No description available.

Orientadores: Anderson Campos Fauth, Cecilia Bertoni Martha Hadler Chirenti / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-22T06:58:02Z (GMT). No. of bitstreams: 1 Souza_GibranHenriquede_M.pdf: 5723676 bytes, checksum: 46d33c50292611540243a93798239014 (MD5) Previous issue date: 2013 / Resumo: Usando como base um código computacional que integra numericamente as equações TOV, que descrevem o interior de corpos relativísticos de simetria esférica, com a equação de estado SLy, que fornece a pressão em função da densidade para a matéria nuclear em condições extremas se comparadas à matéria nuclear convencional, conseguimos descrever uma estrela de nêutrons realista e com esta simular a emissão de ondas gravitacionais, com a previsão de como seria seu tempo de decaimento e frequência / Abstract: Using as base a computer code that integrates numerically the TOV equations, which describe the interior of relativistic bodies of spherical symmetry, with the SLy equation of state, which provides the pressure in function of density for nuclear matter under extreme conditions when compared with conventional nuclear matter, we describe a realistic neutron star and simulate the emission of gravitational waves, with the predictions of how its decay rate and frequency will be / Mestrado / Física / Mestre em Física

The dissertation presents the computational technique Particle-In-Cell, or PIC for short, and its applications in studying the magnetospheres of neutron stars, modeled as conducting rotators with strong magnetic fields. Pigeon, an open-source PIC simulator written by the author in modern C++, is anatomically examined as an instrument to illustrate the principles, algorithms and engineering difficulties of the PIC technique. Two types of rotators are studied using Pigeon. The monopolar rotator, which has an exact solution in the force free limit, serves as a tester for the code, as well as an example of the PIC's capability. The main application of Pigeon is on the ab initio simulation of an (axisymmetric) dipolar rotator with self-consistent gamma ray photon emission and pair creation, the study of which could reveal valuable information of the mechanism of the pulsars. Thanks to the performance boost brought by Pigeon's dynamic load balancing functionality, we are able to perform the simulation with a 4096x4096 high resolution grid. The high resolution is critical in obtaining a Lorentz factor of 10000 of the polar cap potential drop, which in turn enables good separations of energy levels and hence makes the simulation closer to representing the real-life pulsars. With the high resolution, we are also able to study the Y point more closely, where we find that the angular momentum conservation dictates the process of magnetic flux surface crossing that is responsible for the release of electromagnetic energies into the plasma.

No description available.

Thesis (MSc (Physics))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The overall goal of this project is to study neutron star properties and locate the transition density from the core to the crust using fifteen parameter sets of the effective Skyrme nucleon-nucleon interaction within a method called the dynamical method. Although another approach used to describe nucleon-nucleon interactions called the modified Gogny interaction is briefly discussed in this work, along with a second method for locating the transition density called the thermodynamical method, results using this interaction and method were not generated, but lays some foundation for a PhD project to be undertaken and potentially showing the relation between the interactions and results. The importance of results depends on how well other theoretical approaches to the problem can reproduce those results and to what accuracy. For models to be valid there also has to be good agreement between the theoretical results and known observables. In this project some properties of neutron stars, such as the equation of state, saturation density, binding energy, symmetry energy, slope and incompressibility parameters of symmetry energy are studied. The transition density is located using the dynamical method. Results of the fifteen Skyrme parameter sets show excellent agreement with the published values of the properties of neutron stars and are consistent with their empirical values inferred from nuclear laboratory data, thus validating the use of the Skyrme interactions for describing nuclear matter. / AFRIKAANSE OPSOMMING: Die hoofdoel van hierdie projek is om neutron ster eienskappe te bestudeer en die oorgangsdigtheid vanaf die kors na die kern te vind deur gebruik te maak van vyftien parameter stelle van die effektiewe Skyrme nukleon-nukleon interaksie binne ‘n metode genaamd die dinamiese metode. Alhoewel ‘n ander benadering vir die beskrywing van nukleon-nukleon interaksies, genaamd die gewysigde Gogny interaksie kortliks in hierdie werk beskryf word, asook ‘n tweede metode, genaamd die termodinamiese metode om die oorgangsdigtheid te bepaal, was resultate vir hierdie interaksie en metode nie gegenereer nie, maar l die fondasie vir verdere werk aan ‘n PhD projek wat die verband tussen die twee interaksies en resultate kan wys. Die belangrikheid van resultate hang af van hoe goed ander teoretiese benaderinge tot die problem daardie resultate kan herproduseer en tot watter akkuraatheid. Vir modelle om geldig te wees moet daar ook goeie ooreenkomste wees tussen teoretiese resultate en bekende waarneembare eienskappe. In hierdie projek word sommige eieskappe van neutron sterre, soos die toestandandsvergelyking, versadigingsdigtheid, bindingsenergie, simmetrie-energie, gradiënt en onsaampersbaarheids parameters van die simmetrie-energie bestudeer. Die oorgangsdigtheid word dan gevind deur gebruik te maak van die dinamiese metode. Resultate van die vyftien Skyrme interaksie parameter stelle wys goeie ooreenstemming met die gepubliseerde waardes van die eienskappe van neutron sterre en is konsistent met hulle empiriese waardes afgelei van kern laboratorium data, wat die geldigheid van Skyrme interaksies vir die beskrywing van kernmaterie bevestig.

The starting point of any general relativistic numerical simulation is a solution of the Hamiltonian and momentum constraints that (ideally) represents an astrophysically realistic scenario. This dissertation presents a new method to produce initial data sets for binary neutron stars with arbitrary spins and orbital eccentricities. The method only provides approximate solutions to the constraints. However, it was shown that the corresponding constraint violations subside after a few orbits, becoming comparable to those found in evolutions of standard conformally flat, helically symmetric binary initial data. This dissertation presents the first spinning neutron star binary simulations in circular orbits with a orbital eccentricity less then 0.01. The initial data sets corresponding to binaries with spins aligned, zero and anti-aligned with the orbital angular momentum were evolved in time. These simulations show the orbital “hang-up” effect previously seen in binary black holes. Additionally, they show orbital eccentricities that can be up to one order of magnitude smaller than those found in helically symmetric initial sets evolutions. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2013.

O evento estraordinário de SN1987A vem sendo investigado há mais de vinte e cinco anos. O fascínio que cerca tal evento astronômico está relacionado com a observação em tempo real da explosão à luz da Física de neutrinos. Detectores espalhados pelo mundo observaram um surto neutrinos que dias mais tarde foi confirmado como sendo a SN1987A. Kamiokande, IMB e Baksan apresentaram os eventos detectados que permitiu o estudo de modelos para a explosão e resfriamento da hipotética estrela de nêutrons remanescente. Até hoje não há um consenso a origem do progenitor e a natureza do objeto compacto remanescente. O trabalho se divide em duas partes: estudo dos neutrinos de SN1987A através de Análise Estatística Bayesiana através de um modelo proposto com duas temperaturas que evidenciam dois surtos de neutrinos. A motivação está na hipótese do segundo surto como resultado da formação de matéria estranha no objeto compacto. A metodologia empregada foi a desenvolvida por um trabalho interessante de Loredo (2002) que permite modelar e testar hipóteses sobre os modelos via Bayesian Information Criterion (BIC). A segunda parte do trabalho, a mesma metodologia estatística é usada no estudo da distribuição de massas das estrelas de nêutrons usando a base de dados disponível (http://stellarcollapse.org). A base de dados foi analisada utilizando somente o valor do objeto e seu desvio padrão. Construindo uma função de verossimilhança e utilizando distribuições ``a priori\'\' com hipótese de bimodalidade da distribuição das massas contra uma distribuição unimodal sobre todas as massas dos objetos. O teste BIC indica forte tendência favorável à existência da bimodalidade com valores centrados em 1.37M para objetos de baixa massa e 1.73M para objetos de alta massa e a confirmação da fraca evidência de um terceiro pico esperado em 1.25M. / The extraordinary event of supernova has been investigated twenty five years ago. The fascination surrounds such astronomical event is on the real time observation the explosion at light to neutrino Physics. Detectors spread for the world had observed one burst neutrinos that days later it was confirmed as being of SN1987A. Kamiokande, IMB and Baksan had presented the detected events that allowed to the study of models for the explosion and cooling of hypothetical neutron star remain. Until today it does not have a consensus the origin of the progenitor and the nature of the remaining compact object. The work is divided in two parts: study of the neutrinos of SN1987A through Analysis Bayesiana Statistics through a model considered with two temperatures that two evidence bursts of neutrinos. The motivation is in the hypothesis of as burst as resulted of the formation of strange matter in the compact object. The employed methodology was developed for an interesting work of Loredo & Lamb (2002) that it allows shape and to test hypotheses on the models saw Bayesian Information Criterion (BIC). The second part of the work, the same methodology statistics is used in the study of the distribution of masses of the neutron stars using the available database http://stellarcollapse.org/. The database was analyzed only using the value of the object and its shunting line standard. Constructing to a a priori function likelihood and using distributions with hypothesis of bimodal distribution of the masses against a unimodal distribution on all the masses of objects. Test BIC indicates fort favorable trend the existence of the bimodality with values centered in 1.37M for objects of low mass and 1.73M for objects of high mass and week evidence of one third peak around 1.25M.

This dissertation investigates the signatures of electromagnetic radiation that may accompany two specific sources of gravitational radiation: the inspiral and merger of massive black hole binaries (MBHBs) in galactic nuclei, and the coalescence of black hole neutron star (BHNS) pairs. Part I considers the interaction of MBHBs, at sub-pc separations, with a circumbinary gas disk. Accretion rates onto the MBHB are calculated from two-dimensional hydrodynamical simulations as a function of the relative masses of the black holes. The results are applied to interpretation of the recent, sub-pc separation MBHB candidate in the nucleus of the periodically variable Quasar PG 1302-102. We advance an interpretation of the variability observed in PG 1302-102 as being caused by Doppler-boosted emission sourced by the orbital velocity of the smaller black hole in a MBHB with disparate relative masses. Part II considers BHNS binaries in which the black hole is large enough to swallow the neutron star whole before it is disrupted. As the pair nears merger, orbital motion of the black hole through the magnetosphere of the neutron star generates an electromotive force, a black-hole-battery, which, for the strongest neutron star magnetic field strengths, could power luminosities large enough to make the merging pair observable out to cosmic distances. Relativistic solutions for vacuum fields of a magnetic dipole near a horizon are given, and a mechanism for harnessing the power of the black-hole-battery is put forth in the form of a fireball emitting in hard X-rays to to gamma-rays.

Este trabalho visa o estudo das perturbações de sistemas gravitacionais altamente compactos, como buracos negros e estrelas de nêutrons e de quarks. As perturbações em questão podem ser de diversas naturezas (escalar, eletromagnética ou gravitacional), sendo que detivemo-nos mais atentamente naquelas de natureza gravitacional, pois estas têm despertado mais interesse por serem astronomicamente mais fáceis de detectar. Além de estudarmos tais perturbações, procedemos a uma comparação dos resultados para buracos negros, estrelas de nêutrons e de quarks. Tal comparação justifica-se pelo fato de que a confrontação de previsões teóricas com resultados experimentais pode ajudar-nos a identificar objetos astronômicos de interesse, distingüi-los e, no caso de estrelas, aprender algo sobre sua estrutura interna, particularmente sobre a equação de estado (EDE) do fluido estelar. No que se segue, dividimos o trabalho em sete partes. Em primeiro lugar, damos uma introdução bastante sucinta ao mesmo (Capítulo 1). Depois, falamos sobre a física de estrelas de nêutrons e de quarks (Capítulo 2). A seguir, fazemos um estudo comparativo dos dois tipos de estrelas (Capítulo 3). Mais adiante, discutimos as perturbações de diversos tipos, além de definir os MQNs (Modos Quasi-Normais) de buracos negros de Schwarzschild (Capítulo 4). Prosseguimos a discussão com a métrica de Reissner-Nordström-de Sitter (Capítulo 5) e introduzimos, na seqüência, os MQNs estelares, de forma muito breve (Capítulo 6). Por fim, apresentamos nossas conclusões (Capítulo 7). A parte inédita deste trabalho está concentrada nos capítulos 5 e 6, os quatro anteriores servindo de preparativo e de base comparativa para estes dois. / This work aims the detailed study of the perturbations of highly compact gravitational systems, such as black holes and both neutron and quark stars. Such perturbations may have several different characters, such as scalar and electromagnetic fields as well as gravitational (either axial or polar) disturbances. We have focused more closely on the latter kind of perturbation, since they offer better possibilities of detection in the near future, in the form of gravitational waves. Besides studying the aforementioned perturbations, we have proceeded to a comparison between black holes and neutron and quark stars , when it comes to the outcomes of the perturbations, usually called QNMs (quasi-normal modes). Such a comparison is actually in order, since a direct comparison of theoretical and observational data may help us identify astronomical objects and, in the case of compact stars, may provide valuable insights into these stars' inner structure, particularly when it comes to their equation of state (EOS). In what follows, we have subdivided this work in seven parts. We begin with a brief introduction (Chapter 1), then proceed to a description of the physics of both neutron and quark stars (Chapter 2) and, in the sequence, to a comparative study of both kinds of star (Chapter 3). Subsequently, we develop the perturbation theory of the Schwarzschild black holes, discussing their QNMs (Chapter 4) and doing the same, later, for a more general Reissner-Nordström-de Sitter geometry (chapter 5). After that, we provide a very brief introduction to the stellar MQNs (Chapter 6). Finally, we present our conclusions (Chapter 7). The chapters 5 and 6 carry the inedit part of this work, and the chapters from 1 to 4 pave the way and provide a comparative basis for them.

The study of matter at extreme densities has been a major focus in theoretical physics in the last half-century. The wide spectrum of information that the field produces provides an invaluable contribution to our knowledge of the world in which we live. Most fascinatingly, the insight into the world around us is provided from knowledge of the intangible, at both the smallest and largest scales in existence. Through the study of nuclear physics we are able to investigate the fundamental construction of individual particles forming nuclei, and with further physics we can extrapolate to neutron stars. The models and concepts put forward by the study of nuclear matter help to solve the mystery of the most powerful interaction in the universe; the strong force. In this study we have investigated a particular state-of-the-art model which is currently used to refine our knowledge of the workings of the strong interaction and the way that it is manifested in both neutron stars and heavy nuclei, although we have placed emphasis on the former for reasons of personal interest. The main body of this work has surrounded an effective field theory known as Quantum Hadrodynamics (QHD) and its variations, as well as an extension to this known as the Quark-Meson Coupling (QMC) model, and variations thereof. We further extend these frameworks to include the possibility of a phase transition from hadronic matter to deconfined quark matter to produce hybrid stars, using various models. We have investigated these pre-existing models to deeply understand how they are justified, and given this information, we have expanded them to incorporate a modern understanding of how the strong interaction is manifest. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1458960 / Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2010