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Numerical-relativity surrogate model for hyperbolic encounters of black holes: Challenges in parameter estimation

Physical Review D 2025年第4期111卷 044024-044024页

作者： Joan Fontbuté Tomas Andrade Raimon Luna Juan Calderón Bustillo Gonzalo Morrás Santiago Jaraba Juan García-Bellido Germán López Izquierdo Departament de Física Quàntica i Astrofísica Institut de Ciències del Cosmos Universitat de Barcelona Martí i Franquès 1 E-08028 Barcelona Spain Theoretisch-Physikalisches Institut Friedrich-Schiller-Universität Jena 07743 Jena Germany Departamento de Astronomía y Astrofísica Universitat de València Dr. Moliner 50 46100 Burjassot (València) Spain Departamento de Matemática da Universidade de Aveiro and Centre for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago 3810-193 Aveiro Portugal Instituto Galego de Física de Altas Enerxías Universidade de Santiago de Compostela 15782 Santiago de Compostela Galicia Spain Department of Physics The Chinese University of Hong Kong Shatin New Territories Hong Kong Instituto de Física Teórica IFT-UAM/CSIC Universidad Autónoma de Madrid Cantoblanco 28049 Madrid Spain

We present a surrogate numerical-relativity model for close hyperbolic black-hole encounters with equal masses and spins aligned with the orbital momentum. Our model, generated in terms of the Newman–Penrose scalar ψ4, spans impact parameters b/M∈[11,15] and spin components χi∈[−0.5,0.5], modeling the (ℓ,m)=(2,0), (2,±2), (3,±2), and (4,±4) emission multipoles. The model is faithful to numerical-relativity simulations, yielding mismatches lower than 10−3. We test the ability of our model to recover the parameters of numerically simulated signals. We find that, despite the high accuracy of the model, parameter inference struggles to correctly capture the parameters of the source even for SNRs as large as 50 due to the strong degeneracies present in the parameter space. This indicates that correctly identifying these systems will require extremely large signal loudness, which is only typical of third generation detectors. Nevertheless, we also find that, if one attempts to infer certain combinations of such degenerated parameters, there might be a chance to prove the existence of this type of event, even with the current ground-based detectors, as long as these combinations make sense astrophysically and cosmologically.

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Parasitic black holes: The swallowing of a fuzzy dark matter soliton

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Physical Review D 2022年第12期106卷 L121302-L121302页

作者： Vitor Cardoso Taishi Ikeda Rodrigo Vicente Miguel Zilhão CENTRA Departamento de Física Instituto Superior Técnico—IST Universidade de Lisboa—UL Avenida Rovisco Pais 1 1049 Lisboa Portugal Niels Bohr International Academy Niels Bohr Institute Blegdamsvej 17 2100 Copenhagen Denmark Dipartimento di Fisica “Sapienza” Universitá di Roma Piazzale Aldo Moro 5 00185 Roma Italy Institut de Fisica d’Altes Energies (IFAE) The Barcelona Institute of Science and Technology Campus UAB 08193 Bellaterra (Barcelona) Spain Departamento de Matemática da Universidade de Aveiro and Centre for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago 3810-183 Aveiro Portugal

Fuzzy dark matter is an exciting alternative to the standard cold dark matter paradigm, reproducing its large scale predictions, while solving most of the existing tension with small scale observations. These models postulate that dark matter is constituted by light bosons and predict the condensation of a solitonic core—also known as boson star, supported by wave pressure—at the center of halos. However, solitons which host a parasitic supermassive black hole are doomed to be swallowed by their guest. It is thus crucial to understand in detail the accretion process. In this work, we use numerical relativity to self-consistently solve the problem of accretion of a boson star by a central black hole, in spherical symmetry. We identify three stages in the process, a boson quake, a catastrophic stage and a linear phase, as well as a general accurate expression for the lifetime of a boson star with an endoparasitic black hole. Lifetimes of these objects can be large enough to allow them to survive until the present time.

关键词： Dark matter General relativity equations & solutions Classical black holes Numerical relativity

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Magnetized accretion disks around Kerr black holes with scalar hair: Nonconstant angular momentum disks

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Physical Review D 2021年第10期104卷 103008-103008页

作者： Sergio Gimeno-Soler José A. Font Carlos Herdeiro Eugen Radu Departamento de Astronomía y Astrofísica Universitat de València C/ Dr. Moliner 50 46100 Burjassot (València) Spain Observatori Astronòmic Universitat de València C/Catedrático José Beltrán 2 46980 Paterna (València) Spain Departamento de Matemática da Universidade de Aveiro and Centre for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago 3810-183 Aveiro Portugal

We present new equilibrium solutions of stationary models of magnetized thick disks (or tori) around Kerr black holes with synchronized scalar hair. The models reported here largely extend our previous results based on constant radial distributions of the specific angular momentum along the equatorial plane. We introduce a new way to prescribe the distribution of the disk’s angular momentum based on a combination of two previous proposals and compute the angular momentum distribution outside the equatorial plane by resorting to the construction of von Zeipel cylinders. We find that the effect of the scalar hair on the black hole spacetime can yield significant differences in the disk morphology and properties compared to what is found if the spacetime is purely Kerr. Some of the tori built within the most extreme, background hairy black hole spacetime of our sample exhibit the appearance of two maxima in the gravitational energy density which impacts the radial profile distributions of the disk’s thermodynamical quantities. The models reported in this paper can be used as initial data for numerical evolutions with general relativistic magnetohydrodynamic codes to study their stability properties. Moreover, they can be employed as illuminating sources to build shadows of Kerr black holes with scalar hair which might help further constrain the no-hair hypothesis as new observational data are collected.

关键词： Fluids & classical fields in curved spacetime Accretion disk & black-hole plasma Classical black holes

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Estimate of the gravitational-wave background from the observed cosmological distribution of quasars

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Physical Review D 2021年第2期104卷 024027-024027页

作者： Nicolas Sanchis-Gual Vicent Quilis José A. Font Departamento de Matemática da Universidade de Aveiro and Centre for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago 3810-183 Aveiro Portugal Departament d’Astronomia i Astrofísica Universitat de València c/ Dr. Moliner 50 46100 Burjassot València Spain Observatori Astronòmic Universitat de València c/ Catedrático José Beltrán 2 46980 Paterna València Spain

We study the gravitational-wave background from the observed cosmological quasar distribution. Using the DR9Q quasar catalogue from the ninth data release of the Sloan Digital Sky Survey (SDSS), we create a complete, statistically consistent sample of quasars from z=0.3 to 5.4. Employing the spectroscopic information from the catalogue we estimate the masses of the supermassive black holes hosted by the quasars in the sample, resulting in a log-normal distribution of mean 108.32±0.33 M⊙. The computation of the individual gravitational-wave strains relies on specific functional forms derived from simulations of gravitational collapse and mergers of massive black hole binaries. The background gravitational-wave emission is assembled by adding up the individual signals from each quasar modeled as plane waves whose interference can be constructive or destructive depending on the quasar evolutionary state. Our results indicate that the estimated gravitational-wave background discussed in this work could only be marginally detectable by LISA. This conclusion might change if more complete quasar catalogs than that provided by the SDSS become available.

关键词： Classical black holes Gravitational wave sources Gravitational waves Astronomical black holes Galactic nuclei & quasars

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Gravitational-Wave Parameter Inference with the Newman-Penrose Scalar

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Physical Review X 2023年第4期13卷 041048-041048页

作者： Juan Calderón Bustillo Isaac C. F. Wong Nicolas Sanchis-Gual Samson H. W. Leong Alejandro Torres-Forné Koustav Chandra José A. Font Carlos Herdeiro Eugen Radu Tjonnie G. F. Li Instituto Galego de Física de Altas Enerxías Universidade de Santiago de Compostela 15782 Santiago de Compostela Galicia Spain Department of Physics The Chinese University of Hong Kong Shatin New Territories Hong Kong Departamento de Astronomía y Astrofísica Universitat de València Dr. Moliner 50 46100 Burjassot (València) Spain Departamento de Matemática da Universidade de Aveiro and Centre for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago 3810-183 Aveiro Portugal Observatori Astronòmic Universitat de València C/ Catedrático José Beltrán 2 46980 Paterna (València) Spain Department of Physics Indian Institute of Technology Bombay Powai Mumbai Maharashtra 400076 India Institute for Theoretical Physics KU Leuven Celestijnenlaan 200D B-3001 Leuven Belgium Department of Electrical Engineering (ESAT) KU Leuven Kasteelpark Arenberg 10 B-3001 Leuven Belgium

Detection and parameter inference of gravitational-wave signals from compact mergers rely on the comparison of the incoming detector strain data d(t) to waveform templates for the gravitational-wave strain h(t) that ultimately rely on the resolution of Einstein’s equations via numerical relativity simulations. These, however, commonly output a quantity known as the Newman-Penrose scalar ψ4(t) which, under the Bondi gauge, is related to the gravitational-wave strain by ψ4(t)=d2h(t)/dt2. Therefore, obtaining strain templates involves an integration process that introduces artifacts that need to be treated in a rather manual way. By taking second-order finite differences on the detector data and inferring the corresponding background noise distribution, we develop a framework to perform gravitational-wave data analysis directly using ψ4(t) templates. We first demonstrate this formalism, and the impact of integration artifacts in strain templates, through the recovery of numerically simulated signals from head-on collisions of Proca stars injected in Advanced LIGO noise. Next, we reanalyze the event GW190521 under the hypothesis of a Proca-star merger, obtaining results equivalent to those previously published [Phys. Rev. Lett. 126, 081101 (2021)], where we used the classical strain framework. We find, however, that integration errors would strongly impact our analysis if GW190521 was 4 times louder. Finally, we show that our framework fixes significant biases in the interpretation of the high-mass gravitational-wave trigger S200114f arising from the usage of strain templates. We remove the need to obtain strain waveforms from numerical relativity simulations, avoiding the associated systematic errors.

关键词： Experimental studies of gravity General relativity Gravitational waves

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Impact of the wavelike nature of Proca stars on their gravitational-wave emission

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Physical Review D 2022年第12期106卷 124011-124011页

作者： Nicolas Sanchis-Gual Juan Calderón Bustillo Carlos Herdeiro Eugen Radu José A. Font Samson H. W. Leong Alejandro Torres-Forné Departamento de Astronomía y Astrofísica Universitat de València Dr. Moliner 50 46100 Burjassot (València) Spain Departamento de Matemática da Universidade de Aveiro and Centre for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago 3810-183 Aveiro Portugal Instituto Galego de Física de Altas Enerxías Universidade de Santiago de Compostela 15782 Santiago de Compostela Galicia Spain Department of Physics The Chinese University of Hong Kong Shatin 999077 N.T. Hong Kong Observatori Astronòmic Universitat de València C/ Catedrático José Beltrán 2 46980 Paterna (València) Spain

We present a systematic study of the dynamics and gravitational-wave emission of head-on collisions of spinning vector boson stars, known as Proca stars. To this aim we build a catalog of about 800 numerical-relativity simulations of such systems. We find that the wavelike nature of bosonic stars has a large impact on the gravitational-wave emission. In particular, we show that the initial relative phase Δε=ε1−ε2 of the two complex fields forming the stars (or, equivalently, the relative phase at merger) strongly impacts both the emitted gravitational-wave energy and the corresponding mode structure. This leads to a nonmonotonic dependence of the emission on the frequency of the secondary star ω2, for fixed frequency ω1 of the primary. This phenomenology, which has not been found for the case of black-hole mergers, reflects the distinct ability of the Proca field to interact with itself in both constructive and destructive manners. We postulate this may serve as a smoking gun to shed light on the possible existence of these objects.

关键词： Dark matter General relativity Gravitational waves Numerical relativity

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A framework to support quality data mart solutions: An approach developed based on practical cases 4

A framework to support quality data mart solutions: An appro...

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4th International Conference on Quality Engineering and Management, ICQEM 2020

作者： Mendes, A.R. Teixeira, L. Alvelos, H. Department of Economics Management Industrial Engineering and Tourism University of Aveiro Aveiro3810-193 Portugal Department of Economics Management Industrial Engineering and Tourism Institute of Electronics and Informatics Engineering of Aveiro University of Aveiro Aveiro3810-193 Portugal Department of Economics Management Industrial Engineering and Tourism Center for Research and Development in Mathematics and Applications University of Aveiro Aveiro3810-193 Portugal

ISBN: (纸本)9789895491100

Purpose - Today, due to the large amount of data available in companies, solutions for extracting information and knowledge to support decision-making processes are needed. To address this issue, data mart implementation with proper dashboard can represent good solutions. However, due to the complexity involved in this kind of projects and its multidisciplinary nature, appropriate methodologies for conducting data mart development are needed. The present study aims to propose a framework to guide the process of development of quality data marts in a Portuguese electronics company. Methodology - The methodology used to conduct this study combined the principles of two well-known approaches - DMAIC and BPM. The first was useful in addressing and understanding the problem, while the second was used to guide the process. Two practical cases were used, the first as an experimental scenario and the second one as a testing scenario. Findings - The main result of this study is a ready to use framework to guide industrialization teams in development of quality data marts to help users in their decision-making processes. Originality/value - As there are no standard procedures available for companies to implement quality data mart solutions, the proposed framework, which is easy to apply, can be a valuable tool when a company wants to industrialize a new product. It can also be valuable for researchers working at the interface of the Quality and Information Systems areas. © 2020 Universidade do Minho. All rights reserved.

关键词： BPM lifecycle BPMN 2.0 Data Mart DMAIC Quality

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Block belief propagation algorithm for two-dimensional tensor networks

arXiv

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arXiv 2023年

作者： Guo, Chu Poletti, Dario Arad, Itai Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China Science Mathematics and Technology Cluster Singapore University of Technology and Design 8 Somapah Road 487372 Singapore Engineering Product Development Pillar Singapore University of Technology and Design 8 Somapah Road 487372 Singapore Centre for Quantum Technologies National University of Singapore 117543 Singapore MajuLab CNRS-UNS-NUS-NTU International Joint Research Unit UMI 3654 Singapore Faculty of Physics Technion Haifa3200003 Israel

Belief propagation is a well-studied algorithm for approximating local marginals of multivariate probability distribution over complex networks, while tensor network states are powerful tools for quantum and classical many-body problems. Building on a recent connection between the belief propagation algorithm and the problem of tensor network contraction, we propose a block belief propagation algorithm for contracting two-dimensional tensor networks and approximating the ground state of 2D systems. The advantages of our method are three-fold: 1) the same algorithm works for both finite and infinite systems;2) it allows natural and efficient parallelization;3) given its flexibility it would allow to deal with different unit cells. As applications, we use our algorithm to study the 2D Heisenberg and transverse Ising models, and show that the accuracy of the method is on par with state-of-the-art results. Copyright © 2023, The Authors. All rights reserved.

关键词： Tensors

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Identification of binary neutron star mergers in gravitational-wave data using object-detection machine learning models

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Physical Review D 2022年第8期106卷 084059-084059页

作者： João Aveiro Felipe F. Freitas Márcio Ferreira Antonio Onofre Constança Providência Gonçalo Gonçalves José A. Font CFisUC Department of Physics University of Coimbra 3004-516 Coimbra Portugal Departamento de Física da Universidade de Aveiro and Centre for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago 3810-183 Aveiro Portugal Centro de Física das Universidades do Minho e do Porto (CF-UM-UP) Universidade do Minho 4710-057 Braga Portugal LIP Department of Physics University of Coimbra 3004-516 Coimbra Portugal Departamento de Astronomía y Astrofísica Universitat de València Dr. Moliner 50 46100 Burjassot (València) Spain Observatori Astronòmic Universitat de València Catedrático José Beltrán 2 46980 Paterna (València) Spain

We demonstrate the application of the YOLOv5 model, a general purpose convolution-based object detection model, in the task of detecting binary neutron star coalescence events from gravitational-wave data of current generation interferometer detectors. We also present a thorough explanation of the synthetic data generation and preparation tasks based on approximant waveform models used for the model training, validation and testing steps. Using this approach, we achieve mean average precision [0.50] values of 0.945 for a single class validation dataset and as high as 0.978 for test datasets. Moreover, the trained model is successful in identifying the GW170817 event in the LIGO H1 detector data. The identification of this event is also possible for the LIGO L1 detector data with an additional preprocessing step, without the need of removing the large glitch in the final stages of the inspiral. The detection of the GW190425 event is less successful, which attests to performance degradation with the signal-to-noise ratio. Our study indicates that the YOLOv5 model is an interesting approach for first-stage detection alarm pipelines.

关键词： Gravitational wave detection Binary stars Neutron stars & pulsars Gravitational wave detectors

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The main vertices of a star set and related graph parameters

arXiv

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arXiv 2020年

作者： Andelić, Milica Cardoso, Domingos M. Simić, Slobodan K. Stanić, Zoran Department of Mathematics Kuwait University Safat13060 Kuwait Center for Research and Development in Mathematics and Applications Department of Mathematics University of Aveiro Campus de Santiago Aveiro3810-193 Portugal Mathematical Institute of SANU Belgrade Serbia Faculty of Mathematics University of Belgrade Studentski trg 16 Belgrade11 000 Serbia

A vertex v ∈ V (G) is called λ-main if it belongs to a star set X ⊂ V (G) of the eigenvalue λ of a graph G and this eigenvalue is main for the graph obtained from G by deleting all the vertices in X \ {v};otherwise, v is λ-non-main. Some results concerning main and non-main vertices of an eigenvalue are deduced. For a main eigenvalue λ of a graph G, we introduce the minimum and maximum number of λ-main vertices in some λ-star set of G as new graph invariant parameters. The determination of these parameters is formulated as a combinatorial optimization problem based on a simplex-like approach. Using these and some related parameters we develop new spectral tools that can be used in the research of the isomorphism problem. Examples of graphs for which the maximum number of λ-main vertices coincides with the cardinality of a λ-star set are *** Codes 2020: 05C50, 05C60, 90C08 © 2020, CC BY-NC-ND.

关键词： Stars

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