引力波文獻周讀(30 Nov-4 Dec 2020)

每周搜集 arXiv 上 Astrophysics（天體物理） 和 General Relativity（廣義相對論）部分與 Gravitational Wave（引力波）相關的文章，方便快速了解學術前言動態。

Astrophysics

Title: Detection of gravitational waves in circular particle accelerators Authors: Suvrat Rao, Marcus Brüggen, Jochen Liske https://arxiv.org/abs/2012.00529 Abstract:  Here we calculate the effects of astrophysical gravitational waves (GWs) on the travel times of proton bunch test masses in circular particle accelerators. We show that a high-precision proton bunch time-tagging detector could turn a circular particle accelerator facility into a GW observatory sensitive to millihertz (mHz) GWs. We comment on sources of noise and the technological feasibility of ultrafast single photon detectors by conducting a case study of the Large Hadron Collider (LHC) at CERN.       [2/26] 標題：引力波探測器中通過窮舉搜索的多材料塗層設計 Title: Multimaterial Coatings Design via Exhaustive Search for Gravitational Wave Detectors Authors: V. Pierro, V. Fiumara et al.https://arxiv.org/abs/2012.02146 Abstract:  In this work we analyze coatings for gravitational wave detector mirrors obtained by sequencing dielectric layers, with fixed thicknesses, made of three different materials (ternary sequences). Two materials are chosen non-dissipative, i.e. are the standard oxides used in gravitational wave detector coatings technology, the third is a dissipative material. We use the methodology of the exhaustive smart search in the space of sequences to find out the coating design with minimal thermal noise satisfying suitable constraints on transmittance and absorbance. This search has a combinatorial computational complexity and is carried out with a backtracking algorithm. The results obtained show that these ternary sequences can satisfy the optical transmittance and absorbance constraints requested by the mirrors of gravitational wave interferometers, reducing the thermal noise of the coating compared to the standard configuration made of two non-dissipative materials. In all the examined cases the dissipative material is positioned on the bottom of the optimal sequence of the coating layers, close to the substrate. Furthermore, the optimal designs are robust with respect to the uncertainty of the extinction coefficient and have spectral behaviors similar to the quarter wave coatings. Finally, the possibility of further improving performance in terms of thermal noise is demonstrated by considering sequences made of non-quarter wavelength layers.       [3/26] 標題：LISA波段中雙白矮星的質量與本動加速度之間的簡併 Title: Degeneracy between mass and peculiar acceleration for the double white dwarfs in the LISA band Authors: Zeyuan Xuan, Peng Peng, Xian Chen https://arxiv.org/abs/2012.00049 Abstract:  Mass and distance are fundamental quantities to measure in gravitational-wave (GW) astronomy. However, recent studies suggest that the measurement may be biased due to the acceleration of GW source. Here we develop an analytical method to quantify such a bias induced by a tertiary on a double white dwarf (DWD), since DWDs are the most common GW sources in the milli-Hertz band. We show that in a large parameter space the mass is degenerate with the peculiar acceleration, so that from the waveform we can only retrieve a mass of M(1+\Gamma)^{3/5}, where M is the real chirp mass of the DWD and \Gamma is a dimensionless factor proportional to the peculiar acceleration. Based on our analytical method, we conduct mock observation of DWDs by the Laser Interferometer Space Antenna (LISA). We find that in about 9% of the cases the measured chirp mass is biased due to the presence of a tertiary by (5-30)%. Even more extreme cases are found in about a dozen DWDs and they may be misclassified as double neutron stars, binary black holes, DWDs undergoing mass transfer, or even binaries containing lower-mass-gap objects and primordial black holes. The bias in mass also affects the measurement of distance, resulting in a seemingly over-density of DWDs within a heliocentric distance of 1 kpc as well as beyond 100 kpc. Our result highlights the necessity of modeling the astrophysical environments of GW sources to retrieve their correct physical parameters.       Title: Mass-gap Mergers in Active Galactic Nuclei Authors: Hiromichi Tagawa, Bence Kocsis et al.https://arxiv.org/abs/2012.00011 Abstract:  The recently discovered gravitational wave sources GW190521 and GW190814 have shown evidence of BH mergers with masses and spins that could be outside of the range expected from isolated stellar evolution. These merging objects could have undergone previous mergers. Such hierarchical mergers are predicted to be frequent in active galactic nuclei (AGN) disks, where binaries form and evolve efficiently by dynamical interactions and gaseous dissipation. Here we compare the properties of these observed events to the theoretical models of mergers in AGN disks, which are obtained by performing one-dimensional N-body simulations combined with semi-analytical prescriptions. The high BH masses in GW190521 are consistent with mergers of high-generation (high-g) BHs where the initial progenitor stars had high metallicity, 2g BHs if the original progenitors were metal-poor, or 1g BHs that had gained mass via super-Eddington accretion. Other measured properties related to spin parameters in GW190521 are also consistent with mergers in AGN disks. Furthermore, mergers in the lower mass gap or those with low mass ratio as found in GW190814 and GW190412 are also reproduced by mergers of 2g-1g or 1g-1g objects with significant accretion in AGN disks. Finally, due to gas accretion, the massive neutron star merger reported in GW190425 can be produced in an AGN disk.       [5/26] 標題：LISA大質量雙黑洞併合的透鏡選擇效應特徵 Title: Characterisation of lensing selection effects for LISA massive black hole binary mergers Authors: Giulia Cusin, Nicola Tamanini https://arxiv.org/abs/2011.15109 Abstract:  We present a method to include lensing selection effects due to the finite horizon of a given detector when studying lensing of gravitational wave (GW) sources. When selection effects are included, the mean of the magnification distribution is shifted from one to higher values for sufficiently high-redshift sources. This introduces an irreducible (multiplicative) bias on the luminosity distance reconstruction, in addition to the typical source of uncertainty in the distance determination. We apply this method to study lensing of GWs emitted by massive black hole binary mergers at high redshift detectable by LISA. We estimate the expected bias induced by selection effects on the luminosity distance reconstruction as function of cosmological redshift, and discuss its implications for cosmological and astrophysical analyses with LISA. We also reconstruct the distribution of lensing magnification as a function of the observed luminosity distance to a source, that is the observable quantity in the absence of an electromagnetic counterpart. Lensing provides the dominant source of errors in distance measurements of high-redshift GW sources. Its full characterisation, including the impact of selection effects, is of paramount importance to correctly determine the astrophysical properties of the underlying source population and to be able to use gravitational wave sources as a new cosmological probe.       [6/26] 標題：引力波作為球狀星團形成和演化的探針Title: Gravitational Waves as a Probe of Globular Cluster Formation and Evolution Authors: Isobel M. Romero-Shaw, Kyle Kremer et al.https://arxiv.org/abs/2011.14541 Abstract:  Globular clusters are considered to be likely breeding grounds for compact binary mergers. In this paper, we demonstrate how the gravitational-wave signals produced by compact object mergers can act as tracers of globular cluster formation and evolution. Globular cluster formation is a long-standing mystery in astrophysics, with multiple competing theories describing when and how globular clusters formed. The limited sensitivity of electromagnetic telescopes inhibits our ability to directly observe globular cluster formation. However, with future audio-band detectors sensitive out to redshifts of z \approx 50 for GW150914-like signals, gravitational-wave astronomy will enable us to probe the Universe when the first globular clusters formed. We simulate a dataset of gravitational-wave signals from theoretically-motivated globular cluster formation models. We show that data from third-generation detectors can be used to reconstruct the history of globular clusters in the Universe. It may be possible to constrain the peak epochs of cluster formation to within [\order{0.001}--\order{0.1}]{Gyr} at 99% confidence.[7/26] 標題：通過脈衝星到達時間分析揭示脈衝星-雙黑洞三體系統的結構 Title: Unveiling the architecture of a pulsar - binary black-hole triple system with pulsar arrival time analysis Authors: Toshinori Hayashi, Yasushi Suto https://arxiv.org/abs/2011.14261 Abstract:  A large number of binary black holes (BBHs) with longer orbital periods are supposed to exist as progenitors of BBH mergers recently discovered with gravitational wave (GW) detectors. In our previous papers, we proposed to search for such BBHs in triple systems through the radial-velocity modulation of the tertiary orbiting star. If the tertiary is a pulsar, high precision and cadence observations of its arrival time enable an unambiguous characterization of the pulsar -- BBH triples located at several kpc, which are inaccessible with the radial velocity of stars. The present paper shows that such inner BBHs can be identified through the short-term Rømer delay modulation, on the order of 10 msec for our fiducial case, a triple consisting of 20~M_\odot BBH and 1.4~M_\odot pulsar with P_{in}=10 days and P_{out}=100 days. If the relativistic time delays are measured as well, one can determine basically all the orbital parameters of the triple. For instance, this method is applicable to inner BBHs of down to \sim 1 hr orbital periods if the orbital period of the tertiary pulsar is around several days. Inner BBHs with \lesssim 1 hr orbital period emit the GW detectable by future space-based GW missions including LISA, DECIGO, and BBO, and very short inner BBHs with sub-second orbital period can be even probed by the existing ground-based GW detectors. Therefore, our proposed methodology provides a complementary technique to search for inner BBHs in triples, if exist at all, in the near future.       [8/26] 標題：極端質量比引力波源：質量層化和後雙星潮汐擾動俘獲 Title: Extreme mass-ratio gravitational-wave sources: Mass segregation and post binary tidal-disruption captures Authors: Yael Raveh, Hagai B. Perets https://arxiv.org/abs/2011.13952 Abstract:  The gravitational-wave (GW) inspirals of stellar-mass compact objects onto a supermassive black hole (MBH), are some of the most promising GW sources detectable by next-generation space-born GW-detectors. The rates and characteristics of such extreme mass ratio inspirals (EMRIs) sources are highly uncertain. They are determined by the dynamics of stars near MBHs, and the rate at which compacts objects are driven to the close proximity of the MBH. Here we consider weakly and strongly mass-segregated nuclear clusters, and the evolution of stars captured into highly eccentric orbits following binary disruptions by the MBH. We make use of a Monte-Carlo approach to model the diffusion of both captured objects, and compact-objects brought through two-body relaxation processes. We calculate the rates of GW-inspirals resulting from relaxation-driven objects, and characterize EMRIs properties. We correct previous studies and show that relaxation-driven sources produce GW-sources with lower-eccentricity than previously found, and provide the detailed EMRI eccentricity distribution in the weak and strong mass-segregation regimes. We also show that binary-disruption captured-stars could introduce low-eccentricity GW-sources of stellar black-hole EMRIs in mass-segregated clusters. The eccentricities of the GW-sources from the capture channel, however, are strongly affected by relaxation processes, and are significantly higher than previously suggested. We find that both the rate and eccentricity distribution of EMRIs could probe the dynamics near MBHs, and the contribution of captured stars, characterize the mass-function of stellar compact objects, and verify whether weak or strong mass-segregation processes take place near MBHs.       [9/26] 標題：用dart_board建模GW150914的雙黑洞源 Title: Targeted modeling of GW150914's binary black hole source with dart_board Authors: Jeff J. Andrews, Julianne Cronin et al.https://arxiv.org/abs/2011.13918 Abstract:  We present a new method to extract statistical constraints on the progenitor properties and formation channels of individual gravitational-wave sources. Although many different models have been proposed to explain the formation of the binary black holes detected by the LIGO Scientific and Virgo Collaboration (LVC), formation through isolated binary evolution remains the best explored scenario. Under the assumption that these binary systems have been formed through binary evolution, we use the statistical wrapper dart_board coupled with the rapid binary evolution code COSMIC to model GW150914, the first gravitational-wave signal detected by the LVC. Our procedure is a Bayesian method that combines the likelihood function generated from the gravitational-wave signal with a prior distribution describing the population of stellar binaries and the star-formation and metallicity evolution of the Universe. In this example case, we find that the dominant evolutionary channel for GW150914 did not involve any common-envelope phase, but instead the system most probably formed through stable mass transfer. This result is robust against variations of various model parameters, and it is reversed only when dynamical instability in binaries becomes more likely when a strict condition favoring common envelopes is adopted. Our analysis additionally provides a quantitative description of the progenitors relevant to each channel.       [10/26] 標題：建模中子星-黑洞雙星：未來的脈衝星研究和引力波探測器 Title: Modelling Neutron Star-Black Hole Binaries: Future Pulsar Surveys and Gravitational Wave Detectors Authors: Debatri Chattopadhyay, Simon Stevenson et al.https://arxiv.org/abs/2011.13503 Abstract:  Binaries comprised of a neutron star (NS) and a black hole (BH) have so far eluded observations as pulsars and with gravitational waves (GWs). We model the formation and evolution of these NS+BH binaries including pulsar evolution using the binary population synthesis code COMPAS. We predict the presence of a total of 50-1300 binaries containing a pulsar and a BH (PSR+BHs) in the Galactic field. We find the population observable by the next-generation of radio telescopes, represented by the SKA and MeerKAT, current (LIGO/Virgo) and future (LISA) GW detectors. We conclude that the SKA will observe 1-60 PSR+BHs, with 0-4 binaries containing millisecond pulsars. MeerKAT is expected to observe 0-30 PSR+BH systems. Future radio detections of NS+BHs will constrain uncertain binary evolution processes such as BH natal kicks. We show that systems in which the NS formed first (NSBH) can be distinguished from those where the BH formed first (BHNS) by their pulsar and binary properties. We find 40% of the LIGO/Virgo observed NS+BHs from a Milky-Way like field population will have a chirp mass \geq 3.0 M_\odot. We estimate the spin distributions of NS+BHs with two models for the spins of BHs. The remnants of BHNS mergers will have a spin of \sim0.4, whilst NSBH merger remnants can have a spin of \sim0.6 or \sim0.9 depending on the model for BH spins. We estimate that approximately 25-930 PSR+BHs will be radio alive whilst emitting GWs in the LISA frequency band, raising the possibility of joint observation by the SKA and LISA.       Title: Gravitational wave spectra from oscillon formation after inflation Authors: Takashi Hiramatsu, Evangelos I. Sfakianakis, Masahide Yamaguchi https://arxiv.org/abs/2011.12201 Abstract:  We systematically investigate the preheating behavior of single field inflation with an oscillon-supporting potential. We compute the properties of the emitted gravitational waves (GWs) and the number density and characteristics of the produced oscillons. By performing numerical simulations for a variety of potential types, we divide the analyzed potentials in two families, each of them containing potentials with varying large- or small-field dependence. We find that the shape and amplitude of the emitted GW spectrum have a universal feature, with the peak around the physical wavenumber k/a \sim m at the inflaton oscillation period, irrespective of the exact potential shape. This can be used as a smoking-gun for deducing the existence of a violent preheating phase and possible oscillon formation after inflation. Despite this apparent universality, we find differences in the shape of the emitted GW spectra between the two potential families, leading to discriminating features between them. In particular, all potentials show the emergence of a two-peak structure in the GW spectrum, arising at the time of oscillon formation. However, potentials exhibiting efficient parametric resonance tend to smear out this structure and by the end of the simulation the GW spectrum exhibits a single broad peak. We further compute the properties of the produced oscillons for each potential, finding differences in the number density and size distribution of stable oscillons and transient overdensities. We perform a linear fluctuation analysis and use Floquet charts to relate the results of our simulations to the structure of parametric resonance. We find that the growth rate of scalar perturbations and the associated oscillon formation time are sensitive to the small-field potential shape while the macroscopic physical properties of oscillons (e.g. total number) depend on the large-field potential shape.       [12/26] 標題：高紅移原初黑洞雙星的可探測性 Title: Detectability of Primordial Black Hole Binaries at High Redshift https://arxiv.org/abs/2011.13643 Abstract:  We show that the gravitational wave signals from primordial black hole (PBH) binaries at high redshift can be detected. The detectability of PBH binaries is enhanced by redshift bias and more PBH binaries at high redshift. The initial clustering of PBHs is also included and enhances the effectively detectable mass ranges of PBHs at high redshift. Future observations on the gravitational wave at high redshift by space-based detectors such as LISA and SKA can constrain the fraction of PBHs in dark matter and PBHs initial distribution.       

General Relativity

[13/26] 標題：探測黑洞度規：黑洞陰影和雙黑洞旋近Title: Probing the Black Hole Metric. I. Black Hole Shadows and Binary Black-Hole Inspirals Authors: Dimitrios Psaltis, Colm Talbot, Ethan Payne, Ilya Mandel https://arxiv.org/abs/2012.02117 Abstract:  In General Relativity, the spacetimes of black holes have three fundamental properties: (i) they are the same, to lowest order in spin, as the metrics of stellar objects; (ii) they are independent of mass, when expressed in geometric units; and (iii) they are described by the Kerr metric. In this paper, we quantify the upper bounds on potential black-hole metric deviations imposed by observations of black-hole shadows and of binary black-hole inspirals in order to explore the current experimental limits on possible violations of the last two predictions. We find that both types of experiments provide correlated constraints on deviation parameters that are primarily in the tt-components of the spacetimes, when expressed in areal coordinates. We conclude that, currently, there is no evidence for a deviations from the Kerr metric across the 8 orders of magnitudes in masses and 16 orders in curvatures spanned by the two types of black holes. Moreover, because of the particular masses of black holes in the current sample of gravitational-wave sources, the correlations imposed by the two experiments are aligned and of similar magnitudes when expressed in terms of the far field, post-Newtonian predictions of the metrics. If a future coalescing black-hole binary with two low-mass (e.g., ~3 Msun) components is discovered, the degeneracy between the deviation parameters can be broken by combining the inspiral constraints with those from the black-hole shadow measurements.       [14/26] 標題：緻密雙星旋近引力波的後牛頓模板 Title: Post-Newtonian templates for gravitational waves from compact binary inspirals Authors: Soichiro Isoyama, Riccardo Sturani, Hiroyuki Nakano https://arxiv.org/abs/2012.01350 Abstract:  To enable detection and maximise the physics output of gravitational wave observations from compact binary systems, it is crucial the availability of accurate waveform models. The present work aims at giving an overview for non-experts of the (inspiral) waveforms used in the gravitational wave data analysis for compact binary coalescence. We first provide the essential elements of gravitational radiation physics within a simple Newtonian orbital dynamics and the linearized gravity theory, describing the adiabatic approximation applied to binary systems: the key element to construct the theoretical gravitational waveforms in practice. We next lay out the gravitational waveforms in the post-Newtonian approximation to General Relativity, and highlight the basic input for the inspiral waveform of the slowly evolving, spinning, nonprecessing, quasicircular binary black holes, namely, post-Newtonian energy, fluxes and the (absorption-corrected) balance equation. The post-Newtonian inspiral templates are then presented both in the time and frequency domain. Finally, including the merger and subsequent ringdown phase, we briefly survey the two families of the full waveform models of compact binary mergers currently implemented in LSC Algorithm Library Simulation: the effective-one-body approach and the phenomenological frequency domain model.       [15/26] 標題：通過機器學習快速，靈活，準確地評估Malmquist偏差：為即將到來的引力波探測做準備 Title: Fast, flexible, and accurate evaluation of Malmquist bias with machine learning: Preparing for the pending flood of gravitational-wave detections Authors: Colm Talbot, Eric Thrane https://arxiv.org/abs/2012.01317 Abstract:  Many astronomical surveys are limited by the brightness of the sources, and gravitational-wave searches are no exception. The detectability of gravitational waves from merging binaries is affected by the mass and spin of the constituent compact objects. To perform unbiased inference on the distribution of compact binaries, it is necessary to account for this selection effect, which is known as Malmquist bias. Since systematic error from selection effects grows with the number of events, it will be increasingly important over the coming years to accurately estimate the observational selection function for gravitational-wave astronomy. We employ a range of machine learning methods to accurately and efficiently compute the compact binary coalescence selection function. We introduce a simple pre-processing method, which significantly reduces the complexity of the required machine learning models. As a demonstration of our method, we reproduce and extend the results from the recent LIGO--Virgo analysis of events from their second gravitational-wave transient catalog (GWTC-2). While qualitatively consistent with previous work, we find that the method used to compute the selection function noticeably affects the inferred population. The most significant change is a 1\sigma increase in the steepness of the mass ratio distribution and an \sim10% increase in the inferred rate, {R}_{BBH} = 32^{+11}_{-9}{Gpc}^{-3}{yr}^{-1}, when using our new method. Including spin effects in the selection function does not significantly impact the results with current uncertainties.       [16/26] 標題：空間引力波天文臺參數估計的準確性 Title: Accuracy of estimation of parameters with space-borne gravitational wave observatory Authors: Chao Zhang, Yungui Gong, Bin Wang, Chunyu Zhang https://arxiv.org/abs/2012.01043 Abstract:  Employing the Fisher information matrix approximation, we estimate the errors of parameters with TianQin and LISA for monochromatic gravitational waves. With the long-wavelength approximation we give analytical formulas for the parameter estimation errors. We analyze the amplitude modulation due to the changing orientation of the detector plane and the Doppler effect due to the translational motion of the center of the detector around the Sun. We disclose that in the low frequency regimes there exist different patterns in angular resolutions and estimation errors of the signal's parameters between LISA and TianQin. The angular resolutions and the estimation errors of the signal's parameters fall off as S_n(f)/f^2 for TianQin but S_n(f) for LISA. However in the medium frequency regimes we observe the same patterns where the angular resolutions fall off as S_n(f)/f^2 and the estimation errors of the signal's parameters fall off as S_n(f) for both TianQin and LISA. In the high frequency regimes, the long-wavelength approximation fails, we numerically calculate the parameter estimation errors for LISA and TianQin and find that the parameter estimation errors measured by TianQin are better than those by LISA.       [17/26] 標題：根據核心坍縮超新星的引力波數據推斷原中子星的性質 Title: Inference of proto-neutron star properties from gravitational-wave data in core-collapse supernovae Authors: Marie-Anne Bizouard, Patricio Maturana-Russel et al.https://arxiv.org/abs/2012.00846 Abstract:  The eventual detection of gravitational waves from core-collapse supernovae (CCSN) will help improve our current understanding of the explosion mechanism of massive stars. The stochastic nature of the late post-bounce gravitational wave signal due to the non-linear dynamics of the matter involved and the large number of degrees of freedom of the phenomenon make the source parameter inference problem very challenging. In this paper we take a step towards that goal and present a parameter estimation approach which is based on the gravitational waves associated with oscillations of proto-neutron stars (PNS). Numerical simulations of CCSN have shown that buoyancy-driven g-modes are responsible for a significant fraction of the gravitational wave signal and their time-frequency evolution is linked to the physical properties of the compact remnant through universal relations, as demonstrated in [1]. We use a set of 1D CCSN simulations to build a model that relates the evolution of the PNS properties with the frequency of the dominant g-mode, which is extracted from the gravitational-wave data using a new algorithm we have developed for our study. The model is used to infer the time evolution of a combination of the mass and the radius of the PNS. The performance of the method is estimated employing simulations of 2D CCSN waveforms covering a progenitor mass range between 11 and 40 solar masses and different equations of state. Considering signals embedded in Gaussian gravitational wave detector noise, we show that it is possible to infer PNS properties for a galactic source using Advanced LIGO and Advanced Virgo data at design sensitivities. Third generation detectors such as Einstein Telescope and Cosmic Explorer will allow to test distances of O(100 kpc).       Title: Stochastic gravitational-wave background in quantum gravity Authors: Gianluca Calcagni, Sachiko Kuroyanagi https://arxiv.org/abs/2012.00170 Abstract:  Among all cosmological quantum-gravity or quantum-gravity-inspired scenarios, only very few predict a blue-tilted primordial tensor spectrum. We explore five of them and check whether they can generate a stochastic gravitational-wave background detectable by present and future interferometers: non-local quantum gravity, string-gas cosmology, new ekpyrotic scenario, Brandenberger-Ho non-commutative inflation and multi-fractional spacetimes. We show that non-local quantum gravity is unobservable, while all the other models can reach the strain sensitivity of DECIGO but not that of LIGO-Virgo-KAGRA, LISA or Einstein Telescope. Other quantum-gravity models with red-tilted spectra (most loop quantum cosmologies) or with exceptionally tiny quantum corrections (Wheeler-DeWitt quantum cosmology) are found to be non-detectable.[19/26] 標題：緻密雙星併合的快速可靠頻域有效單體波形 Title: Fast, faithful, frequency-domain effective-one-body waveforms for compact binary coalescences Authors: Rossella Gamba, Sebastiano Bernuzzi, Alessandro Nagar https://arxiv.org/abs/2012.00027 Abstract:  The inference of binary neutron star properties from gravitational-wave observations requires the generation of millions of waveforms, each one spanning about three order of magnitudes in frequency range. Thus, waveform models must be efficiently generated and, at the same time, be faithful from the post-Newtonian quasi-adiabatic inspiral up to the merger regime. A simple solution to this problem is to combine effective-one-body waveforms with the stationary phase approximation to obtain frequency-domain multipolar approximants valid from any low frequency to merger. We demonstrate that effective-one-body frequency-domain waveforms generated in post-adiabatic approximation are computationally competitive with current phenomenological and surrogate models, (virtually) arbitrarily long, and faithful up to merger for any binary parameter. The same method can also be used to efficiently generate intermediate mass binary black hole inspiral waveforms detectable by space-based interferometers.       [20/26] 標題：高新LIGO第一次觀測運行中參數估計的可靠性 Title: On the reliability of parameter estimates in the first observing run of Advanced LIGO Authors: Suman Kulkarni, Collin D. Capano https://arxiv.org/abs/2011.13764 Abstract:  Accurate parameter estimation is key to maximizing the scientific impact of gravitational-wave astronomy. Parameters of a binary merger are typically estimated using Bayesian inference. It is necessary to make several assumptions when doing so, one of which is that the the detectors output stationary Gaussian noise. We test the validity of these assumptions by performing percentile-percentile tests in both simulated Gaussian noise and real detector data in the first observing run of Advanced LIGO (O1). We add simulated signals to 512s of data centered on each of the three events detected in O1 -- GW150914, GW151012, and GW151226 -- and check that the recovered credible intervals match statistical expectations. We find that we are able to recover unbiased parameter estimates in the real detector data, indicating that the assumption of Gaussian noise does not adversely effect parameter estimates. However, we also find that both the parallel-tempered emcee sampler emcee_pt and the nested sampler dynesty struggle to produced unbiased parameter estimates for GW151226-like signals, even in simulated Gaussian noise. The emcee_pt sampler does produce unbiased estimates for GW150914-like signals. This highlights the importance of performing percentile-percentile tests in different targeted areas of parameter space.       [21/26] 標題：用Parkes脈衝星計時陣列搜索來自宇宙弦尖的引力波暴Title: Searching for gravitational wave bursts from cosmic string cusps with the Parkes Pulsar Timing Array Authors: N. Yonemaru, S. Kuroyanagi et al.https://arxiv.org/abs/2011.13490 Abstract:  Cosmic strings are potential gravitational wave (GW) sources that can be probed by pulsar timing arrays (PTAs). In this work we develop a detection algorithm for a GW burst from a cusp on a cosmic string, and apply it to Parkes PTA data. We find four events with a false alarm probability less than 1%. However further investigation shows that all of these are likely to be spurious. As there are no convincing detections we place upper limits on the GW amplitude for different event durations. From these bounds we place limits on the cosmic string tension of G mu ~ 10^{-5}, and highlight that this bound is independent from those obtained using other techniques. We discuss the physical implications of our results and the prospect of probing cosmic strings in the era of Square Kilometre Array (SKA).       [22/26] 標題：脈衝星計時陣列搜索引力波的重疊約化函數的解析級數展開 Title: Analytic series expansion of the overlap reduction function for gravitational wave search with pulsar timing arrays Authors: Adrian Boîtier, Shubhanshu Tiwari, Philippe Jetzer https://arxiv.org/abs/2011.13405 Abstract:  In our previous paper {PTA1} we derived a generic expression for the pulse redshift the main observable for the Pulsar Timing Array (PTA) experiment for detection of gravitational waves for all possible polarizations induced by modifications of general relativity (GR). In this work we provide a generic expression of the overlap reduction function for PTA without using the short wavelength approximation for tensorial polarization. We are convinced, that the short wavelength approximation is not applicable to the overlap reduction function for PTA's, since the removal of the exponential terms in the integrand would lead to poles for x, y and l polarizations and discontinuities for + and \times. In this work we provide a series expansion to calculate the integral exactly and investigate the behaviour of the series for short wavelength values via numerical evaluation of the analytical series. We find a disagreement for the limit of co-located pulsars with the Hellings & Downs curve.       [23/26] 標題：在mHz頻帶內關聯多個三角探測器來搜索引力波背景 Title: Gravitational Wave Background Search by Correlating Multiple Triangular Detectors in the mHz Band https://arxiv.org/abs/2010.06877 Abstract:  With the recent strong developments of TianQin and Taiji, we now have an increasing chance to make a correlation analysis in the mHz band by operating them together with LISA. Assuming two LISA-like triangular detectors at general geometrical configurations, we develop a simple formulation to evaluate the network sensitivity to an isotropic gravitational wave background. In our formulation, we fully use the symmetry of data channels within each triangular detector and provide tractable expressions without directly employing cumbersome detector tensors. We concretely evaluate the expected network sensitivities for various potential detector combinations, including the LISA-TianQin pair.[24/26] 標題：頻率論與貝葉斯分析：互相關是LIGO-Virgo隨機背景搜索的（近似）充分統計量 Title: Frequentist versus Bayesian analyses: Cross-correlation as an (approximate) sufficient statistic for LIGO-Virgo stochastic background searches Authors: Andrew Matas, Joseph D. Romano https://arxiv.org/abs/2012.00907 Abstract:  Sufficient statistics are combinations of data in terms of which the likelihood function can be rewritten without loss of information. Depending on the data volume reduction, the use of sufficient statistics as a preliminary step in a Bayesian analysis can lead to significant increases in efficiency when sampling from posterior distributions of model parameters. Here we show that the frequency integrand of the cross-correlation statistic and its variance are approximate sufficient statistics for ground-based searches for stochastic gravitational-wave backgrounds. The sufficient statistics are approximate because one works in the weak-signal approximation and uses measured estimates of the auto-correlated power in each detector. Using analytic and numerical calculations, we prove that LIGO-Virgo's hybrid frequentist-Bayesian parameter estimation analysis is equivalent to a fully Bayesian analysis. This work closes a gap in the LIGO-Virgo literature, and suggests directions for additional searches.       [25/26] 標題：通過引力波發射對擴展引力模型的約束 Title: Constraints on extended gravity models through gravitational wave emission Authors: Gaetano Lambiase, Mairi Sakellariadou, Antonio Stabile https://arxiv.org/abs/2012.00114 Abstract:  Using recent experimental results of detection of gravitational waves from the binary black hole signals by Advanced LIGO and Advanced Virgo, we investigate the propagation of gravitational waves in the context of fourth order gravity nonminimally coupled to a massive scalar field. In particular, we impose constraints on the free parameters of extended gravity models from the current observational data.[26/26] 標題：帶有電荷和磁荷的雙黑洞的引力和電磁輻射：圓錐體上的橢圓軌道 Title: Gravitational and electromagnetic radiation from binary black holes with electric and magnetic charges: Elliptical orbits on a cone Authors: Lang Liu, Øyvind Christiansen et al.https://arxiv.org/abs/2011.13586 Abstract:  By using a Newtonian method with radiation reactions, we calculate the total emission rate of energy and angular momentum due to gravitational and electromagnetic radiation from binary black holes with electric and magnetic charges for precessing elliptical orbits. It is shown that the emission rates of energy and angular momentum due to gravitational radiation and electromagnetic radiation have the same dependence on the conic angle for different orbits. Moreover, we obtain the evolutions of orbits. We find that a circular orbit remains circular and an elliptic orbit becomes quasi-circular due to electromagnetic and gravitational radiation.

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