Pub Date : 2025-01-13DOI: 10.1088/1361-6382/ada2d4
Johanna Borissova, Astrid Eichhorn and Shouryya Ray
The no-global-symmetries conjecture is central to the swampland program that delineates the boundary between effective field theories that can be obtained from a quantum theory of gravity to those that cannot. The conjecture states that virtual black-hole configurations in the path integral generate terms that violate all global symmetries in the effective action for matter. Because of its central role, it is crucial to understand limitations to the validity of this conjecture. In the context of the Lorentzian path integral over spacetime geometries, we explore whether virtual black-hole configurations can be suppressed dynamically. To that end, we work in a spherically symmetric setting and make use of horizon-detecting curvature invariants which vanish on the horizon. By constructing a non-local gravitational action from the inverse of such curvature invariants, we can achieve destructive interference of black-hole configurations in the path integral. Given that non-local gravitational actions appear generically as the result of integrating out matter degrees of freedom from a theory for quantum gravity and matter, our exemplary construction reinforces discussions about the role of non-locality in assessing arguably universal properties of quantum gravity within the framework of path integrals.
{"title":"A non-local way around the no-global-symmetries conjecture in quantum gravity?","authors":"Johanna Borissova, Astrid Eichhorn and Shouryya Ray","doi":"10.1088/1361-6382/ada2d4","DOIUrl":"https://doi.org/10.1088/1361-6382/ada2d4","url":null,"abstract":"The no-global-symmetries conjecture is central to the swampland program that delineates the boundary between effective field theories that can be obtained from a quantum theory of gravity to those that cannot. The conjecture states that virtual black-hole configurations in the path integral generate terms that violate all global symmetries in the effective action for matter. Because of its central role, it is crucial to understand limitations to the validity of this conjecture. In the context of the Lorentzian path integral over spacetime geometries, we explore whether virtual black-hole configurations can be suppressed dynamically. To that end, we work in a spherically symmetric setting and make use of horizon-detecting curvature invariants which vanish on the horizon. By constructing a non-local gravitational action from the inverse of such curvature invariants, we can achieve destructive interference of black-hole configurations in the path integral. Given that non-local gravitational actions appear generically as the result of integrating out matter degrees of freedom from a theory for quantum gravity and matter, our exemplary construction reinforces discussions about the role of non-locality in assessing arguably universal properties of quantum gravity within the framework of path integrals.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"36 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968246","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 : 2025-01-13DOI: 10.1088/1361-6382/ad9f13
Kylan Jersey, Harold Hollis, Han-Yu Chia, Jose Sanjuan, Paul Fulda, Guido Mueller and Felipe Guzman
The optical truss interferometer (OTI) is a contingent subsystem proposed for the LISA telescopes to aid in the verification of a optical path length stability. Each telescope would be equipped with three pairs of compact fiber-coupled units, each forming an optical cavity with a baseline proportional to the telescope length at different points around the aperture. Employing a Pound–Drever–Hall approach to maintain a modulated laser field on resonance with each cavity, the dimensional stability of the telescope can be measured and verified. We have designed and developed prototype OTI units to demonstrate the capability of measuring stable structures, such as the LISA telescope, with a sensitivity using a set of freely mountable fiber-injected cavities. Aside from its initial motivation for the telescope, the OTI can also be readily integrated with other systems to aid in ground testing experiments. In this paper, we outline our experimental setup, measurement results, and analyses of the noise limitations.
{"title":"Picometer sensitive prototype of the optical truss interferometer for LISA","authors":"Kylan Jersey, Harold Hollis, Han-Yu Chia, Jose Sanjuan, Paul Fulda, Guido Mueller and Felipe Guzman","doi":"10.1088/1361-6382/ad9f13","DOIUrl":"https://doi.org/10.1088/1361-6382/ad9f13","url":null,"abstract":"The optical truss interferometer (OTI) is a contingent subsystem proposed for the LISA telescopes to aid in the verification of a optical path length stability. Each telescope would be equipped with three pairs of compact fiber-coupled units, each forming an optical cavity with a baseline proportional to the telescope length at different points around the aperture. Employing a Pound–Drever–Hall approach to maintain a modulated laser field on resonance with each cavity, the dimensional stability of the telescope can be measured and verified. We have designed and developed prototype OTI units to demonstrate the capability of measuring stable structures, such as the LISA telescope, with a sensitivity using a set of freely mountable fiber-injected cavities. Aside from its initial motivation for the telescope, the OTI can also be readily integrated with other systems to aid in ground testing experiments. In this paper, we outline our experimental setup, measurement results, and analyses of the noise limitations.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"11 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968245","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 : 2025-01-10DOI: 10.1088/1361-6382/ad9e67
Kaloian D Lozanov, Shi Pi, Misao Sasaki, Volodymyr Takhistov and Ao Wang
Formation of cosmological solitons is generically accompanied by production of gravitational waves (GWs), with a universal GW background expected at frequency scales below that of non-linear dynamics. Beginning with a general phenomenological description of GWs associated with soliton formation, we demonstrate that universal GW background from axion-like particle solitonic oscillons provides a viable interpretation to the recent NANOGrav 15 year pulsar timing array (PTA) data, which does not suffer from the overproduction of primordial black holes. We show that PTA data displays preference for models where formed solitons do not strongly interact or cluster. Coincidence observations with Nancy Roman telescope will allow to discriminate between distinct scenarios of cosmological solitons.
{"title":"Axion-like universal gravitational wave interpretation of pulsar timing array data","authors":"Kaloian D Lozanov, Shi Pi, Misao Sasaki, Volodymyr Takhistov and Ao Wang","doi":"10.1088/1361-6382/ad9e67","DOIUrl":"https://doi.org/10.1088/1361-6382/ad9e67","url":null,"abstract":"Formation of cosmological solitons is generically accompanied by production of gravitational waves (GWs), with a universal GW background expected at frequency scales below that of non-linear dynamics. Beginning with a general phenomenological description of GWs associated with soliton formation, we demonstrate that universal GW background from axion-like particle solitonic oscillons provides a viable interpretation to the recent NANOGrav 15 year pulsar timing array (PTA) data, which does not suffer from the overproduction of primordial black holes. We show that PTA data displays preference for models where formed solitons do not strongly interact or cluster. Coincidence observations with Nancy Roman telescope will allow to discriminate between distinct scenarios of cosmological solitons.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"67 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142939951","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/ad9f19
Geoffrey Lovelace, Kyle C Nelli, Nils Deppe, Nils L Vu, William Throwe, Marceline S Bonilla, Alexander Carpenter, Lawrence E Kidder, Alexandra Macedo, Mark A Scheel, Azer Afram, Michael Boyle, Andrea Ceja, Matthew Giesler, Sarah Habib, Ken Z Jones, Prayush Kumar, Guillermo Lara, Denyz Melchor, Iago B Mendes, Keefe Mitman, Marlo Morales, Jordan Moxon, Eamonn O’Shea, Kyle Pannone, Harald P Pfeiffer, Teresita Ramirez-Aguilar, Jennifer Sanchez, Daniel Tellez, Saul A Teukolsky and Nikolas A Wittek
Binary black holes are the most abundant source of gravitational-wave observations. Gravitational-wave observatories in the next decade will require tremendous increases in the accuracy of numerical waveforms modeling binary black holes, compared to today’s state of the art. One approach to achieving the required accuracy is using spectral-type methods that scale to many processors. Using the SpECTRE numerical-relativity (NR) code, we present the first simulations of a binary black hole inspiral, merger, and ringdown using discontinuous Galerkin (DG) methods. The efficiency of DG methods allows us to evolve the binary through ∼ 18 orbits at reasonable computational cost. We then use SpECTRE’s Cauchy Characteristic Evolution (CCE) code to extract the gravitational waves at future null infinity. The open-source nature of SpECTRE means this is the first time a spectral-type method for simulating binary black hole evolutions is available to the entire NR community.
{"title":"Simulating binary black hole mergers using discontinuous Galerkin methods","authors":"Geoffrey Lovelace, Kyle C Nelli, Nils Deppe, Nils L Vu, William Throwe, Marceline S Bonilla, Alexander Carpenter, Lawrence E Kidder, Alexandra Macedo, Mark A Scheel, Azer Afram, Michael Boyle, Andrea Ceja, Matthew Giesler, Sarah Habib, Ken Z Jones, Prayush Kumar, Guillermo Lara, Denyz Melchor, Iago B Mendes, Keefe Mitman, Marlo Morales, Jordan Moxon, Eamonn O’Shea, Kyle Pannone, Harald P Pfeiffer, Teresita Ramirez-Aguilar, Jennifer Sanchez, Daniel Tellez, Saul A Teukolsky and Nikolas A Wittek","doi":"10.1088/1361-6382/ad9f19","DOIUrl":"https://doi.org/10.1088/1361-6382/ad9f19","url":null,"abstract":"Binary black holes are the most abundant source of gravitational-wave observations. Gravitational-wave observatories in the next decade will require tremendous increases in the accuracy of numerical waveforms modeling binary black holes, compared to today’s state of the art. One approach to achieving the required accuracy is using spectral-type methods that scale to many processors. Using the SpECTRE numerical-relativity (NR) code, we present the first simulations of a binary black hole inspiral, merger, and ringdown using discontinuous Galerkin (DG) methods. The efficiency of DG methods allows us to evolve the binary through ∼ 18 orbits at reasonable computational cost. We then use SpECTRE’s Cauchy Characteristic Evolution (CCE) code to extract the gravitational waves at future null infinity. The open-source nature of SpECTRE means this is the first time a spectral-type method for simulating binary black hole evolutions is available to the entire NR community.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"82 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142935229","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/ada196
Akihito Katsumata, Tomohiro Harada, Kota Ogasawara and Hayami Iizuka
We propose a prescription for a new series expansion of the periapsis shift. The prescription formulates the periapsis shift in various spacetimes analytically without using special functions and provides simple and highly accurate approximate formulae. We derive new series representations for the periapsis shift in the Kerr and the Chazy–Curzon spacetimes by using the prescription, where the expansion parameter is defined as the eccentricity divided by the non-dimensional quantity that vanishes in the limit of the innermost stable circular orbit (ISCO). That is to say, the expansion parameter characterizes both the eccentricity of the orbit and its proximity to the ISCO. The smaller the eccentricity, the higher the accuracy of the formulae that are obtained by truncating the new series representations up to a finite number of terms. If the eccentricity is sufficiently small, the truncated new representations have higher accuracy than the post-Newtonian (PN) expansion formulae even in strong gravitational fields where the convergence of the PN expansion formula is not guaranteed. On the other hand, even if the orbit is highly eccentric, the truncated new representations have comparable or higher accuracy than the PN expansion formulae if the semi-major axis is sufficiently large. An exact formula for the periapsis shift of the quasi-circular orbit in the Chazy–Curzon spacetime is also obtained as a special case of the new series representation.
{"title":"New series expansion for the periapsis shift","authors":"Akihito Katsumata, Tomohiro Harada, Kota Ogasawara and Hayami Iizuka","doi":"10.1088/1361-6382/ada196","DOIUrl":"https://doi.org/10.1088/1361-6382/ada196","url":null,"abstract":"We propose a prescription for a new series expansion of the periapsis shift. The prescription formulates the periapsis shift in various spacetimes analytically without using special functions and provides simple and highly accurate approximate formulae. We derive new series representations for the periapsis shift in the Kerr and the Chazy–Curzon spacetimes by using the prescription, where the expansion parameter is defined as the eccentricity divided by the non-dimensional quantity that vanishes in the limit of the innermost stable circular orbit (ISCO). That is to say, the expansion parameter characterizes both the eccentricity of the orbit and its proximity to the ISCO. The smaller the eccentricity, the higher the accuracy of the formulae that are obtained by truncating the new series representations up to a finite number of terms. If the eccentricity is sufficiently small, the truncated new representations have higher accuracy than the post-Newtonian (PN) expansion formulae even in strong gravitational fields where the convergence of the PN expansion formula is not guaranteed. On the other hand, even if the orbit is highly eccentric, the truncated new representations have comparable or higher accuracy than the PN expansion formulae if the semi-major axis is sufficiently large. An exact formula for the periapsis shift of the quasi-circular orbit in the Chazy–Curzon spacetime is also obtained as a special case of the new series representation.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"12 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142935230","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/ada339
Guillaume Faye and Ali Seraj
Gravitational waves cause freely falling spinning objects to precess, resulting in a net orientation change called gyroscopic memory. In this paper, we will consider isolated gravitational sources in the post-Newtonian (PN) framework and compute the gyroscopic precession and memory at leading PN orders. We compare two competing contributions: the spin memory and the nonlinear helicity flux. At the level of the precession rate, the former is a 2PN oscillatory effect, while the latter is a 4PN adiabatic effect. However, the gyroscopic memory involves a time integration, which enhances subleading adiabatic effects by the fifth power of the velocity of light, leading to a 1.5PN memory effect. We explicitly compute the leading effects for a quasi-circular binary system and obtain the angular dependence of the memory on the celestial sphere.
{"title":"Gyroscopic gravitational memory from quasi-circular binary systems","authors":"Guillaume Faye and Ali Seraj","doi":"10.1088/1361-6382/ada339","DOIUrl":"https://doi.org/10.1088/1361-6382/ada339","url":null,"abstract":"Gravitational waves cause freely falling spinning objects to precess, resulting in a net orientation change called gyroscopic memory. In this paper, we will consider isolated gravitational sources in the post-Newtonian (PN) framework and compute the gyroscopic precession and memory at leading PN orders. We compare two competing contributions: the spin memory and the nonlinear helicity flux. At the level of the precession rate, the former is a 2PN oscillatory effect, while the latter is a 4PN adiabatic effect. However, the gyroscopic memory involves a time integration, which enhances subleading adiabatic effects by the fifth power of the velocity of light, leading to a 1.5PN memory effect. We explicitly compute the leading effects for a quasi-circular binary system and obtain the angular dependence of the memory on the celestial sphere.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"310 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142935233","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/ada2d2
Zihan Wang, Yanfu Liu, Xida Han, Yuntao Cheng, Ming Li and Hongchao Zhao
The telescope serves as a vital component of the space gravitational wave detector. In TianQin project, the exceptional dimensional stability of the telescope must be better than 1 pm Hz−1/2 @0.1 mHz–1 Hz. To assess the in-orbit dimensional stability of the telescope, a transfer function model was developed to evaluate the stability of the primary and secondary mirror spacing structure, considering the three primary thermal sources. It has been discovered that the stability of the spacer structure is influenced not only by the thermal expansion coefficient of the material but also by its heat capacity, density, and frequency band. Zerodur offers distinct advantages in terms of overall thermal performance. Specifically, the stability of the spacer constructed by it can be effectively controlled at 0.14 pm Hz−1/2@0.1 mHz–1 Hz, which is an achievement in the field of ultra-stability structure design.
{"title":"Dimensional stability sensitivity analysis based on transfer function models for telescope in space gravitational wave detectors","authors":"Zihan Wang, Yanfu Liu, Xida Han, Yuntao Cheng, Ming Li and Hongchao Zhao","doi":"10.1088/1361-6382/ada2d2","DOIUrl":"https://doi.org/10.1088/1361-6382/ada2d2","url":null,"abstract":"The telescope serves as a vital component of the space gravitational wave detector. In TianQin project, the exceptional dimensional stability of the telescope must be better than 1 pm Hz−1/2 @0.1 mHz–1 Hz. To assess the in-orbit dimensional stability of the telescope, a transfer function model was developed to evaluate the stability of the primary and secondary mirror spacing structure, considering the three primary thermal sources. It has been discovered that the stability of the spacer structure is influenced not only by the thermal expansion coefficient of the material but also by its heat capacity, density, and frequency band. Zerodur offers distinct advantages in terms of overall thermal performance. Specifically, the stability of the spacer constructed by it can be effectively controlled at 0.14 pm Hz−1/2@0.1 mHz–1 Hz, which is an achievement in the field of ultra-stability structure design.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"28 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142935234","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/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}
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