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Generating gravitational waveform libraries of exotic compact binaries with deep learning

Physical Review D 2024年第12期109卷 124059-124059页

作者： Felipe F. Freitas Carlos A. R. Herdeiro António P. Morais António Onofre Roman Pasechnik Eugen Radu Nicolas Sanchis-Gual Rui Santos Departamento de Física Centre for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago 3810-183 Aveiro Portugal Departamento de Matemática Centro de Física das Universidades do Minho e do Porto (CF-UM-UP) Department of Astronomy and Theoretical Physics Departamento de Astronomía y Astrofísica ISEL—Instituto Superior de Engenharia de Lisboa Centro de Física Teórica e Computacional Faculdade de Ciências

Current gravitational wave (GW) detections rely on the existence of libraries of theoretical waveforms. Consequently, finding new physics with GWs requires libraries of nonstandard models, which are computationally demanding. We discuss how deep learning frameworks can be used to generate new waveforms “learned” from a simulation dataset obtained, say, from numerical relativity simulations. Concretely, we use the WaveGAN architecture of a generative adversarial network (GAN). As a proof of concept we provide this neural network (NN) with a sample of (>500) waveforms from the collisions of exotic compact objects (Proca stars), obtained from numerical relativity simulations. Dividing the sample into a training and a validation set, we show that after a sufficiently large number of training epochs the NN can produce from 12% to 25% of the synthetic waveforms with an overlapping match of at least 95% with the ones from the validation set. We also demonstrate that a NN can be used to predict the overlapping match score, with 90% accuracy, of new synthetic samples. These are encouraging results for using GANs for data augmentation and interpolation in the context of GWs, to cover the full parameter space of, say, exotic compact binaries, without the need for intensive numerical relativity simulations.

关键词： Gravitation Gravitational wave detection Gravitational wave sources Gravitational waves

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Aspects of regular and singular electromagnetic-generalized-quasitopological-gravities black holes in 2+1 dimensions

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Physical Review D 2024年第2期109卷 024027-024027页

作者： Jeferson de Oliveira R. D. B. Fontana A. B. Pavan Instituto de Física Universidade Federal de Mato Grosso Cuiabá Mato Grosso 78060-900 Brazil Universidade Federal do Rio Grande do Sul Campus Tramandaí-RS Estrada Tramandaí-Osório Rio Grande do Sul 95590-000 Brazil and Departamento de Matemática Universidade de Aveiro and Center for Research and Development in Mathematics and Applications (CIDMA) Campus Santiago 3810-183 Aveiro Portugal Instituto de Física e Química Universidade Federal de Itajubá Itajubá Minas Gerais 37500-903 Brazil

We investigate quasitopological black holes in (2+1) dimensions in the context of electromagnetic-generalized-quasitopological gravities (EM-GQT). For three different families of geometries of quasitopological nature, we study the causal structure and their response to a probe scalar field. To linear order, we verify that the scalar field evolves stably, decaying in different towers of quasinormal modes. The studied black holes are either charged geometries (regular and singular) or a regular Bañados-Teitelboim-Zanelli (BTZ)-like black hole, both coming from the EM-GQT theory characterized by nonminimal coupling parameters between gravity and a background scalar field. We calculate the quasinormal modes applying different numerical methods with convergent results between them. The oscillations demonstrate a very peculiar structure for charged black holes: in the intermediate and near extremal cases, a particular scaling arises, similar to that of the rotating BTZ geometry, with the modes being proportional to the distance between horizons. For the single horizon black hole solution, we identify the presence of different quasinormal families by analyzing the features of that spectrum. In all three considered geometries, no instabilities were found.

关键词： Alternative gravity theories Fluids & classical fields in curved spacetime Gravity in dimensions other than four Spacetime topology & causal structure

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Marketing and religion - Spiritual commitment and church engagement of a Portuguese Parish: A principal component analysis

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AIP Conference Proceedings 2024年第1期3094卷

作者： Jéssica Campos Manuel José Fonseca Helena Sofia Rodrigues Business School Instituto Politécnico de Viana do Castelo Viana do Castelo Portugal UNIAG – Applied Management Research Unit Porto Portugal CIDMA - Center for Research & Development in Mathematics and Applications University of Aveiro Aveiro Portugal

Marketing is an area that has always been updated over time, considering it fundamental to adapt to the changes and evolution of the market and consumers. Consequently, the enlargement of marketing to new areas has been a growing reality. Based on this reality and within the scope of Religious Marketing, a study was carried out for the Parish of Poiares, in Portugal. The general objective was to characterize the profile of the parishioners, with the intention of subsequently defining strategies and implementing religious marketing tactics in the context of the parish of Poiares. To this end, an empirical work of qualitative nature was carried out, through the application of a questionnaire survey to a non-probabilistic convenience sample of 120 individuals. This empirical work had as its main objectives to understand the level of spirituality/involvement of the parishioners and the factors that register their greater or lesser satisfaction.

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Optimization of Cognitive Radio System Using Enhanced Firefly Algorithm

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Intelligent Automation & Soft Computing 2023年第9期37卷 3159-3177页

作者： Nitin Mittal Rohit Salgotra Abhishek Sharma Sandeep Kaur SSAskar Mohamed Abouhawwash University Center for Research and Development Chandigarh UniversityMohaliPunjab140413India Faculty of Physics and Applied Computer Science AGH University of Science&TechnologyKrakowPoland Faculty of Information Technology Middle East UniversityAmman11813Jordan Department of Computer Engineering and Applications GLA UniversityMathura281406India Department of Computer Engineering&Technology Guru Nanak Dev UniversityAmritsarPunjab143005India Department of Statistics and Operations Research College of ScienceKing Saud UniversityP.O.Box 2455Riyadh11451Saudi Arabia Department of Computational Mathematics Science and EngineeringCollege of EngineeringMichigan State UniversityEast LansingMI48824USA Department of Mathematics Faculty of ScienceMansoura UniversityMansoura35516Egypt

The optimization of cognitive radio(CR)system using an enhanced firefly algorithm(EFA)is presented in this *** Firefly algorithm(FA)is a nature-inspired algorithm based on the unique light-flashing behavior of *** has already proved its competence in various optimization prob-lems,but it suffers from slow convergence *** improve the convergence performance of FA,a new variant named EFA is *** effectiveness of EFA as a good optimizer is demonstrated by optimizing benchmark functions,and simulation results show its superior performance compared to biogeography-based optimization(BBO),bat algorithm,artificial bee colony,and *** an application of this algorithm to real-world problems,EFA is also applied to optimize the CR *** is a revolutionary technique that uses a dynamic spectrum allocation strategy to solve the spectrum scarcity ***,it requires optimization to meet specific performance *** results obtained by EFA in CR system optimization are compared with results in the literature of BBO,simulated annealing,and genetic *** results further prove that the proposed algorithm is highly efficient and provides superior results.

关键词： Firefly algorithm cognitive radio bit error rate genetic algorithm simulated annealing biogeography-based optimization

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Epicyclic frequencies for a generic ultracompact object

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Physical Review D 2022年第6期106卷 064054-064054页

作者： Jorge F. M. Delgado Departamento de Matemática Universidade de Aveiro Center for Research and Development in Mathematics and Applications-CIDMA Campus de Santiago Aveiro 3810-183 Portugal Centro de Astrofísica e Gravitação-CENTRA Departamento de Física Instituto Superior Técnico-IST Universidade de Lisboa-UL Av. Rovisco Pais 1 Lisboa 1049-001 Portugal

Recently, it has been shown that the radial stability of a light ring (LR) in a spacetime generated by a stationary, axisymmetric, asymptotically flat object with a Z2 symmetry determines the possibility and radial stability of timelike circular orbits (TCOs) around the LR. In this paper, we generalize this result by also considering the vertical (angular) stability of the orbits through the study of the radial and vertical epicyclic frequencies. We show that the vertical stability of the LR only determines the vertical stability of the TCOs around it. A relation between the sum of the squared epicyclic frequencies and the Ricci tensor is also provided. With such relation, we show that objects with radially and vertically unstable LRs (TCOs) violate the null (strong) energy condition.

关键词： General relativity Gravitation

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Generalized grassmann algebras and applications to stochastic processes

arXiv

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arXiv 2021年

作者： Alpay, Daniel Cerejeiras, Paula Kähler, Uwe Schmid College of Science and Technology Chapman University One University Drive OrangeCA92866 United States CIDMA - Center for Research and Development in Mathematics and Applications Department of Mathematics University of Aveiro Campus Universitário de Santiago Aveiro3810-193 Portugal

In this paper we present the groundwork for an Itô/Malliavin stochastic calculus and Hida's white noise analysis in the context of a supersymmentry with Z3-graded algebras. To this end we establish a ternary Fock space and the corresponding strong algebra of stochastic distributions and present its application in the study of stochastic processes in this *** Codes 30G35, 60H45, 60G22, 15A75 © 2021, CC BY.

关键词： Stochastic systems

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Self-interacting dipolar boson stars and their dynamics

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Physical Review D 2023年第6期108卷 064011-064011页

作者： Pedro Ildefonso Miguel Zilhão Carlos Herdeiro Eugen Radu Nuno M. Santos Institute for Theoretical Physics University of Innsbruck A-6020 Innsbruck Austria 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 Centro de Astrofísica e Gravitação—CENTRA Departamento de Física Instituto Superior Técnico—IST Universidade de Lisboa—UL Avenida Rovisco Pais 1 1049-001 Lisboa Portugal

We construct and dynamically evolve dipolar self-interacting scalar boson stars in a model with sextic (+ quartic) self-interactions. The domain of existence of such dipolar Q-stars has a similar structure to that of the fundamental monopolar stars of the same model. For the latter it is structured in a Newtonian plus a relativistic branch, wherein perturbatively stable solutions exist, connected by a middle unstable branch. Our evolutions support similar dynamical properties of the dipolar Q-stars that: 1) in the Newtonian and relativistic branches are dynamically robust over time scales longer than those for which dipolar stars without self-interactions are seen to decay; 2) in the middle branch migrate to either the Newtonian or the relativistic branch; 3) beyond the relativistic branch decay to black holes. Overall, these results strengthen the observation, seen in other contexts, that self-interactions can mitigate dynamical instabilities of scalar boson star models.

关键词： Dark matter Gravitation Gravitational waves Numerical relativity

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List decoding of convolutional codes over integer residue rings

arXiv

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arXiv 2020年

作者： Lieb, Julia Napp, Diego Pinto, Raquel Department of Mathematics University of Zurich Switzerland Department of Mathematics University of Alicante Spain CIDMA - Center for Research and Development in Mathematics and Applications Department of Mathematics University of Aveiro Portugal

A convolutional code C over Zpr[D] is a Zpr[D]-submodule of Znpr[D] where Zpr[D] stands for the ring of polynomials with coefficients in Zpr. In this paper we study the list decoding problem of these codes when the transmission is performed over an erasure channel, that is, we study how much information one can recover from a codeword w ∈ C when some of its coefficients have been erased. We do that using the p-adic expansion of w and particular representations of the parity-check matrix of the code. From these matrix representations we recursively select certain equations that w must satisfy and have only coefficients in the field pr−1Zpr. This yields a step by step procedure to obtain a list of possible codewords for a given corrupted codeword w. We show that such an algorithm actually computes all possible erased coordinates, that is, it provides a minimal list with the closest codewords to the vector w. Mathematically, this problem amounts to determine the set of all possible solutions of a set of linear equations over Zpr[D] that can be represented by a matrix with Toeplitz structure. Copyright © 2020, The Authors. All rights reserved.

关键词： Convolutional codes

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The importance of color in logos: A statistical analysis for the facebook logo

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AIP Conference Proceedings 2024年第1期3094卷

作者： Alexandra Barbado Helena Sofia Rodrigues Álvaro Cairrão Business School Instituto Politécnico de Viana do Castelo Viana do Castelo Portugal CIDMA - Center for Research & Development in Mathematics and Applications University of Aveiro Aveiro Portugal CECS – Center of Communication and Society Studies University of Minho Minho Portugal

One of the most important tools used in companies is visual communication. A logo is part of a brand entity and therefore, a way to communicate their values or mission. This work aims to verify whether the different colors used in the logo can awaken differentiated emotions in consumers. A questionnaire was prepared with the Facebook logo, varying in color. Through the obtained data, it was possible to conclude that color is a key element of a logo. When a new or reformulated logo is performed, companies should be aware that color could influence consumer perception.

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Preservation of certain vanishing properties of generalized Morrey spaces by some classical operators

Preservation of certain vanishing properties of generalized ...

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作者： Alabalik, Aysegul Ç Almeida, Alexandre Samko, Stefan Department of Mathematics Institute of Natural and Applied Sciences Dicle University Diyarbakir Turkey Department of Mathematics Center for Research and Development in Mathematics and Applications University of Aveiro Aveiro Portugal Department of Mathematics University of Algarve Faro Portugal

We show that certain vanishing properties defining closed subspaces of generalized Morrey spaces are preserved under the action of various classical operators of harmonic analysis, such as maximal operators, singular-type operators, Hardy operators, and fractional integral operators. Those vanishing subspaces were recently used to deal with the delicate problem on the description of the closure of nice functions in Morrey norm. © 2020 John Wiley & Sons, Ltd.

关键词： generalized Morrey spaces Hardy operators maximal functions potential operators singular-type operators vanishing properties

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