisotropic Bianchi type I case","authors":"J. Socorro, J. Juan Rosales, Leonel Toledo Sesma","doi":"10.1007/s10714-025-03363-8","DOIUrl":"10.1007/s10714-025-03363-8","url":null,"abstract":"<div><p>In this work, we explore non-commutative effects in fractional classical and quantum schemes using the anisotropic Bianchi type I cosmological model coupled to a scalar field in the K-essence formalism. We introduce non-commutative variables considering that all minisuperspace variables <span>(q^{i}_{nc})</span> do not commute, so the symplectic structure was modified, resulting in some changes concerning the traditional formalism. In the quantum regime, the probability density presents a new structure in the scalar field corresponding to the value of the non-commutative parameter.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143026535","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":"Covariant single-field formulation of effective cosmological bounces","authors":"Marcello Miranda","doi":"10.1007/s10714-025-03357-6","DOIUrl":"10.1007/s10714-025-03357-6","url":null,"abstract":"<div><p>This study explores the feasibility of an effective Friedmann equation in removing the classical Big Bang initial singularity and replacing it with a non-singular bounce occurring at a critical energy density value. In a spatially flat, homogeneous, and isotropic universe, the effective theory is obtained by introducing a function parametrically dependent on the critical energy density. This function measures the deviation from the benchmark theory, which is recovered as the critical energy density approaches infinity. Focusing on the covariant single-field formulation in viable Horndeski gravity, our analysis shows that both the effective and the benchmark theories belong to the same scalar–tensor theory, without any additional propagating degrees of freedom: the cuscuton and extended cuscuton models.\u0000</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10714-025-03357-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142991937","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}
Maria Andrade, Benedito Leandro, Thamara Policarpo
{"title":"Mass and topology of hypersurfaces in static perfect fluid spaces","authors":"Maria Andrade, Benedito Leandro, Thamara Policarpo","doi":"10.1007/s10714-025-03362-9","DOIUrl":"10.1007/s10714-025-03362-9","url":null,"abstract":"<div><p>We investigate the topological implications of stable minimal surfaces existing in a static perfect fluid space while ensuring that the fluid satisfies certain energy conditions. Based on the main findings, the topology of the level set <span>({f=c})</span> (the boundary of a stellar model) is studied, where <i>c</i> is a positive constant and <i>f</i> is the static potential of a static perfect fluid space. Bounds for the Hawking mass for the level set <span>({f=c})</span> of a static perfect fluid space are derived. Consequently, we prove an inequality that resembles the Penrose inequality for compact and non-compact static perfect fluid spaces, guaranteeing that the Hawking mass is positive for a class of surfaces in a static perfect fluid space. We will present a section dedicated to examples of static stellar models, one of them inspired by Witten’s black hole (or Hamilton’s cigar).\u0000\u0000</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142989917","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 Background Independent Algebra in Quantum Gravity","authors":"Edward Witten","doi":"10.1007/s10714-025-03360-x","DOIUrl":"10.1007/s10714-025-03360-x","url":null,"abstract":"<div><p>I consider the algebra of operators along the world line of an observer as a background independent algebra in quantum gravity.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142989290","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":"Differential curvature invariants and event horizon detection for accelerating Kerr–Newman black holes in (anti-)de Sitter spacetime","authors":"G. V. Kraniotis","doi":"10.1007/s10714-024-03348-z","DOIUrl":"10.1007/s10714-024-03348-z","url":null,"abstract":"<div><p>We compute analytically differential curvature invariants for accelerating, rotating and charged black holes with a cosmological constant <span>(varLambda )</span>. Specifically, we compute novel closed-form expressions for the Karlhede and the Abdelqader-Lake invariants, for accelerating Kerr–Newman black holes in (anti-)de Sitter spacetime or subsets thereof with the aim of detecting physically relevant surfaces, like horizons and ergospheres. We explicitly show that some of the computed invariants of the particular class of spacetimes are vanishing at the event, Cauchy and acceleration horizons or ergosurface. Using the Bianchi identities we calculate in the Newman-Penrose tetrad formalism in closed-form the Page-Shoom curvature invariant for the general class of accelerating, rotating and charged Plebański-Demiański black holes with <span>(varLambda not =0)</span> and we prove that is zero at the relevant surfaces. For the invariants that vanish at horizon radii we show that are non-zero everywhere else, or in the case there are additional roots such roots do not affect their capability to detect the physically relevant surfaces. Such curvature invariants are locally measurable quantities and thus could allow the local experimental detection of the event and acceleration horizons or outer ergosurface. The differential invariants which are norms associated with the gradients of the first two Weyl invariants, are explored in detail. Although both locally single out the horizons, their global behaviour is also intriguing. Both reflect the background angular momentum and electric charge as the volume of space allowing a timelike gradient decreases with increasing spin and charge.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142987811","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":"Kaluza–Klein bubble with massive scalar field","authors":"Darrell Jackson","doi":"10.1007/s10714-025-03350-z","DOIUrl":"10.1007/s10714-025-03350-z","url":null,"abstract":"<div><p>A well-known soliton (bubble) solution of five-dimensional Kaluza–Klein General Relativity is modified by imposing mass on the scalar field. By forcing the scalar field to be short-range, the failure of the original bubble solution to satisfy the equivalence principle is remedied, and the bubble acquires gravitational mass. Most importantly, the mass is quantized, even in this classical setting, and has a value <span>(m_P / (4 sqrt{alpha }))</span>, where <span>(m_P)</span> is the Planck mass, and <span>(alpha )</span> is the fine-structure constant. This result applies for any choice of scalar-field mass, as it is an attractor for the field equations.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10714-025-03350-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142981539","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":"Same as ever: looking for (in)variants in the black holes landscape","authors":"Carlos A. R. Herdeiro","doi":"10.1007/s10714-025-03351-y","DOIUrl":"10.1007/s10714-025-03351-y","url":null,"abstract":"<p><i>\"Is it a goose, a duck or a swan?\"</i>—asked the alien. <i>\"I do not know; and to</i> <i><u>know</u></i> <i>we have to look</i> <i><u>closer</u></i>.\"—said the earthling. <i>\"But even from here we can see it has webbed feet... so it is not a chicken.\" </i></p>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10714-025-03351-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142974538","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":"Black holes beyond General Relativity","authors":"Enrico Barausse, Jutta Kunz","doi":"10.1007/s10714-024-03333-6","DOIUrl":"10.1007/s10714-024-03333-6","url":null,"abstract":"<div><p>Here, we will discuss some ideas for possible classical/semi-classical modifications of the black hole solutions in General Relativity (GR). These modifications/extensions include black holes in higher dimensions; black holes with additional gravitational fields, or fields beyond the Standard Model of Particle Physics; black holes in alternative classical theories of gravity and in semiclassical gravity; phenomenological models that extend the GR black hole solutions.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"57 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10714-024-03333-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968158","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}