{"title":"A note on Weyl gauge symmetry in gravity","authors":"N Mohammedi","doi":"10.1088/1361-6382/ad7186","DOIUrl":"https://doi.org/10.1088/1361-6382/ad7186","url":null,"abstract":"A scale invariant theory of gravity, containing at most two derivatives, requires, in addition to the Riemannian metric, a scalar field and (or) a gauge field. The gauge field is usually used to construct the affine connection of Weyl geometry. In this note, we incorporate both the gauge field and the scalar field to build a generalised scale invariant Weyl affine connection. The Ricci tensor and the Ricci scalar made out of this generalised Weyl affine connection contain, naturally, kinetic terms for the scalar field and the gauge field. This provides a geometric interpretation for these terms. It is also shown that scale invariance in the presence of a cosmological constant and mass terms is not completely lost. It becomes a duality transformation relating various fields.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142158794","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 Fisher information in acceleration parallel to a planar wall","authors":"Ying Yang, Xiangyun Fu and Jiliang Jing","doi":"10.1088/1361-6382/ad7452","DOIUrl":"https://doi.org/10.1088/1361-6382/ad7452","url":null,"abstract":"In this work, we devote to understand how boundaries can help improve parameter estimation against atomic decoherence and dissipation caused by relativistic motion. The system we considered is a two-level atom in uniform linear acceleration parallel to a planar wall in (3+1)-dimensional Minkowski spacetime, which is coupled to a massless scalar field with Dirichlet, Neumann or transparent boundary conditions at the wall. We find that the quantum Fisher information (QFI), which determines the ultimate estimation precision, depends on various factors, such as atomic motional trajectories, evolution time, atomic initial state, and the boundary condition. We identify the optimal estimation strategies that maximize the QFI through all the associated parameters, thus optimizing the estimation precision. Our results show that the QFI has different behaviors and even different magnitudes for different boundary cases. We also determine the boundary conditions that can effectively suppress the influence of atomic relativistic motion on the QFI. Our investigation may help advance the study of relativistic quantum information in cavity quantum electrodynamics.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142158797","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":"Gauge-invariant magnetic charges in linearised gravity","authors":"Chris Hull, Maxwell L Hutt and Ulf Lindström","doi":"10.1088/1361-6382/ad718a","DOIUrl":"https://doi.org/10.1088/1361-6382/ad718a","url":null,"abstract":"Linearised gravity has magnetic charges carried by (linearised) Kaluza–Klein monopoles. A gauge-invariant expression is found for these charges that is similar to Penrose’s gauge-invariant expression for the ADM charges. A systematic search is made for other gauge-invariant charges.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142158796","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":"Effective-one-body numerical-relativity waveform model for eccentric spin-precessing binary black hole coalescence","authors":"Xiaolin Liu, Zhoujian Cao and Zong-Hong Zhu","doi":"10.1088/1361-6382/ad72ca","DOIUrl":"https://doi.org/10.1088/1361-6382/ad72ca","url":null,"abstract":"Waveform models are important to gravitational wave data analysis. People recently pay much attention to the waveform model construction for eccentric binary black hole (BBH) coalescence. Several effective-one-body (EOB) Numerical-Relativity waveform models of eccentric BBH coalescence have been constructed. But none of them can treat orbit eccentricity and spin-precessing simultaneously. The current paper focuses on this problem. The authors previously have constructed waveform model for spin-aligned eccentric BBH coalescence SEOBNRE. Here we extend such waveform model to describe eccentric spin-precessing BBH coalescence. We calculate the 2PN orbital radiation-reaction forces and the instantaneous part of the decomposed waveform for a general spinning precessing BBH system in EOB coordinates. We implement these results based on our previous SEOBNRE waveform model. We have also compared our model waveforms to both SXS and RIT numerical relativity waveforms. We find good consistency between our model and numerical relativity. Based on our new waveform model, we analyze the impact of the non-perpendicular spin contributions on waveform accuracy. We find that the non-perpendicular spin contributions primarily affect the phase of the gravitational waveforms. For the current gravitational wave detectors, this contribution is not significant. The future detectors may be affected by such non-perpendicular spin contributions. More importantly our SEOBNRE waveform model, as the first theoretical waveform model to describe eccentric spin-precessing BBH coalescence, can help people to analyze orbit eccentricity and spin precession simultaneously for gravitational wave detection data.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142142517","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}
Abdel Nasser Tawfik, Antonio Pasqua, Muhammad Waqas, Azzah A Alshehri and Prabir Kr Haldar
{"title":"Quantum geometric perspective on the origin of quantum-conditioned curvatures","authors":"Abdel Nasser Tawfik, Antonio Pasqua, Muhammad Waqas, Azzah A Alshehri and Prabir Kr Haldar","doi":"10.1088/1361-6382/ad7451","DOIUrl":"https://doi.org/10.1088/1361-6382/ad7451","url":null,"abstract":"The quantization of the gravitational field, which includes the metric field, has been investigated using various methods such as loop quantum gravity, quantum field theory, and string theory. Nevertheless, an alternative strategy to tackle the challenge of merging the fundamentally different theories of general relativity (GR) and quantum mechanics (QM) is through a quantum geometric approach. This particular approach entails extending QM to relativistic energies and finite gravitational fields, while also expanding the continuous Riemann to a discretized (quantized) Finsler–Hamilton geometry. By embracing this method, it may be feasible to bridge the gap between GR and QM or even achieve their unification. The resulting fundamental tensor appears to blend its original classical and quantum characteristics, effectively integrating quantum-mechanically induced revisions to the affine connections and spacetime curvatures. Our study primarily focuses on investigating the Ricci curvature tensor in the context of the Einstein–Gilbert–Straus metric. By employing both analytical and numerical methods, we have identified quantum-conditioned curvatures (QCC) that act as additional sources of gravitation. These QCC exhibit a fundamental difference from the traditional curvatures described by Einsteinian GR. While the Ricci curvatures are predominantly positive across most regions, the quantized Ricci curvatures display negativity. We conclude that the QCC (a) possess an intrinsic, essential, and real character, (b) should not be disregarded due to their significant magnitude, and (c) are fundamentally different from the curvatures found in classical GR. Moreover, we conclude that the proposed quantum geometric approach may offer an alternative mathematical framework for understanding the emergence of quantum gravity.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142142541","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":"Comparing eccentric waveform models based on post-Newtonian and effective-one-body approaches","authors":"Balázs Kacskovics and Dániel Barta","doi":"10.1088/1361-6382/ad72cb","DOIUrl":"https://doi.org/10.1088/1361-6382/ad72cb","url":null,"abstract":"In the present study, two numerical models were compared to each other, namely the CBWaves and SEOBNRE algorithms, developed using the post-Newtonian and effective-one-body approaches, respectively, for the study of binary black holes evolving on eccentric orbits. To map the mismatch between the two models 260 000 simulations were conducted – 20 000 for non-spinning configurations and 240 000 for spinning ones—on a common grid of parameter values over the parameter space. This space is defined by the mass ratio , the gravitational mass of each component labeled by i, the corresponding spin magnitude and a constant initial orbital eccentricity e0. A comprehensive investigation was conducted to determine whether there was a discrepancy in the waveforms generated by the two codes. This entailed an in-depth analysis of the mismatch, and an extensive comparison was carried out on the outlier points between the two codes.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142138138","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}
Raúl Arias, Marcelo Botta-Cantcheff and Pedro J Martinez
{"title":"Real-time methods in JT/SYK holography","authors":"Raúl Arias, Marcelo Botta-Cantcheff and Pedro J Martinez","doi":"10.1088/1361-6382/ad721b","DOIUrl":"https://doi.org/10.1088/1361-6382/ad721b","url":null,"abstract":"We study the conventional holographic recipes and its real-time extensions in the context of the correspondence between Sachdev–Ye–Kitaev quantum mechanics and JT gravity. We first observe that only closed contours are allowed to have a 2d space-time holographic dual and standard holographic formulas. Thus, in a real-time formulation of the duality, the boundaries of a classical connected geometry are a set of closed curves, parameterized by a complex time contour as in the Schwinger–Keldysh framework. In this context, a consistent extension of the standard holographic formulas can be proposed, describing the (real-time) correspondence between gravity and boundary quantum models that include averaging on the coupling constants. We investigate the proposed prescription in different AdS solutions with Schwinger–Keldysh boundary condition, dual to a boundary quantum theory at finite temperature defined on a complex time contour, and consider also classical, asymptotically AdS solutions (wormholes) with two disconnected boundaries. In doing this, we revisit the so-called factorization problem, and its resolution in conventional holography by virtue of some (non-local) coupling between disconnected boundaries, and we show how in specific contexts, the averaging proposal by-passes the paradox as well, since it induces a similar effective coupling.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142130598","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 new 2+1 coherent spin-foam vertex for quantum gravity","authors":"J D Simão","doi":"10.1088/1361-6382/ad721e","DOIUrl":"https://doi.org/10.1088/1361-6382/ad721e","url":null,"abstract":"We propose an explicit spin-foam amplitude for Lorentzian gravity in three dimensions, allowing for both space- and time-like boundaries. The model is based on two main requirements: that it should be structurally similar to its well-known Euclidean analog, and that geometricity should be recovered in the semiclassical regime. To this end we introduce new coherent states for space-like boundary edges, derived from the continuous series of unitary representations. We show that the relevant objects in the amplitude can be written in terms of the defining representation of the group, just as so happens in the Euclidean case. We derive an expression for the semiclassical amplitude at large spins, showing it relates to the Lorentzian Regge action.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142130647","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":"Improved model of large-field inflation with primordial black hole production in Starobinsky-like supergravity","authors":"Ryotaro Ishikawa and Sergei V Ketov","doi":"10.1088/1361-6382/ad7187","DOIUrl":"https://doi.org/10.1088/1361-6382/ad7187","url":null,"abstract":"A viable model of large-field (chaotic) inflation with efficient production of primordial black holes is proposed in Starobinsky-like (modified) supergravity leading to the ‘no-scale-type’ Kähler potential and the Wess-Zumino-type (‘renormalizable’) superpotential. The cosmological tilts are in good (within 1σ) agreement with Planck measurements of the cosmic microwave background radiation. In addition, the power spectrum of scalar perturbations has a large peak at smaller scales, which leads to a production of primordial black holes from gravitational collapse of large perturbations with the masses about 1017 g. The masses are beyond the Hawking (black hole) evaporation limit of 1015 g, so that those primordial black holes may be viewed as viable candidates for a significant part or the whole of the current dark matter. The parameters of the superpotential were fine-tuned for those purposes, while the cubic term in the superpotential is essential whereas the quadratic term should vanish. The vacuum after inflation (relevant to reheating) is Minkowskian. The energy density fraction of the gravitational waves induced by the production of primordial black holes and their frequency were also calculated in the second order with respect to perturbations.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123474","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}
Alexander Franke, Nils Sültmann, Christoph Reinhardt, Sandy Croatto, Jörn Schaffran, Hossein Masalehdan, Axel Lindner and Roman Schnabel
{"title":"Measurement of the thermal accommodation coefficient of helium on a crystalline silicon surface at low-temperatures","authors":"Alexander Franke, Nils Sültmann, Christoph Reinhardt, Sandy Croatto, Jörn Schaffran, Hossein Masalehdan, Axel Lindner and Roman Schnabel","doi":"10.1088/1361-6382/ad7184","DOIUrl":"https://doi.org/10.1088/1361-6382/ad7184","url":null,"abstract":"Proposals for next-generation gravitational wave observatories include cryogenically cooled 200 kg test mass mirrors suspended from pendulums and made of a crystalline material such as crystalline silicon. During operation of the observatories, these mirrors undergo heating due to the absorption of laser radiation of up to a watt. Low noise cooling techniques need to be developed. Low-pressure helium exchange gas at 5 K might contribute to the challenging task. Here, we report the measurement of the helium accommodation coefficient , which is the probability that a helium atom thermalises with a surface at a given temperature when reflected from it. We find for temperatures K, which increases the cooling power compared to recently used assumptions. The idea of free molecular flow helium gas cooling is thus supported and might find application in some observatory concepts.","PeriodicalId":10282,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123473","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}