We study the radiative efficiency and the jet power in the spacetime of the rotating black hole in loop quantum gravity (LQG), which has an extra LQG parameter. It is shown that with the increase of the LQG parameter, the conversion efficiency decreases for the slowly rotating black hole, but increases for the rapidly rotating black hole, the jet power increases for different black hole spins. With the observed data from the well-known sources A0620-00, H1743-322, XTE J1550-564, GRS1124-683, GRO J1655-40, and GRS1915+105, we make some constraints on the black hole spin parameter and the LQG parameter. The presence of the LQG parameter broadens the allowed range of the black hole spin parameter for sources A0620-00, H1743-322, XTE J1550-564 and GRO J1655-40. However, for the source GRS 1915+105, there is no overlap between observational constrain parameter regions, which implies that the rotating LQG black hole cannot simultaneously account for the observed jet power and the radiative efficiency as in other black hole spacetimes.
{"title":"Signatures from the observed jet power and the radiative efficiency for rotating black holes in loop quantum gravity","authors":"Zhengwei Cheng, Songbai Chen, Jiliang Jing","doi":"arxiv-2409.06950","DOIUrl":"https://doi.org/arxiv-2409.06950","url":null,"abstract":"We study the radiative efficiency and the jet power in the spacetime of the\u0000rotating black hole in loop quantum gravity (LQG), which has an extra LQG\u0000parameter. It is shown that with the increase of the LQG parameter, the\u0000conversion efficiency decreases for the slowly rotating black hole, but\u0000increases for the rapidly rotating black hole, the jet power increases for\u0000different black hole spins. With the observed data from the well-known sources\u0000A0620-00, H1743-322, XTE J1550-564, GRS1124-683, GRO J1655-40, and GRS1915+105,\u0000we make some constraints on the black hole spin parameter and the LQG\u0000parameter. The presence of the LQG parameter broadens the allowed range of the\u0000black hole spin parameter for sources A0620-00, H1743-322, XTE J1550-564 and\u0000GRO J1655-40. However, for the source GRS 1915+105, there is no overlap between\u0000observational constrain parameter regions, which implies that the rotating LQG\u0000black hole cannot simultaneously account for the observed jet power and the\u0000radiative efficiency as in other black hole spacetimes.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199298","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yehui Hou, Jiewei Huang, Yosuke Mizuno, Minyong Guo, Bin Chen
Extracting information about the gravitational background from black hole images is both important and challenging. In this study, we use a physically motivated plasma model, typically applied to stationary, axisymmetric spacetimes, to demonstrate that in a rotating black hole spacetime, the polarizations of emitted light near the event horizon depend solely on the spacetime geometry, independent of the plasma flow geometry. We confirm that the frame-dragging effect of a rotating black hole governs the observed polarization structure in the near-horizon image. This finding indicates a unique imprint of the black hole spin on the polarization of the near-horizon image. We anticipate that refined observations of near-horizon emissions by the next-generation Event Horizon Telescope will enable us to determine the black hole spin in a straightforward manner.
{"title":"Unique Imprint of Black Hole Spin on the Polarization of Near-Horizon Images","authors":"Yehui Hou, Jiewei Huang, Yosuke Mizuno, Minyong Guo, Bin Chen","doi":"arxiv-2409.07248","DOIUrl":"https://doi.org/arxiv-2409.07248","url":null,"abstract":"Extracting information about the gravitational background from black hole\u0000images is both important and challenging. In this study, we use a physically\u0000motivated plasma model, typically applied to stationary, axisymmetric\u0000spacetimes, to demonstrate that in a rotating black hole spacetime, the\u0000polarizations of emitted light near the event horizon depend solely on the\u0000spacetime geometry, independent of the plasma flow geometry. We confirm that\u0000the frame-dragging effect of a rotating black hole governs the observed\u0000polarization structure in the near-horizon image. This finding indicates a\u0000unique imprint of the black hole spin on the polarization of the near-horizon\u0000image. We anticipate that refined observations of near-horizon emissions by the\u0000next-generation Event Horizon Telescope will enable us to determine the black\u0000hole spin in a straightforward manner.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sizheng Ma, Kyle C. Nelli, Jordan Moxon, Mark A. Scheel, Nils Deppe, Lawrence E. Kidder, William Throwe, Nils L. Vu
Cauchy-characteristic evolution (CCE) is a powerful method for accurately extracting gravitational waves at future null infinity. In this work, we extend the previously implemented CCE system within the numerical relativity code SpECTRE by incorporating a scalar field. This allows the system to capture features of beyond-general-relativity theories. We derive scalar contributions to the equations of motion, Weyl scalar computations, Bianchi identities, and balance laws at future null infinity. Our algorithm, tested across various scenarios, accurately reveals memory effects induced by both scalar and tensor fields and captures Price's power-law tail ($u^{-l-2}$) in scalar fields at future null infinity, in contrast to the $t^{-2l-3}$ tail at future timelike infinity.
{"title":"Einstein-Klein-Gordon system via Cauchy-characteristic evolution: Computation of memory and ringdown tail","authors":"Sizheng Ma, Kyle C. Nelli, Jordan Moxon, Mark A. Scheel, Nils Deppe, Lawrence E. Kidder, William Throwe, Nils L. Vu","doi":"arxiv-2409.06141","DOIUrl":"https://doi.org/arxiv-2409.06141","url":null,"abstract":"Cauchy-characteristic evolution (CCE) is a powerful method for accurately\u0000extracting gravitational waves at future null infinity. In this work, we extend\u0000the previously implemented CCE system within the numerical relativity code\u0000SpECTRE by incorporating a scalar field. This allows the system to capture\u0000features of beyond-general-relativity theories. We derive scalar contributions\u0000to the equations of motion, Weyl scalar computations, Bianchi identities, and\u0000balance laws at future null infinity. Our algorithm, tested across various\u0000scenarios, accurately reveals memory effects induced by both scalar and tensor\u0000fields and captures Price's power-law tail ($u^{-l-2}$) in scalar fields at\u0000future null infinity, in contrast to the $t^{-2l-3}$ tail at future timelike\u0000infinity.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Massive black hole binary (MBHB) mergers will be detectable in large numbers by the Lisa Interferometer Space Antenna (LISA), which will thus provide new insights on how they form via repeated dark matter (DM) halo and galaxy mergers. Here we present a simple analytical model to generate a population of MBHB mergers based on a theoretical prescription that connects them to DM halo mergers. The high flexibility of our approach allows us to explore the broad and uncertain range of MBH seeding and growth mechanisms, as well as the different effects behind the interplay between MBH and galactic astrophysics. Such a flexibility is fundamental for the successful implementation and optimisation of the hierarchical Bayesian parameter estimation approach that here we apply to the MBHB population of LISA for the first time. Our inferred population hyper-parameters are chosen as proxies to characterise the MBH--DM halo mass scaling relation, the occupation fraction of MBHs in DM halos and the delay between halo and MBHB mergers. We find that LISA will provide tight constraints at the lower-end of the MBH-halo scaling relation, well complementing EM observations which are biased towards large masses. Furthermore, our results suggest that LISA will constrain some features of the MBH occupation fraction at high redshift, as well as merger time delays of the order of a few hundreds of Myr, opening the possibility to constrain dynamical evolution time scales such as the dynamical friction. The analysis presented here constitutes a first attempt at developing a hierarchical Bayesian inference approach to the LISA MBHB population, opening the way for several further improvements and investigations.
大质量黑洞双星(MBHB)合并将通过丽莎干涉仪空间天线(LISA)被大量探测到,这将为我们提供关于它们如何通过重复的暗物质(DM)光环和星系合并形成的新见解。在这里,我们提出了一个简单的分析模型,根据将MBHB合并与DM光环合并联系起来的理论处方,生成MBHB合并群。这种灵活性是成功实施和优化分层贝叶斯参数估计方法的基础,我们在这里首次将这种方法应用于 LISA 的 MBHB 群体。我们推断出的种群超参数被选作描述MBH--DM光环质量比例关系、DM光环中MBH的占据比例以及光环和MBHB合并之间的延迟的代理参数。我们发现,LISA 将在 MBH-halo 缩放关系的低端提供严格的约束,很好地补充了偏向于大质量的电磁观测。此外,我们的结果表明,LISA 将约束高红移下 MBH 占有率的某些特征,以及合并时间延迟到几百 Myr 的数量级,从而为约束动力学演变时间尺度(如动力学摩擦)提供了可能性。这里介绍的分析是针对 LISA MBHB 群体开发分层贝叶斯推断方法的首次尝试,为进一步的改进和研究开辟了道路。
{"title":"Hierarchical Bayesian inference on an analytical model of the LISA massive black hole binary population","authors":"Vivienne Langen, Nicola Tamanini, Sylvain Marsat, Elisa Bortolas","doi":"arxiv-2409.06527","DOIUrl":"https://doi.org/arxiv-2409.06527","url":null,"abstract":"Massive black hole binary (MBHB) mergers will be detectable in large numbers\u0000by the Lisa Interferometer Space Antenna (LISA), which will thus provide new\u0000insights on how they form via repeated dark matter (DM) halo and galaxy\u0000mergers. Here we present a simple analytical model to generate a population of\u0000MBHB mergers based on a theoretical prescription that connects them to DM halo\u0000mergers. The high flexibility of our approach allows us to explore the broad\u0000and uncertain range of MBH seeding and growth mechanisms, as well as the\u0000different effects behind the interplay between MBH and galactic astrophysics.\u0000Such a flexibility is fundamental for the successful implementation and\u0000optimisation of the hierarchical Bayesian parameter estimation approach that\u0000here we apply to the MBHB population of LISA for the first time. Our inferred\u0000population hyper-parameters are chosen as proxies to characterise the MBH--DM\u0000halo mass scaling relation, the occupation fraction of MBHs in DM halos and the\u0000delay between halo and MBHB mergers. We find that LISA will provide tight\u0000constraints at the lower-end of the MBH-halo scaling relation, well\u0000complementing EM observations which are biased towards large masses.\u0000Furthermore, our results suggest that LISA will constrain some features of the\u0000MBH occupation fraction at high redshift, as well as merger time delays of the\u0000order of a few hundreds of Myr, opening the possibility to constrain dynamical\u0000evolution time scales such as the dynamical friction. The analysis presented\u0000here constitutes a first attempt at developing a hierarchical Bayesian\u0000inference approach to the LISA MBHB population, opening the way for several\u0000further improvements and investigations.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We study wave metrics in the context of Cotton Gravity and Conformal Killing Gravity. First, we consider pp-wave metrics with flat and non-flat wave surfaces and show that they are exact solutions to the field equations of these theories. More explicitly, the field equations reduce to an inhomogeneous Laplace and Helmholtz differential equations, depending on the curvature of the two-dimensional geometry of the wave surfaces. An interesting point here is that the ones with non-flat wave surfaces are not present in classical GR, which manifests a crucial distinction between these theories and GR. Moreover, we investigate Kerr-Schild-Kundt metrics in the context of these theories and show that, from among these metrics, only the AdS wave metrics solve the field equations of these theories. However, AdS spherical and dS hyperbolic wave metrics do not solve the field equations of these theories, which is in contrast to the classical GR. In the case of AdS wave metrics, the field equations of these theories reduce to an inhomogeneous Klein-Gordon equation. We give all the necessary and sufficient conditions for the metric function $V$ to solve these field equations. Lastly, we address the colliding gravitational plane waves problem only in Cotton gravity due to the complexity of the field equations in Conformal Killing Gravity.
我们在科顿引力(Cotton Gravity)和共形基灵引力(Conformal KillingGravity)的背景下研究波度量。首先,我们考虑了具有平坦和非平坦波面的pp波度量,并证明它们是setheories场方程的精确解。更明确地说,场方程简化为非均质拉普拉斯微分方程和亥姆霍兹微分方程,这取决于波面二维几何的曲率。这里有趣的一点是,经典 GR 中不存在非平面波面,这体现了这些理论与 GR 的重要区别。此外,我们还研究了这些理论背景下的克尔-希尔德-昆特度量,结果表明,在这些度量中,只有AdS波度量解决了这些理论的场方程。然而,AdS球面波度量和dS双曲面波度量并不能求解这些理论的场方程,这与经典GR是不一致的。我们给出了求解这些场方程的度量函数 $V$ 的所有必要条件和充分条件。最后,由于共形基林引力中场方程的复杂性,我们只在科顿引力中讨论引力面波对撞问题。
{"title":"Wave Metrics in the Cotton and Conformal Killing Gravity Theories","authors":"Metin Gürses, Yaghoub Heydarzade, Çetin Şentürk","doi":"arxiv-2409.06257","DOIUrl":"https://doi.org/arxiv-2409.06257","url":null,"abstract":"We study wave metrics in the context of Cotton Gravity and Conformal Killing\u0000Gravity. First, we consider pp-wave metrics with flat and non-flat wave\u0000surfaces and show that they are exact solutions to the field equations of these\u0000theories. More explicitly, the field equations reduce to an inhomogeneous\u0000Laplace and Helmholtz differential equations, depending on the curvature of the\u0000two-dimensional geometry of the wave surfaces. An interesting point here is\u0000that the ones with non-flat wave surfaces are not present in classical GR,\u0000which manifests a crucial distinction between these theories and GR. Moreover,\u0000we investigate Kerr-Schild-Kundt metrics in the context of these theories and\u0000show that, from among these metrics, only the AdS wave metrics solve the field\u0000equations of these theories. However, AdS spherical and dS hyperbolic wave\u0000metrics do not solve the field equations of these theories, which is in\u0000contrast to the classical GR. In the case of AdS wave metrics, the field\u0000equations of these theories reduce to an inhomogeneous Klein-Gordon equation.\u0000We give all the necessary and sufficient conditions for the metric function $V$\u0000to solve these field equations. Lastly, we address the colliding gravitational\u0000plane waves problem only in Cotton gravity due to the complexity of the field\u0000equations in Conformal Killing Gravity.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"2013 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bobur Turimov, Akbar Davlataliev, Ahmadjon Abdujabbarov, Bobomurat Ahmedov
In this paper, we investigated the motion of massive particles in the presence of scalar and gravitational fields, particularly focusing on the Janis-Newman-Winicour (JNW) naked singularity solution. It is shown that the innermost stable circular orbit (ISCO) radius strongly depends on scalar coupling parameter. Additionally, we explored the radiation reaction effects on particle dynamics, incorporating a reaction term into the motion equations. Numerical simulations indicated minimal impact on particle trajectories from radiation reaction. We also examined the oscillatory motion of particles around compact objects in the JNW spacetime, focusing on radial and vertical oscillations. Our analysis indicated that the scalar field's coupling parameter and the spacetime deformation parameter $n$ significantly alter the fundamental frequencies of these oscillations. Furthermore, we studied quasi-periodic oscillations (QPOs) in X-ray binaries, using the relativistic precession (RP) model to analyze upper and lower frequency relationships. Our results indicated that increasing parameters ($n$ and $g_s$) shifts the frequency ratio of 3:2 QPOs closer to the naked singularity, with $n$ decreasing and $g_s$ increasing both frequencies. Finally, we analyzed QPO data from selected four X-ray binary systems using Markov Chain Monte Carlo (MCMC) analysis to constrain JNW parameters. Our findings provided insights into the mass, coupling and deformation parameter for each system, enhancing our understanding of compact object dynamics in strong gravitational fields.
{"title":"Influence of scalar field in massive particle motion in JNW spacetime","authors":"Bobur Turimov, Akbar Davlataliev, Ahmadjon Abdujabbarov, Bobomurat Ahmedov","doi":"arxiv-2409.06225","DOIUrl":"https://doi.org/arxiv-2409.06225","url":null,"abstract":"In this paper, we investigated the motion of massive particles in the\u0000presence of scalar and gravitational fields, particularly focusing on the\u0000Janis-Newman-Winicour (JNW) naked singularity solution. It is shown that the\u0000innermost stable circular orbit (ISCO) radius strongly depends on scalar\u0000coupling parameter. Additionally, we explored the radiation reaction effects on\u0000particle dynamics, incorporating a reaction term into the motion equations.\u0000Numerical simulations indicated minimal impact on particle trajectories from\u0000radiation reaction. We also examined the oscillatory motion of particles around\u0000compact objects in the JNW spacetime, focusing on radial and vertical\u0000oscillations. Our analysis indicated that the scalar field's coupling parameter\u0000and the spacetime deformation parameter $n$ significantly alter the fundamental\u0000frequencies of these oscillations. Furthermore, we studied quasi-periodic\u0000oscillations (QPOs) in X-ray binaries, using the relativistic precession (RP)\u0000model to analyze upper and lower frequency relationships. Our results indicated\u0000that increasing parameters ($n$ and $g_s$) shifts the frequency ratio of 3:2\u0000QPOs closer to the naked singularity, with $n$ decreasing and $g_s$ increasing\u0000both frequencies. Finally, we analyzed QPO data from selected four X-ray binary\u0000systems using Markov Chain Monte Carlo (MCMC) analysis to constrain JNW\u0000parameters. Our findings provided insights into the mass, coupling and\u0000deformation parameter for each system, enhancing our understanding of compact\u0000object dynamics in strong gravitational fields.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199307","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study considers the specific case of a flat, minimally coupled to gravity, quintessence cosmology with a dark energy quartic polynomial potential that has the same mathematical form as the Higgs potential. Previous work on this case determined that the scalar field is given by a simple expression of the Lambert W function in terms of the easily observable scale factor. This expression provides analytic equations for the evolution of cosmological dark energy parameters as a function of the scale factor for all points on the Lambert W function principal branch. The Lambert W function is zero at a scale factor of zero that marks the big bang. The evolutionary equations beyond the big bang describe a canonical universe that is similar to {Lambda}CDM, making it an excellent dynamical template to compare with observational data. The portion of the W function principal before the big bang extends to the infinite pre-bang past. It describes a noncanonical universe with an initially very low mass density that contracts by rolling down the dark energy potential to a singularity, big bang, at the scale factor zero point. This provides a natural origin for the big bang. It also raises the possibility that the universe existed before the big bang and is far older, and that it was once far larger than its current size. The recent increasing interest in the possibility of a dynamical universe instead of {Lambda}CDM makes the exploration of the nature of such universes particularly relevant.
本研究考虑的是一种平坦的、与引力最小耦合的五元宇宙学,其暗能量四元多项式势的数学形式与希格斯势相同。以前关于这种情况的研究确定,标量场是由易于观测的尺度因子的朗伯 W 函数的简单表达式给出的。这个表达式为宇宙学暗能量参数的演化提供了解析方程,它是兰伯特 W 函数主支上所有点的尺度因子的函数。兰伯特 W 函数在大爆炸尺度因子为零时为零。大爆炸之后的演化方程描述了一个与{Lambda}CDM相似的典型宇宙,使其成为与观测数据进行比较的绝佳动力学模板。大爆炸之前的W函数本构部分一直延伸到大爆炸之前的无限远的过去。它描述了一个非正则宇宙,其初始质量密度非常低,在尺度因子零点时,暗能量势能向下滚动,从而收缩为奇点,即大爆炸。这为大爆炸提供了一个自然起源。这也提出了一种可能性,即宇宙在大爆炸之前就已经存在,而且要古老得多,它曾经比现在的大小要大得多。最近,人们对{Lambda}CDM之外的ynamical宇宙的可能性越来越感兴趣,这使得探索这种宇宙的性质变得尤为重要。
{"title":"Non-Canonical Dark Energy Parameter Evolution in a Canonical Quintessence Cosmology","authors":"Rodger I. Thompson","doi":"arxiv-2409.06792","DOIUrl":"https://doi.org/arxiv-2409.06792","url":null,"abstract":"This study considers the specific case of a flat, minimally coupled to\u0000gravity, quintessence cosmology with a dark energy quartic polynomial potential\u0000that has the same mathematical form as the Higgs potential. Previous work on\u0000this case determined that the scalar field is given by a simple expression of\u0000the Lambert W function in terms of the easily observable scale factor. This\u0000expression provides analytic equations for the evolution of cosmological dark\u0000energy parameters as a function of the scale factor for all points on the\u0000Lambert W function principal branch. The Lambert W function is zero at a scale\u0000factor of zero that marks the big bang. The evolutionary equations beyond the\u0000big bang describe a canonical universe that is similar to {Lambda}CDM, making\u0000it an excellent dynamical template to compare with observational data. The\u0000portion of the W function principal before the big bang extends to the infinite\u0000pre-bang past. It describes a noncanonical universe with an initially very low\u0000mass density that contracts by rolling down the dark energy potential to a\u0000singularity, big bang, at the scale factor zero point. This provides a natural\u0000origin for the big bang. It also raises the possibility that the universe\u0000existed before the big bang and is far older, and that it was once far larger\u0000than its current size. The recent increasing interest in the possibility of a\u0000dynamical universe instead of {Lambda}CDM makes the exploration of the nature\u0000of such universes particularly relevant.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We revisit the gravitational lensing of light or gravitational waves by Schwarzschild black hole in geometric optics. Instead of a single massless particle, we investigate the collective behavior of a congruence of light/gravitational rays, described by the geodesic deviation equation (GDE). By projecting on the Newman-Penrose tetrad, GDE is decoupled, and we find an analytical Dyson-like series solution in the weak deflection and thin lens limits. Based on such a solution, we study the evolution of cross-sectional area and axis ratio. Finally, we reproduce the magnification and axis ratio of the lensing images up to the second order of weak deflection approximation and improve some missing corrections in previous works.
{"title":"Schwarzschild Lensing From Geodesic Deviation","authors":"Zhao Li, Xiao Guo, Tan Liu, Tao Zhu, Wen Zhao","doi":"arxiv-2409.06281","DOIUrl":"https://doi.org/arxiv-2409.06281","url":null,"abstract":"We revisit the gravitational lensing of light or gravitational waves by\u0000Schwarzschild black hole in geometric optics. Instead of a single massless\u0000particle, we investigate the collective behavior of a congruence of\u0000light/gravitational rays, described by the geodesic deviation equation (GDE).\u0000By projecting on the Newman-Penrose tetrad, GDE is decoupled, and we find an\u0000analytical Dyson-like series solution in the weak deflection and thin lens\u0000limits. Based on such a solution, we study the evolution of cross-sectional\u0000area and axis ratio. Finally, we reproduce the magnification and axis ratio of\u0000the lensing images up to the second order of weak deflection approximation and\u0000improve some missing corrections in previous works.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"90 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Black hole (BH) - neutron star (NS) binary mergers are not only strong sources of gravitational waves (GWs), but they are also candidates for joint detections in the GW and electromagnetic (EM) spectra. However, the possible emergence of an EM signal from these binaries is determined by a complex combination of the equation of state (EOS), the BH spin, and the mass ratio. In this second paper in a series, we present a systematic exploration of the possible space of binary parameters in terms of the mass ratio and BH spin so as to construct a complete description of the dynamical processes accompanying a BHNS binary merger. This second work relies not only on the initial data presented in the companion paper I, but also on the predictions via quasi-equilibrium (QE) sequences on the outcome of the binary. In this way, and for the first time, we are able to relate the predictions of QE analyses with the results of accurate general-relativistic magnetohydrodynamic simulations. In addition to a careful investigation of the evolution of the BH mass and spin as a result of the merger, the total remnant rest-mass of the resulting accretion disk and its properties, and of the corresponding post-merger GW emission, special attention is paid to the conditions that lead to tidal disruption. Leveraging QE calculations, we are able to verify the reliability of stringent predictions about the occurrence or not of a plunge and to measure the `strength' of the tidal disruption when it takes place. Finally, using a novel contraction of the Riemann tensor in a tetrad comoving with the fluid introduced in paper I, we are able to point out the onset of the instability to tidal disruption. This new diagnostic can be employed not only to determine the occurrence of the disruption, but also to characterize it in terms of the binary parameters.
黑洞(BH)-中子星(NS)双星合并不仅是引力波(GW)的强大来源,而且也是引力波和电磁波(EM)光谱联合探测的候选者。然而,这些双星可能产生的电磁信号是由状态方程(EOS)、BH自旋和质量比的综合组合决定的。在本系列的第二篇论文中,我们从质量比和BH自旋的角度,对双星参数的可能空间进行了系统的探索,从而构建出伴随BHNS双星合并的动力学过程的完整描述。这第二项工作不仅依赖于论文 I 中提供的初始数据,还依赖于通过准平衡(QE)序列对双星结果的预测。除了仔细研究合并后 BH 质量和自旋的演化、所产生的增殖盘的总剩余静止质量及其性质,以及相应的合并后 GW 发射之外,我们还特别关注了导致潮汐破坏的条件。利用 QE 计算,我们能够验证关于发生或不发生暴跌的严格预测的可靠性,并测量潮汐扰动发生时的 "强度"。最后,利用与论文 I 中引入的流体相向的四面体中黎曼张量的水平收缩,我们能够指出潮汐扰动不稳定性的开始。这种新的诊断方法不仅可以用来确定破坏的发生,还可以根据二元参数来描述破坏的特征。
{"title":"Black hole - neutron star binaries with high spins and large mass asymmetries: II. Properties of dynamical simulations","authors":"Konrad Topolski, Samuel Tootle, Luciano Rezzolla","doi":"arxiv-2409.06777","DOIUrl":"https://doi.org/arxiv-2409.06777","url":null,"abstract":"Black hole (BH) - neutron star (NS) binary mergers are not only strong\u0000sources of gravitational waves (GWs), but they are also candidates for joint\u0000detections in the GW and electromagnetic (EM) spectra. However, the possible\u0000emergence of an EM signal from these binaries is determined by a complex\u0000combination of the equation of state (EOS), the BH spin, and the mass ratio. In\u0000this second paper in a series, we present a systematic exploration of the\u0000possible space of binary parameters in terms of the mass ratio and BH spin so\u0000as to construct a complete description of the dynamical processes accompanying\u0000a BHNS binary merger. This second work relies not only on the initial data\u0000presented in the companion paper I, but also on the predictions via\u0000quasi-equilibrium (QE) sequences on the outcome of the binary. In this way, and\u0000for the first time, we are able to relate the predictions of QE analyses with\u0000the results of accurate general-relativistic magnetohydrodynamic simulations.\u0000In addition to a careful investigation of the evolution of the BH mass and spin\u0000as a result of the merger, the total remnant rest-mass of the resulting\u0000accretion disk and its properties, and of the corresponding post-merger GW\u0000emission, special attention is paid to the conditions that lead to tidal\u0000disruption. Leveraging QE calculations, we are able to verify the reliability\u0000of stringent predictions about the occurrence or not of a plunge and to measure\u0000the `strength' of the tidal disruption when it takes place. Finally, using a\u0000novel contraction of the Riemann tensor in a tetrad comoving with the fluid\u0000introduced in paper I, we are able to point out the onset of the instability to\u0000tidal disruption. This new diagnostic can be employed not only to determine the\u0000occurrence of the disruption, but also to characterize it in terms of the\u0000binary parameters.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. A. Sarmiento Alvarado, Maribel Hernández Márquez, Tonatiuh Matos
Recent observations on the large-scale structure of the universe indicate that the cosmological constant cannot be the definitive answer to the nature of dark energy. Therefore, it is a good time to propose alternatives to understand the late-accelerated expansion of the universe. In this work we study the possibility that the acceleration of space-time is due to the topology of the universe. We assume that the topology of the universe is a principal fiber bundle whose base space is our 4-dimensional spacetime and the fiber is an $N$-dimensional Lie group that evolves with time. For the base space we consider a homogeneous and isotropic spacetime, we find that the base space is currently accelerating for $1 < N$ compact semi-simple Lie groups whose scale-factors are equal and for $1 < N$ non-Abelian Lie groups whose scale-factors are different and as long as its structure constants satisfy some conditions. However when we study the evolution of the density parameters these differ from the evolution within the $Lambda$CDM model, this led us to think in the possibility of use a different group as fiber in order to obtain the right evolution of the density parameters. We conclude that it is possible that the accelerated expansion of the universe is due to consider a different topology of the universe as a principal fiber bundle.
最近对宇宙大尺度结构的观测表明,宇宙常数并不能成为暗能量性质的最终答案。因此,现在是提出替代方案来理解宇宙晚期加速膨胀的好时机。在这项工作中,我们研究了时空加速是由于宇宙拓扑造成的这一可能性。我们假设宇宙的拓扑结构是一个主纤维束,其基底空间是我们的四维时空,纤维是一个随时间演化的 N 维李群。我们认为基底空间是均质和各向同性的时空,我们发现,只要基底空间的结构常数满足某些条件,那么对于1<N$的紧凑半简单李群(其阶跃因子是相等的)和1<N$的非阿贝尔李群(其阶跃因子是不同的),基底空间目前是加速的。然而,当我们研究密度参数的演化时,它们与$Lambda$CDM模型中的演化有所不同,这促使我们思考是否有可能使用不同的群作为纤维,以获得密度参数的正确演化。我们的结论是,宇宙的加速膨胀有可能是由于考虑了不同的宇宙拓扑结构作为主纤维束。
{"title":"Cosmic Acceleration from topological considerations III: Lie group","authors":"I. A. Sarmiento Alvarado, Maribel Hernández Márquez, Tonatiuh Matos","doi":"arxiv-2409.06893","DOIUrl":"https://doi.org/arxiv-2409.06893","url":null,"abstract":"Recent observations on the large-scale structure of the universe indicate\u0000that the cosmological constant cannot be the definitive answer to the nature of\u0000dark energy. Therefore, it is a good time to propose alternatives to understand\u0000the late-accelerated expansion of the universe. In this work we study the\u0000possibility that the acceleration of space-time is due to the topology of the\u0000universe. We assume that the topology of the universe is a principal fiber\u0000bundle whose base space is our 4-dimensional spacetime and the fiber is an\u0000$N$-dimensional Lie group that evolves with time. For the base space we\u0000consider a homogeneous and isotropic spacetime, we find that the base space is\u0000currently accelerating for $1 < N$ compact semi-simple Lie groups whose\u0000scale-factors are equal and for $1 < N$ non-Abelian Lie groups whose\u0000scale-factors are different and as long as its structure constants satisfy some\u0000conditions. However when we study the evolution of the density parameters these\u0000differ from the evolution within the $Lambda$CDM model, this led us to think\u0000in the possibility of use a different group as fiber in order to obtain the\u0000right evolution of the density parameters. We conclude that it is possible that\u0000the accelerated expansion of the universe is due to consider a different\u0000topology of the universe as a principal fiber bundle.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}