京都大学 / 新制・課程博士 / 博士(理学) / 甲第25120号 / 理博第5027号 / 新制||理||1717(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)教授 上田 佳宏, 准教授 野上 大作, 教授 前田 啓一 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Made available in DSpace on 2015-05-14T12:14:11Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2344020 bytes, checksum: 1d77972a45b8beef7c3fe6631dfddaa2 (MD5) Previous issue date: 2014-02-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this dissertation we consider the influence of gravitational fields due to the black holes of Kerr-Newman and Kerr-Newman-de Sitter, on a massive scalar field, with and without charge. We obtain the exact solutions of the radial Klein-Gordon equation in the spacetime of Kerr-Newman which are given in terms of the confluent Heun functions. In the particular case of a extreme Kerr-Newman black hole, the solution is given in terms of double confluent Heun functions. We also investigate the solutions close to the exterior event horizon and very far from the black hole. For a charged scalar field, we obtain exact solutions corresponding to the angular Klein-Gordon equation in the Kerr-Newman-de Sitter spacetime which are given in terms of the Heun functions. Using a method due to Damour and Ruffini, we study the Hawking radiation of massive scalar particles. In the Kerr-Newman black hole, we obtain the exact solutions for both the angular and radial Klein-Gordon equations, which are given in terms of the confluent Heun functions. From the radial solution, we obtain the exact wave solutions near to the exterior horizon of the black hole, and discuss the Hawking radiation of charged massive scalar particles. / Nesta dissertação tratamos da influência do campo gravitacional produzido pelos buracos negros de Kerr-Newman e Kerr-Newman-de Sitter sobre um campo escalar massivo com e sem carga. Obtemos as soluções exatas da parte radial da equação de Klein-Gordon em um espaço-tempo de Kerr-Newman, que são dadas em termos das funções confluentes de Heun. No caso particular correspondente ao buraco negro de Kerr-Newman extremo, a solução é dada em termos das funções duplamente confluentes de Heun. Investigamos, também, as soluções nas proximidades do horizonte de evento exterior e longe do buraco negro. Para um campo escalar massivo carregado, obtemos as soluções exatas para a parte angular da equação de Klein-Gordon em um espaço-tempo de Kerr-Newman-de Sitter, que são dadas em temos das funções de Heun. Utilizando o método de Damour & Ruffini, estudamos a radiação Hawking para partículas escalares massivas. No buraco negro de Kerr-Newman, obtemos as soluções exatas de ambas as partes radial e angular da equação de Klein-Gordon, que são dadas em termos das funções confluentes de Heun. A partir da solução radial, obtemos as soluções de ondas exatas próximas ao horizonte exterior do buraco negro e discutimos a radiação Hawking para partículas escalares massivas carregadas.

We will consider the scenario of the co-rotation of a fluid star (in specific, a neutron star) and a black hole. The neutron star (or primary)is assumed to have constant angular velocity. The tidal effects on the primary are investigated. First, the centrally condensed approximation is applied, where both bodies are considered as point sources. In the second treatment, the primary is treated as an incompressible and homogeneous fluid mass, which in addition to its own gravity is subject to centrifugal and Coriolis forces, derived from fluid motions. The black hole (or secondary) is treated as a rigid sphere and can be regarded as a point mass. The equilibrium figure is derived. The problem is then adapted to include vorticity and a pseudo-Newtonian potential. The coalescence of neutron star - black hole binaries and their importance to gravitational wave detection is also discussed. / Mathematical Sciences / M. Sc. (Applied Mathematics)

Black hole jets and accretion discs are the most extreme objects in modern astrophysics whilst dark energy is undoubtedly the most mysterious. This thesis focuses on understanding these three topics. The majority of this thesis is dedicated to investigating the structure and properties of black hole jets by modelling their emission. I develop an inhomogeneous jet model with a magnetically dominated parabolic accelerating base, transitioning to a slowly decelerating conical jet, with a geometry set by radio observations of M87. This model is able to reproduce the simultaneous multiwavelength spectra of all 38 Fermi blazars with redshifts in unprecendented detail across all wavelengths. I constrain the synchrotron bright region of the jet to occur outside the BLR and dusty torus for FSRQs using the optically thick to thin synchrotron break. At these large distances their inverse-Compton emission originates from scattering CMB photons. I find an approximately linear relation between the jet power and the transition region radius where the jet first comes into equipartition, transitions from parabolic to conical and stops accelerating. The decreasing magnetic field strength and increasing bulk Lorentz factor with jet power are the physical reasons behind the blazar sequence. I calculate the conditions for instability in a thin accretion disc with an α parameter which depends on the magnetic Prandtl number, as suggested by MHD simulations. The global behaviour of the instability induces cyclic flaring in the inner regions of the disc, for parameters appropriate for X-ray binary systems, thereby offering a potential solution to a long standing problem. Finally, I calculate the effect of an interacting quintessence model of dark energy on cosmological observables. I find that a scalar-tensor type interaction in the dark sector results in an observable increase in the matter power spectrum and integrated Sachs-Wolfe effect at horizon scales.

Over recent years there has been an increase of the number of secure supermassive black hole (SMBH) detections. These SMBH measurements have lead astronomers to establish well defined empirical relationships between the SMBH mass and some of the properties of the host galaxy. The number of galaxies with SMBH mass measurements is currently limited to about 100. One approach of expanding the study of the SMBH is to use the empirical relations for estimating M[subscript(bh)] for larger samples of galaxies. The investigation of the SMBH population (or SMBH mass function) for large sample of galaxies in the nearby universe has helped to constrain the SMBH and the galaxy evolution. Previous estimates of the SMBH mass function at low redshift were produced mainly by combining the measurements of the galaxy luminosity or velocity function with one of the SMBH scaling relations. In the first part of the thesis I will present an independent construction of the nearby supermassive black hole mass function by applying the optical M[subscript(bh)]–L relation onto the Millennium Galaxy Catalogue (MGC). Additionally, in the second part I will provide photometric analysis of all UKIDSS galaxies for which SMBH masses have been measured. I will derive composite profiles of brightness, ellipticity and position angles of each galaxy. I will show that the Sérsic function fits the brightness profile of the majority of the elliptical galaxies and the bulge of disk galaxies and I will provide alternative multi-component fits when necessary. Then these photometric parameters will be used for constructing the M[subscript(bh)]–L relation in the near-IR and to investigate the M[subscript(bh)]–n relation. In the third part I will construct the near-IR SMBH mass function for the Galaxy and Mass Assembly (GAMA) survey. For this purpose I will apply the newly derived M[subscript(bh)]–L relation onto an elliptical subsample of K-band images. The advantage of this SMBH mass function is that during the M[subscript(bh)]–L construction I used the same quality images and techniques used on the GAMA survey. Apart from the M[subscript(bh)]–L relation, the M[subscript(bh)]–sigma relation was used as an alternative approach for a subsample of galaxies for which the velocity dispersions were available. Furthermore, I employed both local SMBH mass functions (MGC & GAMA) for estimating the SMBH mass density at redshift zero and accounted for the dependence of the total SMBH density on the look-back time by comparing with semi-analytic SMBH mass functions. Finally, from the SMBH mass density I estimated the baryon fraction that is locked into SMBHs.

I modify the quasilocal energy formalism of Brown and York into a purely Hamiltonian form. As part of the reformulation, I remove their restriction that the time evolution of the boundary of the spacetime be orthogonal to the leaves of the time foliation. Thus the new formulation allows an arbitrary evolution of the boundary which physically corresponds to allowing general motions of the set of observers making up that boundary. I calculate the rate of change of the quasilocal energy in such situations, show how it transforms with respect to boosts of the boundaries, and use the Lanczos-Israel thin shell formalism to reformulate it from an operational point of view. These steps are performed both for pure gravity and gravity with attendant matter fields. I then apply the formalism to characterize naked black holes and study their properties, investigate gravitational tidal heating, and combine it with the path integral formulation of quantum gravity to analyze the creation of pairs of charged and rotating black holes. I show that one must use complex instantons to study this process though the probabilities of creation remain real and consistent with the view that the entropy of a black hole is the logarithm of the number of its quantum states.

String theory is currently the best-known candidate for a theory of quantum gravity, having the necessary ingredients to describe all known elementary particles and interactions. It also includes several novel features, arising, for instance, from the additional six compact dimensions required for its internal consistency, making it the natural arena to construct extensions of the Standard Model. In this thesis, we analyze some of the new phenomenological aspects introduced by string theory within the framework of low energy effective theories, focusing on their applications to cosmology, astrophysics and collider experiments. We first consider a particular realization of the brane-world scenario in branonium bound states, showing that the orbital motion of a probe antibrane about a central brane stack leads to a resonant amplification of its world-volume scalar modes. We analyze the cosmological development of this process and also its potential relevance for either dark or baryonic matter generation in the early universe. We then focus on the spectrum of quark and lepton string excitations in warped compactifications, modeled by an effective 5-dimensional Randall- Sundrum throat. Motivated by the observed fermion mass hierarchy, we show that the spin-3/2 Regge excitation of the right-handed top quark is the lightest of such resonances in a significant region of parameter space, possibly lying below the TeV scale, and discuss its potential signatures at the Tevatron and at the LHC. Finally, we study the emission of sub-eV scalar particles by maximally rotating Kerr black holes, motivated by the recent string axiverse proposal. We focus on the spectrum of unstable scalar bound states in the superradiant regime, leading to an exponentially large axion cloud around astrophysical black holes, and analyze two semi-analytical methods for computing the growth rate of this instability, comparing the obtained results with previous analytical and numerical analyses.

Nous analysons des bulles d'espace-temps d'épaisseur finie en relativité générale. Les conditions d'énergie sont utilisées afin d'obtenir un ensemble de critères permettant de restreindre la structure du bord de la bulle. Dans le cas des bulles statiques et à symétrie sphérique, nous obtenons quatre inégalités différentielles équivalentes aux trois conditions d'énergie les plus communes. Nous montrons qu'elles sont équivalentes à un ensemble de deux inégalités différentielles simples lorsque le potentiel gravitationnel effectif a une forme particulière. Nous paramétrons alors l'espace-temps de manière à rendre la vérification de ces inégalités plus simple lorsqu'il sera question de bulles d'espace-temps. Nous traitons en particulier quatre formes de bulles, toutes caractérisées par un extérieur de type Schwarzschild de Sitter. Nous montrons que notre méthode donne les bons résultats lorsque la limite où l'épaisseur de la bulle tend vers zéro est prise. Nous terminons par un traitement succinct du problème d'une onde gravitationnelle se propageant dans un nuage de bulles d'espace-temps. / We analyze space-time bubbles of finite thickness in general relativity. We use the energy conditions to restrict their structures. In the case of static, spherically symmetric bubbles, we get a set of four differential inequalities. If the effective gravitational potential is taken of a particular form, we show that they can be further reduced to a set of two differential inequalities. We then parameterize the bubble's wall in a particular way, simplifying the inequalities, and easing the application of boundary conditions on our solutions. We then treat four different cases of bubbles that all have a Schwarzschild de Sitter exterior. We show that in the limit where the thickness of the bubble's wall goes to zero, we recover the standard results. Lastly, we treat gravitational waves propagating in a dilute gas of non-interacting space-time bubbles.

No description available.

In this thesis we look at mobile agent solutions to black hole search and related problems. Mobile agents are computational entities that are autonomous, mobile, and can interact with their environment and each other. The black hole search problem is for a team of these agents to work together to map or explore a graph-like network environment where some elements of the network are dangerous to the agents. Most research into black hole search has focussed on finding a single dangerous node: a black hole. We look at the problem of finding multiple black holes and, in the case of dangerous graph exploration, multiple black links as well. We look at the dangerous graph exploration problem in the network model. The network model is based on a normal static computer network modelled as a simple graph. We give an optimal solution to the dangerous graph exploration problem using agents that start scattered on nodes throughout the network. We then make the problem more difficult by allowing an adversary to delete links during the execution of the algorithm and provide a solution using scattered agents. In the last decade or two, types of networks have emerged, such as ad hoc wireless networks, that are by their nature dynamic. These networks change quickly over time and can make distributed computations difficult. We look at black hole search in one type of dynamic network described by the subway model, which we base on urban subway systems. The model allows us to look at the cost of opportunistic movement by requiring the agents to move using carriers that follow routes among the network's sites, some of which are black holes. We show that there are basic limitations on any solution to black hole search in the subway model and prove lower bounds on any solution's complexity. We then provide two optimal solutions that differ in the agents' starting locations and how they communicate with one another. Our results provide a small window into the cost of deterministic distributed computing in networks that have dynamic elements, but which are not fully random.