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Metric symmetry by design in general relativity
IF 3.5 3区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-12-24 DOI: 10.1088/1361-6382/ad9f15
Viktor T Toth
The usual derivation of Einstein’s field equations from the Einstein–Hilbert action is performed by silently assuming the metric tensor’s symmetric character. If this symmetry is not assumed, the result is a new theory, such as Einstein’s attempted Unified Field Theory or Moffat’s Nonsymmetric Gravitational Theory. Explicitly enforcing the constraint by means of a Lagrange-multiplier term restores Einstein’s field equations, but the multiplier appears as an additional, unconstrained antisymmetric term. We briefly discuss the possible significance of this term with respect to a nonvanishing cosmological angular momentum, a sourced spin current, the nonsymmetric nature of the Einstein pseudotensor characterizing the energy–momentum of the gravitational field, and possible implications on attempts to obtain a quantum theory of gravity.
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引用次数: 0
Amplitude stability research and experimental investigation of the actuation circuit of the inertial sensor for space gravitational wave detection
IF 3.5 3区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-12-24 DOI: 10.1088/1361-6382/ad9c0d
Jiawei Zhang, Peilong Yu, Shuyang Lin, Qinbo Ma, Zhe Han and Jianping Huang
The primary measure of scientific performance for inertial sensors used in space gravitational wave detection is the residual acceleration noise of the test mass (TM). This residual noise arises from both the internal circuit and the external environment. The actuation circuit, a crucial component of the internal circuit, significantly affects the TM’s residual acceleration noise through its amplitude stability, thereby impacting the scientific performance of the inertial sensor. In this study, we designed the actuation circuit for an inertial sensor, developed a mathematical model to describe its amplitude stability, and experimentally verified the model’s accuracy. Experimental results demonstrate that the current design enables the actuation circuit to achieve an amplitude stability of 3.6 ppm Hz−1/2 at 1 mHz, thereby offering theoretical support for achieving a higher amplitude stability in the millihertz frequency band.
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引用次数: 0
GEO 600 beam splitter thermal compensation system: new design and commissioning
IF 3.5 3区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-12-20 DOI: 10.1088/1361-6382/ad9b69
Séverin Nadji, Holger Wittel, Nikhil Mukund, James Lough, Christoph Affeldt, Fabio Bergamin, Marc Brinkmann, Volker Kringel, Harald Lück, Michael Weinert and Karsten Danzmann
Gravitational waves (GW) have revolutionised the field of astronomy by providing scientists with a new way to observe the Universe and gain a better understanding of exotic objects like black holes. Several large-scale laser interferometric GW detectors have been constructed worldwide, with a focus on achieving the best possible sensitivity. However, in order for a detector to operate at its intended sensitivity, its optics must be free from imperfections such as thermal lensing effects. In the GEO 600 GW detector, the beam splitter experiences a significant thermal lensing effect due to the high power build-up in the power recycling cavity combined with a very small beam waist. This causes the fundamental mode to be converted into higher order modes, subsequently impacting the detector’s performance. To address this issue, the GEO 600 detector is equipped with a thermal compensation system (TCS) applied to the beam splitter. This involves projecting a spatially tunable heating pattern through an optical system onto the beam splitter. The main objective of the TCS is to counteract the thermal lens at the beam splitter and restore the detector to its ideal operating condition. This paper presents the new beam splitter TCS in GEO 600, its commissioning and its effect on strain sensitivity. It also outlines the planned upgrade to further enhance the performance of the TCS.
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引用次数: 0
Properties of interacting quark star in light of Rastall gravity
IF 3.5 3区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-12-20 DOI: 10.1088/1361-6382/ad9c0f
Ayan Banerjee, Anirudh Pradhan, İzzet Sakallı and Archana Dixit
This study explores the properties of quark stars (QSs) formulated with an interacting quark matter equation of state within the framework of Rastall gravity, a modified theory of gravity. We derive the mass-radius relationships and calculate the maximum gravitational masses and their corresponding radii, comparing these results under both Rastall gravity and general relativity. Our analysis incorporates recent observational data, including the GW190425 event, to constrain the model parameters ( ). We also assess the stability of these QSs by evaluating their static stability, adiabatic index, and sound velocity profiles, thus confirming their viability within the modified gravitational framework.
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引用次数: 0
Non-local quantum field theory from doubly special relativity
IF 3.5 3区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-12-20 DOI: 10.1088/1361-6382/ad9c10
J J Relancio and L Santamaría-Sanz
Doubly special relativity (DSR) is usually regarded as a low-energy limit of a quantum gravity theory with testable predictions. On the other hand, non-local quantum field theories have been presented as a solution to the inconsistencies arising when quantizing gravity. Here, we present a new formulation of quantum field theories in DSR with non-local behavior. Our construction restricts the models to those showing linear Lorentz invariance. We derive the deformed Klein–Gordon, Dirac, and electromagnetic Lagrangians, as well as the deformed Maxwell equations. We also discuss the electric potential of a point charge. Finally, we analyze the connection between the nonlocality of field theories and DSR.
双狭义相对论(DSR)通常被视为量子引力理论的低能极限,其预言是可以检验的。另一方面,非局域量子场论被认为是解决量子化引力时产生的不一致性的方法。在这里,我们提出了一种具有非局域行为的 DSR 量子场理论的新表述。我们的构造将模型限制为那些显示线性洛伦兹不变性的模型。我们推导了变形克莱因-戈登、狄拉克和电磁拉格朗日,以及变形麦克斯韦方程。我们还讨论了点电荷的电动势。最后,我们分析了场论的非局域性与 DSR 之间的联系。
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引用次数: 0
Noncommutative lightcones from quantum SO(2,1) conformal groups
IF 3.5 3区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-12-19 DOI: 10.1088/1361-6382/ad9a49
Martina Adamo, Angel Ballesteros and Flavio Mercati
Five new families of noncommutative lightcones in dimensions are presented as quantizations of the inequivalent Poisson homogeneous structures that emerge when the lightcone is constructed as a homogeneous space of the SO(2,1) conformal group. Each of these noncommutative lightcones maintains covariance under the action of the respective quantum deformation of the SO(2,1) conformal group. We discuss the role played by SO(2,1) automorphisms in the classification of inequivalent Poisson homogeneous lightcones, as well as the geometric aspects of this construction. The localization properties of the novel quantum lightcones are analyzed and shown to be deeply connected with the geometric features of the Poisson homogeneous spaces.
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引用次数: 0
Observational prospects of self-interacting scalar superradiance with next-generation gravitational-wave detectors
IF 3.5 3区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-12-19 DOI: 10.1088/1361-6382/ad96ff
Spencer Collaviti, Ling Sun, Marios Galanis and Masha Baryakhtar
Current- and next-generation gravitational-wave observatories may reveal new, ultralight bosons. Through the superradiance process, these theoretical particle candidates can form clouds around astrophysical black holes and result in detectable gravitational-wave radiation. In the absence of detections, constraints—contingent on astrophysical assumptions—have been derived using LIGO-Virgo-KAGRA data on boson masses. However, the searches for ultralight scalars to date have not adequately considered self-interactions between particles. Self-interactions that significantly alter superradiance dynamics are generically present for many scalar models, including axion-like dark matter candidates and string axions. We implement the most complete treatment of particle self-interactions available to determine the gravitational-wave signatures expected from superradiant scalar clouds and revisit the constraints obtained in a past gravitational-wave search targeting the black hole in Cygnus X-1. We also project the reach of next-generation gravitational-wave observatories to scalar particle parameter space in the mass-coupling plane. We find that while proposed observatories have insufficient reach to self-interactions that can halt black hole spin-down, next-generation observatories are essential for expanding the search beyond gravitational parameter space and can reach a mass and interaction scale of –10−12 eV and GeV, respectively.
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引用次数: 0
Double copy, Kerr–Schild gauges and the effective-one-body formalism
IF 3.5 3区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-12-18 DOI: 10.1088/1361-6382/ad987f
Anna Ceresole, Thibault Damour, Alessandro Nagar and Piero Rettegno
We look for a classical double-copy-inspired relation between gravity and electrodynamics by connecting the descriptions of the scattering of two point masses, and of two point charges, in terms of perturbative (post-Minkowskian or post-Lorentzian) expansions. We do so by recasting available analytical information within the effective-one-body formalism using Kerr–Schild gauges in both cases. Working at the third perturbative level, we find that the usual linear relation (holding in the probe limit) between the adimensionalized electric potential, , and the Schwarzschild-like gravitational one, , is deformed, in the comparable-mass, comparable-charge, case, into a nonlinear relation which becomes universal in the high energy limit: .
我们通过将两个点质量和两个点电荷的散射描述与扰动(后明考夫斯基或后洛伦兹)展开联系起来,寻找引力和电动力学之间的经典双拷贝启发关系。我们在这两种情况下都使用了克尔-希尔德量规,在有效单体形式主义中重铸了现有的分析信息。在第三扰动层次上,我们发现,在可比质量、可比电荷的情况下,加维电势Ⅳ与施瓦兹丘尔德引力Ⅳ之间通常的线性关系(在探测极限中保持不变)被变形为一种非线性关系,在高能极限中成为普遍关系:Ⅳ......。
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引用次数: 0
Effective geometry of Bell-network states on a dipole graph
IF 3.5 3区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-12-17 DOI: 10.1088/1361-6382/ad997b
B Baytaş and N Yokomizo
Bell-network states are a class of entangled states of the geometry that satisfy an area-law for the entanglement entropy in a limit of large spins and are automorphism-invariant, for arbitrary graphs. We present a comprehensive analysis of the effective geometry of Bell-network states on a dipole graph. Our main goal is to provide a detailed characterization of the quantum geometry of a class of diffeomorphism-invariant, area-law states representing homogeneous and isotropic configurations in loop quantum gravity, which may be explored as boundary states for the dynamics of the theory. We found that the average geometry at each node in the dipole graph does not match that of a flat tetrahedron. Instead, the expected values of the geometric observables satisfy relations that are characteristic of spherical tetrahedra. The mean geometry is accompanied by fluctuations with considerable relative dispersion for the dihedral angle, and perfectly correlated for the two nodes.
贝尔网络态是一类几何纠缠态,它满足大自旋极限下纠缠熵的面积律,并且对于任意图都是自形变不变的。我们全面分析了偶极图上贝尔网络态的有效几何。我们的主要目标是详细描述一类衍射不变、区域律态的量子几何,它们代表了环量子引力中的同质和各向同性构型,可以作为理论动力学的边界态来探索。我们发现偶极图中每个节点的平均几何形状与平面四面体并不匹配。相反,几何观测值的预期值满足球形四面体的特征关系。平均几何形状伴随着波动,二面角有相当大的相对分散性,而两个节点则完全相关。
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引用次数: 0
Formulating the complete initial boundary value problem in numerical relativity to model black hole echoes 提出数值相对论中的完整初始边界值问题以模拟黑洞回声
IF 3.5 3区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-12-17 DOI: 10.1088/1361-6382/ad9701
Conner Dailey, Erik Schnetter and Niayesh Afshordi
In an attempt to simulate black hole echoes (generated by potential quantum-gravitational structure) in numerical relativity, we recently described how to implement a reflecting boundary outside of the horizon of a black hole in spherical symmetry. Here, we generalize this approach to spacetimes with no symmetries and implement it numerically using the generalized harmonic formulation. We cast the evolution equations and the numerical implementation into a Summation By Parts scheme, which seats our method closer to a class of provably numerically stable systems. We implement an embedded boundary numerical framework that allows for arbitrarily shaped domains on a rectangular grid and even boundaries that evolve and move across the grid. As a demonstration of this framework, we study the evolution of gravitational wave scattering off a boundary either inside, or just outside, the horizon of a black hole. This marks a big leap toward the goal of a generic framework to obtain gravitational waveforms for behaviors motivated by quantum gravity near the horizons of merging black holes.
为了在数值相对论中模拟黑洞回声(由潜在量子引力结构产生),我们最近描述了如何在球对称黑洞视界外实现反射边界。在这里,我们将这种方法推广到无对称性的时空,并使用广义谐波公式进行数值计算。我们将演化方程和数值实现转换为部分求和方案,使我们的方法更接近于一类可证明的数值稳定系统。我们实施了一个嵌入式边界数值框架,允许在矩形网格上实现任意形状的域,甚至允许边界在网格上演化和移动。作为该框架的演示,我们研究了黑洞视界内或视界外边界引力波散射的演变。这标志着我们朝着建立一个通用框架的目标迈出了一大步,这个框架可以获取由量子引力激发的黑洞合并视界附近的引力波形。
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Classical and Quantum Gravity
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