Dans cette thèse expérimentale, nous nous intéressons à la réponse non-linéaire d’un miroir plasma sous l’influence d’un laser d’intensité sous-relativiste (~10^18 W/cm^2), et de très courte durée (~30fs). Nous avons en particulier étudié la génération d’impulsions attosecondes (1as=10^(-18) s) et de faisceaux d’électrons en effectuant des expériences dites de « pompe-sonde » contrôlées. Un premier résultat important est l’observation d’une anti-corrélation entre l’émission X-UV attoseconde et l’accélération d’électron lorsque l’on change la longueur caractéristique du plasma, résultats confirmés par des simulations numériques. Un second résultat important concerne le diagnostique de l’expansion du plasma sous vide par « interférométrie en domaine spatial » (SDI), technique élaborée dans le cadre de cette thèse. Enfin nous discutons à deux reprises l’utilisation d’algorithmes de reconstruction de phase dans le domaine spatiale ou temporel.De manière plus générale, nous avons cherché à replacer ce travail de thèse dans un contexte scientifique plus général. En particulier, nous tentons de convaincre le lecteur qu’à travers l’intéraction laser-miroir plasma, il devient concevable de fournir un jour aux utilisateurs des sources peu onéreuses d’impulsions X-UV et de faisceaux d’électrons de résolutions temporelles inégalées. / The experimental work presented in this manuscript focuses on the non-linear response of plasma mirrors when driven by a sub-relativistic (~10^18 W/cm^2) ultra-short (~30fs) laser pulse. In particular, we studied the generation of attosecond pulses (1as=10^(-18) s) and electron beams from plasma mirror generated in controlled pump-probe experiment. One first important result exposed in this manuscript is the experimental observation of the anticorrelated emission behavior between high-order harmonics and electron beams with respect to plasma scale length. The second important result is the presentation of the « spatial domain interferometry » (SDI) diagnostic, developed during this PhD to measure the plasma expansion in vacuum. Finally, we will discuss the implementation of phase retrieval algorithms for both spatial and temporal phase reconstructions.From a more general point of view, we replace this PhD in its historical context. We hope to convince the reader that through laser-plasma mirror interaction schemes, we could tomorrow conceive cost-efficient X-UV and energetic electron sources with unprecedented temporal resolutions.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20169号 / 理博第4254号 / 新制||理||1612(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 柴田 大, 教授 川合 光, 教授 井岡 邦仁 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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

The experience of time passing is a fundamental part of the human experience, but what is the relationship between conscious experiences in time and the relativistic nature of space and time? It is natural to think that our phenomenal experiences are realised by neuralevents in our brains. And it seems plausible that the order of these neural events makes a difference to our phenomenology. Yet, relativity theory entails that in some cases these neural events lack objective temporal orders. Instead, their temporal order is different relative to different, equally valid frames of reference. How then is this relativity compatible that intuitively there is only a single, objective way in which things appear to us? This question is at the centre of this thesis. I will present the context of the debate within the theory of Special Relativity and how different problems seem to arise between consciousness and Special Relativity. I will then introduce some basic key concepts for understanding Special Relativity. After introducing the foundation of the problem and a specific formulation that provides the structure of the rest of the thesis, I will present four different possible solutions to the problems, analysing their strengths and weaknesses. Finally, I will use one of the proposed solutions, the objective objection, to argue that the problem never actually arises to begin with and that it is based on a misreading of Special Relativity. I also argue that the objective objection is much more general than its originator proposes. / Att uppleva att tiden går är en central del av våra medvetna upplevelser, men vad är relationen mellan medvetna upplevelser i tiden och den relativistiska rumtiden? Våra fenomenologiska upplevelser måste vara formade av den temporala ordningen av neurologiska händelser och olika ordningar bör då ge upphov till olika fenomenologiska upplevelser. Den speciella teorin om relativitet tillåter olika ordningar av neurologiska händelser men detta står i kontrast med det faktum att vi endast kan ha en fenomenologisk upplevelse. I denna uppsats kommer jag undersöka relationen mellan speciell relativitet och medvetandet och varför det verkar som om relativitetsteorin ger upphov till flera fenomenologiska upplevelser när vi bara upplever en. Jag kommer presentera speciell relativitet och dess kontext i debatten om medvetandet och tid samt även ett par problem som verkar dyka upp mellan medvetandet och speciell relativitet. Därefter kommer jag att introducera några nyckelbegrepp för att underlätta förståelsen av speciell relativitet. Efter attha lagt fram problemet som uppsatsen undersöker kommer jag presentera fyra möjliga lösningar som jag har identifierat och deras styrkor samt svagheter. Slutligen kommer jag diskutera den lösning som jag tycker är mest sannolik, vilket är den objektiva invändningen, men jag argumenterar även att invändningen är mycket mer generell än dess ursprungliga författare föreslår och att problemet med flera sekvenser av neurologiska händer endast uppstår på grund av en missuppfattning om speciell relativitet.

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A numerical approach to including electromagnetism with general relativity is developed using GRAXI as a starting point. We develop a mathematical model describing electromagnetism coupled to a scalar field in an evolving axisymmetric spacetime. As there are numerous formulations of electromagnetism, we evalute different formulations in a limited flat space case. The full curved space system is then developed, using the flat case as a guide to implementing electromagnetism. This model is then implemented using GRAXI as a code base.

Over the last decade, linguistic relativity has seen a resurgence in research and discourse on thought, language, and culture. One particular facet of this research, multilingualism, has been relatively sparse in comparison to the wealth of research available focusing on individual languages and monolingual speakers. This study represents a preliminary investigation that enters this arena by focusing specifically on how speakers of English as a second language use English basic color terms in respect to monolingual speakers. This is done by using a modified methodology from the World Color Survey as a comparative model of a speaker’s division of colors. Participants in this study illicit responses for 160 color tiles taken from the Munsell color chart used as the basis of the World Color Survey. The results of this study show that three of the ten multilingual participants division of the color space per English color terms falls outside of the normal range of variation between the monolingual English speakers who participated in this study. Though future research is needed to definitively posit the reasons for those participants color maps, this study provides a new window and inquiry into an under-researched area of linguistic relativity.

In this report, we analyze general relativistic effects on celestial bodies, including gravitational strength in different metrics, gravitational radiation, and frame-dragging. We present simulation methods for classical and general relativistic motion, through the use of systems of equations that may be numerically integrated. The amount of energy leaving the system as gravitational radiation is approximated using the quadrupole formula, and by using a binary pair of planetary bodies as an approximation for orbital motion. Here we demonstrate that classical approximations may be suitable in low-mass high-distance scenarios. The eccentricity of an orbit also affects the gravitational radiation and would have to be much less than one for reliable results. It is concluded that frame-dragging effects are negligible for slowly rotating objects only, which is a well-known result.

One focus of research in cosmology regards the growth of structure in the universe: how we end up with stars, galaxies, galaxy clusters, and large scale structure in a universe that appears homogeneous and isotropic on large scales. Using cosmological perturbation theory, we investigate the evolution of density and velocity perturbations corresponding to a universe that is slowly contracting (Ijjas and Steinhardt), testing with and comparing different values for the equation-of-state parameter. This allows for the comparison of the growth of large scale structure in scenarios including a matter-dominated expanding universe, a dark energy-dominated expanding universe, and now, an ekpyrotic scalar field-dominated contracting universe. Further, we consider the timescales on which deviations from ΛCDM in favor of the model considered could become relevant.

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