In this research, we study how a finite-temperature nuclear equation of state suitable for astrophysical simulations impacts the oscillation modes of neutron stars. We chose the Shen equation of state (EOS) because it accurately describes both stable and unstable nuclei as well as nuclear incompressibilities. I modified the existing MHD code at BYU, the HAD code, to call a lookup table for the Shen EOS for use at run time, and added a Newton-Raphson method algorithm to convert conserved variables to primitive variables. The algorithm was tested and verified by evolving a stable neutron star for several dynamical times and evolving the same star at different resolutions. The normal mode frequency of the neutron star with the Shen EOS was measured and compared to those for neutron stars with an ideal gas EOS found by Font et. al. We found that the fundamental mode of the neutron star using the Shen EOS was slightly larger than that of the ideal gas EOS. This difference is due to the Shen EOS producing stars that are stiffer, increasing the sound speed.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第25105号 / 理博第5012号 / 新制||理||1715(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 菅沼 秀夫, 准教授 福間 將文, 教授 橋本 幸士 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Estudamos duas classes de teorias de campos com métrica indefinida: os modelos sigma não linear não-compactos e as teorias quárticas da gravitação. Mostramos que a prova da unitariedade para os modelos sigma de simetria não compacta é a mesma que para os modelos compactos nas regiões fisicamente relevantes. Além disso, analisamos a possibilidade de ocorrer geração dinâmica de massa nos modelos sigma sob influência de temperatura finita, em várias dimensões. No que se refere às teorias quárticas da gravitação, calculamos o valor esperado no vácuo da função de dois pontos com inserção da relação de Gauss-Bonnet. Encontramos que a identidade clássica não é preservada quando empregamos a regularização dimensional, mesmo num espaço sem singularidades. Isto revela o surgimento de anomalias gravitacionais / Two classes of field theories with indefinite metric are studied: noncompact nonlinear sigma models and higher-derivative quantum gravity. We show that the proof of unitarity for noncompact sigma models is the same as the one for compact models in the physically relevant regions. Moreover, we analyze the possibility of dynamical mass generation at finite temperature in various space-time dimensions. Concerning to the higher-derivative quantum gravity, we calculate the vacuum expectation value of the two-point function with the insertion of Gauss-Bonnet Relation. In the quantum context, we also show, using dimensional regularization, that the Gauss-Bonnet relation is not satisfied due to gravitational anomalies.

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-10-18T18:02:30Z No. of bitstreams: 1 MARCÍLIO VERAS CARDOSO – DISSERTAÇÃO (PPGFísica) 2013.pdf: 2135603 bytes, checksum: c8ee99ac200c27d2c1445f0b6404a635 (MD5) / Made available in DSpace on 2018-10-18T18:02:30Z (GMT). No. of bitstreams: 1 MARCÍLIO VERAS CARDOSO – DISSERTAÇÃO (PPGFísica) 2013.pdf: 2135603 bytes, checksum: c8ee99ac200c27d2c1445f0b6404a635 (MD5) Previous issue date: 2013-03-27 / Capes / Neste trabalho vamos fazer correções quânticas ao potencial clássico de uma teoria com simetria ZN na intenção de entender os efeitos quânticos da teoria via correções radiativas do potencial efetivo em um loop. Para que isso aconteça é preciso que os n campos que compõem a teoria com simetria discreta, tenha valores esperado de vácuo não nulo minimizando o potencial. No entanto, sabemos que o potencial possui termos de interação, e que se olharmos para o vácuo quântico que tem interpretação física de estado de partículas, estes termos produzirão correções ao potencial e obteremos o verdadeiro valor esperado de vácuo da teoria que minimiza o potencial efetivo. Com isso esperamos que surja o fenômeno de quebra espontânea de simetria cuja nalidade é produzir defeitos topológicos tipo paredes de domínio e junções. No presente estudo também avançaremos na introdução de efeitos de temperatura nita via mecanismo de Matsubara. / In this work we make quantum corrections to the potential of a classical theory with symmetry ZN with the intention of understanding the effects quantum of theory via the radiative corrections of effective potential in a loop. For this to happen we need the n elds that make up the theory with discrete symmetry, expected values have nonzero vacuum that minimizes the potential. However, we know that the potential has interaction terms, and that if we look at the quantum vacuum that has physical interpretation of the state of particles, these terms yield corrections to the potential and obtain the true vacuum expectation value of the theory that minimizes the effective potential. With this we hope that arises the phenomenon of spontaneous symmetry breaking whose purpose is to produce topological defects like domain walls and junctions. In the present study advance the introduction of nite temperature effects via mechanism Matsubara.

Estudamos duas classes de teorias de campos com métrica indefinida: os modelos sigma não linear não-compactos e as teorias quárticas da gravitação. Mostramos que a prova da unitariedade para os modelos sigma de simetria não compacta é a mesma que para os modelos compactos nas regiões fisicamente relevantes. Além disso, analisamos a possibilidade de ocorrer geração dinâmica de massa nos modelos sigma sob influência de temperatura finita, em várias dimensões. No que se refere às teorias quárticas da gravitação, calculamos o valor esperado no vácuo da função de dois pontos com inserção da relação de Gauss-Bonnet. Encontramos que a identidade clássica não é preservada quando empregamos a regularização dimensional, mesmo num espaço sem singularidades. Isto revela o surgimento de anomalias gravitacionais / Two classes of field theories with indefinite metric are studied: noncompact nonlinear sigma models and higher-derivative quantum gravity. We show that the proof of unitarity for noncompact sigma models is the same as the one for compact models in the physically relevant regions. Moreover, we analyze the possibility of dynamical mass generation at finite temperature in various space-time dimensions. Concerning to the higher-derivative quantum gravity, we calculate the vacuum expectation value of the two-point function with the insertion of Gauss-Bonnet Relation. In the quantum context, we also show, using dimensional regularization, that the Gauss-Bonnet relation is not satisfied due to gravitational anomalies.

This master thesis is framed in the striking correspondence between gravity theories in Anti-de Sitter spacetime (AdS) and Conformal Field Theories (CFT). This is usually known as AdS/CFT duality and relates gravity theories in the bulk with CFTs that live in their conformal boundary. We start by presenting the notion of CFTs and some of the results and techniques that are widely used in this field. This includes conformal correlators for scalar and spin operators, the state-operator correspondence and the operator product expansion (OPE) of operators. The embedding formalism and the index-free notation to encode tensors in polynomials are also discussed and used throughout this work. The basic notions of AdS are outlined and CFT at finite temperature is then introduced. We include a review of thermal blocks and thermal coefficients for a thermal two-point function between scalar fields in mean field theory. We then analyse the thermal two-point function for conserved currents, which was not known in the literature. Finally, we start a study of its thermal blocks and thermal coefficients for the mean field theory application.

The imaginary part of the retarded self energy is of particular interest as it contains a lot of physical information about particle interactions. In higher order loop diagrams the calculation become extremely tedious and if we have to do the same at finite temperature, it includes an extra dimension to the difficulty. In such a condition we require to switch between bases and select the best basis for a particular diagram. We have shown in our calculation that in higher order loop diagrams, at finite temperature, the R/A basis is most convenient on summing over the internal vertices and very efficient on calculating some particular diagrams while the result is most easily interpretable in the Keldysh basis for most other complex diagrams. / February 2010

No âmbito da teoria quântica de campos (TQC) foram estudados modelos de quench exatamente solúveis. Nestes modelos, obteve-se uma generalização do ansatz de Kadanoff-Baym que se mantém em todos intervalos de tempo. Algumas hipóteses sobre fenômenos de não-equilíbrio em TQC em temperaturas finitas foram analisadas e estendidas neste contexto. Para tanto, examinamos as funções de Green nesses modelos e os comparamos com os resultados aproximados que são frequentemente usados na literatura. Um dos modelos descreve sistemas de não-equilíbrio do tipo vítreo. Esses sistemas exibem um comportamento que é compatível com o esperado do teorema de flutuação-dissipação. As propriedades básicas foram consistentemente deduzidas e resultados explícitos para a temperatura efetiva e frequências características foram obtidas. / We have studied exactly quenched models in the context of Quantum Field Theory(QFT). In these models, a generalization of the Kadanoff-Baym ansatz was obtained which holds at all times. Some assumptions concerning non-equilibrium phenomena in QFT at finite temperatures were analysed and extended in this framework. To this end, we have examined the Green\'s functions in these models and compared them with the approximated results which are often used in the literature. One of the models describes non-equilibrium systems of the glassy-kind. Such systems exhibit a behaviour which is compatible with that expected from the fluctuation-dissipation theorem. The basic properties were consistently deduced and explicit results for the effective temperature and characteristic frequencies were obtained.

In this master’s thesis the width of the <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Ceta'" /> meson is studied as a function of temperature. We consider a background medium consisting of a pion gas and assume a vanishing net baryon chemical potential. The width is obtained in the framework of large <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?N_%7Bc%7D" /> chiral perturbation theory and we consider terms up to next-to-leading order in the effective Lagrangian. We use a low-density approximation to calculate the width increase due to scattering with pions from the heat bath. The results suggest that the in-medium width for the <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Ceta'" /> may become of considerable size: at a temperature <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?T%5Capprox%2075" /> MeV we find a width increase of <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5CDelta%5CGamma%5Capprox%203-4" /> MeV, comparable to the inverse lifetime of the fireball created in a heavy-ion collision. The <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Ceta'" /> is of particular interested since it is intimately connected to the <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?U(1)_%7BA%7D" /> anomaly of Quantum Chromodynamics (QCD). It has been speculated that <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?U(1)_%7BA%7D" /> may become a symmetry of QCD at high temperatures and studies of the <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Ceta'" /> could indicate if that is the case. Depending on for how large temperatures the results from large <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?N_%7Bc%7D" /> can be trusted, they indicate that the <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Ceta'" /> may be possible to study experimentally in heavy-ion collisions due to its sizable in-medium width.

The imaginary part of the retarded self energy is of particular interest as it contains a lot of physical information about particle interactions. In higher order loop diagrams the calculation become extremely tedious and if we have to do the same at finite temperature, it includes an extra dimension to the difficulty. In such a condition we require to switch between bases and select the best basis for a particular diagram. We have shown in our calculation that in higher order loop diagrams, at #12;finite temperature, the R/A basis is most convenient on summing over the internal vertices and very efficient on calculating some particular diagrams while the result is most easily interpretable in the Keldysh basis for most other complex diagrams.