Classical and Quantum Gravity最新文献

{"title":"Pathology of the unified dark sectors in modified general relativity","authors":"Mohsen Khodadi","doi":"10.1088/1361-6382/ae4200","DOIUrl":"https://doi.org/10.1088/1361-6382/ae4200","url":null,"abstract":"This paper presents a comprehensive stability analysis of the black hole solution within modified general relativity (MGR), a theory proposing a unified geometric description of dark matter and dark energy. A rigorous gauge-invariant formalism is employed to analyze gravitational perturbations of the extended Schwarzschild metric. The central finding is a critical pathology within the polar perturbation sector, where metric fluctuations couple to the theory’s fundamental line element field. This coupling is governed by a factor that, while well-behaved at the horizon, diverges powerfully in the far-field limit as a direct consequence of the theory’s non-asymptotically flat nature. This indicates a strong infrared instability that overwhelms perturbations at large distances. In stark contrast, the axial perturbation sector is found to be completely stable. This dichotomy proves that the instability is not inherent to the background metric but is specifically generated by the novel coupling mechanism encoding MGR’s unified dark sectors. The results reveal a fundamental strong-coupling problem within the MGR framework, challenging its physical viability as an alternative to Einstein’s general relativity.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"18 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146198491","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":"Template-free gravitational wave detection with CWT-LSTM autoencoders: a case study of run-dependent calibration effects in LIGO data","authors":"Jericho Cain","doi":"10.1088/1361-6382/ae415e","DOIUrl":"https://doi.org/10.1088/1361-6382/ae415e","url":null,"abstract":"Gravitational wave detection requires sophisticated signal processing to identify weak astrophysical signals buried in instrumental noise. Traditional matched filtering approaches face computational challenges with diverse signal morphologies and non-stationary noise. This work presents an unsupervised deep learning methodology integrating continuous wavelet transform (CWT) preprocessing with long short-term memory autoencoder architecture for template-free gravitational wave detection. The CWT provides optimal time–frequency decomposition capturing chirp evolution and transient characteristics essential for compact binary coalescence identification. We train and evaluate our model on LIGO H1 data from Observing Run 4 (O4, 2023–2024), comprising 102 confirmed gravitational wave events from the GWTC-4.0 catalog and 1991 noise segments. During development, we discovered that reconstruction errors from multi-run training (O1–O4) clustered by observing run rather than astrophysical parameters, revealing systematic batch effects from GWOSC’s evolving calibration procedures. Following LIGO’s established practice of per-run optimization, we adopted single-run (O4) training, which eliminated these batch effects and improved recall from 52% to 96% while maintaining 97% precision. The final model achieves exceptional performance on O4 test data: 97.0% precision, 96.1% recall, F1-score 96.6%, and ROC-AUC 0.994 (102 test signals, 399 noise segments). The reconstruction error distribution shows clean unimodal separation between noise (mean 0.48) and signals (mean 0.77), with only 4 missed detections and 3 false alarms. This unsupervised approach demonstrates that anomaly detection can achieve performance competitive with supervised methods while maintaining template-free operation. While the template-free nature of this approach suggests potential for detecting signals outside current template bank coverage, this capability remains to be validated with exotic signal injections. Our identification and resolution of cross-run batch effects provides methodological guidance for future machine learning applications to multi-epoch gravitational wave datasets.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"30 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146184290","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":"A canonical and relational analysis of reference frames and gauge-fixing in general relativity","authors":"Nicola Bamonti","doi":"10.1088/1361-6382/ae415c","DOIUrl":"https://doi.org/10.1088/1361-6382/ae415c","url":null,"abstract":"This study develops a canonical framework that relates gauge-fixing procedures with the dynamics of reference frames in general relativity. The central idea is that gauge-fixing conditions can be reinterpreted as the dynamical equations obeyed by the physical systems used for spacetime localisation. Within the Hamiltonian formalism, this link provides a principled criterion for determining when relationally expressed quantities qualify as Dirac observables. The analysis distinguishes three regimes of reference frames: idealised frames, whose own equations of motion and stress-energy are neglected; dynamical frames, which evolve according to specified equations but do not backreact on the metric; and fully coupled frames, which contribute to the gravitational dynamics. In the idealised regime the relational metric remains gauge-variant under the canonical flow, reflecting the persistence of diffeomorphism freedom. By contrast, once the reference fields satisfy suitable dynamical equations, they supply four functionally independent conditions that combine with the Hamiltonian and momentum constraints to form a second-class set. The resulting Dirac bracket defines a non-degenerate reduced symplectic structure in which relationally local quantities, such as the metric expressed in the reference-frame variables, strongly commute with all constraints and thereby become genuine Dirac observables. This construction also clarifies the correspondence between gauge-fixed quantities and complete observables: the frame dynamics internalises the gauge choice, making gauge-fixed quantities coincide with complete observables whenever the gauge conditions arise from the physical evolution of the reference fields. Familiar coordinate gauges, including harmonic and transverse-traceless gauges, thereby admit a relational interpretation: they arise from, and are constrained by, the dynamics of the physical frames used for localisation. This work thereby clarifies the interplay between diffeomorphism symmetry and operational localisation and offers a unified canonical characterisation of classical reference frames.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"331 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146184297","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":"Entanglement and particle production from cosmological perturbations: a quantum optical simulation approach","authors":"Pramod Kamal Kharel, Mausam Ghimire, Ashish Khanal, Samyam Pudasaini, Nabaraj Khatri, Sayujya Bhandari, Divash Rai, Kiran Adhikari and Rajeev Singh","doi":"10.1088/1361-6382/ae3afc","DOIUrl":"https://doi.org/10.1088/1361-6382/ae3afc","url":null,"abstract":"In this work, we develop a computational framework based on the Gaussian formalism and symplectic circuit representation to explore cosmological perturbations during inflation. These tools offer an efficient means to study entanglement generation and particle production, particularly when analytical methods become insufficient and numerical simulations are essential. By evolving an initial Bunch–Davies vacuum through a two-mode squeezer, we simulate the behavior of the von Neumann entropy and logarithmic negativity (LN) across a wide range of cosmological backgrounds, each characterized by a distinct equation of state. The von Neumann entropy obtained via QuGIT simulations (a numerical toolbox that computes the evolution of Gaussian states by applying symplectic transformations to their covariance matrices) is compared with analytic Rényi entropy bounds, thereby validating the accuracy of our circuit implementation of the cosmological squeezing Hamiltonian in both accelerating and decelerating scenarios. We further investigate the role of thermal noise and demonstrate how the von Neumann entropy and LN are affected by its presence.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"32 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146161046","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":"Homothetic expansion of polyhedra in the two-vertex model: emergence of FLRW","authors":"Iñaki Garay, Sergio Rodríguez-González and Raül Vera","doi":"10.1088/1361-6382/ae36dd","DOIUrl":"https://doi.org/10.1088/1361-6382/ae36dd","url":null,"abstract":"The cosmological behavior associated to a -symmetry reduced sector of the loop-quantum-gravity truncation known as the two-vertex model is further explored in this work. We construct convenient frame bases that encode the classical phase space of the twisted geometry associated to the graph. We show that the polyhedra of the twisted geometry suffer under evolution an homothetic expansion, which strengthens the correspondence to the Robertson–Walker geometry.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"30 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146153570","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":"Metric-induced principal symbols in nonlinear electrodynamics","authors":"Érico Goulart and Eduardo Bittencourt","doi":"10.1088/1361-6382/ae415b","DOIUrl":"https://doi.org/10.1088/1361-6382/ae415b","url":null,"abstract":"We present a geometrical formulation of nonlinear electrodynamics by expressing its principal symbol as an optical metric-induced object. Under the assumption of no birefringence, we show that the evolution of linear perturbations can be recast as a covariant divergence on a curved, field-dependent background, enabling the application of quantum field theory techniques as in Maxwell’s theory in curved backgrounds. This geometric reformulation opens a new route for analog models potentially implementable in laboratory via tailored nonlinear metamaterials.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"32 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146153608","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":"Using gravitational waves & multi-messenger astronomy to reverse-engineer the properties of galactic nuclei","authors":"K E Saavik Ford and Barry McKernan","doi":"10.1088/1361-6382/ae0aad","DOIUrl":"https://doi.org/10.1088/1361-6382/ae0aad","url":null,"abstract":"Active galactic nuclei (AGN) are powered by accretion disks onto supermassive black holes (SMBHs) in the centers of galaxies. AGN are believed to play important roles in the evolution of both SMBHs and their host galaxies over cosmic time. AGN and the nuclear star clusters (NSCs) that interact with them remain unresolved with present and planned telescopes. As a result, the properties of AGN and NSCs are highly uncertain. Here we review how binary black hole (BBH) mergers can occur in AGN disks and how both the gravitational wave and electromagnetic wave properties of such mergers allow us to reverse-engineer the properties of AGN disks and NSCs over cosmic time. We point out that the feature in the BBH mass spectrum around is an excellent probe of hierarchical merger models. Likewise constraints on the spins of upper-mass gap BH ( ) test the AGN channel. The effective spin ( ) distribution, including asymmetry, islands of structure and magnitudes are excellent tests of AGN model predictions. We also argue, that the rate of AGN-driven BBH mergers as a function of redshift should scale slightly shallower than the AGN number density, at least out to redshifts of , and should turnover at the same redshift as the AGN number density. Finally, we emphasize a determination of an AGN fraction of observed BBH mergers ( ), regardless of the actual value, allows us to infer the average properties of AGN disks and NSCs out to high redshift.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"15 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146188","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":"Overview of the NASA LISA laser system development","authors":"Anthony W Yu, Molly E Fahey, Kenji Numata, Yvonne Kandem Manewa, Ali Feizi, Frankie Micalizzi, Hua Jiao, Joseph Hart, Xiaozhen Xu, Stewart Wu, Kylan Jersey, Will Drobnick, Pat Burns, Jennifer Lee and Scott Merritt","doi":"10.1088/1361-6382/ae3b91","DOIUrl":"https://doi.org/10.1088/1361-6382/ae3b91","url":null,"abstract":"NASA Goddard Space Flight Center (GSFC) is developing a laser system (LS) for the Laser Interferometer Space Antenna (LISA) mission, led by the European Space Agency with a launch date of 2035. The LS under development at NASA GSFC consists of a laser head, a frequency reference system, and power monitor detector assemblies. The LS development, which began in late 2016, follows the established NASA process in demonstrating the performance requirements through the development of various models to advance the technology readiness level (TRL) (www.nasa.gov/directorates/somd/space-communications-navigation-program/technology-readiness-levels/). The effort began with a successful demonstration of a laboratory breadboard (TRL 4) and has achieved a status of TRL-6 (flight-qualified) through rigorous testing and performance verification for space applications. In this paper, we provide an overview of the development and roadmap for advancing the LISA LS toward spaceflight by the NASA GSFC. Optomechanical and electronic details of each component and subsystems are presented in this paper, as well as test results and technical challenges that have been or are being overcome. As the project progresses, more detailed results will be reported in future publications including representative scientific data in support of the LISA launch, which is planned for 2035.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"284 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146189","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":"Quantum cosmology as a hydrogen atom: discrete Λ and cyclic universes from Wheeler–DeWitt quantization","authors":"Dipayan Mukherjee, Harkirat Singh Sahota and S Shankaranarayanan","doi":"10.1088/1361-6382/ae3e4b","DOIUrl":"https://doi.org/10.1088/1361-6382/ae3e4b","url":null,"abstract":"Building upon our recently established correspondence between quantum cosmology and the hydrogen atom (Sahota et al 2025 arXiv:2505.16863 [gr-qc]), we investigate the specific sector of a negative cosmological constant ( ) in a flat FLRW Universe with dust. While the positive Λ sector (Sahota et al 2025 arXiv:2505.16863 [gr-qc]) yields a continuous spectrum and a single bounce, we show here that the negative Λ sector leads to a discrete spectrum of energy eigenvalues, effectively quantizing the cosmological constant. Within this dual description, the operator-ordering ambiguity parameter appears as the azimuthal quantum number of the hydrogen atom. A skewed Bohr correspondence emerges for the bound states, matching classical evolution at large volumes but deviating near the bounce. By constructing wave packets from these bound states, we demonstrate that the classical Big Bang and Big Crunch singularities are resolved, and the Universe oscillates between quantum bounces and classical turnaround points. The expectation values of the observables indicate a cyclic Universe—with vanishing Hubble parameter at turnarounds—undergoing quantum bounces. This exactly solvable model offers a tractable setting to explore quantum gravitational effects in cosmology. We analyze the properties of this cyclic Universe, contrasting its bound-state dynamics with the scattering states of the de Sitter case.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"4 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138513","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":"AC actuation carrier frequency optimization for cross-coupling suppression in space inertial sensor","authors":"Jinfeng Lu, Yizhou Zhang, Chujie Zhang, Ming Hu, Yanzheng Bai and Zebing Zhou","doi":"10.1088/1361-6382/ae399b","DOIUrl":"https://doi.org/10.1088/1361-6382/ae399b","url":null,"abstract":"The space inertial sensor (IS) is a critical payload in space-based gravitational wave detection missions. The test mass, serving as the gravitational reference, should be maintained at the center of its electrode housing through AC electrostatic control and drag-free attitude control. However, excessive electrostatic actuation cross-coupling between degrees of freedom can significantly deteriorate the residual acceleration performance along the sensitive axis (x-axis). This paper investigates the influence of carrier frequency selection on the electrostatic actuation noise coupling from the ϕ-axis to the x-axis. The analysis shows that the coupling coefficient can be suppressed below over the 0.1 mHz–1 Hz band by properly choosing the AC carrier frequencies. Specifically, both the sum and the difference of the carrier frequencies should be integer multiples of the desired force/torque update rate . Furthermore, the difference frequency should exceed 180 Hz with a deviation smaller than 0.4% to satisfy TianQin’s requirement. These conclusions are validated through a dedicated Simulink simulation platform. The proposed frequency configuration guideline offers a clear basis for AC feedback design in IS, effectively suppressing cross-coupling and enhancing low-frequency performance for future space-based gravitational wave missions.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"48 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146122221","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}