The AdS/CFT correspondence is one of the most important discoveries in theoretical physics in recent years. It states that certain quantum mechanical theories can actually be described by classical gravity in one higher dimension, in a spacetime called anti-de Sitter (AdS) space. This means that to compute any measurable quantity in the quantum theory, we can instead do a computation in classical general relativity, and vice versa. What makes this duality so useful is that it relates theories with weak coupling to theories with strong coupling and thus provides a new tool for tackling strongly coupled quantum field theories, which are notoriously difficult to handle using conventional methods. Originally discovered in the context of string theory, this duality has now found a wide range of applications, from condensed matter physics to high temperature plasmas in quantum chromodynamics (QCD).During the course of my PhD I have mostly studied time dependent processes, in particular thermalization processes, in quantum field theories using the AdS/CFT correspondence. On the gravity side, this is dual to dynamical formation of black holes from the collapse of matter fields. By studying the gravitational collapse process in detail, we can then draw conclusions about the dynamical formation of a thermal state in the dual quantum field theory. Certain quantum field theories (such as QCD) enjoy a property called confinement, which in the case of QCD states that quarks can not be isolated. Using mostly numerical methods, I have studied how confinement affects thermalization in quantum field theories. We found that sometimes the system never thermalizes and field theory observables undergo interesting quasiperiodic behaviour. In another line of research, I have studied formation of black holes in three dimensions which due to the simplified nature of three-dimensional gravity can be done using analytical methods. This has led to the discovery of new solutions of three-dimensional gravity corresponding to the formation of black holes without spherical symmetry, which can provide a deeper understanding of thermalization in two-dimensional quantum field theories. In a third line of research, I have studied higher spin gravity in three dimensions, an exotic extension of three-dimensional gravity which includes fields with spin higher than two, and found a new method to construct black hole solutions carrying higher spin charge. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Cette thèse se concentre sur des aspects de dualités holographiques reliant une théorie gravitationnelle en trois dimensions à une théorie des champs sur le bord de cette espace, c'est-à-dire en dimensions deux. Dans le premier chapitre, nous passons en revue diverses méthodes, utilisées tout au long de la thèse, pour calculer des quantités conservées en théorie de jauge et plus particulièrement en gravitation. Ensuite, dans le deuxième chapitre, nous rappelons le cas d'école des espaces-temps localement anti-de Sitter (AdS) à trois dimensions et de leur théorie duale, les théories des champs conformes en deux dimensions. Les chapitres trois et quatre sont dédiés à la présentation d'espaces-temps non-AdS considérés dans cette thèse et de la dualité dans laquelle ils sont impliqués. Le premier s'intéresse aux espace-temps warped AdS, qui peuvent être vus comme une déformation d'AdS. Leur théorie des champs duale serait une théorie des champs conforme warped. Le second se concentre sur des solutions cosmologiques, localement plates, qui seraient duales à des théories des champs invariantes sous le groupe BMS$_3$ (groupe de symétrie des espaces asymptotiquement plats). Dans le chapitre cinq, nous révisons des notions de thermodynamique que nous utiliserons pour discuter des transitions de phase entre deux géométries appartenant au même espace des phases. Par exemple, entre l'espaces-temps AdS thermique et le trou noir localement AdS. La partie originale de la thèse traite d'abord des solutions maximalement symétriques dans n'importe quelle théorie invariante sous difféomorphisme. Nous prouvons que le calcul d'entropie gravitationnel est reproduit par le comptage asymptotique d'états dans la théorie duale. Ce travail est étendu au cas des espaces-temps warped. Nous montrons également que leur entropie du bulk et du bord sont en correspondance et ce pour toutes théories de gravitation. Ceci constitue une vérification non triviale des correspondances holographiques. Nous étudions aussi leurs transitions de phase. Finalement, nous posons les premières pierres d'une nouvelle correspondance holographique, impliquant une corde noire, en trouvant un ensemble de conditions au bord cohérent. Nous discutons également la thermodynamique des cordes noires. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

This thesis deals with two classes of space-time symmetries: emergent symmetries in the near-horizon region of rapidly rotating Kerr black holes and residual gauge symmetries. The main aim of the thesis is to investigate consequences and effects of these symmetries on black holes and gravitational radiation. The first class of symmetries is exploited to address questions of astrophysical relevance for force-free magnetospheres, thin accretion discs, and strong magnetic fields around Kerr black holes. We investigate how the dynamics of electromagnetic and matter fields is constrained by global conformal symmetries of the near-horizon geometry. In the context of force-free electrodynamics, we find exact solutions and classify them according to the highest weight representation of the isometry group. We introduce novel criteria to distinguish physical solutions and deduce bounds on conformal weights of electromagnetic fields. For thin accretion discs, within the Novikov-Thorne model, new properties arise in the high spin regime of the Kerr black hole. We find a novel self-similar solution and we explain the critical behaviour of the observables by symmetry arguments. Afterwards, we study an exact analytic solution to the Einstein-Maxwell theory. It describes a black hole immersed in a strong magnetic field and it shares the same near-horizon geometry of extreme Kerr black holes. We compute its total conserved mass by means of the covariant phase space formalism and study its thermodynamics. The second class of symmetries is considered in order to provide a new definition of gravitational multipole moments by means of Noether charges and by adopting the covariant phase space formalism. We show that such a definition in terms of Noether charges reproduces multipole moments in General Relativity. We propose to apply it to an arbitrary generally covariant metric theory of gravity. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

According to general relativity, appropriately accelerated masses emit gravitational radiation. With the gravitational-wave detectors reaching sufficient sensitivities for detecting astrophysical gravitational-waves, a new messenger for observing the astrophysical events has become available. However, with the current number of gravitational-wave detections, there are many unanswered questions whose answers are waiting to be discovered. Analogous to the Malmquist bias in other astronomical observation techniques, gravitational-wave detections also have an observation bias. In order to infer astrophysical distribution of the properties of gravitational-wave events from detections, this bias needs to be well understood. In this collection of studies, by investigating statistical and physical properties of gravitational-wave detection, an efficient semi-analytical method for calculating the bias was found. Further, the estimated bias was used for doing the first unmodelled inference on the mass distribution of binary black holes which showed additional structures not found by modelled inferences. Vast majority of gravitational-wave detections are binary black hole mergers. One of the mysteries of binary black holes is their formation channels. There are several proposed formation scenarios none of which is strongly favored by data. One of these channels is the so-called hierarchical triple mergers which is an dynamical formation scenario expected to have in dense environments such as globular clusters. This scenario considers a bound three black hole system which gives two consecutive mergers. In this collection of studies, it was directly tested with the detections from the three observing runs of Advanced LIGO and Advanced Virgo detectors. No significant evidence for this scenario was found, individually interesting event pairs were identified for further investigation and upper limits on the occurrence of the scenario were obtained. Gravitational-wave detectors have sensitivity on the significant portion of the sky. However, the localizations of the gravitational-wave detections are not very precise. Multi-messenger follow-ups guided by gravitational-wave detections can precisely locate the astrophysical source and gather more information by probing it with different messengers. The multi-messenger searches are done with statistical methods and it is necessary to have powerful statistical methods not to miss the valuable multi-messenger events. In the final parts of this collection of studies, optimal statistical methods for multi-messenger searches were developed and joint gravitational-wave and high-energy neutrino events were searched, both in realtime and with archival data.

Let K(v,w) denote the complete graph on v vertices with a hole of size w (i.e., K(v, w) = Kv\Kw). We give necessary and sufficient conditions for the existence of a minimum 4-cycle covering of K (v,w).

The work in this thesis was based on analyzing water samples collected from three exploratory boreholes drilled during Project Hotspot. The water samples were analyzed for their chemical properties. The chemical properties of the water samples were used as a basis for further analysis.Geophysical logs, mainly temperature logs, were also analyzed for this project. Temperature logs measure temperature in relation to depth within a borehole.All the analyses were made in order to estimate the geothermal potential of the project areas. The exploratory boreholes were all drilled in different areas and each had unique characteristics. The Mountain Home borehole provided the most promising evidence for future geothermal potential. Geothermal energy is a form of renewable energy and potential production areas are difficult and expensive to locate.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18065号 / 理博第3943号 / 新制||理||1568(附属図書館) / 30923 / 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 中村 卓史, 教授 鶴 剛, 教授 畑 浩之 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18797号 / 理博第4055号 / 新制||理||1583(附属図書館) / 31748 / 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 上田 佳宏, 教授 太田 耕司, 教授 嶺重 慎 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

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Accretion disks around black holes with gas radiating out parts of its gravitational potential energy have long served as objects of both theoretical and observational studies. By solving the structure equations of the disk it is possible to predict the outgoing radia- tive flux and the observed spectrum of the disk and test the validity of the theory against direct observations. The standard thin disk model (Shakura-Sunyaev, Novikov-Thorne) shows, however, a still unexplained non-negligible deviance in the observed spectrum at higher mass accretion rates. To amend to the set of proposed explanations, in this thesis we examine the effect of the magnetic pressure on the trapping of some of the internal energy generated by viscous dissipation processes in the disk and advecting this energy to the black hole. A phenomenological description of heat advection mediated by a highly heterogenous magnetic field will be given, as well as its effect on the spectrum and observed effective temperature. 1