{"title":"Timelike boundary and corner terms in the causal set action","authors":"Fay Dowker, Roger Liu and Daniel Lloyd-Jones","doi":"10.1088/1361-6382/ae0be5","DOIUrl":"https://doi.org/10.1088/1361-6382/ae0be5","url":null,"abstract":"The causal set action of dimension d is investigated for causal sets that are Poisson sprinklings into manifolds that are regions of d-dimensional Minkowski space. Evidence, both analytic and numerical, is provided for the conjecture that as the discreteness length l tends to zero, the mean of the causal set action over Poisson sprinklings into a manifold with a timelike boundary, is dominated by a term proportional to the volume of the timelike boundary and diverges like l−1. A novel conjecture for the contribution to the causal set action from co-dimension two corners, also known as joints, is proposed and justified.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"124 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277429","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}
{"title":"Sourced metric perturbations of Kerr spacetime in Lorenz gauge","authors":"Barry Wardell, Chris Kavanagh and Sam R Dolan","doi":"10.1088/1361-6382/ae0918","DOIUrl":"https://doi.org/10.1088/1361-6382/ae0918","url":null,"abstract":"We derive a formalism for solving the Lorenz gauge equations for metric perturbations of Kerr spacetime sourced by an arbitrary stress-energy tensor. The metric perturbation is obtained as a sum of differential operators acting on a set of six scalars, with two of spin-weight ±2, two of spin-weight ±1, and two of spin-weight 0. We derive the sourced Teukolsky equations satisfied by these scalars, with the sources given in terms of differential operators acting on the stress-energy tensor. The method can be used to obtain both linear and higher-order nonlinear metric perturbations, and it fully determines the metric perturbation up to a time integral, omitting only static contributions which must be handled separately.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"117 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277472","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}
{"title":"Gravitational waves decohere quantum superpositions","authors":"Flynn Linton and Shubhanshu Tiwari","doi":"10.1088/1361-6382/ae0d27","DOIUrl":"https://doi.org/10.1088/1361-6382/ae0d27","url":null,"abstract":"Understanding the interplay between quantum mechanical systems and gravity is a crucial step towards unifying these two fundamental ideas. Recent theoretical developments have explored how global properties of spacetime would cause a quantum spatial superposition to lose coherence. In particular, this loss of coherence is closely related to the memory effect, which is a prominent feature of gravitational radiation. In this work, we explore how a burst of gravitational radiation from a far-away source would decohere a quantum superposition. We identify the individual contributions to the decoherence from the memory and oscillatory components of the gravitational wave source, corresponding to hard and soft graviton emissions, respectively. In general, the memory contributions dominate, while the oscillatory component of the decoherence is strongly dependent on the phase of the burst when it is switched off. This work demonstrates how quantum systems can lose coherence from interactions with a classical gravitational field. We also comment on the electromagnetic analogue of this effect and discuss its correspondence to the gravitational case.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"53 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277435","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}
{"title":"Search for echoes on the edge of quantum black holes","authors":"Jahed Abedi","doi":"10.1088/1361-6382/ae008c","DOIUrl":"https://doi.org/10.1088/1361-6382/ae008c","url":null,"abstract":"I perform a template-based search for stimulated emission of Hawking radiation (or Boltzmann echoes) by combining the gravitational wave data from 47 binary black hole merger events observed by the LIGO-Virgo-KAGRA collaboration. With a Bayesian inference approach, I found no statistically significant evidence for this signal in either of the 3 Gravitational Wave Transient Catalogs GWTC-1, GWTC-2 and GWTC-3. While the data does not provide definitive evidence against the presence of Boltzmann echoes, the Bayesian evidence for most events falls within the range of 0.3–1.6, with the hypothesis of a common (non-vanishing) echo amplitude for all mergers being weakly disfavored at 2:5 odds. The only exception is GW190521, the most massive and confidently detected event ever observed, which shows a positive evidence of 9.2 for stimulated Hawking radiation. The ‘look-elsewhere’ effect for this outlier event is assessed by applying two distinct methods to add simulated signals in real data, before and after the event, giving false (true) positive detection probabilities for higher Bayes factors of , ( , ). An optimal combination of posteriors yields an upper limit of A < 0.4 (at 90% confidence level) for a universal echo amplitude, whereas was predicted in the canonical model. To ensure the robustness of the results, I have employed an additional method to combine the events hierarchically. This approach involves using a target Gaussian distribution and extracting the parameters from multiple uncertain observations, which may be affected by selection biases.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"37 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145255685","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}
{"title":"Collinear corrections to the Cachazo–Strominger soft theorem","authors":"Eivind Jørstad and Sruthi A Narayanan","doi":"10.1088/1361-6382/ae09eb","DOIUrl":"https://doi.org/10.1088/1361-6382/ae09eb","url":null,"abstract":"Soft theorems describe the behavior of scattering amplitudes when one or several external particles are taken to be energetically soft. In tree-level gravity there are universal soft theorems for the three leading orders in the soft expansion, and they can be shown to be equivalent to Ward identities of asymptotic symmetries. While the leading and subleading symmetries are understood as supertranslations and superrotations respectively, the precise symmetry interpretation of the sub-subleading soft theorem is still a matter of investigation. The form of the sub-subleading soft graviton theorem was elucidated by Cachazo and Strominger using a BCFW expansion of graviton amplitudes. In this work we show that consistency with results based on asymptotic charges requires a careful treatment of collinear singularities in the amplitude, giving rise to collinear corrections to the usual Cachazo–Strominger soft theorem.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"14 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145241516","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}
{"title":"Cosmological scalar and tensor perturbations with a scalar field: quadratic-order effective energy-momentum tensor","authors":"Inyong Cho","doi":"10.1088/1361-6382/ae0aae","DOIUrl":"https://doi.org/10.1088/1361-6382/ae0aae","url":null,"abstract":"We introduce the scalar and tensor modes of the gravitational perturbation in the presence of a scalar field which describes inflation. We investigate the back-reaction of the perturbations to the background by studying the effective energy-momentum tensor (2EMT) which is the second order constructed by the quadratic terms of the linear perturbations. 2EMT is gauge dependent due to the scalar mode. We obtain 2EMT in the slow-roll stage of inflation, and get its cosmological expressions in three (longitudinal, spatially flat, and comoving) gauge conditions. We find that the pure scalar-mode part in 2EMT is stronger in the short-wavelength limit, while the parts involved with the tensor mode (the pure tensor-mode part and the scalar-tensor coupled part) are stronger in the long-wavelength limit.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"348 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145241518","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}
Sk Jahanur Hoque, Pavel Krtouš and Carlos Peón-Nieto
{"title":"Conformal Einstein equation and symplectic flux with a positive cosmological constant","authors":"Sk Jahanur Hoque, Pavel Krtouš and Carlos Peón-Nieto","doi":"10.1088/1361-6382/ae09ea","DOIUrl":"https://doi.org/10.1088/1361-6382/ae09ea","url":null,"abstract":"We analyze the conformal Einstein equation with a positive cosmological constant to extract fall-off conditions of the gravitational fields. The fall-off conditions are consistent with a finite, non-trivial presymplectic current on the future boundary of de Sitter. Hence our result allows a non-zero gravitational flux across the boundary of the de Sitter. We present an explicit gauge-free computation to show that the Gibbons–Hawking boundary term, counterterm in the action, and fall-off condition of gravitational field in conformal Einstein equation are crucial to reproduce the finite symplectic flux.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"1 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145241515","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}
Theodore Anton, Timothy Clifton and Daniel B Thomas
{"title":"Gravitational slip in the parameterized post-Newtonian cosmology","authors":"Theodore Anton, Timothy Clifton and Daniel B Thomas","doi":"10.1088/1361-6382/ae085e","DOIUrl":"https://doi.org/10.1088/1361-6382/ae085e","url":null,"abstract":"A key signature of general relativity is that the two scalar potentials Φ and Ψ, when expressed in the longitudinal gauge, are equal in the absence of fluids with anisotropic stress. This is often expressed by stating that their ratio, the ‘gravitational slip’, is equal to unity. However, the equality of Φ and Ψ is typically broken in alternative theories of gravity. Observational constraints on the slip parameter are therefore of direct interest for testing Einstein’s theory. In this paper we derive theory-independent expressions for the slip parameter on both large and small scales in Friedmann cosmologies, expressing it as a function of the post-Newtonian parameters. This is the final ingredient required for a complete parameterization of dust and dark energy-dominated cosmologies within the framework of parameterized post-Newtonian cosmology, which allows for the fully self-consistent modeling of cosmological observables without assuming any specific theory of gravity.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"78 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145228821","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}
Kevin Cunningham, Chris Kavanagh, Adam Pound, David Trestini, Niels Warburton and Jakob Neef
{"title":"Addendum: Gravitational memory: new results from post-Newtonian and self-force theory (2025 Class. Quantum Grav. 42 135009)","authors":"Kevin Cunningham, Chris Kavanagh, Adam Pound, David Trestini, Niels Warburton and Jakob Neef","doi":"10.1088/1361-6382/ae09e8","DOIUrl":"https://doi.org/10.1088/1361-6382/ae09e8","url":null,"abstract":"In Cunningham et al (2025 Class. Quantum Grav.42 135009), we made use of the recent completion of the oscillatory piece of the waveform at third-and-a-half post-Newtonian (3.5PN) order (Henry 2023 Phys. Rev. D107 044057) to obtain the GW memory piece for non-spinning binary black holes. However, the latter reference also contains the spinning contributions to the oscillatory waveform for non-precessing systems. In this Addendum, we take advantage of this fact to compute the non-oscillatory, memory piece at 3.5PN for non-precessing, spinning binary black holes. This completes the 3.5PN waveform, including both oscillatory and memory effects in the non-spinning and spinning sectors. Crucially, this computation required controlling the spin-induced absorption effects due to the black-hole horizons. Our result is fully consistent with the results at 5PN and leading order in the mass ratio obtained in our main paper using analytical self-force techniques for a non-spinning particle around a Kerr black hole (a ≠ 0). We also take advantage of this computation to present in one place a certain number of important quantities (energy, energy flux at infinity, horizon energy flux, and phasing) in the case of spinning, non-precessing, binary black hole systems on circular orbits, at 3.5PN and to all orders in spin. These results were for the most part known, but were scattered throughout the literature. Finally, we include in this Addendum an ancillary file, which contains most lengthy results in machine-readable form.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"7 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145228744","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}
{"title":"Penrose inequality for integral energy conditions","authors":"Eduardo Hafemann and Eleni-Alexandra Kontou","doi":"10.1088/1361-6382/ae0405","DOIUrl":"https://doi.org/10.1088/1361-6382/ae0405","url":null,"abstract":"The classical Penrose inequality, a relation between the ADM mass and the area of any cross section of the black hole event horizon, was introduced as a test of the weak cosmic censorship conjecture: if it fails, the trapped surface is not necessarily behind the event horizon and a naked singularity could form. Since that original derivation, a variety of proofs have developed, mainly focused on the initial data formulation on maximal spacelike slices of spacetime. Most of these proofs are applicable only for classical fields, as the energy conditions required are violated in the context of quantum field theory. In this work we provide two generalizations of the Penrose inequality for spherically symmetric spacetimes: a proof of a classical Penrose inequality using initial data and an average energy condition, and a proof of a modified Penrose inequality for evaporating black holes with a connection to the weak cosmic censorship conjecture. The latter case could also be applicable to quantum fields as it uses a condition inspired by quantum energy inequalities. Finally, we provide physically motivated examples for both.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"20 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145228745","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}