Localized structures of the magnetic field strength depression are often observed in the interplanetarymedium, and they are called ‘magnetic holes’ after the original work of Turner et al. 1977. A numberof observations of similar features have been reported, while the mechanisms of their origin have notfully understood yet. The scale size of their structures varies from several to a few thousand of the protongyro radii, and their characteristic orientations of the magnetic field also vary, and therefore differenttypes of the magnetic holes have been suggested. To date, the magnetic holes are classified into Mirrormode and magnetic decreases (Tsurutani et al. 2011). Despite a large number of papers that report theobservational characteristics of the magnetic holes, many identify the feature using only the magneticfield data. This is due to the scale size of the structure at a large speed of the solar wind medium, thespatial resolution of the plasma instruments is often insufficient while the magnetic field instrument canusually obtain the data in high enough time resolution.The Cassini spacecraft orbited Saturn for almost 17 years and obtained a large amount of data in/near theKronian magnetosphere, where the series of the magnetic depletions have been also observed (Smith et al.1980). The Langmuir Probe (LP) onboard Cassini measures the spacecraft potential and, in turn, measuresthe electron density in in-situ in the outer magnetosphere and solar wind region. This measurement hasbeen done using the LP sweep mode which samples the current-voltage curve of the probe every 10 minin the outer magnetosphere. The LP has also been operated in the continuous mode that measures theprobe current at a fixed bias potential every 16 s allowing to calculate the electron density in a smallerscale that is required for the studies magnetic holes. However, there is no general calibration so far inorder to conduct a statistical study in the outer magnetosphere region. The goal of this project is toinvestigate the possibility to use the LP data for the magnetic hole study, calibrate the LP continuousmode to derive the plasma density near the magnetospheric of Saturn, and investigate the scale size of theplasma density structure in the magnetic holes, i. e. plasma β, the field strength and density.The calibration of the continuous data was done by finding a relation between the current at 11 V, whichis a typical bias voltage of continuous mode, and the spacecraft potential obtained by the LP the sweepmode data. Is is expected that the current at 11V is linearly proportional to the floating potential andtherefore can be used to derive the electron density with the potential and density relationship presentedby Morooka et al. 2009. I found that the spacecraft attitude against the sun has a strong effect on therelation, and derived 11V current-floating potential relationship depending on the different spacecraftattitude.Using the LP continuous data calibration above, I investigated the electron density characteristics aroundthe magnetic hold structure, and confirmed that they are generally in anticorrelation relationship. I estim-ated also the plasma β assuming a constant temperature of 100 eV and investigated their characteristicsfor the different types of magnetic holes (linear and rotational holes) both in the magnetosheath and theholes in the solar wind for the year 2011. For the Cassini dataset during 2011, various different shapeand sizes of magnetic hole events have been found. Most (80%) of the MHs appeared within a groupedstructure, while the rest (20%) are found as isolated type holes in the magnetosheath. Among the isolatedMHs, about 30% had "Gaussian shape" and about 40% had a substructure. The scale size for the electrondensity for the isolated holes were on average 50 s in the solar wind, and 75 s (the rotational holes) and120 s (the linear holes) in the magnetosheath. Therefore, I confirmed that the LP can obtain enough datapoints to resolve the magnetic holes structure in the magnetosheath. The Cassini LP data resolution isalso capable to resolve some of the magnetic hole structure in the solar wind.In summary, I confirmed that the Cassini LP continuous data calibrated in this study is capable toinvestigate the different types of magnetic hole structures. Using this calibrated electron data statisticallyfor the large number of Cassini orbit would helpful to further identify the MHs structures in the solar wind and the magnetosheath that can be a key to understand the generation mechanisms of the magneticholes. / Lokaliserade strukturer med låg magnetfältstyrkan ses ofta i interplanetära mediet och de kallas ’mag-netiska hål’ (MH) (Turner et al. 1977). Trots et antal observationer av sådana strukturer har observeratsär deras generationsmekanism ännu förstådd. Storleken av strukturerna varierar från ett fåtal till någratusen protongyroradier och även deras kännetecknande inriktningar i magnetfältet varierar. På grund avdetta har olika typer av MH förslagits. Idag klassificerar man MH som ’mirror mode’ och magnetiskaminskningar (Tsurutani et al. 2011). Många studier har undersökt de magnetiska hålens egenskaper,men tyvärr oftast baserats endast på magnetfältsdata. Detta kan bero på strukturernas storlek vid en storsolvindshastighet, där plasmainstrumenten oftast inte har tillräckligt hög tidsupplösning för mätningar,medan magnetfältsinstrumenten kan oftast tillhandahålla data i hög tidsupplösning.Cassini-rymdfarkosten kretsade runt Saturnus i nästan 17 år och erhöll stora mängder data i och näraSaturnus magnetosfär. Langmuir-sonden (LP) ombord Cassini mäter rymdfarkostens potential ochdärmed mäter den elektrontätheten i rymden. Instrumentet fungerar som en slags väderstation för rym-dplasma och möjliggör mätningen av fundamentala plasmaparametrar såsom elektrontäthet, jontäthet,elektrontemperatur och jonmassa i en tät plasmaområdet av nära Saturnus. I den yttre magnetosfären därden plasmatätheten är låg, kan LP mäta rymdfarkosts potential och plasmatätheten. Mätningen, så kallade’sweep mode’ kan skaffades var 10:e minuter. LP:en mäter också i ’kontinuerlig mode’ som möjligenkan mäta plasmatätheten i mer frekventa men den behöver allmän kalibrering. I detta projekt undersökerjag möjligheten att använda LP kontinuerlig data för att studera MH, skapa kalibraring funktion för’kontinuerlig mode’ för att uppskatta plasmatätheten i Saturnus magnetosfär, och även att undersökastorleken och karaktär av plasmatäthetenstrukturen i MH.Jag undersökte först relationen mellan LP ström vid 11V och rymdfarkostens potential i sweep mode data.De härledda funktionerna användes vidare för att uppskatta densiteten med användning av relationenmellan rymdfarkostens potential och elektrontätheten (Morooka et al. 2009). Jag upptäckte också attden kontinuerlig mode funktionen är olika beroende på LP sensors läge i förhållande till solen ochrymdfarkosten. Hur Cassini är inriktad har en stor effekt på relationen och därför beskriva jag fyra olikarelationer för olika inriktningsregioner. Med den kontinuerlig mode funktionen jag härlett, undersöktejag struktur av magnetiska hålen som har listats av Tomas Karlsson på KTH. År 2011 innehåller MH medmycket olika former och storlekar. Den mest (80%) MH identifierades som grupp och resten (20%) varsom isolerade MH i magnetosheath. Av dessa isolerande hål har ca. 30% en Gauss-form och nästan 40%av MH verkar ha en understruktur. Genom att jämföra magfältdatan med elektrontätheten bekräftadejag den allmänna antikorrelationen mellan magnetfältstyrkan och elektrontätheten i MH-strukturerna.Dessutom hittar jag en ökning av elektron β som beräknas med en temperatur av 100 eV för linjära ochroterade MH i den magnetosheath samt MH i solvinden under 2011. Storleken av de isolerade magnetiskahålen är i genomsnitt 50 s i solvinden, 75 s (roterade magnetiska hål) och 120 s (linjära magnetiska hålen)i magnetosheath:en. Därför kan Cassini LP ha tillräcklig många datapoäng för att upplösa struktur avMH i magnetosheath. I solvinden kan LP upplösa en del av relativt stora MH.Sammanfattningsvis kan LP:s kontinuerlig kalibreringen från detta projekt användas för att analyserade olika strukturerna och storlekar av MH. Med denna kalibrerade plasmatäthet data är det möjligt attidentifiera olika MH karaktär i statistiskt för det stora antalet Cassini data. Det skulle vara en stor hjälpför att förstå genereringsmekanismerna av de magnetiska hålen.

This thesis is devoted to various aspects of electric-magnetic duality and its gravitational generalization, with an emphasis on the case of maximal supergravity. It is divided into three parts.In the first part, we review the symmetries of maximal supergravity in various dimensions, with a particular focus on the exceptional ``hidden" symmetries that appear upon toroidal dimensional reduction of eleven-dimensional supergravity. Two new results are obtained. First, we prove in detail that these hidden symmetries appear if and only if the Chern-Simons coupling of the eleven-dimensional theory takes the value predicted by supersymmetry. Second, we obtain a manifestly E7(7)-invariant formula for the entropy of non-extremal black holes in four-dimensional N = 8 supergravity.The second part of the thesis concerns the gaugings of extended supergravities in four dimensions. We first show that the embedding tensor formalism does not allow for deformations that cannot be reached by working with the usual Lagrangian in the duality frame picked by the embedding tensor. We then examine through BRST methods the deformations of a large class of non-minimally coupled scalars and abelian vector fields in four dimensions, of which ungauged supergravities offer a prime example. We prove that all local deformations of these models which modify the gauge transformations are of the usual Yang-Mills type, i.e. correspond to the gauging of some rigid symmetries of the undeformed theory. Combined with the first result, this shows that the embedding tensor formalism correctly captures the most general local deformations of these theories.In the third part, we construct self-contained action principles for several types of free fields in six dimensions, whose field strengths satisfy a self-duality condition. These fields are motivated by two considerations. First, their existence allows for a remarkable geometric interpretation of the electric-magnetic duality symmetries of vector fields and linearized gravity in four dimensions. Second, they appear in the spectrum of the chiral N = (4,0) and N = (3,1) ``exotic supergravities" in place of the usual metric. The free action and supersymmetry transformations for those theories are explicitly constructed. We also check that they reduce to linearized maximal supergravity in five dimensions, thus completing the picture of higher-dimensional parents of N = 8 supergravity, at least at the free level. Along the way, we also generalize previous works on linearized supergravity by other authors, in which the graviton and its dual appear on the same footing at the level of the action.We conclude with some open questions, perspectives for future work, and a series of technical appendices. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

The cores of galaxy clusters contain the most massive galaxies in the Universe, the brightest cluster galaxies. These galaxies are unique compared to their counterpart galaxies outside of clusters as they have much brighter cores, and vast spatially- extended stellar envelopes. The theoretical picture of how they reached their huge masses relied on the idea of gradual stellar mass growth during the second half of the history of the Universe. However, recent observational evidence of highly-overdense protoclusters, the progenitors of these galaxies, demonstrates that some brightest cluster galaxies may have assembled within the first few billion years after the Big Bang – seemingly contradicting our theoretical predictions. I include my theoretical work that shows the short timescales over which these observed protoclusters trans- form into the brightest cluster galaxies and discuss the likelihood of finding these rare protoclusters in the early Universe. To push our understanding of the rapid evolution of these galaxies even further for- ward demands the use of numerical simulations due to the highly coupled, non-linear astrophysical processes that occur during the process. In this dissertation, I include improvements to our numerical models of hydrodynamical turbulence and supermas- sive black holes that I incorporated into a state-of-the-art hydrodynamical+gravity simulation code, in effort to provide the groundwork to improving our understanding of the build-up of the brightest cluster galaxies in the early Universe, and galaxy evolution in general. / Graduate

The deformation on cylindrical surfaces of holes in tensile loaded laminated composite specimens was measured using new moire interferometry techniques. These new techniques were developed and evaluated using a 7075-T6 aluminum control specimen. Grating replication techniques were developed for replicating high quality diffraction gratings onto the cylindrical surfaces of holes. Replicas of the cylindrical specimen gratings (undeformed and deformed) were fabricated onto circular steel sectors. Narrow angular regions of these sector gratings were directly evaluated in a moire interferometer. This moire interferometry approach eliminated potential sources of error associated with other moire interferometry approaches. Two composite tensile specimens, fabricated from IM7/5250-4 pre-preg with ply layups of [0₄/90₄]_3s and [+30₂/-30₂/90₄]_3s, were examined using the newly developed moire interferometry techniques. Circumferential and thickness direction displacement fringe patterns (each 3 degrees wide) were assembled into 90 degrees wide mosaics around the hole periphery for both composite specimens. Distributions of strain were calculated with high confidence on a sub-ply basis at select angular locations. Measured strain behavior was complex and displayed ply-by-ply trends. Large ply related variations in the circumferential strain were observed at certain angular locations around the periphery of the holes in both composites. Extremely large ply-by-ply variations of the shear strain were also documented in both composites. Peak values of shear strain approached 30 times the applied far-field axial strain. Post-loaded viscoelastic shearing strains were recorded that were associated with the regions of large load-induced shearing strains. Large ply-grouping related variations in the thickness direction strain were observed in the [+30₂/-30₂/90₄]_3s specimen. An important large-scale trend was observed where the thickness direction strain tended to be more tensile near the outside faces of the laminate than near the mid-ply region. The measured strains were compared with the three-dimensional analysis technique known as Spline Variational Elastic Laminate Technology (SVELT), resulting in a very close match and corroborating the usefulness of SVELT. / Ph. D.

Dans l’Univers, on observe des galaxies lointaines ne formant plus d’étoiles, mais les astrophysiciens n’ont pas encore identifié avec certitude les phénomènes physiques à l’origine de leur “mort”. Pour apporter des éléments de réponse, je me suis penchée sur l’étude de phénomènes qui pourraient y jouer un rôle : les processus de rétroaction des étoiles et des trous noirs supermassifs actifs, la formation stellaire, et les vents galactiques. Le Chapitre 1 présente toutes les notions nécessaires à la compréhension du problème : les caractéristiques des galaxies typiques de l’Univers proche et lointain ; les vents galactiques ; la mort des galaxies; les trous noirs supermassifs actifs (noyaux actifs de galaxies, AGN) et les étoiles ; et leur rétroaction. Dans le Chapitre 2, je présente les techniques numériques utilisées : le code de simulations astrophysiques RAMSES et le code de transfert radiatif Cloudy, que j’ai utilisé pour développer une méthode de calcul de l’état d’ionisation d’une galaxie, détaillée au Chapitre 3. Le Chapitre 4 étudie le couplage entre les trous noirs actifs et les étoiles, avec le projet POGO, Origines Physiques des Vents Galactiques. Durant cette thèse, j’ai montré que les trous noirs actifs n’étaient pas en mesure de tuer subitement leur hôte, même en prenant en compte la rétroaction des étoiles, et que leur couplage peut réduire ou renforcer les vents dans les galaxies en fonction de leur masse. Le Chapitre 5 fait un état de l’art du domaine avant et pendant mon doctorat, reprend les conclusions de cette thèse et donne quelques perspectives, notamment en ce qui concerne le rôle additionnel des rayons cosmiques dans la mort des galaxies / In the Universe, we observe galaxies forming no, or almost no, stars anymore, but astrophysicists do not know yet what physical mechanisms cause their “death”. To give clues to solve the problem, I studied feedback processes from stars and active supermassive black holes, star formation and galactic outflows. Chapter 1 presents all the notions to understand the problem: the characteristics of typical galaxies in the local and distant Universe, galactic outflows, galaxy death, active supermassive black holes, stars, and their feedback processes. In Chapter 2, I describe the numerical techniques I used: the simulation code RAMSES, and the radiative transfer code Cloudy, which I used to develop a computation method to get the ionization state of an entire galaxy. This method is presented in Chapter 3. Chapter 4 studies the coupling between the feedback processes of active supermassive black holes and stars, with the POGO project, Physical Origins of Galactic Outflows. During this thesis, I showed that typical active supermassive black hole cannot suddenly kill their host, even when stellar feedback processes are accounted for, and that their coupling either reduces or enhances the mass outflow rate depending on the mass of the host. In Chapter 5, I give a state-of-the-art about active supermassive black holes before and during my thesis, sum up the conclusions of the work, and give perspectives to enlarge the scope of the study, especially regarding the additional role of cosmic rays in the death of galaxies

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18796号 / 理博第4054号 / 新制||理||1583(附属図書館) / 31747 / 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 長田 哲也 / 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20179号 / 理博第4264号 / 新制||理||1613(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 上田 佳宏, 教授 嶺重 慎, 教授 長田 哲也 / 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20903号 / 理博第4355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)教授 佐々木 節, 教授 柴田 大, 教授 川合 光 / 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20912号 / 理博第4364号 / 新制||理||1626(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 井岡 邦仁, 教授 川合 光, 教授 田中 貴浩 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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