General Relativity and Gravitation最新文献

{"title":"Algebraic properties of Riemannian manifolds","authors":"Youngjoo Chung,&nbsp;Chi-Ok Hwang,&nbsp;Hyun Seok Yang","doi":"10.1007/s10714-023-03141-4","DOIUrl":"10.1007/s10714-023-03141-4","url":null,"abstract":"<div><p>Algebraic properties are explored for the curvature tensors of Riemannian manifolds, using the irreducible decomposition of curvature tensors. Our method provides a powerful tool to analyze the irreducible basis as well as an algorithm to determine the linear dependence of arbitrary Riemann polynomials. We completely specify 13 independent basis elements for the quartic scalars and explicitly find 13 linear relations among 26 scalar invariants. Our method provides several completely new results, including some clues to identify 23 independent basis elements from 90 quintic scalars, that are difficult to find otherwise.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"55 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48648542","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":"Dissipative properties of relativistic fluids in a general curved space–time","authors":"A. L. García-Perciante,&nbsp;A. R. Méndez","doi":"10.1007/s10714-023-03137-0","DOIUrl":"10.1007/s10714-023-03137-0","url":null,"abstract":"<div><p>Dissipative force–flux relations are established in a strict covariant fashion for a relativistic fluid in a general curved space–time within the framework of kinetic theory. The Boltzmann equation is addressed to first order in the gradients by employing the Chapman–Enskog expansion and the corresponding constitutive equations are derived by considering a relaxation approximation. It is shown that in the heat flux, only the corresponding transport coefficient is modified when the gradients of the state variables are considered as the thermodynamic forces. On the other hand, the viscous terms features new driving terms due to the curvature of space–time that only vanish in particular cases.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"55 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4448872","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":"GUP corrected Casimir wormholes in f(Q) gravity","authors":"Zinnat Hassan,&nbsp;Sayantan Ghosh,&nbsp;P. K. Sahoo,&nbsp;V. Sree Hari Rao","doi":"10.1007/s10714-023-03139-y","DOIUrl":"10.1007/s10714-023-03139-y","url":null,"abstract":"<div><p>We have systematically presented the effect of the generalized uncertainty principle (GUP) in Casimir wormhole space-time in the recently proposed modified gravity, the so-called symmetric teleparallel gravity, or <i>f</i>(<i>Q</i>) gravity. We consider two famous GUP models, such as the Kempf, Mangano, and Mann (KMM) model and the Detournay, Gabriel, and Spindel (DGS) model, in this study. Also, to find the solutions, we assumed two different <i>f</i>(<i>Q</i>) forms and obtained analytic as well as numerical solutions under the effect of GUP. Besides this, we investigate the solutions with three different redshift functions under an anisotropic fluid located at the throat. Further, we analyzed the obtained wormhole solutions with energy conditions, especially null energy conditions at the wormhole’s throat, and encountered that some arbitrary quantity disrespects the classical energy conditions at the wormhole throat of radius <span>(r_0)</span>. Later, the ADM mass and the volume integral quantifier are also discussed to calculate the amount of exotic matter required near the wormhole throat. Additionally, we show the behavior of the equation of state parameters under the effect of GUP.\u0000</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"55 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4414064","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":"String-like brane splitting in the context of (f(T,mathcal {B})) gravity","authors":"A. R. P. Moreira,&nbsp;C. A. S. Almeida","doi":"10.1007/s10714-023-03136-1","DOIUrl":"10.1007/s10714-023-03136-1","url":null,"abstract":"<div><p>In this work, the influence of the boundary term <span>(mathcal {B})</span> is analyzed in a string-like thick brane scenario in the gravity context <span>(f(T,mathcal {B}))</span>. For that, three models of <span>(f(T,mathcal {B}))</span> are proposed, i. e., <span>(f_1(T,mathcal {B})=T+kmathcal {B}^{n})</span>, <span>(f_2(T,mathcal {B})=T+k(-T+mathcal { B})^{n})</span> and <span>(f_3(T,mathcal {B})=T+k_1T^2+k_2mathcal {B}^2)</span>, where <i>n</i>, <i>k</i> and <span>(k_{1,2})</span> are parameters that control the deviation from the usual teleparallelism. The first relevant result obtained was the appearance of a super-located tower in the core for energy density. Furthermore, the greater the influence of the boundary term, the new maximums and minimums appear in the energy density. All this indicates the emergence of capable structures from split to the brane. The second relevant result was obtained by analyzing the gravitational perturbations, where the effective potential presents the supersymmetric form of quantum mechanics, leading to well-localized massless modes.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"55 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5179626","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":"Short-term effects of a speech feminization program for transgender women: listener perceptions, self-perception and satisfaction of the voice.","authors":"Clara Leyns, Iris Meerschman, Guy T'Sjoen, Evelien D'haeseleer","doi":"10.1080/26895269.2023.2237009","DOIUrl":"10.1080/26895269.2023.2237009","url":null,"abstract":"<p><p><b><i>Purpose:</i></b> This study measured and compared the short-term impact of pitch elevation training (PET) and articulation-resonance training (ART) in transgender women, on self-perception, satisfaction and masculinity-femininity perceptions of listeners. <b><i>Methods:</i></b> A randomized controlled study with cross-over design was used. Thirty transgender women were included and received fourteen weeks of speech training. All participants started with sham training (four weeks), after which they were randomly assigned to one of two groups: one group continued with PET (five weeks), followed by ART (five weeks), the second group received both trainings in opposite order. Participants were recorded four times, in between the training blocks: pre, post 1 (after sham), post 2 (after training 1) and post 3 (after training 2). Participants did a self-evaluation through the Trans Woman Voice Questionnaire (TWVQ) and visual analogues scales (VAS) concerning their self-perception and satisfaction. Two listening experiments (<i>n</i> = 75) were conducted researching the continuous masculinity-femininity rating (through a VAS) and categorical masculinity-femininity attribution. <b><i>Results and conclusions:</i></b> Transgender women perceive their voices more feminine after the training and experience a positive impact on the vocal functioning and the voice-related impact on their daily life. However, a lot of the participants acknowledge that they need more speech training after ten weeks. Listeners rate the participants' voices more feminine after training, both during the continuous and categorical questions. Higher femininity scores were detected during self-perception and listener perceptions after the combination of both ART and PET, compared to the separate trainings. No order effects were detected between ART and PET, both for self-perception and listener perceptions. Defining outcome predictors is crucial in future research.</p>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"42 7","pages":"719-737"},"PeriodicalIF":10.5,"publicationDate":"2023-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11500558/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41293478","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":"Solutions of a charged scalar field in five-dimensional helicoid solution with electromagnetic field","authors":"Tolga Birkandan","doi":"10.1007/s10714-023-03134-3","DOIUrl":"10.1007/s10714-023-03134-3","url":null,"abstract":"<div><p>We study a charged and massive scalar field in the background of the Nutku-Ghezelbash-Kumar metric which is obtained by the addition of a time coordinate to the Nutku helicoid metric in a non-trivial way. The angular part of the Klein-Gordon equation can be written as a double confluent Heun equation. The radial equation cannot be solved in terms of a known function in its general form. However, in some special cases, the radial equation can also be written explicitly as a double confluent Heun equation. We study the full radial equation numerically and observe that the electromagnetic field parameter defines an effective cut-off on the range of the radial coordinate. Finally, we obtain a quasi-exact solution with an approximation.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"55 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5477499","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":"Cosmological solutions through gravitational decoupling in (f({mathcal {R}},{mathcal {T}},{mathcal {R}}_{textrm{ab}}{mathcal {T}}^{textrm{ab}})) gravity","authors":"M. Sharif,&nbsp;Tayyab Naseer","doi":"10.1007/s10714-023-03135-2","DOIUrl":"10.1007/s10714-023-03135-2","url":null,"abstract":"<div><p>In this paper, we adopt minimal gravitational decoupling scheme to extend a non-static spherically symmetric isotropic composition to anisotropic interior in <span>(f({mathcal {R}},{mathcal {T}},{mathcal {R}}_{textrm{ab}}{mathcal {T}}^{textrm{ab}}))</span> theory. A geometric deformation is applied only on <span>(g_{rr})</span> metric component through which the modified field equations are separated into two sets, each of them correspond to their parent (seed and newly added) source. An isotropic model suggested by the Friedmann–Lemaitre–Robertson–Walker metric is adopted to reduce the unknowns in the first set. We then obtain an isotropic solution by making use of a linear equation of state and a particular form of the scale factor. A density-like constraint is chosen to solve the other sector containing the deformation function and multiple components of an additional matter source. Further, the graphical interpretation of the developed model is carried out to analyze how a decoupling parameter and modified gravity influence the evolutionary phases of the universe. It is concluded that only the radiation-dominated era meets stability criteria everywhere in this matter-geometry coupled theory.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"55 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5042758","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":"Einstein’s equations and the pseudo-entropy of pseudo-Riemannian information manifolds","authors":"Hassan Alshal","doi":"10.1007/s10714-023-03130-7","DOIUrl":"10.1007/s10714-023-03130-7","url":null,"abstract":"<div><p>Motivated by the corrected form of the entropy-area law, and with the help of von Neumann entropy of quantum matter, we construct an emergent spacetime by the virtue of the geometric language of statistical information manifolds. We discuss the link between Wald and Jacobson approaches of thermodynamic/gravity correspondence and Fisher <i>pseudo</i>-Riemannian metric of information manifold. We derive in detail Einstein’s field equations in statistical information geometric forms. This results in finding a quantum origin of a positive cosmological constant that is founded on Fisher metric. This cosmological constant resembles those found in Lovelock’s theories in a de Sitter background as a result of using the complex extension of spacetime and the Gaussian exponential families of probability distributions, and we find a time varying dynamical gravitational constant as a function of Fisher metric together with the corresponding Ryu–Takayanagi formula of such system. Consequently, we obtain a dynamical equation for the entropy in information manifold using Liouville–von Neumann equation from the Hamiltonian of the system. This Hamiltonian is suggested to be non-Hermitian, which corroborates the approaches that relate non-unitary conformal field theories to information manifolds. This provides some insights on resolving “the problem of time”.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"55 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49613927","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":"Higgs phonon: conformal phonon and Hawking temperature in a two-dimensional acoustic black hole model","authors":"Jun Yan","doi":"10.1007/s10714-023-03133-4","DOIUrl":"10.1007/s10714-023-03133-4","url":null,"abstract":"<div><p>The present study investigates the coupling of the hyperbolic potential and conformal Liouville potential to the phonon field in two-dimensional gravity. The specific values of the horizon coordinate, Hawking temperature, phonon mass, and fluid velocity were calculated, and the change in physical quantities with the field coefficient <span>(delta)</span> and central charge <i>c</i> was discussed. In the hyperbolic potential model, it was found that the phonon was very similar to the Higgs particle. The size of the horizon was 10 µm, the magnitude of the Hawking temperature was 1 nK, the magnitude of the fluid velocity was 1 mm/s, and the magnitude of the Higgs phonon mass was between 10^–8 eV and 10^–7 eV. In the conformal Liouville model, it was found that the variation trend of each physical quantity in the different branches was opposite, the size of the horizon was 10 µm, the magnitude of the Hawking temperature was between 0.1 and 1.0 nK, the magnitude of the fluid velocity was 1 mm/s, and the magnitude of the conformal phonon mass was 10^–7 eV. The calculation results of the present study were basically consistent with the results obtained by Barcelo and Steinhauer et al., but completely different physical models and new calculation methods were used.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"55 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4760988","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":"Fluid nature constrains Horndeski gravity","authors":"Marcello Miranda,&nbsp;Daniele Vernieri,&nbsp;Salvatore Capozziello,&nbsp;Valerio Faraoni","doi":"10.1007/s10714-023-03128-1","DOIUrl":"10.1007/s10714-023-03128-1","url":null,"abstract":"<div><p>The elusive physical nature of Horndeski gravity is elucidated in a new approach depicting this class of theories as a dissipative effective fluid. Requiring the constitutive equations of the latter to be those of a Newtonian fluid restricts the theory to only two disconnected subclasses of “viable” Horndeski gravity. Therefore, a stress-energy tensor of the Horndeski effective fluid, linear in the first derivatives of the fluid’s 4-velocity, is a sufficient condition for gravitational waves to propagate at light speed. All other Horndeski theories correspond to exotic non-Newtonian effective fluids. The two linear Horndeski classes are studied in the framework of first-order thermodynamics of viscous fluids, which further constrains the functional form of the theory.</p></div>","PeriodicalId":578,"journal":{"name":"General Relativity and Gravitation","volume":"55 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2023-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10714-023-03128-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4389928","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}