In this thesis we exploit the setup of AdS3/CFT2 holography, and in particular the D1D5 two-dimensional CFT, to describe states dual to geometries relevant for the \fuzzball" proposal for the description of six-dimensional black hole microstates. Precise holographic dualities between CFT and bulk geometric objects are established and checked, both for 2 and 3-charge states. In particular, VEVs of CFT operators of small conformal dimension are checked to encode deviations from AdS3 geometry near the spacetime boundary. 4-point functions of the \heavy-heavy-light-light" type are also considered and matching is found between CFT and bulk computations via the usual AdS/CFT prescription, with the heavy states being dual to (simple) microstate geometries. In this context, the issue of the presence of spurious singularities at leading order in the large N limit is assessed and cancellations are found even without considering sub-leading corrections, at the cost of considering the full detail of the D1D5 CFT (i.e. including the Virasoro blocks of operators of small dimension charged under the internal SU(2)L SU(2)R R-symmetry group). Finally, more complicated 4-point functions, involving operators in the twisted sector of the CFT, are computed and the results are checked against known results in the literature with the aim of verifying the robustness of the (new) techniques used. Supersymmetric Ward identities are also derived, and checked for some cases, between correlators written in terms of bosons and in terms of fermions.

No description available.

No description available.

The rapid advancements in the field of machine learning and artificial intelligence has led to the emergence of technologies like the Brain Computer Interface (BCI), which has revolutionized rehabilitation protocols. However, given the neural basis of BCIs and the dependence of its performance on cognitive factors, BCIs may be used to characterize the functional capacity of the user. A resting state segment can also be considered for characterization of the functional network integrity, creating a two part framework that probes the functional networks and their cognitive manifestations. This thesis explores such a two part framework using a simultaneous EEG-fMRI setup on a healthy population. The BCI accuracies for all subjects increased over the course of the scan and is thought to be due to learning processes on the subject's part. Since such learning processes require cognitive faculties such as attention and working memory, these factors might modulate the BCI performance profile, making it a potential metric for the integrity of such cognitive factors. The resting state analysis identified four EEG Microstates that have been previously found to be associated with verbal, visual, saliency and attention reorientation tasks. The proportion of each microstate that composed the corresponding fMRI resting state networks (RSN) were identified, opening up the potential for predicting fMRI-based RSN information, from EEG microstates alone. The developed protocol can be used to diagnose potential conditions that negatively affect the functional capacity of the user by using the results from this study as healthy control data. This is the first known BCI based system for characterization of the user's functional integrity, opening up the possibility of using BCIs as a metric for diagnosing a neuropathology. / Thesis / Master of Applied Science (MASc)

Il existe des nombreuses solutions lisses dans le domaine de la théorie des cordes, caractérisées par une topologie non triviale (bulles) et sans sources localisées. Dans cette thèse nous analysons quelques-unes parmi les solutions les plus importantes avec les différents objectifs pour lesquels ils sont étudiés. Des solutions lisses en onze dimensions peuvent être interprétées comme microétats BPS de trou noir dans le cadre de la Fuzzball proposal. On peut promouvoir ces microétats à être quasi-BPS en plaçant de supertubes au minimum métastable à l’intérieur de ces solutions. Nous montrons que ces minima peuvent abaisser leur énergie lorsque les bulles se déplacent dans certaines directions dans l’espace des modules, ce qui implique que ces microétats quasi-BPS sont en fait instables. L’énergie dissipée par ces solutions correspond au rayonnement Hawking et on compare le taux d’émission et la fréquence à celles du trou noir correspondant. En modifiant la géométrie asymptotique de ces microétats on pourrait construire des microétats pour des trous noirs BPS sans charge électrique en cinq dimensions. Il faut donc trouver une nouvelle solution de supergravité en cinq dimensions dont la norme du vecteur de Killing passe de positive à nulle dans certaines régions. Nous construisons des exemples explicites où la norme du vecteur de Killing supersymétrique est une fonction réelle non-analytique telle que tous ses dérivés sont nulles à un point où le vecteur de Killing devient nul. Dans la solution de Lin-Lunin-Maldacena on trouve un mécanisme pour briser la supersymétrie similaire à celui utilisé pour les microétats quasi-BPS. Nous analysons l’énergie potentielle de branes M2 polarisés en branes M5. Lorsque les charges des M2 sont parallèles à ceux de la solution, nous trouvons des configurations stables. Lorsque les charges des M2 ne sont pas parallèles, nous trouvons des états métastables qui brisent la supersymétrie et nous analysons le processus de rayonnement d’énergie. Nous analysons aussi la solution de Klebanov-Strassler et construisons sa version T- duale dans la supergravité de type IIA. Pour cela une analyse approfondie est nécessaire pour choisir l’isomérie la plus appropriée. Notre construction est la première étape d’un programme pour tester la stabilité des antibranes dans la supergravité de type IIA. / There exist many smooth solutions in String Theory characterized by a nontrivial topology threaded by fluxes and no localized sources. In this thesis we analyze some of the most important bubbled solutions along with the different purposes they are studied for. Some smooth, eleven-dimensional solutions can be interpreted as BPS black hole microstates in the context of the Fuzzball proposal. One can promote these to be microstates for near-BPS black holes by placing probe supertubes at a metastable minimum inside these solutions. We show that these minima can lower their energy when the bubbles move in certain directions in the moduli space, which implies that these near-BPS microstates are in fact unstable. The decay of these solutions corresponds to Hawking radiation and we compare the emission rate and frequency to those of the corresponding black hole. By modifying the asymptotic behavior of these microstates one could be able to construct microstates for five-dimensional BPS black holes with no electric charge. To do so one needs to find a new supergravity solution in five-dimensions whose Killing vector switches from timelike to null in some open regions. We construct explicit examples where the norm of the supersymmetric Killing vector is a real not-everywhere analytic function such that all its derivatives vanish at a point where the Killing vector becomes null. In the Lin-Lunin-Maldacena solution we find a supersymmetry-breaking mechanism similar to that used for near-BPS microstates. We analyze the potential energy of M2 probes polarized into M5 brane shells. When the charges of the probe are parallel to those of the solution we find stable configurations, while when the charges are opposite we find metastable states that break supersymmetry and analyze the decay process to supersymmetric configurations. We analyze also the Klebanov-Strassler solution and construct its T-dual version in Type IIA. This is done by just reconstructing the solution expanded on a small region of the deformed conifold, after a thorough analysis to choose the most suitable isometry. Our construction is the first step in a program to test the stability of antibranes in Type IIA backgrounds.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20907号 / 理博第4359号 / 新制||理||1625(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 國友 浩, 教授 高柳 匡, 教授 川合 光 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

This exploratory case study aimed to investigate patterns in student reasoning in statistical mechanics, in order to identify difficulties and develop ideas for future research. Upper-division undergraduate students, taking a course in statistical mechanics, were interviewed in groups. Here we present our findings regarding student difficulties in distinguishing microstates and macrostates, as well as distinguishable versus indistinguishable particles. We also present observed patterns of student reasoning about a simple, discrete system in contact with a heat bath. Our findings reveal problematic student intuitions of the high temperature limit. Several students were, however, able to transfer knowledge from a similar problem involving spin to improve their reasoning. / Denna explorativa fallstudie ämnade att undersöka mönster i studenters resonemang i statistisk mekanik, för att identifiera svårigheter och utveckla idéer för framtida forskning. Studenter i sista året på kandidatprogrammet i fysik, som läste en kurs i statistisk mekanik, intervjuades i grupper. Här presenterar vi våra fynd gällande studenters svårigheter med att skilja på mikrotillstånd och makrotillstånd, såväl som urskiljbara och ourskiljbara partiklar. Vi presenterar också observerade mönster i studenters resonemang kring ett simpelt, diskret system i kontakt med en värmereservoar. Våra fynd avslöjar problematiska intuitioner för gränsvärdet vid hög temperatur. Flera studenter kunde dock överföra kunskap från ett liknande problem, som handlade om spin, för att förbättra deras resonemang.

Taking research as a tool to learn how new technology can develop new diagnosis and treatment methods in the physical field, takes place the education in motor sciences. On one hand, current research has shed light into novel methods to improve motor performance for athletes as well as for people learning new motor gestures. On the other hand it has also helped to improve treatment efficiency for people suffering motor cerebral lesions like: cerebrovascular attack (CVA) and cerebral palsy. This doctoral thesis addresses different protocols to analyze motor gestures and brain oscillations through visual perception.Our brain encompasses a changing symphony of oscillating activity throughout our lives. Up to the time we are born, we are ready to feel and move to interact with our world. Our senses develop rapidly and we start to perceive the world and learn. We visually perceive and process big amounts of information on a daily basis. At the same time we see movements from ourselves and from others in order to communicate and interact with our environment. We watch the world move. Moreover, from the links that exist between motor and sensory systems in human beings we may approach individual motor activity as a loop between a control (brain) over the effectors (muscles) which act, perceive and send the information back to the control source.The present group of works presented in this doctoral thesis is based on the correlation between human brain scalp activity, measured by means of electroencephalography (EEG) recordings, visual perception and its interpretation through different approaches. / Doctorat en Sciences de la motricité / info:eu-repo/semantics/nonPublished