Ultracold Fermi gas is an exciting field benefiting from atomic physics, optical physics and condensed matter physics. It covers many aspects of quantum mechanics. Here I introduce some of my work during my graduate study. We proposed an optical spectroscopic method based on electromagnetically-induced transparency (EIT) as a generic probing tool that provides valuable insights into the nature of Fermi paring in ultracold Fermi gases of two hyperfine states. This technique has the capability of allowing spectroscopic response to be determined in a nearly non-destructive manner and the whole spectrum may be obtained by scanning the probe laser frequency faster than the lifetime of the sample without re-preparing the atomic sample repeatedly. Both quasiparticle picture and pseudogap picture are constructed to facilitate the physical explanation of the pairing signature in the EIT spectra. Motivated by the prospect of realizing a Fermi gas of 40 K atoms with a synthetic non-Abelian gauge field, we investigated theoretically BEC-HCS crossover physics in the presence of a Rashba spin-orbit coupling in a system of two-component Fermi gas with and without a Zeeman field that breaks the population balance. A new bound state (Rashba pair) emerges because of the spin-orbit interaction. We studied the properties of Rashba pairs using a standard pair fluctuation theory. As the two-fold spin degeneracy is lifted by spin-orbit interaction, bound pairs with mixed singlet and triplet pairings (referred to as rashbons) emerge, leading to an anisotropic superfluid. We discussed in detail the experimental signatures for observing the condensation of Rashba pairs by calculating various physical observables which characterize the properties of the system and can be measured in experiment. The role of impurities as experimental probes in the detection of quantum material properties is well appreciated. Here we studied the effect of a single classical impurity in trapped ultracold Fermi superfluids. Although a non-magnetic impurity does not change macroscopic properties of s-wave Fermi superfluids, depending on its shape and strength, a magnetic impurity can induce single or multiple mid-gap bound states. The multiple mid-gap states could coincide with the development of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase within the superfluid. As an analog of the Scanning Tunneling Microscope, we proposed a modified radio frequency spectroscopic method to measure the focal density of states which can be employed to detect these states and other quantum phases of cold atoms. A key result of our self consistent Bogoliubov-de Gennes calculations is that a magnetic impurity can controllably induce an FFLO state at currently accessible experimental parameters.

The Swedish Nuclear Fuel and Waste Management Company (SKB) has developed a method for final disposal of spent nuclear fuel. This technique requires accurate measurement of the residual decay heat of every assembly. For this purpose, depletion codes as well as calorimetric and gamma-ray spectroscopy experimental methods have been developed and evaluated. In this work a prototype analysis tool has been developed to automate the analysis of both calorimetric and gamma-ray spectroscopy measurements. The performance of the analysis tool has been investigated by comparing its output with earlier results and calculations. Parallel to the software development, new measurements on 73 BWR assemblies were performed. The results obtained for the determination of the residual decay heat are presented. Finally, suggestions for further development are outlined and discussed.

Lab measurements and Monte Carlo simulations have been carried out for the evaluation of the Straw-type detectors used in the NA62 experiment at CERN. In addition, analyses of experiment data was used in corrections to improve the reconstruction of particle tracks, ultimately leading to improved resolution of the detector system as a whole. 97.7 percent of the Straws were aligned to within 30 microns, quantified as the deviation from zero of the mean of the inherent residual distribution of each Straw. A drift time dependence on where along the Straw the particle ionized have been corrected for; before the correction the dependence was as big as 6 ns. A radius-drift time relation based on the leading edge timing distribution has been deduced and implemented. Upon implementation artifacts from the piecewise fits used became evident. An alternative approach using residuals has been put forward.

Dans les prochaines années, le complexe d'accélérateur du CERN va subir une profonde mise a jour dont le but est une augmentation de la luminosité du LHC. Le projet LIU ( LHC Injectors Upgrade) coordonne les mises a jour des différentes parties de la chaine d'injection. Le projet LINAC4 s'inscrit dans ce cadre et sera la première étape de la mise à jour. Cette thèse présente les différentes études conduites lors du développement de l'instrumentation nécessaire à la mesure du faisceau. Ce travail est limité aux instruments permettant la mesure des profils transverses (taille et emittance). La thèse se divise en quatre parties. La première partie, composée des trois premiers chapitres, est vue comme une partie d'introduction où il sera présenté le projet LINAC4 ainsi que les différents aperçus théoriques nécessaires à la conception de types d'instruments requis. Le chapitre 2 décrit brièvement la dynamique des faisceaux dans un accélérateur et présente également des rappels théoriques sur l'effet de charge d'espace induit par le faisceau. Le chapitre 3 est un rappel sur les interactions entre particules et matière. La seconde partie, comprenant les chapitres 4 a 6, décrit les différentes études menées lors de la conception des SEM grid, wire scanner et emittance mètre. Le lecteur trouvera dans cette partie une description des instruments mentionnés et qui seront déployés lors de la phase de test et pendant la phase d'opération du LINAC4. Le chapitre 4 s'attarde sur les effet de charge thermique induite sur les fils des SEM grid et wire beam scanner par le faisceau et leur conséquence sur la survit de ces fils. Le LINAC4 va produire un faisceau intense d'ion H-, avec une taille de faisceau de l'ordre du millimètre, cette densité de particule va, à basse énergie, induire un grand dépôt d'énergie dans la matière. La hausse de température qui en résulte peut dépasser les limites thermomécaniques des matériaux usuels employés pour ce type de mesure. Cette étude permet de déterminer le matériau idéal pour le fil et d'imposer certaines restrictions sur l'utilisation des différents moniteurs de profils. Au sein de ce chapitre il est aussi présente une estimation des signaux obtenus pour des géométries et des matériaux de fils différents. Les chapitres 5 et 6 sont une études de l'emittance mètre a moyenne énergie du LINAC4 (3 et 12 MeV), le système employé est un système dit "Slit & grid", ou une fente permet de sélectionner une faible partie du faisceau, le reste étant absorbé, le profil du faisceau non perturbé est mesuré par une grille. Le chapitre 5 présente une étude sur les erreurs systématiques des mesures d'emittance dû a la diffusion multiple et a l'effet de charge d'espace du faisceau, ces deux phénomènes constituant les principales erreurs conduisant à une mauvaise reconstruction de l'emittance mesurée. Le chapitre 6 quant a lui est dédié à l'étude mécanique de la fente de l'emittance mètre. Comme pour les fils des moniteurs de profils, la charge thermique sur la partie supportant la slit est importante. Ce chapitre décrit les études effectuées pour le choix des matériaux et de la géométrie des pièces mécaniques. La troisième partie de la thèse, qui se résume au chapitre 7, est consacrée aux différents résultats expérimentaux obtenus dans la phase de test de la source de particule du LINAC4 ainsi que ceux obtenus lors d'une visite d'étude à SNS. Une partie de se chapitre décrira la mise au point de l'instrumentation aux banc test de la source, une autre présente l'effet de la diffusion multiple sur les mesures d'emittance à SNS et propose une mise a jour de l'instrument. Le chapitre 8 constitue la dernière partie de cette thèse. Dans ce dernier chapitre, le lecteur pourra lire une étude préliminaire sur l'utilisation d'un faisceau laser pour la mesure d'emittance et de profil aux hautes énergies du linac. / LINAC4 is part of the CERN Large Hadron Collider injector chain upgrade (LIU) and will accelerate H− ions from 45 keV to 160 MeV, it will be the first step of the upgrade with the replacement of LINAC2 in 2018. In order to measure beam profiles along the LINAC, several SEM grid and wire beam scanner (WS) monitors will be installed between the RF cavities from 50 MeV to 160 MeV. This thesis covers all monitor design aspects intended to cope with the required specifications. In particular, the overall measurement robustness, accuracy and sensitivity must be satisfied for different commissioning and operational scenarios. The physics mechanisms generating the wire signals and the wire resistance to beam induced thermal loads have been considered in order to determine the most appropriate monitor design in terms of wire material and dimensions. In addition, for the commissioning phase, a movable diagnostics test bench will be used to adjust the machine parameters during different stages of installation. One of the main instruments on this movable bench is a transverse emittance meter. This thesis presents the different studies done for the mechanical design of the slit and for the estimation of the systematical error on the measurement due to space charge and multiple scattering. To complete this section, the first results of the commissioning of the LINAC4 ions source and LEBT are presented, together with results form emittance measurement taken at the Spallation Neutron Source in Oak Ridge (Tennessee, USA). This last part of the thesis presents different studies done for a beam profiles and emittance measurements with a laser wire, with a large input from the SNS beam diagnostic group.

In a collaboration with limnologists at Uppsala University a planar HPGe detector has been used to find 210Pb in lake bottom sediment in hopes of getting an estimation for the sedimentation rate. Using a least squares fit to the data, the sedimentation rate was calculated to 0.08 ± 0.01 cm/year with background subtraction, and with it a timescale for the age of the sediment could be implemented. With this timescale the lake bottom sediment can be dated as far back as a century. Along with this, using 137Cs traces from the Chernobyl disaster of 1986 a consistency check can be made for our timescale. It is estimated that the Chernobyl disaster occurred at 1989 ± 7 years which is consistent with reality since 1986 is included in the interval 1982-1989. This helps us validate the determined sedimentation rates.

The aim of this project is to understand the structure of the Standard Model of the particle physics. Therefore quantum field theories (QFT) are studied in the both cases of abelian and non-abelian gauge theories i.e. quantum electrodynamics (QED), quantum chromodynamics (QCD) and electroweak interaction are reviewed. The solution to the mass problem arising in these theories i.e. spontaneous symmetry breaking is also studied. / Syftet med detta projekt är att förstå strukturen för partikelfysikens standardmodell. Därför studeras kvantfältsteorier (QFT) i båda fallen av abelska och icke-abelska gaugeteorier, dvs kvantelektrodynamik (QED), kvantkromodynamik (QCD) och elektrosvag växelverkan granskas. Lösningen på massproblemet som uppstår i dessa teorier, dvs. spontant symmetribrott studeras också.

The vast majority of all experimental results in particle physics can be described by the Standard Model (SM) of particle physics. However, neither the existence of neutrino masses nor the mixing in the leptonic sector, which have been observed, can be described within this model. In fact, the model only describes a fraction of the known energy in the Universe. Thus, we know there must exist a theory beyond the SM. There is a plethora of possible candidates for such a model, such as supersymmetry, extra dimensional theories, and string theory. So far, there are no evidence in favor of these models. These theories often reside at high energies, and will therefore be manifest as effective theories at the low energies experienced here on Earth. A first example in extra-dimensional theories. From our four-dimensional point of view, particles which propagate through the extra dimensions will effectivel be perceived as towers of heavy particles. In this thesis we consider an extra-dimensional model with universal extra dimensions, where all SM particles are allowed to propagate through the extra dimensions. Especially, we place a bound on the range of validity for this model. We study the renormalization group running of the leptonic parameters as well as the Higgs self-coupling in this model with the neutrino masses generated by a Weinberg operator. Grand unified theories, where the gauge couplings of the SM are unified into a single oe at some high energy scale, are motivated by the electroweak unification. The unification must necessarily take place at energies many orders of magnitude greater than those that ever can be achieved on Earth. In order to make sense of the theoru, ehich is given at the grand unified scale, at the electroweak scale, the symmetry at the grand unified scale is broken down to the SM symmetry. Within these models the SM is considered as an effective field theory. We study renormalization group running of the leptonic parameters in a non-supersymmetric SO(10) model which is broken in two steps via the Pati-Salam group. Finally, the discovery of the new boson at the LHC provides a new opportunity to search for physics beyond the SM. We consider an effective model where the magnitudes of the couplings in the Higgs sector are scaled by so-called coupling scale factors. We perform Bayesian parameter inference based on the LHC data. Furthermore, we perform Bayesian model comparison, comparing models where one or several of the Higgs couplings are allowed, to the SM, where the couplings are fixed. / <p>QC 20141020</p>

In this thesis, compactifications of F-theory on six dimensional symmetric toroidalorbifolds are explored. These orbifold geometries have been mathematically classified and it is natural to ask what the physical implications of string theorycompactifications on those geometries are. Since compactifications of string theory to six dimensions describe a sweet spot in terms of developed methods andrich model-building possibilities, it is interesting to investigate the landscape ofthese theories opposed to the swampland of only apparently consistent quantumtheories of gravity. Additionally, superconformal field theories can exist in at mostsix dimensions. These emerge naturally in the considered F-theory constructions. The present work explores effects of compactifications on such orbifolds buildingon the work of [arXiv:1905.00116v1 [hep-th]]. It constitutes a step towards extendingthe geometric classification of these orbifolds to a classification of the physical models. Beyond [arXiv:1905.00116v1 [hep-th]], roto-translations have severe effects on thegeometry and thus the field theory and the spectrum. These effects are discussedin this thesis and include, amongst others, twisted affine folding of gauge groups, the emergence of superconformal points away from intersecting branes as well assuperconformal sectors related to the multiple fibre. / In dieser Thesis werden Kompaktifizierungen von F-Theorie auf sechs dimensionalen symmetrischen, toroidalen Orbifaltigkeiten untersucht. Da diese Orbifaltigkeiten mathematisch klassifiziert wurden, stellt sich auf natürliche Weisedie Frage nach den physikalischen Implikationen von Kompaktifizierungen vonString Theorie auf diesen. In Kompaktifizierungen von String Theorie zu sechs Dimensionen balancieren sich der Fortschritt der Methoden und die Möglichkeitenphysikalische Theorien zu modellieren optimal. Daher ist es wichtig das "Landscape" dieser Theorien zu untersuchen, im Gegensatz zu dem so genannten "Swampland" von vermeintlich konsistenten Quantentheorien der Gravitation. Darüber hinaus stellt sich heraus, dass superkonforme Feldtheorien höchstens insechs Dimensionen existieren können. Die vorliegende Arbeit erkundet die Effekte von Kompaktifizierungen auf solchen Orbifaltigkeiten aufbauend auf der Arbeit von [arXiv:1905.00116v1 [hep-th]]. Sie stellt einen wichtigen Schritt dar auf dem Weg zu einer Ausweitung der geometrischen Klassifikation dieser Orbifaltigkeiten zu einer Klassifikation der physikalischen Modelle. Über [arXiv:1905.00116v1 [hep-th]] hinaus resultieren Roto-Translationen in Effekten auf die Feldtheorie sowie deren Spektrum. Diese Effekte werden in dieser Thesis diskutiert. Beispiele reichen von getwisteten affinen Faltungen von Eichgruppen, zu dem Auftreten von superkonformen Punkten ohne sich schneidende Branen und superkonforme Sektoren in Verbindung mit dem "mehrfach Faser"-Phänomen. / <p>This thesis was conducted under the regulations of Heidelberg University under the joint supervision of Professor Luca Amendola (University of Heidelberg) and Assistant Professor Magdalena Larfors (Uppsala University) during a one-year ERASMUS-exchange.</p>

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This work is included in a broader research of the hadron theory group of Uppsala University and its collaborators tackling the quest for an understanding of the quark distribution inside hadrons by joining threedifferent approaches of QCD namely chiral perturbation theory, dispersion theory and lattice QCD. This thesis contributes by computing in chiral perturbation theory, the quark-masses dependence of form factors. The next-to-next-to-Leading order (NNLO) contribution to the form factors is calculated from one-loop diagrams which brings hadron-masses dependences. The hadron masses are themselves dependent on quark masses. Consequently, the quark-mass dependence of the hadron masses is also addressed in this thesis.The studied process Ω− → W−Ξ0 possesses too many one-loop diagrams to be treated entirely here. This work focuses on the axial-vector sector and more specifically the part coming from the diagrams linear in the low-energy constant hA (see figure 2).To do so, Mathematica and specifically the packages FeynCalc, FeynHelpers and Package X are used. Vector transition form factors at NNLO are presented in the thesis of my colleague Magnus Bertilsson.The present thesis demonstrates that the calculational framework is feasible and paves the way for a complete NNLO calculation.