Pub Date : 2026-02-04DOI: 10.1088/1361-6382/ae3afb
Thomas Schürmann
In quantum theory on curved backgrounds, Heisenberg’s uncertainty principle is usually discussed in terms of ensemble variances and flat-space commutators. Here we take a different, preparation-based viewpoint tailored to sharp position measurements on spacelike hypersurfaces in general relativity. A projective localization is modeled as a von Neumann–Lüders projection onto a geodesic ball of radius r on a Cauchy slice , with the post-measurement state described by Dirichlet data. Using DeWitt-type momentum operators adapted to an orthonormal frame, we construct a geometric, coordinate-invariant momentum standard deviation σp and show that strict confinement to enforces an intrinsic kinetic-energy floor. The lower bound is set by the first Dirichlet eigenvalue λ1 of the Laplace–Beltrami operator on the ball, , and is manifestly invariant under changes of coordinates and foliation. A variance decomposition separates the contribution of the modulus from phase-gradient fluctuations and clarifies how the spectral geometry of controls momentum uncertainty. Assuming only minimal geometric information, weak mean-convexity of the boundary yields a universal, scale-invariant Heisenberg-type product bound, , depending only on the proper radius r.
{"title":"Intrinsic Heisenberg-type lower bounds on spacelike hypersurfaces in general relativity","authors":"Thomas Schürmann","doi":"10.1088/1361-6382/ae3afb","DOIUrl":"https://doi.org/10.1088/1361-6382/ae3afb","url":null,"abstract":"In quantum theory on curved backgrounds, Heisenberg’s uncertainty principle is usually discussed in terms of ensemble variances and flat-space commutators. Here we take a different, preparation-based viewpoint tailored to sharp position measurements on spacelike hypersurfaces in general relativity. A projective localization is modeled as a von Neumann–Lüders projection onto a geodesic ball of radius r on a Cauchy slice , with the post-measurement state described by Dirichlet data. Using DeWitt-type momentum operators adapted to an orthonormal frame, we construct a geometric, coordinate-invariant momentum standard deviation σp and show that strict confinement to enforces an intrinsic kinetic-energy floor. The lower bound is set by the first Dirichlet eigenvalue λ1 of the Laplace–Beltrami operator on the ball, , and is manifestly invariant under changes of coordinates and foliation. A variance decomposition separates the contribution of the modulus from phase-gradient fluctuations and clarifies how the spectral geometry of controls momentum uncertainty. Assuming only minimal geometric information, weak mean-convexity of the boundary yields a universal, scale-invariant Heisenberg-type product bound, , depending only on the proper radius r.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"28 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146116218","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 : 2026-02-04DOI: 10.1088/1361-6382/ae30c8
Reinosuke Kusano, Miguel Yulo Asuncion and Keith Horne
We present a parametric study of the spacetime structures obtainable in Weyl conformal gravity’s dyonic Reissner-Nordström solution. We derive expressions for photon sphere radii and horizons for this metric in terms of the conformal gravity parameters, from which we then determine analytic formulae for extremal limits and Hawking temperatures. Due to the surprising lack of the inverse quadratic term in this fourth-order metric, there is no guarantee for the innermost horizon of a black hole spacetime to be a Cauchy horizon, which is in direct contrast to the corresponding metric in general relativity. For example, for certain parameter values, a ‘nested black hole’ is seen to exist; in such a spacetime, we find a Cauchy horizon trapped between two event horizons, which is not a structure known to be obtainable in standard general relativity. In addition to such exotic spacetimes, we also find a critical value for the electric and magnetic charges, at which the stable and unstable photon spheres of the metric merge, and we obtain extremal limits where three horizons collide.
{"title":"Charged black holes in Weyl conformal gravity","authors":"Reinosuke Kusano, Miguel Yulo Asuncion and Keith Horne","doi":"10.1088/1361-6382/ae30c8","DOIUrl":"https://doi.org/10.1088/1361-6382/ae30c8","url":null,"abstract":"We present a parametric study of the spacetime structures obtainable in Weyl conformal gravity’s dyonic Reissner-Nordström solution. We derive expressions for photon sphere radii and horizons for this metric in terms of the conformal gravity parameters, from which we then determine analytic formulae for extremal limits and Hawking temperatures. Due to the surprising lack of the inverse quadratic term in this fourth-order metric, there is no guarantee for the innermost horizon of a black hole spacetime to be a Cauchy horizon, which is in direct contrast to the corresponding metric in general relativity. For example, for certain parameter values, a ‘nested black hole’ is seen to exist; in such a spacetime, we find a Cauchy horizon trapped between two event horizons, which is not a structure known to be obtainable in standard general relativity. In addition to such exotic spacetimes, we also find a critical value for the electric and magnetic charges, at which the stable and unstable photon spheres of the metric merge, and we obtain extremal limits where three horizons collide.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"287 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146115687","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 : 2026-02-04DOI: 10.1088/1361-6382/ae3b92
Clémentine Dassy and Jan Govaerts
The gravimagnetic dipole spacetime consists of two counter-rotating black holes of equal mass connected by a Misner string. For a particular distance in between them, the string is tensionless with the black holes at equilibrium with each other. The geodesics of relativistic massive, or massless particles are considered, leading to the identification of circular rotation trajectories. The velocities of these trajectories are computed.
{"title":"Velocity rotation curves in the equal mass and net null NUT charge gravimagnetic dipole spacetime","authors":"Clémentine Dassy and Jan Govaerts","doi":"10.1088/1361-6382/ae3b92","DOIUrl":"https://doi.org/10.1088/1361-6382/ae3b92","url":null,"abstract":"The gravimagnetic dipole spacetime consists of two counter-rotating black holes of equal mass connected by a Misner string. For a particular distance in between them, the string is tensionless with the black holes at equilibrium with each other. The geodesics of relativistic massive, or massless particles are considered, leading to the identification of circular rotation trajectories. The velocities of these trajectories are computed.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"15 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146115689","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 : 2026-02-02DOI: 10.1088/1361-6382/ae351b
N Heidari
This work presents a comprehensive investigation of the gravitational phenomena that correspond to a non-commutative (NC) charged black hole, by incorporating NC geometry through a Moyal twist. We derive the deformed metric up to the second order of NC parameter Θ, utilizing the Seiberg–Witten map for Reissner–Nordström black hole. We explore how non-commutativity modifies key thermodynamic properties, such as the Hawking temperature and heat capacity, and the existence of a remnant mass at the final stage of the evaporation. Additionally, the study of Hawking radiation for bosonic and fermionic particles is discussed. Applying a perturbative method, scalar quasinormal modes are analyzed numerically. Furthermore, null geodesics and photon sphere stability are explored via curvature and topological methods. The shadow radius and deflection angle are computed to understand observational signatures. Lensing observables are compared to Event Horizon Telescope observations to provide probable constraints on the non-commutativity parameter. This study bridges theoretical predictions with astrophysical observations, offering insights into quantum gravity effects on black hole physics.
{"title":"Imprints of non-commutativity on charged black holes","authors":"N Heidari","doi":"10.1088/1361-6382/ae351b","DOIUrl":"https://doi.org/10.1088/1361-6382/ae351b","url":null,"abstract":"This work presents a comprehensive investigation of the gravitational phenomena that correspond to a non-commutative (NC) charged black hole, by incorporating NC geometry through a Moyal twist. We derive the deformed metric up to the second order of NC parameter Θ, utilizing the Seiberg–Witten map for Reissner–Nordström black hole. We explore how non-commutativity modifies key thermodynamic properties, such as the Hawking temperature and heat capacity, and the existence of a remnant mass at the final stage of the evaporation. Additionally, the study of Hawking radiation for bosonic and fermionic particles is discussed. Applying a perturbative method, scalar quasinormal modes are analyzed numerically. Furthermore, null geodesics and photon sphere stability are explored via curvature and topological methods. The shadow radius and deflection angle are computed to understand observational signatures. Lensing observables are compared to Event Horizon Telescope observations to provide probable constraints on the non-commutativity parameter. This study bridges theoretical predictions with astrophysical observations, offering insights into quantum gravity effects on black hole physics.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"92 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146097943","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 : 2026-02-02DOI: 10.1088/1361-6382/ae3a30
Jeroen Tromp
We develop a metric-free theory of gravitation generated by geometrical defects. Spacetime geometry is described by a velocity-distortion coframe and a spin-bend-twist connection , defined in terms of the motion field ϕµ and the intrinsic deformation field . Their field strengths are the intrinsic torsion and intrinsic curvature . The fundamental field equations and balance these geometric quantities against spacetime dislocationsαa and disclinations —incompatibilities in the motion and intrinsic deformation fields. Geometrical point defects correspond to incompatible coframe transformations. The Newtonian limit of the time-space field equations results in the conversion between the geometric mass density time-space wedge disclination and physical mass-energy ρ. Gravitation thus emerges directly from geometric incompatibility rather than from curvature sourced by matter. An invariant volume capacity—a 4-form constructed from orientation and deformation determinants—replaces and enables variational principles and integration without a metric. Variation of an intrinsic-coframe gravitational Lagrangian capacity produces the corresponding stress and couple-stress capacity currents and their dynamical equations. In this formulation, there is no Newtonian gravitational potential: gravitational accelerations are carried by the time-space components of the connection, which act as the fundamental dynamical variables. The theory reproduces gravitational waves, black hole exteriors, and the Newtonian limit in a metric-free formulation; when needed, a metric-compatible sector restriction and metric reconstruction are used only for comparison with standard general relativity. It provides a natural foundation for extensions such as theories that may remain valid where metric descriptions fail.
{"title":"Metric-free gravitation from geometrical defects","authors":"Jeroen Tromp","doi":"10.1088/1361-6382/ae3a30","DOIUrl":"https://doi.org/10.1088/1361-6382/ae3a30","url":null,"abstract":"We develop a metric-free theory of gravitation generated by geometrical defects. Spacetime geometry is described by a velocity-distortion coframe and a spin-bend-twist connection , defined in terms of the motion field ϕµ and the intrinsic deformation field . Their field strengths are the intrinsic torsion and intrinsic curvature . The fundamental field equations and balance these geometric quantities against spacetime dislocationsαa and disclinations —incompatibilities in the motion and intrinsic deformation fields. Geometrical point defects correspond to incompatible coframe transformations. The Newtonian limit of the time-space field equations results in the conversion between the geometric mass density time-space wedge disclination and physical mass-energy ρ. Gravitation thus emerges directly from geometric incompatibility rather than from curvature sourced by matter. An invariant volume capacity—a 4-form constructed from orientation and deformation determinants—replaces and enables variational principles and integration without a metric. Variation of an intrinsic-coframe gravitational Lagrangian capacity produces the corresponding stress and couple-stress capacity currents and their dynamical equations. In this formulation, there is no Newtonian gravitational potential: gravitational accelerations are carried by the time-space components of the connection, which act as the fundamental dynamical variables. The theory reproduces gravitational waves, black hole exteriors, and the Newtonian limit in a metric-free formulation; when needed, a metric-compatible sector restriction and metric reconstruction are used only for comparison with standard general relativity. It provides a natural foundation for extensions such as theories that may remain valid where metric descriptions fail.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"79 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146097819","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 : 2026-02-02DOI: 10.1088/1361-6382/ae3a2f
Allan Freitas, Benedito Leandro, Ernani Ribeiro Jr and Guilherme Sabo
In this article, we investigate electrostatic systems with a nonzero cosmological constant on compact manifolds with boundary. We establish new geometric properties for electrostatic manifolds in higher dimensions, extending previous results in the literature. Moreover, we prove sharp boundary estimates and isoperimetric-type inequalities for electrostatic manifolds, as well as volume and boundary inequalities involving the Brown–York and Hawking masses.
{"title":"Geometric inequalities for electrostatic systems with boundary","authors":"Allan Freitas, Benedito Leandro, Ernani Ribeiro Jr and Guilherme Sabo","doi":"10.1088/1361-6382/ae3a2f","DOIUrl":"https://doi.org/10.1088/1361-6382/ae3a2f","url":null,"abstract":"In this article, we investigate electrostatic systems with a nonzero cosmological constant on compact manifolds with boundary. We establish new geometric properties for electrostatic manifolds in higher dimensions, extending previous results in the literature. Moreover, we prove sharp boundary estimates and isoperimetric-type inequalities for electrostatic manifolds, as well as volume and boundary inequalities involving the Brown–York and Hawking masses.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"78 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146097944","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 : 2026-01-30DOI: 10.1088/1361-6382/ae134a
Torben C Frost
Astrophysical observations in the electromagnetic spectrum as well as detected gravitational wave signals indicate that the Kerr spacetime can be used to describe the spacetime around candidates for rotating black holes. While the geodesic structure of the Kerr spacetime is already well known for decades, using exact analytic solutions to the equations of motion for applications to astrophysical problems has only attracted attention relatively recently. In particular using the exact analytic solutions to investigate gravitational lensing of light and gravitational waves emitted by sources outside the accretion disk has only received limited attention so far. Therefore, the focus of this paper will be to address this point. For this purpose we assume that we have a standard observer in the domain of outer communication. We introduce a local orthonormal tetrad to relate the constants of motion of light rays and high-frequency gravitational waves detected by the observer to latitude–longitude coordinates on the observer’s celestial sphere. We show that in this parametrisation we can derive the radius coordinates of the photon orbits and their latitudinal projections onto the observer’s celestial sphere as functions of the celestial longitude. We use the latitude–longitude coordinates to classify the different types of motion, and solve the equations of motion analytically using elementary and Jacobi’s elliptic functions as well as Legendre’s elliptic integrals. We use the analytic solutions to write down an exact lens equation, and to calculate the redshift and the travel time. Here, this approach allows us to visualise them with much higher resolution than numerical techniques, in particular close to the boundary of the shadow. We discuss their sky projections for different stationary sources and the implications of the results in the context of conventional astronomical observations and the observation of high-frequency gravitational waves gravitationally lensed by supermassive black hole candidates.
{"title":"Gravitational lensing in the Kerr spacetime: an analytic approach for light and high-frequency gravitational waves","authors":"Torben C Frost","doi":"10.1088/1361-6382/ae134a","DOIUrl":"https://doi.org/10.1088/1361-6382/ae134a","url":null,"abstract":"Astrophysical observations in the electromagnetic spectrum as well as detected gravitational wave signals indicate that the Kerr spacetime can be used to describe the spacetime around candidates for rotating black holes. While the geodesic structure of the Kerr spacetime is already well known for decades, using exact analytic solutions to the equations of motion for applications to astrophysical problems has only attracted attention relatively recently. In particular using the exact analytic solutions to investigate gravitational lensing of light and gravitational waves emitted by sources outside the accretion disk has only received limited attention so far. Therefore, the focus of this paper will be to address this point. For this purpose we assume that we have a standard observer in the domain of outer communication. We introduce a local orthonormal tetrad to relate the constants of motion of light rays and high-frequency gravitational waves detected by the observer to latitude–longitude coordinates on the observer’s celestial sphere. We show that in this parametrisation we can derive the radius coordinates of the photon orbits and their latitudinal projections onto the observer’s celestial sphere as functions of the celestial longitude. We use the latitude–longitude coordinates to classify the different types of motion, and solve the equations of motion analytically using elementary and Jacobi’s elliptic functions as well as Legendre’s elliptic integrals. We use the analytic solutions to write down an exact lens equation, and to calculate the redshift and the travel time. Here, this approach allows us to visualise them with much higher resolution than numerical techniques, in particular close to the boundary of the shadow. We discuss their sky projections for different stationary sources and the implications of the results in the context of conventional astronomical observations and the observation of high-frequency gravitational waves gravitationally lensed by supermassive black hole candidates.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"3 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146072384","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 : 2026-01-30DOI: 10.1088/1361-6382/ae3046
Jan Gutowski, Chettha Saelim and Martin Wolf
The uniqueness and rigidity of black holes remain central themes in gravitational research. In this work, we investigate the construction of all extremal black hole solutions to the Einstein equation for a given near-horizon geometry, employing the homotopy algebraic perspective, a powerful and increasingly influential framework in both classical and quantum field theory. Utilising Gaußian null coordinates, we recast the deformation problem as an analysis of the homotopy Maurer–Cartan equation associated with an -algebra. Through homological perturbation theory, we systematically solve this equation order by order in directions transverse to the near-horizon geometry. As a concrete application of this formalism, we examine the deformations of the extremal Kerr horizon. Notably, this homotopy-theoretic approach enables us to characterise the moduli space of deformations by studying only the lowest-order solutions, offering a systematic way to understand the landscape of extremal black hole geometries.
{"title":"Extremal black holes from homotopy algebras","authors":"Jan Gutowski, Chettha Saelim and Martin Wolf","doi":"10.1088/1361-6382/ae3046","DOIUrl":"https://doi.org/10.1088/1361-6382/ae3046","url":null,"abstract":"The uniqueness and rigidity of black holes remain central themes in gravitational research. In this work, we investigate the construction of all extremal black hole solutions to the Einstein equation for a given near-horizon geometry, employing the homotopy algebraic perspective, a powerful and increasingly influential framework in both classical and quantum field theory. Utilising Gaußian null coordinates, we recast the deformation problem as an analysis of the homotopy Maurer–Cartan equation associated with an -algebra. Through homological perturbation theory, we systematically solve this equation order by order in directions transverse to the near-horizon geometry. As a concrete application of this formalism, we examine the deformations of the extremal Kerr horizon. Notably, this homotopy-theoretic approach enables us to characterise the moduli space of deformations by studying only the lowest-order solutions, offering a systematic way to understand the landscape of extremal black hole geometries.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"30 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146072385","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 : 2026-01-29DOI: 10.1088/1361-6382/ae351a
Mathyn van Dael, Marjolein Daanen, Koen Tiels, Gert Witvoet, Bas Swinkels, Diego Bersanetti, Julia Casanueva, Manuel Pinto, Maddalena Mantovani, Piernicola Spinicelli, Camilla de Rossi, Mattia Boldrini, Paolo Ruggi and Tom Oomen
Noise from auxiliary subsystems, amplified by their own control system, can couple to the output signal of gravitational wave detectors, limiting the maximum attainable sensitivity. Subtraction filters can be used to mitigate this coupling of noise by adding a secondary disturbance path with the purpose of canceling the noise in the output of the detector. The aim of this paper is to develop a systematic approach for the design and online adaptive estimation of subtraction filters. The proposed method adaptively updates the subtraction filter without the need for external perturbations to the system, providing a robust approach towards handling the time-varying couplings in the system as well as reducing the need for detector downtime. The method is validated on a representative simulation of the Advanced Virgo+ gravitational wave detector, illustrating that the method is capable of suppressing the coupling of noise from an auxiliary subsystem while the coupling varies over time.
{"title":"Parametrization selection and online adaptation of subtraction filters for gravitational wave detectors *","authors":"Mathyn van Dael, Marjolein Daanen, Koen Tiels, Gert Witvoet, Bas Swinkels, Diego Bersanetti, Julia Casanueva, Manuel Pinto, Maddalena Mantovani, Piernicola Spinicelli, Camilla de Rossi, Mattia Boldrini, Paolo Ruggi and Tom Oomen","doi":"10.1088/1361-6382/ae351a","DOIUrl":"https://doi.org/10.1088/1361-6382/ae351a","url":null,"abstract":"Noise from auxiliary subsystems, amplified by their own control system, can couple to the output signal of gravitational wave detectors, limiting the maximum attainable sensitivity. Subtraction filters can be used to mitigate this coupling of noise by adding a secondary disturbance path with the purpose of canceling the noise in the output of the detector. The aim of this paper is to develop a systematic approach for the design and online adaptive estimation of subtraction filters. The proposed method adaptively updates the subtraction filter without the need for external perturbations to the system, providing a robust approach towards handling the time-varying couplings in the system as well as reducing the need for detector downtime. The method is validated on a representative simulation of the Advanced Virgo+ gravitational wave detector, illustrating that the method is capable of suppressing the coupling of noise from an auxiliary subsystem while the coupling varies over time.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"44 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146070379","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 : 2026-01-29DOI: 10.1088/1361-6382/ae3879
Jochen Zahn
We study scalar (not necessarily conformal) quantum fields on self-similar spacetimes. It is shown that in states respecting the self-similarity the expectation value of the stress tensor gives rise to a Lyapunov exponent , with a leading coefficient which is state-independent and geometric. Three examples for states respecting self-similarity are presented.
{"title":"Quantum fields on self-similar spacetimes","authors":"Jochen Zahn","doi":"10.1088/1361-6382/ae3879","DOIUrl":"https://doi.org/10.1088/1361-6382/ae3879","url":null,"abstract":"We study scalar (not necessarily conformal) quantum fields on self-similar spacetimes. It is shown that in states respecting the self-similarity the expectation value of the stress tensor gives rise to a Lyapunov exponent , with a leading coefficient which is state-independent and geometric. Three examples for states respecting self-similarity are presented.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":"17 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146070380","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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