Pub Date : 2026-01-16DOI: 10.1088/1361-6382/ae3424
Pradosh Keshav MV
We develop a stochastic extension of the Wheeler–DeWitt equation in Friedmann–Lemaître–Robertson–Walker (FLRW) minisuperspace and show that quantum backreaction can dynamically regulate the big bang singularity without imposing external boundary conditions. Using Laplace–Beltrami (LB) quantisation and an open-system treatment of coarse-grained graviton modes, we obtain a stochastic Hamiltonian evolution equation in which the diffusion coefficient takes the form . This multiplicative noise vanishes at the origin and renders a = 0 an entrance boundary in Feller’s classification, leading to super-exponential suppression of the LB weighted stationary density and zero probability flux into the singular point. At large scale factor, the global behaviour depends on the cosmological sector: de Sitter and positive potential-dominated regimes exhibit power-law stationary tails, whereas confining potentials or negative effective cosmological constant lead to an entrance boundary at infinity and a globally normalisable steady state. Taken together, these results indicate that stochastic backreaction arising from semiclassical coarse-graining provides a consistent and dynamical mechanism for singularity avoidance in minisuperspace quantum cosmology.
{"title":"Can stochastic clocks in FLRW minisuperspace prevent dynamical singularities?","authors":"Pradosh Keshav MV","doi":"10.1088/1361-6382/ae3424","DOIUrl":"https://doi.org/10.1088/1361-6382/ae3424","url":null,"abstract":"We develop a stochastic extension of the Wheeler–DeWitt equation in Friedmann–Lemaître–Robertson–Walker (FLRW) minisuperspace and show that quantum backreaction can dynamically regulate the big bang singularity without imposing external boundary conditions. Using Laplace–Beltrami (LB) quantisation and an open-system treatment of coarse-grained graviton modes, we obtain a stochastic Hamiltonian evolution equation in which the diffusion coefficient takes the form . This multiplicative noise vanishes at the origin and renders a = 0 an entrance boundary in Feller’s classification, leading to super-exponential suppression of the LB weighted stationary density and zero probability flux into the singular point. At large scale factor, the global behaviour depends on the cosmological sector: de Sitter and positive potential-dominated regimes exhibit power-law stationary tails, whereas confining potentials or negative effective cosmological constant lead to an entrance boundary at infinity and a globally normalisable steady state. Taken together, these results indicate that stochastic backreaction arising from semiclassical coarse-graining provides a consistent and dynamical mechanism for singularity avoidance in minisuperspace quantum cosmology.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"18 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145972327","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 : 2026-01-14DOI: 10.1088/1361-6382/ae30c7
Thomas Chehab, Olivier Minazzoli and Aurélien Hees
Entangled Relativity is a recent non-linear reformulation of General Relativity that does not include Planck’s constant or Newton’s gravitational constant G in its fundamental structure. One of its key predictions is that emerges as a dynamical field, potentially varying across space and time. In this study, we estimate the magnitude of such variations in three different astrophysical environments: the weak gravitational fields of the Sun and Earth, the intermediate regime of white dwarfs, and the strong fields found in neutron stars. In the Solar System, the relative change in is minimal, reaching at most . In white dwarfs, depending on central density, variations range from to . For neutron stars, the variation can be as high as 1.5% at the surface relative to a remote observer, and up to 5.7% at the center. These results suggest that, if Entangled Relativity accurately describes gravity, spatial variations of Planck’s constant could become an observable signature, particularly in the context of dense stellar objects.
{"title":"Variation of Planck’s quantum of action in Entangled Relativity","authors":"Thomas Chehab, Olivier Minazzoli and Aurélien Hees","doi":"10.1088/1361-6382/ae30c7","DOIUrl":"https://doi.org/10.1088/1361-6382/ae30c7","url":null,"abstract":"Entangled Relativity is a recent non-linear reformulation of General Relativity that does not include Planck’s constant or Newton’s gravitational constant G in its fundamental structure. One of its key predictions is that emerges as a dynamical field, potentially varying across space and time. In this study, we estimate the magnitude of such variations in three different astrophysical environments: the weak gravitational fields of the Sun and Earth, the intermediate regime of white dwarfs, and the strong fields found in neutron stars. In the Solar System, the relative change in is minimal, reaching at most . In white dwarfs, depending on central density, variations range from to . For neutron stars, the variation can be as high as 1.5% at the surface relative to a remote observer, and up to 5.7% at the center. These results suggest that, if Entangled Relativity accurately describes gravity, spatial variations of Planck’s constant could become an observable signature, particularly in the context of dense stellar objects.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"709 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145961998","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 : 2026-01-12DOI: 10.1088/1361-6382/ae32db
Jie Chang, Wei Wang, Yiyan Xu, Bingwei Cai, Ji Wang, Shengping Huang, Hengxu Yang and Chao Xue
The TianQin project aims to detect gravitational waves from space using a constellation of satellites, each carrying test masses (TMs) as inertial references. A critical subsystem is the grabbing, positioning and release mechanism (GPRM), which must release the TM with extreme precision. A key challenge is the lateral deflection of the inchworm piezoelectric actuator that drives the GPRM, which may compromise release accuracy. This study combines ground experiments, dynamic modeling, and finite element simulation to investigate the origin and characteristics of these deflections. Experimental results show significant lateral displacements during axial motion, which are attributed to force imbalances caused by inconsistent step lengths among piezoelectric legs. The dynamic model reveals that asymmetric driving forces induce rotational torque, leading to lateral deflections. Finite element simulations confirm this mechanism and accurately reproduce the three-axis motion. These findings provide critical insight into the actuator’s non-ideal behavior, supporting the optimization of the GPRM for reliable on-orbit operation and the success of the TianQin project.
{"title":"Research on lateral deflection in inchworm piezoelectric actuator of TianQin’s test mass release mechanism","authors":"Jie Chang, Wei Wang, Yiyan Xu, Bingwei Cai, Ji Wang, Shengping Huang, Hengxu Yang and Chao Xue","doi":"10.1088/1361-6382/ae32db","DOIUrl":"https://doi.org/10.1088/1361-6382/ae32db","url":null,"abstract":"The TianQin project aims to detect gravitational waves from space using a constellation of satellites, each carrying test masses (TMs) as inertial references. A critical subsystem is the grabbing, positioning and release mechanism (GPRM), which must release the TM with extreme precision. A key challenge is the lateral deflection of the inchworm piezoelectric actuator that drives the GPRM, which may compromise release accuracy. This study combines ground experiments, dynamic modeling, and finite element simulation to investigate the origin and characteristics of these deflections. Experimental results show significant lateral displacements during axial motion, which are attributed to force imbalances caused by inconsistent step lengths among piezoelectric legs. The dynamic model reveals that asymmetric driving forces induce rotational torque, leading to lateral deflections. Finite element simulations confirm this mechanism and accurately reproduce the three-axis motion. These findings provide critical insight into the actuator’s non-ideal behavior, supporting the optimization of the GPRM for reliable on-orbit operation and the success of the TianQin project.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"9 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145950004","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 : 2026-01-08DOI: 10.1088/1361-6382/ae3044
Enrique Gaztañaga, K Sravan Kumar and João Marto
The formulation of quantum field theory in Minkowski spacetime, which emerges from the unification of special relativity and quantum mechanics, is based on treating time as a parameter, assuming a fixed arrow of time, and requiring that field operators commute for spacelike distances. This procedure is questioned here in the context of quantum field theory in curved spacetime (QFTCS). In 1935, Einstein and Rosen (ER), in their seminal paper (Einstein and Rosen 1935 Phys. Rev.48 73–77) proposed that ‘a particle in the physical Universe has to be described by mathematical bridges connecting two sheets of spacetime’ which involved two arrows of time. Recently proposed direct-sum quantum theory reconciles this ER’s vision by introducing geometric superselection sectors associated with the regions of spacetime related by discrete transformations. We further establish that the quantum effects at gravitational horizons involve the physics of quantum inverted harmonic oscillators that have phase space horizons. This new understanding of the ER bridges is not related to classical wormholes, it addresses the original ER puzzle and promises a unitary description of QFTCS, along with observer complementarity. Furthermore, we present compelling evidence for our new understanding of ER bridges in the form of large-scale parity asymmetric features in the cosmic microwave background, which is statistically 650 times stronger than the standard scale-invariant power spectrum from the typical understanding of inflationary quantum fluctuations when compared with the posterior probabilities associated with the model given the data. We finally discuss the implications of this new understanding in combining gravity and quantum mechanics.
{"title":"A new understanding of Einstein–Rosen bridges","authors":"Enrique Gaztañaga, K Sravan Kumar and João Marto","doi":"10.1088/1361-6382/ae3044","DOIUrl":"https://doi.org/10.1088/1361-6382/ae3044","url":null,"abstract":"The formulation of quantum field theory in Minkowski spacetime, which emerges from the unification of special relativity and quantum mechanics, is based on treating time as a parameter, assuming a fixed arrow of time, and requiring that field operators commute for spacelike distances. This procedure is questioned here in the context of quantum field theory in curved spacetime (QFTCS). In 1935, Einstein and Rosen (ER), in their seminal paper (Einstein and Rosen 1935 Phys. Rev.48 73–77) proposed that ‘a particle in the physical Universe has to be described by mathematical bridges connecting two sheets of spacetime’ which involved two arrows of time. Recently proposed direct-sum quantum theory reconciles this ER’s vision by introducing geometric superselection sectors associated with the regions of spacetime related by discrete transformations. We further establish that the quantum effects at gravitational horizons involve the physics of quantum inverted harmonic oscillators that have phase space horizons. This new understanding of the ER bridges is not related to classical wormholes, it addresses the original ER puzzle and promises a unitary description of QFTCS, along with observer complementarity. Furthermore, we present compelling evidence for our new understanding of ER bridges in the form of large-scale parity asymmetric features in the cosmic microwave background, which is statistically 650 times stronger than the standard scale-invariant power spectrum from the typical understanding of inflationary quantum fluctuations when compared with the posterior probabilities associated with the model given the data. We finally discuss the implications of this new understanding in combining gravity and quantum mechanics.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"77 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145920053","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 : 2026-01-08DOI: 10.1088/1361-6382/ae2377
Leo J A Parry, Diego Vidal-Cruzprieto, Christopher J Fewster and Jorma Louko
How long does a uniformly rotating observer need to interact with a quantum field in order to register an approximately thermal response due to the circular motion Unruh effect? We address this question for a massless scalar field in dimensions, defining the effective temperature via the ratio of excitation and de-excitation rates of an Unruh–DeWitt detector in the long interaction time limit. In this system, the effective temperature is known to be significantly smaller than the linear motion Unruh effect prediction when the detector’s energy gap is small: the effective temperature tends to zero in the small gap limit, linearly in the gap. We show that a positive small gap temperature at long interaction times can be regained via a controlled long-time-small-gap double limit, provided the detector’s coupling to the field is allowed to change sign. The resulting small gap temperature depends on the parameters of the circular motion but not on the details of the detector’s switching. The results broaden the energy range for pursuing an experimental verification of the circular motion Unruh effect in analogue spacetime experiments. As a mathematical tool, we provide a new implementation of the long interaction time limit that controls in a precise way the asymptotics of both the switching function and its Fourier transform.
{"title":"Waiting around for Unruh","authors":"Leo J A Parry, Diego Vidal-Cruzprieto, Christopher J Fewster and Jorma Louko","doi":"10.1088/1361-6382/ae2377","DOIUrl":"https://doi.org/10.1088/1361-6382/ae2377","url":null,"abstract":"How long does a uniformly rotating observer need to interact with a quantum field in order to register an approximately thermal response due to the circular motion Unruh effect? We address this question for a massless scalar field in dimensions, defining the effective temperature via the ratio of excitation and de-excitation rates of an Unruh–DeWitt detector in the long interaction time limit. In this system, the effective temperature is known to be significantly smaller than the linear motion Unruh effect prediction when the detector’s energy gap is small: the effective temperature tends to zero in the small gap limit, linearly in the gap. We show that a positive small gap temperature at long interaction times can be regained via a controlled long-time-small-gap double limit, provided the detector’s coupling to the field is allowed to change sign. The resulting small gap temperature depends on the parameters of the circular motion but not on the details of the detector’s switching. The results broaden the energy range for pursuing an experimental verification of the circular motion Unruh effect in analogue spacetime experiments. As a mathematical tool, we provide a new implementation of the long interaction time limit that controls in a precise way the asymptotics of both the switching function and its Fourier transform.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"78 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145920468","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 : 2026-01-07DOI: 10.1088/1361-6382/ae2c35
Xiaokai He, Xiaoning Wu and Naqing Xie
Spacetimes with metrics admitting an expansion in terms of a combination of powers of and are known as polyhomogeneous spacetimes. The asymptotic behaviour of the Newman–Penrose quantities for the vacuum polyhomogeneous spacetimes is presented under certain gauges. The Bondi mass is revisited via the Iyer–Wald formalism. The memory effect of the gravitational radiation in the vacuum polyhomogeneous spacetimes is also discussed. It is found that the appearance of the logarithmic terms does not affect the balance law and it remains identical to that of spacetimes with metrics admitting an expansion in terms of powers of .
{"title":"Bondi mass, memory effect and balance law of polyhomogeneous spacetime","authors":"Xiaokai He, Xiaoning Wu and Naqing Xie","doi":"10.1088/1361-6382/ae2c35","DOIUrl":"https://doi.org/10.1088/1361-6382/ae2c35","url":null,"abstract":"Spacetimes with metrics admitting an expansion in terms of a combination of powers of and are known as polyhomogeneous spacetimes. The asymptotic behaviour of the Newman–Penrose quantities for the vacuum polyhomogeneous spacetimes is presented under certain gauges. The Bondi mass is revisited via the Iyer–Wald formalism. The memory effect of the gravitational radiation in the vacuum polyhomogeneous spacetimes is also discussed. It is found that the appearance of the logarithmic terms does not affect the balance law and it remains identical to that of spacetimes with metrics admitting an expansion in terms of powers of .","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"2 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145908265","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 : 2026-01-07DOI: 10.1088/1361-6382/ae2b1e
K Liu, L Liu, X D Hu and Z B Zhou
Space gravitational wave detection missions impose extremely stringent requirements for non-gravitational disturbances on the inertial reference, where gas-related noise may be the most critical source. The gas-related noise mainly includes Brownian noise, radiometer effect, and outgassing effect. In general, Brownian noise and radiometer effects can be evaluated by introducing a thermal accommodation coefficient (TAC). However, TAC cannot accurately represent the proportion of inelastic collisions σ. In order to address this limitation, we introduced a theoretical value of σ based on three assumptions that the single-component gas molecules will be adsorbed on the empty sites of the solid surface with a fixed probability under equilibrium conditions, that the single-component gas molecules will also be adsorbed by the occupied sites with another fixed probability under equilibrium conditions, and that the average desorption activation energy of the adsorbed gas molecules remained on the solid surface increases progressively over time during the outgassing process. With the σ, we proposed an enhanced gas-related noise model which exhibits an excellent fit to the in-orbit experimental data of LISA Pathfinder and the torsion experimental results in our group. This model theoretically derives an improved expression for outgassing rate, revealing that the pressure decay scaling as t−0.8 and the activation temperature of residual gases is (8450 ± 224) K. This model demonstrates predictive capability in forecasting gas-related noise for the LISA mission. Furthermore, this work also provides a universal tool for optimizing future gravitational wave observatory designs and accelerating their operational readiness.
{"title":"Enhanced model for prediction of residual gas effects in space gravitational wave detection missions","authors":"K Liu, L Liu, X D Hu and Z B Zhou","doi":"10.1088/1361-6382/ae2b1e","DOIUrl":"https://doi.org/10.1088/1361-6382/ae2b1e","url":null,"abstract":"Space gravitational wave detection missions impose extremely stringent requirements for non-gravitational disturbances on the inertial reference, where gas-related noise may be the most critical source. The gas-related noise mainly includes Brownian noise, radiometer effect, and outgassing effect. In general, Brownian noise and radiometer effects can be evaluated by introducing a thermal accommodation coefficient (TAC). However, TAC cannot accurately represent the proportion of inelastic collisions σ. In order to address this limitation, we introduced a theoretical value of σ based on three assumptions that the single-component gas molecules will be adsorbed on the empty sites of the solid surface with a fixed probability under equilibrium conditions, that the single-component gas molecules will also be adsorbed by the occupied sites with another fixed probability under equilibrium conditions, and that the average desorption activation energy of the adsorbed gas molecules remained on the solid surface increases progressively over time during the outgassing process. With the σ, we proposed an enhanced gas-related noise model which exhibits an excellent fit to the in-orbit experimental data of LISA Pathfinder and the torsion experimental results in our group. This model theoretically derives an improved expression for outgassing rate, revealing that the pressure decay scaling as t−0.8 and the activation temperature of residual gases is (8450 ± 224) K. This model demonstrates predictive capability in forecasting gas-related noise for the LISA mission. Furthermore, this work also provides a universal tool for optimizing future gravitational wave observatory designs and accelerating their operational readiness.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"40 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145908264","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 : 2026-01-07DOI: 10.1088/1361-6382/ae3045
Jack C M Hughes and Fedor V Kusmartsev
We show that the structure of the Lorentz group in four dimensions is such that unimodular (trace-free) gravity can be consistently represented as an algebraic condition on the symmetric product space of 2-forms. This condition states that the commutator between the Riemann tensor and the Hodge dual must be equal to the commutator between the Kulkarni–Nomizu product of the energy-momentum and the metric with the Hodge dual; symbolically, . We show that this condition is equivalent to the trace-free field equations, that the right-hand-side vanishes if and only if the energy-momentum tensor vanishes (recovering the appropriate Einstein spacetime limit) and that this condition can be solved for electrovacuum in the spherically symmetric ansatz to yield Reissner–Nordström–de Sitter uniquely. This analysis suggests that the conceptual distinction between unimodular gravity and General Relativity is one of emphasis on how irreducible representations of the Riemann tensor are constrained by the existence of energy-momentum and the associated field equations.
{"title":"Encoding the Einstein equations into an algebraic commutator condition","authors":"Jack C M Hughes and Fedor V Kusmartsev","doi":"10.1088/1361-6382/ae3045","DOIUrl":"https://doi.org/10.1088/1361-6382/ae3045","url":null,"abstract":"We show that the structure of the Lorentz group in four dimensions is such that unimodular (trace-free) gravity can be consistently represented as an algebraic condition on the symmetric product space of 2-forms. This condition states that the commutator between the Riemann tensor and the Hodge dual must be equal to the commutator between the Kulkarni–Nomizu product of the energy-momentum and the metric with the Hodge dual; symbolically, . We show that this condition is equivalent to the trace-free field equations, that the right-hand-side vanishes if and only if the energy-momentum tensor vanishes (recovering the appropriate Einstein spacetime limit) and that this condition can be solved for electrovacuum in the spherically symmetric ansatz to yield Reissner–Nordström–de Sitter uniquely. This analysis suggests that the conceptual distinction between unimodular gravity and General Relativity is one of emphasis on how irreducible representations of the Riemann tensor are constrained by the existence of energy-momentum and the associated field equations.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"18 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145908292","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 : 2026-01-05DOI: 10.1088/1361-6382/ae2e78
Virinchi Rallabhandi
This work considers positive energy theorems in asymptotically, locally AdS spacetimes. Particular attention is given to spacetimes where conformal infinity has compact, Einstein cross-sections admitting Killing or parallel spinors; a positive energy theorem is derived for such spacetimes in terms of geometric data intrinsic to the cross-section. This is followed by the first complete proofs of the BPS inequalities in (the bosonic sectors of) 4D and 5D minimal, gauged supergravity, including with magnetic fields, provided the Maxwell field is exact. The BPS inequalities are proven for asymptotically AdS spacetimes, but also generalised to the aforementioned class of asymptotically, locally AdS spacetimes.
{"title":"On energy bounds in asymptotically locally AdS spacetimes","authors":"Virinchi Rallabhandi","doi":"10.1088/1361-6382/ae2e78","DOIUrl":"https://doi.org/10.1088/1361-6382/ae2e78","url":null,"abstract":"This work considers positive energy theorems in asymptotically, locally AdS spacetimes. Particular attention is given to spacetimes where conformal infinity has compact, Einstein cross-sections admitting Killing or parallel spinors; a positive energy theorem is derived for such spacetimes in terms of geometric data intrinsic to the cross-section. This is followed by the first complete proofs of the BPS inequalities in (the bosonic sectors of) 4D and 5D minimal, gauged supergravity, including with magnetic fields, provided the Maxwell field is exact. The BPS inequalities are proven for asymptotically AdS spacetimes, but also generalised to the aforementioned class of asymptotically, locally AdS spacetimes.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"4 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145897786","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}
We report a simple yet powerful technique to reduce the effect of inhomogeneity in an input optics substrate in a high-precision measurement device such as a gravitational-wave detector. An asymmetric pattern in the transmission profile of an optic produces an offset in the alignment sensing signal, and the offset fluctuates with the moving position of the beam. By optimizing the weighting coefficients of a segmented photodetector, we can trade off the reduction in offset for a slight increase in shot noise. We demonstrated that our proposed method can reduce the beam jitter noise in a Fabry–Perot cavity through numerical simulations with measured data.
{"title":"Mitigation of optics non-uniformity using optimally combined segmented photodetector","authors":"Daiki Haba, Kento Takeshita, Ruizhe Wan, Hayato Tanaka, Seiya Sasaoka, Wang Haoyu, Kentaro Somiya","doi":"10.1088/1361-6382/ae2db4","DOIUrl":"https://doi.org/10.1088/1361-6382/ae2db4","url":null,"abstract":"We report a simple yet powerful technique to reduce the effect of inhomogeneity in an input optics substrate in a high-precision measurement device such as a gravitational-wave detector. An asymmetric pattern in the transmission profile of an optic produces an offset in the alignment sensing signal, and the offset fluctuates with the moving position of the beam. By optimizing the weighting coefficients of a segmented photodetector, we can trade off the reduction in offset for a slight increase in shot noise. We demonstrated that our proposed method can reduce the beam jitter noise in a Fabry–Perot cavity through numerical simulations with measured data.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"28 1","pages":"015017"},"PeriodicalIF":3.5,"publicationDate":"2025-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894160","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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