Pub Date : 2025-01-07DOI: 10.1088/1361-6382/ad9e66
Alessio Belfiglio, Orlando Luongo, Stefano Mancini and Sebastiano Tomasi
We discuss the entanglement entropy for a massive scalar field in two Schwarzschild-like quantum black hole spacetimes, also including a nonminimal coupling term with the background scalar curvature. To compute the entanglement entropy, we start from the standard spherical shell discretization procedure, tracing over the degrees of freedom residing inside an imaginary surface. We estimate the free parameters for such quantum metrics through a simple physical argument based on Heisenberg uncertainty principle, along with alternative proposals as asymptotic safety, trace anomaly, and graviton corpuscular scaling. Our findings reveal a significant decrease in entropy compared to the area law near the origin for the quantum metrics. In both scenarios, the entanglement entropy converges to the expected area law sufficiently far from the origin. We then compare these results to the entropy scaling in regular Hayward and corrected-Hayward spacetimes to highlight the main differences with such regular approaches.
{"title":"Entanglement entropy in quantum black holes","authors":"Alessio Belfiglio, Orlando Luongo, Stefano Mancini and Sebastiano Tomasi","doi":"10.1088/1361-6382/ad9e66","DOIUrl":"https://doi.org/10.1088/1361-6382/ad9e66","url":null,"abstract":"We discuss the entanglement entropy for a massive scalar field in two Schwarzschild-like quantum black hole spacetimes, also including a nonminimal coupling term with the background scalar curvature. To compute the entanglement entropy, we start from the standard spherical shell discretization procedure, tracing over the degrees of freedom residing inside an imaginary surface. We estimate the free parameters for such quantum metrics through a simple physical argument based on Heisenberg uncertainty principle, along with alternative proposals as asymptotic safety, trace anomaly, and graviton corpuscular scaling. Our findings reveal a significant decrease in entropy compared to the area law near the origin for the quantum metrics. In both scenarios, the entanglement entropy converges to the expected area law sufficiently far from the origin. We then compare these results to the entropy scaling in regular Hayward and corrected-Hayward spacetimes to highlight the main differences with such regular approaches.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"32 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142935227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Pub Date : 2025-01-07DOI: 10.1088/1361-6382/ada197
Dalia Saha and Abhik Kumar Sanyal
The ‘generalized symmetric teleparallel gravity’ (GSTG) does not admit diffeomorphic invariance, since the auxiliary field as well as the shift vector act as non-propagating dynamical variables carrying 1/2 degrees of freedom each. We show that in a minisuperspace model, which is devoid of the shift vector, the problem is alleviated for locally Lorentz invariant GSTG theory, and diffeomorphic invariance is established at least for one connection. However, the eerie structure of the Hamiltonian constructed even in the background of spatially flat isotropic and homogeneous Robertson–Walker space-time, can not be maneuvered. In contrast, the other two spatially flat connections containing an arbitrary time dependent function, doesʼnt admit non-linear extension to ‘symmetric teleparallel equivalent to general relativity’ (STEGR). We therefore construct the phase-space structure with three different spatially flat connections for the ‘Lorentz invariant’ linear-scalar–vector–tensor GSTG action. Diffeomorphic invariance is established and the associated Hamiltonians are found to be well behaved for all the three cases.
{"title":"Phase space structure of symmetric teleparallel theory of gravity","authors":"Dalia Saha and Abhik Kumar Sanyal","doi":"10.1088/1361-6382/ada197","DOIUrl":"https://doi.org/10.1088/1361-6382/ada197","url":null,"abstract":"The ‘generalized symmetric teleparallel gravity’ (GSTG) does not admit diffeomorphic invariance, since the auxiliary field as well as the shift vector act as non-propagating dynamical variables carrying 1/2 degrees of freedom each. We show that in a minisuperspace model, which is devoid of the shift vector, the problem is alleviated for locally Lorentz invariant GSTG theory, and diffeomorphic invariance is established at least for one connection. However, the eerie structure of the Hamiltonian constructed even in the background of spatially flat isotropic and homogeneous Robertson–Walker space-time, can not be maneuvered. In contrast, the other two spatially flat connections containing an arbitrary time dependent function, doesʼnt admit non-linear extension to ‘symmetric teleparallel equivalent to general relativity’ (STEGR). We therefore construct the phase-space structure with three different spatially flat connections for the ‘Lorentz invariant’ linear-scalar–vector–tensor GSTG action. Diffeomorphic invariance is established and the associated Hamiltonians are found to be well behaved for all the three cases.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"98 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142935232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Pub Date : 2025-01-06DOI: 10.1088/1361-6382/ada2d5
Seokcheon Lee
The formalism provides a structured approach to analyzing spacetime by separating it into spatial and temporal components. When applied to the Robertson–Walker metric, it simplifies the analysis of cosmological evolution by dividing the Einstein field equations into constraint and evolution equations. It introduces the lapse function N and the shift vector Ni, which control how time and spatial coordinates evolve between hypersurfaces. In standard model cosmology, N = 1 and for the Robertson–Walker metric. However, the N becomes a function of time when we apply the metric to the minimally extended varying speed of light model. This approach allows for a more direct examination of the evolution of spatial geometry and offers flexibility in handling scenarios where the lapse function and shift vector vary. In this manuscript, we derive the model's N, Ni, along with the constraint and evolution equations, and demonstrate their consistency with the existing Einstein equations. We have shown in a previous paper that the possibility of changes in the speed of light in the Robertson–Walker metric is due to cosmological time dilation. Through the formalism, we can make the physical significance more explicit and demonstrate that it can be interpreted as the lapse function. From this, we show that the minimally extended varying speed of light model is consistent.
{"title":"3+1 formalism of the minimally extended varying speed of light model","authors":"Seokcheon Lee","doi":"10.1088/1361-6382/ada2d5","DOIUrl":"https://doi.org/10.1088/1361-6382/ada2d5","url":null,"abstract":"The formalism provides a structured approach to analyzing spacetime by separating it into spatial and temporal components. When applied to the Robertson–Walker metric, it simplifies the analysis of cosmological evolution by dividing the Einstein field equations into constraint and evolution equations. It introduces the lapse function N and the shift vector Ni, which control how time and spatial coordinates evolve between hypersurfaces. In standard model cosmology, N = 1 and for the Robertson–Walker metric. However, the N becomes a function of time when we apply the metric to the minimally extended varying speed of light model. This approach allows for a more direct examination of the evolution of spatial geometry and offers flexibility in handling scenarios where the lapse function and shift vector vary. In this manuscript, we derive the model's N, Ni, along with the constraint and evolution equations, and demonstrate their consistency with the existing Einstein equations. We have shown in a previous paper that the possibility of changes in the speed of light in the Robertson–Walker metric is due to cosmological time dilation. Through the formalism, we can make the physical significance more explicit and demonstrate that it can be interpreted as the lapse function. From this, we show that the minimally extended varying speed of light model is consistent.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"38 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142929583","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Pub Date : 2025-01-06DOI: 10.1088/1361-6382/ada1c1
Bowen Zhao, Lars Andersson and Shing-Tung Yau
We review the definition of Wang–Yau quasi-local mass from the point of view of the gravitational Hamiltonian. This makes clear the relation between Wang–Yau definition and Brown–York or even global ADM definition. We make a brief comment on admissibility condition in the definition of the Wang–Yau quasi-lcoal mass. We extend the positivity proof for Wang–Yau quasi-local energy to allow possible presence of strictly stable apparent horizons through establishing solvability of Dirac equation in certain 3-manifolds that possess cylindrical ends, as in the case of Jang graph blowing up at marginally outer trapped surfaces.
{"title":"Some remarks on Wang–Yau quasi-local mass","authors":"Bowen Zhao, Lars Andersson and Shing-Tung Yau","doi":"10.1088/1361-6382/ada1c1","DOIUrl":"https://doi.org/10.1088/1361-6382/ada1c1","url":null,"abstract":"We review the definition of Wang–Yau quasi-local mass from the point of view of the gravitational Hamiltonian. This makes clear the relation between Wang–Yau definition and Brown–York or even global ADM definition. We make a brief comment on admissibility condition in the definition of the Wang–Yau quasi-lcoal mass. We extend the positivity proof for Wang–Yau quasi-local energy to allow possible presence of strictly stable apparent horizons through establishing solvability of Dirac equation in certain 3-manifolds that possess cylindrical ends, as in the case of Jang graph blowing up at marginally outer trapped surfaces.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"37 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142929573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Pub Date : 2025-01-06DOI: 10.1088/1361-6382/ada2d6
Kinjalk Lochan and T Padmanabhan
The Bogoliubov transformation connecting the standard inertial frame mode functions to the standard mode functions defined in the Rindler frame R0, leads to the result that the inertial vacuum appears as a thermal state with temperature where a0 is the acceleration parameter of R0. We construct an infinite family of nested Rindler-like coordinate systems within the right Rindler wedge, with time coordinates and acceleration parameters by shifting the origin along the inertial x-axis by amounts . We show that, apart from the inertial vacuum, the Rindler vacuum of the frame Rn also appears to be a thermal state in the frame with the temperature . In fact, the Rindler frame attributes to all the Rindler vacuum states of , as well as to the inertial vacuum state, the same temperature . We further show that our result is discontinuous in an essential way in the coordinate shift parameters. For a Rindler frame Ri, this thermality turns on with smallest non-zero allowed in the semiclassical framework and remains insensitive to thereafter, indicating its universal Planckian origin. Similar structures can be introduced in the right wedge of any spacetime with bifurcate Killing horizon, like, for e.g. Schwarzschild spacetime. Apart from providing unsuppressed observables capturing Planck scale effects, these results have important implications for quantum gravity (QG) when flat spacetime is treated as the ground state of QG. Furthermore, a frame with the shift and the corresponding acceleration parameter can be thought of as a Rindler frame which is instantaneously comoving with the Einstein's elevator moving with a variable acceleration. Our result suggests that the quantum temperature associated with such an Einstein's elevator is the same as that defined in the comoving Rindler frame. The implications of these results are wide ranging, from having a definitive signature of Planck shifts in the horizon to the existence of a new set of observers in black hole exterior having thermodynamic description of the horizon they perceive.
{"title":"A nested sequence of inequivalent Rindler vacua : universal relic thermality of Planckian origin","authors":"Kinjalk Lochan and T Padmanabhan","doi":"10.1088/1361-6382/ada2d6","DOIUrl":"https://doi.org/10.1088/1361-6382/ada2d6","url":null,"abstract":"The Bogoliubov transformation connecting the standard inertial frame mode functions to the standard mode functions defined in the Rindler frame R0, leads to the result that the inertial vacuum appears as a thermal state with temperature where a0 is the acceleration parameter of R0. We construct an infinite family of nested Rindler-like coordinate systems within the right Rindler wedge, with time coordinates and acceleration parameters by shifting the origin along the inertial x-axis by amounts . We show that, apart from the inertial vacuum, the Rindler vacuum of the frame Rn also appears to be a thermal state in the frame with the temperature . In fact, the Rindler frame attributes to all the Rindler vacuum states of , as well as to the inertial vacuum state, the same temperature . We further show that our result is discontinuous in an essential way in the coordinate shift parameters. For a Rindler frame Ri, this thermality turns on with smallest non-zero allowed in the semiclassical framework and remains insensitive to thereafter, indicating its universal Planckian origin. Similar structures can be introduced in the right wedge of any spacetime with bifurcate Killing horizon, like, for e.g. Schwarzschild spacetime. Apart from providing unsuppressed observables capturing Planck scale effects, these results have important implications for quantum gravity (QG) when flat spacetime is treated as the ground state of QG. Furthermore, a frame with the shift and the corresponding acceleration parameter can be thought of as a Rindler frame which is instantaneously comoving with the Einstein's elevator moving with a variable acceleration. Our result suggests that the quantum temperature associated with such an Einstein's elevator is the same as that defined in the comoving Rindler frame. The implications of these results are wide ranging, from having a definitive signature of Planck shifts in the horizon to the existence of a new set of observers in black hole exterior having thermodynamic description of the horizon they perceive.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"27 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142929639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Pub Date : 2024-12-31DOI: 10.1088/1361-6382/ada083
Thiago H Moreira and Lucas C Céleri
Understanding the quantum nature of the gravitational field is undoubtedly one of the greatest challenges in theoretical physics. Despite significant progress, a complete and consistent theory remains elusive. However, in the weak field approximation—where curvature effects are small—we can explore some expected properties of such a theory. Particularly relevant to this study is the quantum nature of gravitational waves, which are represented as small perturbations in flat spacetime. In this framework, a quantum description of these perturbations, as a quantum field, is feasible, leading to the emergence of the graviton. Here we consider a non-relativistic quantum system interacting with such a field. We employ the consistent histories approach to quantum mechanics, which allows us to frame classical questions in a quantum context, to define a fluctuation relation for this system. As a result, thermodynamic entropy must be produced in the system due to its unavoidable interaction with the quantum fluctuations of spacetime.
{"title":"Entropy production due to spacetime fluctuations","authors":"Thiago H Moreira and Lucas C Céleri","doi":"10.1088/1361-6382/ada083","DOIUrl":"https://doi.org/10.1088/1361-6382/ada083","url":null,"abstract":"Understanding the quantum nature of the gravitational field is undoubtedly one of the greatest challenges in theoretical physics. Despite significant progress, a complete and consistent theory remains elusive. However, in the weak field approximation—where curvature effects are small—we can explore some expected properties of such a theory. Particularly relevant to this study is the quantum nature of gravitational waves, which are represented as small perturbations in flat spacetime. In this framework, a quantum description of these perturbations, as a quantum field, is feasible, leading to the emergence of the graviton. Here we consider a non-relativistic quantum system interacting with such a field. We employ the consistent histories approach to quantum mechanics, which allows us to frame classical questions in a quantum context, to define a fluctuation relation for this system. As a result, thermodynamic entropy must be produced in the system due to its unavoidable interaction with the quantum fluctuations of spacetime.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"3 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Pub Date : 2024-12-31DOI: 10.1088/1361-6382/ad9f17
Goutam Mandal and Sujay Kr Biswas
The present work aims to investigate an interacting Umami Chaplygin gas (UCG) in the background dynamics of a spatially flat Friedmann–Lemaitre–Robertson–Walker Universe when adiabatic particle creation is allowed. Here, the Universe is taken to be an open thermodynamical model where the particle is created irreversibly and consequently, the creation pressure comes into the energy-momentum tensor of the material content. The particle creation rate is assumed to have a linear relationship with the Hubble parameter ( ) and the created particle is dark matter (pressureless). With this creation rate a single fluid model studied and found no phase transition. Then, we studied an interacting two-fluid model where second fluid is taken as perfect fluid equation of state (EOS) and late-time acceleration is obtained. Next, interacting UCG is studied in context of particle creation. Dynamical stability of the model is performed by perturbing the autonomous system around critical points upto first order. Classical stability of the model is also studied at each critical point. This study explores some cosmologically viable scenarios when we constrain the model parameters. Some critical points exhibit the accelerated de Sitter expansion of the Universe at both the early phase as well as the late phase of evolution which is characterized by completely Umami Chaplygin fluid EOS. Scaling solutions are also described by some other critical points showing late-time accelerated attractors in phase space satisfying present observational data, and solving the coincidence problem. In a specific region of parameters, a sequence of critical points is achieved exhibiting a unified cosmic evolution of the Universe starting from early inflation (represented by source point), which is followed by a decelerated intermediate phase (described by saddle solution), and finally goes through the late-time dark energy dominated Universe (represented by stable point). Finally, non-singular bouncing behavior of the Universe is also investigated for this model numerically.
{"title":"Dynamical systems analysis of a cosmological model with interacting Umami Chaplygin fluid in adiabatic particle creation mechanism: some bouncing features","authors":"Goutam Mandal and Sujay Kr Biswas","doi":"10.1088/1361-6382/ad9f17","DOIUrl":"https://doi.org/10.1088/1361-6382/ad9f17","url":null,"abstract":"The present work aims to investigate an interacting Umami Chaplygin gas (UCG) in the background dynamics of a spatially flat Friedmann–Lemaitre–Robertson–Walker Universe when adiabatic particle creation is allowed. Here, the Universe is taken to be an open thermodynamical model where the particle is created irreversibly and consequently, the creation pressure comes into the energy-momentum tensor of the material content. The particle creation rate is assumed to have a linear relationship with the Hubble parameter ( ) and the created particle is dark matter (pressureless). With this creation rate a single fluid model studied and found no phase transition. Then, we studied an interacting two-fluid model where second fluid is taken as perfect fluid equation of state (EOS) and late-time acceleration is obtained. Next, interacting UCG is studied in context of particle creation. Dynamical stability of the model is performed by perturbing the autonomous system around critical points upto first order. Classical stability of the model is also studied at each critical point. This study explores some cosmologically viable scenarios when we constrain the model parameters. Some critical points exhibit the accelerated de Sitter expansion of the Universe at both the early phase as well as the late phase of evolution which is characterized by completely Umami Chaplygin fluid EOS. Scaling solutions are also described by some other critical points showing late-time accelerated attractors in phase space satisfying present observational data, and solving the coincidence problem. In a specific region of parameters, a sequence of critical points is achieved exhibiting a unified cosmic evolution of the Universe starting from early inflation (represented by source point), which is followed by a decelerated intermediate phase (described by saddle solution), and finally goes through the late-time dark energy dominated Universe (represented by stable point). Finally, non-singular bouncing behavior of the Universe is also investigated for this model numerically.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"175 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142904830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Pub Date : 2024-12-31DOI: 10.1088/1361-6382/ada082
Vitalii Vertogradov and Ali Övgün
In this paper, we present three exact solutions to the Einstein field equations, each illustrating different black hole models. The first solution introduces a black hole with a variable equation of state, , which can represent both singular and regular black holes depending on the parameters M0 and w0. The second solution features a black hole with Hagedorn fluid, relevant to the late stages of black hole formation, and reveals similarities to the first solution by also describing both singular and regular black holes in a specific case. Furthermore, we investigate the shadows cast by these black hole solutions to constrain their parameters. Recognizing that real astrophysical black holes are dynamic, we developed a third, dynamical solution that addresses gravitational collapse and suggests the potential formation of naked singularities. This indicates that a black hole can transition from regular to singular and back to regular during its evolution.
{"title":"Exact regular black hole solutions with de Sitter cores and Hagedorn fluid","authors":"Vitalii Vertogradov and Ali Övgün","doi":"10.1088/1361-6382/ada082","DOIUrl":"https://doi.org/10.1088/1361-6382/ada082","url":null,"abstract":"In this paper, we present three exact solutions to the Einstein field equations, each illustrating different black hole models. The first solution introduces a black hole with a variable equation of state, , which can represent both singular and regular black holes depending on the parameters M0 and w0. The second solution features a black hole with Hagedorn fluid, relevant to the late stages of black hole formation, and reveals similarities to the first solution by also describing both singular and regular black holes in a specific case. Furthermore, we investigate the shadows cast by these black hole solutions to constrain their parameters. Recognizing that real astrophysical black holes are dynamic, we developed a third, dynamical solution that addresses gravitational collapse and suggests the potential formation of naked singularities. This indicates that a black hole can transition from regular to singular and back to regular during its evolution.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"65 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Pub Date : 2024-12-31DOI: 10.1088/1361-6382/ad9f16
Paulo Mourão, José Natário and Rodrigo Vicente
We derive the equations of motion for relativistic elastic membranes, that is, two-dimensional elastic bodies whose internal energy depends only on their stretching, starting from a variational principle. We show how to obtain conserved quantities for the membrane’s motion in the presence of spacetime symmetries, determine the membrane’s longitudinal and transverse speeds of sound in isotropic states, and compute the coefficients of linear elasticity with respect to the relaxed configuration. We then use this formalism to discuss two physically interesting systems: a rigidly rotating elastic disk, widely discussed in the context of Ehrenfest’s paradox, and a Dyson sphere, that is, a spherical membrane in equilibrium in Schwarzschild’s spacetime, with the isotropic tangential pressure balancing the gravitational attraction. Surprisingly, although spherically symmetric perturbations of this system are linearly stable, the axi-symmetric dipolar mode is already unstable. This may be taken as a cautionary tale against misconstruing radial stability as true stability.
{"title":"Relativistic elastic membranes: rotating disks and Dyson spheres","authors":"Paulo Mourão, José Natário and Rodrigo Vicente","doi":"10.1088/1361-6382/ad9f16","DOIUrl":"https://doi.org/10.1088/1361-6382/ad9f16","url":null,"abstract":"We derive the equations of motion for relativistic elastic membranes, that is, two-dimensional elastic bodies whose internal energy depends only on their stretching, starting from a variational principle. We show how to obtain conserved quantities for the membrane’s motion in the presence of spacetime symmetries, determine the membrane’s longitudinal and transverse speeds of sound in isotropic states, and compute the coefficients of linear elasticity with respect to the relaxed configuration. We then use this formalism to discuss two physically interesting systems: a rigidly rotating elastic disk, widely discussed in the context of Ehrenfest’s paradox, and a Dyson sphere, that is, a spherical membrane in equilibrium in Schwarzschild’s spacetime, with the isotropic tangential pressure balancing the gravitational attraction. Surprisingly, although spherically symmetric perturbations of this system are linearly stable, the axi-symmetric dipolar mode is already unstable. This may be taken as a cautionary tale against misconstruing radial stability as true stability.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"72 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Pub Date : 2024-12-30DOI: 10.1088/1361-6382/ad9131
Katharine Cella, Stephen R Taylor and Luke Zoltan Kelley
Massive black hole binaries (MBHBs) produce gravitational waves (GWs) that are detectable with pulsar timing arrays. We determine the properties of the host galaxies of simulated MBHBs at the time they are producing detectable GW signals. The population of MBHB systems we evaluate is from the Illustris cosmological simulations taken in tandem with post processing semi-analytic models of environmental factors in the evolution of binaries. Upon evolving to the GW frequency regime accessible by pulsar timing arrays, we calculate the detection probability of each system using a variety of different values for pulsar noise characteristics in a plausible near-future International Pulsar Timing Array dataset. We find that detectable systems have host galaxies that are clearly distinct from the overall binary population and from most galaxies in general. With conservative noise factors, we find that host stellar metallicity, for example, peaks at as opposed to the total population of galaxies which peaks at . Additionally, the most detectable systems are much brighter in magnitude and more red in color than the overall population, indicating their likely identity as large ellipticals with diminished star formation. These results can be used to develop effective search strategies for identifying host galaxies and electromagnetic counterparts following GW detection by pulsar timing arrays.
{"title":"Host galaxy demographics of individually detectable supermassive black-hole binaries with pulsar timing arrays","authors":"Katharine Cella, Stephen R Taylor and Luke Zoltan Kelley","doi":"10.1088/1361-6382/ad9131","DOIUrl":"https://doi.org/10.1088/1361-6382/ad9131","url":null,"abstract":"Massive black hole binaries (MBHBs) produce gravitational waves (GWs) that are detectable with pulsar timing arrays. We determine the properties of the host galaxies of simulated MBHBs at the time they are producing detectable GW signals. The population of MBHB systems we evaluate is from the Illustris cosmological simulations taken in tandem with post processing semi-analytic models of environmental factors in the evolution of binaries. Upon evolving to the GW frequency regime accessible by pulsar timing arrays, we calculate the detection probability of each system using a variety of different values for pulsar noise characteristics in a plausible near-future International Pulsar Timing Array dataset. We find that detectable systems have host galaxies that are clearly distinct from the overall binary population and from most galaxies in general. With conservative noise factors, we find that host stellar metallicity, for example, peaks at as opposed to the total population of galaxies which peaks at . Additionally, the most detectable systems are much brighter in magnitude and more red in color than the overall population, indicating their likely identity as large ellipticals with diminished star formation. These results can be used to develop effective search strategies for identifying host galaxies and electromagnetic counterparts following GW detection by pulsar timing arrays.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"34 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142901829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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