Дисертації з теми "Physics"

This study describes a detailed investigation of quantifying key micro-structural parameters of the unconsolidated granular media and their relationship with the grain shape factors calculated from micro-CT images. These parameters are combined with the contact based effective medium models to calculate the elastic properties of the constituent grains after utilising stress dependent ultrasonic velocities of the samples. Thus developed techniques produce good results for mono-mineral quartz sands and one of the poly-mineral rock powder.

La recherche indirecte des effets de la physique au-delà du Modèle Standard à travers les processus de la saveur est complémentaire aux efforts au LHC pour observer directement la nouvelle physique. Dans cette thèse nous discutons plusieurs scénarios au-delà du Modèle Standard (a) en utilisant une approche basée sur les théories de champs effective et (b) en considérant des extensions explicites du Modèle Standard, à savoir les modèles à deux doublets de Higgs et les scénarios postulant l'existence des bosons leptoquarks scalaires à basse énergie. En particulier, nous discutons le phénomène de la brisure de l'universalité des couplages leptoniques dans les désintégrations basées sur les transitions b → sℓℓ et b → cτν, et la possibilité de chercher les signatures de la violation de la saveur leptonique à travers les modes de désintégration similaires. Une proposition pour tester la présence d'un boson pseudoscalaire léger à travers les désintégrations des quarkonia est aussi présentée
Indirect searches of physics beyond the Standard Model through flavor physics processes at low energies are complementary to the ongoing efforts at the LHC to observe the New Physic phenomena directly. In this thesis we discuss several scenarios of physics beyond the Standard Model by (a) reusing the effective field theory approach and (b) by considering explicit extensions of the Standard Model, namely the two-Higgs doublet models and the scenarios involving the low energy scalar leptoquark states. Particular emphasis is devoted to the issue of the lepton flavor universality violation in the exclusive decays based on b → sℓℓ and b → cτν, and to the possibility of searching for signs of lepton flavor violation through similar decay modes. A proposal for testing the presence of the light CP-odd Higgs through quarkonia decays is also made

The purpose of this study was to investigate four in-service physics teachers&rsquo
beliefs related to Turkish High School Physics Curriculum (THSPC) and to what extent these beliefs are reflected in their instructional practices. Data were collected through interviews, classroom observations and an open-ended questionnaire. Teachers&rsquo
responses to interview questions showed that they believed that teaching physics according to the THSPC helped students use their skills, become interested in physics lessons, relate physics to their daily life and have a permanent knowledge. Besides, teachers believe that they can teach physics according to the THSPC generally by giving examples from daily life and creating a discussion environment. The data obtained from classroom observations showed that the beliefs of teachers about how to teach physics according to the THSPC were reflected in their instructional practices. Teachers&rsquo
responses to open-ended questionnaire showed that teachers believed the necessity of attainment of majority of the skill objectives in the THSPC by students. However, they do not consider that students can attain many of the problem solving and information and communication skills. The data obtained from classroom observations showed that they seldom attempted to help students attain them or they never attempted. The data gathered from interviews and an open questionnaire showed that there were some factors that influence teachers&rsquo
instructional practices according to the THSPC. For example, they believe that students&rsquo
interest in physics lessons and teacher&rsquo
s opportunity to give more examples about daily life made their teaching physics according to the THSPC easy. However, they believe that university entrance exam, inadequacy of laboratory environment and lesson hours, students&rsquo
low economic status and lack of information and communication technologies affected their teaching physics according to the THSPC negatively.

This work is a revised edition of the former article "Evolution and Mutation Physics” by the same author. Some unclear formulations have been eliminated. New ideas and new calculations have been included, especially the important connection between successive entropy - changes and increasing DNA –length at slowly decreasing temperature-decrease of surroundings.

I introduce and define Quantum Chromodynamics. I describe various well-known nonperturbative techniques for calculating quantities from the theory and discuss their merits and deficiencies. I then motivate and define a non-relativistic formulation (NRQCD) of the theory. I discuss the mechanics of the extraction of numbers from numerical simulations, and present general arguments as to the expected form of these data. I present results and details of their extraction from simulations of heavy-heavy and heavy-light mesons using NRQCD. I compare these results with those from other calculations and with experimental data, where they exist. I make suggestions for further work. An appendix contains details of the code used in the simulation together with the input parameters of the simulation.

In a process called 'base rivalry', irreparable mutations are provoked in the replication of monotonous sequences, which depend on the cell temperature, the cell viscosity and monotonous sequence length. This explains the very long monotonous sequences and very long DNAs that occur over long evolutionary epochs. Presumably, base rivalry (with tautomerism or too low cell viscosity) also provokes the formation of tumors and the emergence of dangerous viral mutations.

In a previous publication [1] the author described the base rivalry in monotonous DNA sequences and their effect on the DNA repair mechanism. As described in the article, during the monotonous sequence replication, energies appear theoretically to increase with a progressive replication fork up to the quantum mechanical energy level n=2 because of the base rivalry, and these rivalry energies affect the bond strength between the complementary bases. If there is a tautomeric base pair in the replication position where the rivalry energy is large enough, then in this position an irreparable mutation will occur, since the DNA repair mechanism cannot repair that error because too much binding energy. Thus a mutation (caused by base rivalry) can occur only on condition that a transition of a base pair into its tautomeric form is happened. It is remarkable that this transition likewise can occur by the effect of base rivalry energy. The base rivalry - energy which has an effect on a normal base pair provokes a tunnel process in its hydrogen bond, and produces the tautomeric form. After whose replication a different, irreparable base pair develops from the tautomeric base pair, when the rivalry - energy leads into a very strong hydrogen bond. This happens, however, by chance and in the following we will compute the probabilities of such accidental events. The result of these calculations is the equation (32) which could be useful for the theory of evolution and besides for clearing up of virus mutations. It is remarkable that follows from these calculations that the length of DNA increases itself in the course of evolution (section 7).

We use non-adiabatic ab initio molecular dynamics to study the influence of substituent side groups on the photoactive unit (Z)-hexa-1,3,5-triene (HT). The Time-Dependent Density Functional Theory Surface Hopping method (TDDFT-SH) is used to investigate the influence of substituted isopropyl and methyl groups on the excited state dynamics. The 1,4 and 2,5-substituted molecules are simulated: 2,5-dimethylhexa-1,3,5-triene (DMHT), 2-isopropyl-5-methyl-1,3,5-hexatriene (2,5-IMHT), 3,7-dimethylocta-1,3,5-triene (1,4-IMHT), and 2,5-diisopropyl-1,3,5-hexatriene (DIHT). We find that HT and 1,4-IMHT have the lowest ring-closing branching ratios of 5.3% and 1.0%, respectively. For the 2,5-substituted derivatives, the branching ratio increases with increasing size of the substituents, exhibiting yields of 9.78%, 19%, and 24% for DMHT, 2,5-IMHT, and DIHT, respectively. The reaction channels are shown to prefer certain conformation configurations at excitation, where the ring-closing reaction tends to originate from the gauche-Z-gauche (gZg) rotamer almost exclusively. In addition, there is a conformational dependency on absorption, gZg conformers have on average lower S₁ ← S₀ excitation energies that the other rotamers. Furthermore, we develop a method to calculate a predicted quantum yield that is in agreement with the wavelength-dependence observed in experiment for DMHT. In addition, the quantum yield method also predicts DIHT to have the highest CHD yield of 0.176 at 254 nm and 0.390 at 290 nm.

Additionally, we study the vitamin D derivative Tachysterol (Tachy) which exhibits similar photochemical properties as HT and its derivatives. We find the reaction channels of Tachy also have a conformation dependency, where the reactive products toxisterol-D1 (2.3%), previtamin D (1.4%) and cyclobutene toxisterol (0.7%) prefer cEc, cEt, and tEc configurations at excitation, leaving the tEt completely non-reactive. The rotamers similarly have a dependence on absorption as well, where the cEc configuration has the lowest energy S ₁ ← S₀ excitation of the rotamers. The wavelength dependence of the rotamers should lead to selective properties of these molecules at excitation. An excitation to the red-shifted side of the maximum absorption peak will on average lead to excitations of the gZg rotamers more exclusively.

Physics education is facing a crisis of meaning: students can “plug” numbers into formulas, but research shows they do not give much meaning to physical concepts. This thesis explores how the cultural context of physics education, in particular the mind/body cartesian split, contributes to a loss of meaning. Drawing from sensory scholarship, cognitive linguistics, feminist critiques of science, her own teaching experience and education research on student misconceptions and intuitive knowledge, the author challenges the mind/body dichotomy by exploring how the body can make sense of the physical world through the senses. Physical concepts can be more-than-representational, exist beyond mathematical symbols and signifiers, but nevertheless be perceived through touch. In her quest for a mind/body truce, the author has created provocative stories for the physics classroom that welcome the body and its physic-al knowledge, and that reconcile intuition and Newtonian physics. This subtle change of perspective leads her to replace the alleged mind/body war with a respectful quest for compromise and fine tuning, and to analyze the dominant patriarchal narratives of the physics community. The author advocates for an intuition-based, sensory, student-centred pedagogy that redefines traditional power relationships in the physics classroom and challenges indoctrinating scientific discourses, hoping it will contribute to improving the inclusiveness of the physics community. Such a paradigm shift requires a re-storying of collective narratives. Physics is not about dominating nature but about learning from nature; it is time to abandon the myth of the detached observer and study nature from inside, at the confluence of everything that make us humans.

This thesis is in two parts: Part 1 is a collection of 39 poems which use a range of visual and digital techniques to explore, express and explain key concepts in contemporary physics. The poems are presented in three major sections, devoted (respectively) to themes of light, probability & uncertainty, and university. Part 2 is the commentary, comprising four chapters: the first is a strategic overview of the relationship between poetry and science, focusing on major indicative instances and moments, concerning Lucretius, Pope, Blake, Keats, MacDiarmid, and Morgan, and then moving on to consider a series of explorations of how physical principles bear striking similarities to the mechanics of digital poetics. The remaining three chapters address in turn the scientific issues which form the subject matter of each of the three sections of poetry, as well as providing poem-specific commentary and procedural analysis for each one, arranged as follows: Chapter 2 discusses poems 1-13 inclusive, Chapter 3 poems 14-28 inclusive, and Chapter 4 poems 29-39 inclusive. Within each of these chapters, further thematic sub-divisions of the three major themes are employed, as indicated in the list of contents. In the procedures, imagery, metaphors, and motifs they employ, the poems draw upon and develop some of those used in a range of prose works written by scientists and science writers to explain and elucidate the complex theories and concepts of contemporary physics to a lay audience. The poems are intended to work cumulatively in combination with each other, and also in juxtaposition with the poem-specific commentaries and the broader explicatory parts of the commentary to explore the scientific concepts and familiarise readers with them.

We look at models of neutrino mass and mixing which represent an important aspect of physics beyond the Standard Model (SM). We derive approximate analytic formulae for the neutrino mixing angles in general SD involving NLO and NNLO corrections. These expressions, which are given in terms of input see-saw parameters, provide a useful guide for unified model building. We then evaluate these formulae in the cases of CSD and PCSD for two numerical GUT inspired models in order to measure the effect of NLO and NNLO corrections. In addition to this, we analyse the effects of charged lepton corrections and Renormalisation Group (RG) running on neutrino mixing angles and various sum rules, in models where tri-bimaximal mixing is exactly achieved at high energy scale. We find the RG corrections to neutrino sum rules to be typically small for the case of hierarchical neutrinos. Another aspect of physics beyond the Standard Model concerns the search for viable four dimensional string models. We look at moduli stabilisation in the framework of four dimensional models arising from heterotic and type IIA string theories. The superpotentials in these models involve ux and non-perturbative terms. We consider a set of conditions which lead to moduli solutions for Minkowski minima of the scalar potential. Following this procedure, we correct models presented in the literature and uplift the at directions. We also study inflation in the framework of these models. We find that it is successfully achieved along the axionic directions of the moduli fields for values of the initial conditions within substantial regions of parameter space. A very interesting structure of the potential is obtained when considering the evolution of two axionic directions in one of the models in the presence of a gaugino condensate term. This structure, which involves the existence of multiple local minima surrounding the global one, represents a perfect background for realising in ation.

La presente dissertazione descrive il design, la caratterizzazione e il funzionamento di sistemi elettronici per esperimenti di Fisica delle particelle (LHCb) e Fisica del neutrino (CUORE e CUPID). A partire dal 2019, l'esperimento LHCb presso l'acceleratore LHC sarà aggiornato per lavorare a luminosità più elevata e molti dei suoi rivelatori dovranno essere riprogettati. Il rivelatore RICH, in particolare, dovrà adottare un sistema optoelettronico totalmente nuovo. Lo sviluppo di questo sistema ha già raggiunto una fase avanzata e diversi test eseguiti su fascio hanno permesso di verificare le prestazioni dell'intero sistema. Per migliorare la stabilità, il filtraggio e la regolazione delle tensioni di alimentazione del circuito di front-end, è stato sviluppato un regolatore lineare a basso dropout e resistente alla radiazione, denominato ALDO. Sono qui presentate le strategie di progetto, la misurazione delle prestazioni e i risultati delle campagne di irraggiamento di questo dispositivo. Nel campo della fisica del neutrino, grandi array di macrobolometri, come quelli adottati dall'esperimento CUORE e dal suo futuro aggiornamento CUPID, offrono delle caratteristiche uniche per lo studio del doppio decadimento beta senza neutrini. Il loro funzionamento richiede particolari strategie progettuali nel sistema elettronico di lettura, che è qui descritto nella sua interezza. Sono anche presentate nel dettaglio le misure di qualifica e ottimizzazione dei parametri di funzionamento di tutto il sistema, oltre che l'integrazione all'interno dell'area sperimentale. Infine sono presentati gli aggiornamenti di alcuni sottosistemi elettronici in vista della fase finale di CUPID.
The present dissertation describes design, qualification and operation of several electronic instrumentations for High Energy Particle Physics experiments (LHCb) and Neutrino Physics experiments (CUORE and CUPID). Starting from 2019, the LHCb experiment at the LHC accelerator will be upgraded to operate at higher luminosity and several of its detectors will be redesigned. The RICH detector will require a completely new optoelectronic readout system. The development of such system has already reached an advanced phase, and several tests at particle beam facilities allowed to qualify the performance of the entire system. In order to achieve a higher stability and a better power supply regulation for the front-end chip, a rad-hard low dropout linear regulator, named ALDO, has been developed. Design strategies, performance tests and results from the irradiation campaign are presented. In the Neutrino Physics field, large-scale bolometric detectors, like those adopted by CUORE and its future upgrade CUPID, offer unique opportunities for the study of neutrinoless double beta decay. Their operation requires particular strategies in the readout instrumentation, which is described here in its entirety. The qualification and optimization of the working parameters as well as the integration of the system in the experimental area are also thoroughly discussed, together with the latest upgrades of two electronic subsystems for the future CUPID experiment.

This is a masters thesis (20p) in computer science at the University of Linköping. This thesis will give an introduction to what a physics engine is and what it consist of. It will put some engines under the magnifying glass and test them in a couple of runtime tests. Two cutting edge commercial physics engines have been examined, trying to predict the future of physics engines. From the research and test results, an interface for physics engine independency has been implemented for a company called Craft Animations in Gothenburg, Sweden.

This investigation utilized collaborative strategies to look at how a more social approach to teaching physics curriculum would affect students' interest, knowledge and self-efficacy towards the science of physics. Students went on field trips to meet physicists and worked together in the regular classroom on physics concept questions through Interactive Engagement teaching methods called the 'Collaborative Group Concept Conflict Process' and 'Physics by Inquiry'. The Force Concept Inventory was used as a formative and summative assessment tool and student percentiles ranked at the top of existing data that utilizes Normalized Gain as a formula for summative assessment. It was found that students gained curricular knowledge, interest and self-efficacy towards the field of physics.

We study the small-z limit of the structure functions for deep inelastic scattering in Quantum Chromodynamics. The standard approach to this process, based on the DGLAP equations, runs into difficulties in the small-x region due to the higher order corrections becoming large. As an attempt to overcome these obstacles we reinterpret the small-z limit in terms of high energy asymptotics. The relevant high energy formalism is developed in terms of Reggeon Field Theory, which leads to the BFKL equation for the scattering amplitude. These results are reviewed fully, for completeness. We then apply the resulting formalism to structure functions at small-z to determine the phenomenological implications of this high energy resummation. The DESY electron-proton collider HERA is presently exploring the region of the structure functions for x ≤ 10(^-3), Q(^2) ~ 10 GeV(^2) and the results of these experiments are compared with our theoretical analysis. The structure functions are a very inclusive measurement; so in order to try and focus on some cleaner indication of the BFKL behaviour we then turn to an analysis of dijet production in deep inelastic scattering. The results of the BFKL formalism are compared with standard analysis in terms of the DGLAP equations.

Two assumptions pervade contemporary metaphysics: that there is a fundamental level to reality, and that physics will one day describe it. In the first part of this thesis, I consider whether physics may have a greater role for fundamentality metaphysics than that which it is typically accorded. In particular, I consider whether physics might contribute not just to questions of the content of an assumed fundamental level, but to the existence of such a level itself. I argue that if we are to use physics to do such a thing, it must be through what I call the 'internal' approach, in which fundamentality questions are addressed through the lens of extant physical theory. Through two case studies drawn from particle physics, I show that it is indeed possible to deny fundamentality through this means - or at least, that one may do so as legitimately as one may make other propositions of physicalistic metaphysics. While this is a non-trivial achievement, the internal approach nevertheless imposes a profound limitation on the sort of fundamentality that we can use physics to deny, in that it precludes the denial of fundamental physical principles. This raises the question of whether such principles ought to be regarded as somehow more fundamental even than particles. I argue that this question is naturally construed as the question of whether we ought to regard the category of dynamical structures as more ontologically fundamental than the category of objects. The claim that structure is ontologically prior to objects is the signature claim of ontic structuralism, and in the second part of this thesis I consider whether it can be defended. I ultimately argue that structuralism can indeed be supported, but that it is only its moderate version that is vindicated.

The basic building blocks of all biomembranes are lipid molecules, which self-assemble to form a very thin and stable barrier, where a variety of proteins can be incorporated into its structure. These two-dimensional systems exhibit a plethora of physical phenomena, which are an abundant source of inspiration for a physicist. The physical aspects of biomembranes are described within a phenomenological model, the so-called Canhan{Helfrich theory, which relies primarily on the geometrical aspects of the membrane surface at large scales. Using this theory, we study the response of a membrane to the inclusion of a transmembrane protein or a protein coat by coupling the composition to the mean curvature. A transition is found from an overdamped to an underdamped regime for the membrane shape and its compositional variation. This leads to large membrane undulations near the inclusion, resulting in the activity suppression of mechanosensitive channels and a preference for the formation of protein coats. We also re-examine the methodology for inferring the bending modulus of membranes from their observed thermal fluctuations. Particularly, we analyse the effect due to the optical projection of such shape undulations across the focal depth of the microscope. A comparison of this with the literature approaches reveals a systematic decrease in the value of the bending modulus, resolving a previously recognised discrepancy between shape measurements and other known techniques. Lastly, we investigate an non-equilibrium model for the formation of membrane domains that also involves membrane recycling. The dynamics and the steady-state features of the domain size distribution are analytically revealed and the implication to the heterogeneity observed in biomembranes is discussed.

Quantum Monte Carlo techniques stochastically evaluate integrals to solve the many-body Schrödinger equation. QMC algorithms scale favorably in the number of particles simulated and enjoy applicability to a wide range of quantum systems. Advances in the core algorithms of the method and their implementations paired with the steady development of computational assets have carried the applicability of QMC beyond analytically treatable systems, such as the Homogeneous Electron Gas, and have extended QMC’s domain to treat atoms, molecules, and solids containing as many as several hundred electrons.

FN-DMC projects out the ground state of a wave function subject to constraints imposed by our ansatz to the problem. The constraints imposed by the fixed-node Approximation are poorly understood. One key step in developing any scientific theory or method is to qualify where the theory is inaccurate and to quantify how erroneous it is under these circumstances.

I investigate the fixed-node errors as they evolve over changing charge density, system size, and effective core potentials. I begin by studying a simple system for which the nodes of the trial wave function can be solved almost exactly. By comparing two trial wave functions, a single determinant wave function flawed in a known way and a nearly exact wave function, I show that the fixed-node error increases when the charge density is increased. Next, I investigate a sequence of Lithium systems increasing in size from a single atom, to small molecules, up to the bulk metal form. Over these systems, FN-DMC calculations consistently recover 95% or more of the correlation energy of the system. Given this accuracy, I make a prediction for the binding energy of Li₄ molecule. Last, I turn to analyzing the fixed-node error in first and second row atoms and their molecules. With the appropriate pseudo-potentials, these systems are iso-electronic, show similar geometries and states. One would expect with identical number of particles involved in the calculation, errors in the respective total energies of the two iso-electronic species would be quite similar. I observe, instead, that the first row atoms and their molecules have errors larger by twice or more in size. I identify a cause for this difference in iso-electronic species. The fixed-node errors in all of these cases are calculated by careful comparison to experimental results, showing that FN-DMC to be a robust tool for understanding quantum systems and also a method for new investigations into the nature of many-body effects.

The Baranger model is used to compute collisional broadening and shift of the D1 and D2 spectral lines of M + Ng, where M = K, Rb, Cs and Ng = He, Ne, Ar, using scattering phase shift differences which are calculated from scattering matrix elements. Scattering matrix elements are calculated using the Channel Packet Method where the collisions are treated non-adiabatically and include spin-orbit and Coriolis couplings. Non-adiabatic wavepacket dynamics are determined using the split-operator method together with a unitary transformation between adiabatic and diabatic representations. Scattering phase shift differences are thermally weighted and integrated over energies ranging from E = 0 Hartree up to E = 0.0075 Hartree and averaged over values of total angular momentum that range from J = 0.5 up to J = 400.5. Phase shifts are extrapolated linearly to provide an approximate extension of the energy regime up to E = 0.012 Hartree. Broadening and shift coefficients are obtained for temperatures ranging from T = 100 K up to T = 800 K and compared with experiment. Predictions from this research find application in laser physics and specifically with improvement of total power output of Optically Pumped Alkali Laser systems.

The generalized local-spin-density functional (G-LSD) theory is proposed which avoids (a) the physical restriction used in the generalized exchange local-spin-density functional (GX-LSD) theory; (b) the homogeneous electron-density approximation in the Hartree-Fock-Slater (HFS) theory and in the Gaspar-Kohn-Sham (GKS) theory; and (c) the time-consuming step to search the optimal exchange parameter for each atom or ion in the X$ alpha$ and $ Xi$a theories. Theoretically, the G-LSD theory is more rigorous than the GX-LSD, HFS, GKS, and $ Xi$a theories. Numerically, the statistical total energies for atoms are better in the G-LSD theory than in the GKS theory.
Ionization potentials and electron affinities of atoms, the stability of singly and doubly charged negative ions, and the electronegativities, and hardnesses of the fractional charged atoms with Z $<$ 37 are calculated by the SIC-GX-LSD theory with the GWB Fermi-hole parameters and electron-correlation correction.
The self-interaction correction (SIC) is introduced into the multiple-Scattering X$ alpha$ (MS-X$ alpha$) method and used to calculate some molecules and molecular anions. The results show that the ionization potentials from the negative of the one-electron eigenvalues are as good as those obtained in the transition state calculation and in very good agreement with experiment.

Superconducting radio frequency (SRF) technology is widely adopted in particle accelerators. The shallow penetration (∼ 40 nm) of the RF into superconducting niobium lends great importance to SRF cavity interior surface chemistry and topography. These in turn are strongly influenced by the chemical etching "surface clean-up" that follows fabrication.;The principal surface smoothing methods are buffered chemical polish (BCP) and electropolish (EP). The resulting topography is characterized by atomic force microscopy (AFM). The power spectral density (PSD) of AFM data provides a more thorough description of the topography than a single-value roughness measurement. In this work, one dimensional average PSD functions derived from topography of BCP and EP with different controlled starting conditions and durations have been fitted with a combination of power law, K-correlation, and shifted Gaussian models to extract characteristic parameters at different spatial harmonic scales. While the simplest characterizations of these data are not new, the systematic tracking of scale-specific roughness as a function of processing is new and offers feedback for tighter process prescriptions more knowledgably targeted at beneficial niobium topography for SRF applications.;Process development suffers because the cavity interior surface cannot be viewed directly without cutting out pieces, rendering the cavities unavailable for further study. Here we explore replica techniques as an alternative, providing imprints of cavity internal surface that can be readily examined. A second matter is the topography measurement technique used. Atomic force microscopy (AFM) has proven successful, but too time intensive for routine use. We therefore introduce white light interferometry (WLI) approach as an alternative. We examined real surfaces and their replicas, using AFM and WLI. We find that the replica/WLI is promising to provide the large majority of desired information, so that use of the time-intensive AFM approach can be limited to where it is genuinely necessary.;The prevalent idea is that sharp features could lead to magnetic quench or enhance the thermal quench. In this report, a calculation on magnetic field is numerically given on fine structure by finite element and conformal mapping methods. Corresponding RF Ohmic loss will be simulated. A certain thermal tolerant will be calculated. A Q∼E curve will be predicted from this model.;A perturbation model is utilized to calculate rough surface additional RF loss based on PSD statistical analysis. This model will not consider that superconductor will become iormal at field higher than transition field. Therefore, it is only expected to explain midfield Q performance. One can calculate the RF power dissipation ratio between rough surface and ideal smooth surface within this field range. Additionally, the resistivity of Nb is temperature and magnetic field dependent from classic thermal feedback model theory. Combining with topographic PSD analysis and Rs temperature and field ependency, a middle field Q slope model could be modeled and the contribution from topography can be simulated.

Fa més d'un segle els físics de tot el món desenvolupaven una teoria per descriure comportaments estranys recentment descobertes d'alguns sistemes físics, això marca el naixement de la Teoria Quàntica. Algunes dècades més tard, la idea revolucionària de separar la informació de la seva companyia física va conduir a l'establiment de la Teoria de la Informació. Aquests al principi es van unir les teories independents en les últimes dècades del segle anterior deixant-nos de Teoria de la Informació Quàntica. Aquesta tesi explorarà una intersecció entre matemàtiques, física i informàtica, tractant d'aclarir l'entrellaçat de l'anterior. Tot seguit, es van establir els resultats que es van establir durant els anys d'estudis que van dur a aquest treball. La pregunta plantejada en el títol no es respondrà plenament ja que pot ser massa aviat per donar una resposta definitiva a aquesta àmplia pregunta.
Hace más de un siglo, los físicos de todo el mundo estaban desarrollando una teoría para describir comportamientos extraños recientemente descubiertos de algunos sistemas físicos, lo que marca el nacimiento de la teoría cuántica. Algunas décadas más tarde, la idea innovadora de separar la información de su portador físico llevó al establecimiento de la teoría de la información. Estas teorías independientes al principio se fusionaron en las últimas décadas del siglo anterior, dando lugar a la teoría de la información cuántica. Esta tesis explorará temas en la intersección entre matemáticas, física y ciencias de la computación, tratando de dilucidar la interconexión entre las tres. Dicha exploración se llevará a cabo junto con la presentación de los resultados obtenidos durante estos años de estudio. La pregunta planteada en el título no será respondida completamente, ya que puede ser demasiado pronto para dar una respuesta definitiva a esta amplia pregunta.
More than a century ago, physicists around the world were collectively developing a theory to describe the newly discovered strange behaviours of some physical systems. This marks the birth of quantum theory. Few decades later, the groundbreaking idea to separate information from its physical carrier led to the establishment of information theory. These, initially independent theories, merged together in the last decades of the former century, leaving us with quantum information theory. This thesis will explore topics at the intersection of mathematics, physics and computer science, trying to elucidate the interwovenness of these three disciplines. While doing so, the results that were established during the years of studies leading up to this work are introduced. The question posed in the title will not be answered fully, as it may be too early still to give a definite answer to this multifaceted question.

Research at the intersection of machine learning (ML) and quantum physics is a recent growing field due to the enormous expectations and the success of both fields. ML is arguably one of the most promising technologies that has and will continue to disrupt many aspects of our lives. The way we do research is almost certainly no exception and ML, with its unprecedented ability to find hidden patterns in data, will be assisting future scientific discoveries. Quantum physics on the other side, even though it is sometimes not entirely intuitive, is one of the most successful physical theories and we are on the verge of adopting some quantum technologies in our daily life. Quantum many-body physics is a subfield of quantum physics where we study the collective behavior of particles or atoms and the emergence of phenomena that are due to this collective behavior, such as phases of matter. The study of phase transitions of these systems often requires some intuition of how we can quantify the order parameter of a phase. ML algorithms can imitate something similar to intuition by inferring knowledge from example data. They can, therefore, discover patterns that are invisible to the human eye, which makes them excellent candidates to study phase transitions. At the same time, quantum devices are known to be able to perform some computational task exponentially faster than classical computers and they are able to produce data patterns that are hard to simulate on classical computers. Therefore, there is the hope that ML algorithms run on quantum devices show an advantage over their classical analog. This thesis is devoted to study two different paths along the front lines of ML and quantum physics. On one side, we study the use of neural networks (NN) to classify phases of mater in many-body quantum systems. On the other side, we study ML algorithms that run on quantum computers. The connection between ML for quantum physics and quantum physics for ML in this thesis is an emerging subfield in ML, the interpretability of learning algorithms. A crucial ingredient in the study of phase transitions with NNs is a better understanding of the predictions of the NN, to eventually infer a model of the quantum system and interpretability can assist us in this endeavor. The interpretability method that we study analyzes the influence of the training points on a test prediction and it depends on the curvature of the NN loss landscape. This further inspired an in-depth study of the loss of quantum machine learning (QML) applications which we as well will discuss. In this thesis, we give answers to the questions of how we can leverage NNs to classify phases of matter and we use a method that allows to do domain adaptation to transfer the learned "intuition" from systems without noise onto systems with noise. To map the phase diagram of quantum many-body systems in a fully unsupervised manner, we study a method known from anomaly detection that allows us to reduce the human input to a mini mum. We will as well use interpretability methods to study NNs that are trained to distinguish phases of matter to understand if the NNs are learning something similar to an order parameter and if their way of learning can be made more accessible to humans. And finally, inspired by the interpretability of classical NNs, we develop tools to study the loss landscapes of variational quantum circuits to identify possible differences between classical and quantum ML algorithms that might be leveraged for a quantum advantage.
La investigación en la intersección del aprendizaje automático (machine learning, ML) y la física cuántica es una área en crecimiento reciente debido al éxito y las enormes expectativas de ambas áreas. ML es posiblemente una de las tecnologías más prometedoras que ha alterado y seguirá alterando muchos aspectos de nuestras vidas. Es casi seguro que la forma en que investigamos no es una excepción y el ML, con su capacidad sin precedentes para encontrar patrones ocultos en los datos ayudará a futuros descubrimientos científicos. La física cuántica, por otro lado, aunque a veces no es del todo intuitiva, es una de las teorías físicas más exitosas, y además estamos a punto de adoptar algunas tecnologías cuánticas en nuestra vida diaria. La física cuántica de los muchos cuerpos (many-body) es una subárea de la física cuántica donde estudiamos el comportamiento colectivo de partículas o átomos y la aparición de fenómenos que se deben a este comportamiento colectivo, como las fases de la materia. El estudio de las transiciones de fase de estos sistemas a menudo requiere cierta intuición de cómo podemos cuantificar el parámetro de orden de una fase. Los algoritmos de ML pueden imitar algo similar a la intuición al inferir conocimientos a partir de datos de ejemplo. Por lo tanto, pueden descubrir patrones que son invisibles para el ojo humano, lo que los convierte en excelentes candidatos para estudiar las transiciones de fase. Al mismo tiempo, se sabe que los dispositivos cuánticos pueden realizar algunas tareas computacionales exponencialmente más rápido que los ordenadores clásicos y pueden producir patrones de datos que son difíciles de simular en los ordenadores clásicos. Por lo tanto, existe la esperanza de que los algoritmos ML que se ejecutan en dispositivos cuánticos muestren una ventaja sobre su analógico clásico. Estudiamos dos caminos diferentes a lo largo de la vanguardia del ML y la física cuántica. Por un lado, estudiamos el uso de redes neuronales (neural network, NN) para clasificar las fases de la materia en sistemas cuánticos de muchos cuerpos. Por otro lado, estudiamos los algoritmos ML que se ejecutan en ordenadores cuánticos. La conexión entre ML para la física cuántica y la física cuántica para ML en esta tesis es un subárea emergente en ML: la interpretabilidad de los algoritmos de aprendizaje. Un ingrediente crucial en el estudio de las transiciones de fase con NN es una mejor comprensión de las predicciones de la NN, para inferir un modelo del sistema cuántico. Así pues, la interpretabilidad de la NN puede ayudarnos en este esfuerzo. El estudio de la interpretabilitad inspiró además un estudio en profundidad de la pérdida de aplicaciones de aprendizaje automático cuántico (quantum machine learning, QML) que también discutiremos. En esta tesis damos respuesta a las preguntas de cómo podemos aprovechar las NN para clasificar las fases de la materia y utilizamos un método que permite hacer una adaptación de dominio para transferir la "intuición" aprendida de sistemas sin ruido a sistemas con ruido. Para mapear el diagrama de fase de los sistemas cuánticos de muchos cuerpos de una manera totalmente no supervisada, estudiamos un método conocido de detección de anomalías que nos permite reducir la entrada humana al mínimo. También usaremos métodos de interpretabilidad para estudiar las NN que están entrenadas para distinguir fases de la materia para comprender si las NN están aprendiendo algo similar a un parámetro de orden y si su forma de aprendizaje puede ser más accesible para los humanos. Y finalmente, inspirados por la interpretabilidad de las NN clásicas, desarrollamos herramientas para estudiar los paisajes de pérdida de los circuitos cuánticos variacionales para identificar posibles diferencias entre los algoritmos ML clásicos y cuánticos que podrían aprovecharse para obtener una ventaja cuántica.

Motivated by reductionism's current inability to encompass the quantum theory we explore an indivisible and dynamical wholeness as an underlying foundation for physics. After reviewing the role of wholeness in the quantum theory we set a philosophical background aiming at introducing an ontology, based on a dynamical wholeness. Equipped with the philosophical background we then propose a mathematical realization by representing the dynamics with a non-trivial elementary embedding from the mathematical universe to itself. By letting the embedding interact with itself through application we obtain a left-distributive universal algebra that is isomorphic to special braids. Via the connection between braids and quantum and statistical physics we show that a the mathematical structure obtained from wholeness yields known physics in a special case. In particular we point out the connections to algebras of observables, spin networks, and statistical mechanical models used in solid state physics, such as the Potts model. Furthermore we discuss the general case and there the possibility of interpreting the mathematical structure as a dynamics beyond unitary evolution, where entropy increase is involved.

The ATLAS experiment is used to observe the √s=7 TeV proton-proton collisions produced by the LHC at CERN. This gives an unprecedented opportunity to search for physics beyond the Standard Model at hitherto unexplored kinematic regimes. Supersymmetry (SUSY) provides interesting solutions to a variety of theoretical problems that may be encountered in the Standard Model at high energy scales, while providing signatures that may be observed at the LHC. However, in order to produce a search that is sensitive to SUSY it is vital to understand how the physics that has been discovered to date may produce signatures that mimic those expected from SUSY. Statistical models are constructed using both Monte Carlo and data-driven predictions of various background processes. The expectations are compared to the observed data for selections containing one electron or muon, each in association with jets and missing transverse momentum. Kinematic variable shapes, in the form of histograms, are used to enhance the sensitivity of the search. Squark and gluino masses in a MSUGRA SUSY model are excluded up to 1200 GeV, while gluino masses up to 900 GeV are excluded in a simplified SUSY model. Model-independent limits are also set, excluding theoretical models with efficiency times cross section above 1 fb.

This study examined traditional instruction and problem-based learning (PBL) approaches to teaching and the extent to which they foster the development of desirable cognitive processes, including metacognition, critical thinking, physical intuition, and problem solving among undergraduate physics students. The study also examined students' approaches to learning and their perceived role as physics students. The research took place in the context of advanced courses of electromagnetism at a Canadian research university. The cognitive science, expertise, physics and science education, instructional psychology, and discourse processes literature provided the framework and background to conceptualize and structure this study. A within-stage mixed-model design was used and a number of instruments, including a survey, observation grids, and problem sets were developed specifically for this study. A special one-week long problem-based learning (PBL) intervention was also designed. Interviews with the instructors participating in the study provided complementary data.
Findings include evidence that students in general engage in metacognitive processes in the organization of their personal study time. However, this potential, including the development of other cognitive processes, might not be stimulated as much as it could in the traditional lecture instructional context. The PBL approach was deemed as more empowering for the students. An unexpected finding came from the realisation that a simple exposure to a structured exercise of problem-solving (pre-test) was sufficient to produce superior planning and solving strategies on a second exposure (post-test) even for the students who had not been exposed to any special treatment. Maturation was ruled out as a potential threat to the validity of this finding. Another promising finding appears to be that the problem-based learning (PBL) intervention tends to foster the development of cognitive competencies, particularly physical intuition, even if it was only implemented for a short period of time. Other findings relate to the nature of the cognitive actions and activities that the students engage in when learning to solve electromagnetism problems in a PBL environment for the first time and the tutoring actions that guide students in this context.

Accurate treatment of the long-range electron correlation energy, including dispersion interactions, is essential for describing the structure, dynamics, and function of a wide variety of systems. Among the most accurate models for including dispersion into density functional theory (DFT) is the range-separated many-body dispersion (MBD) method [A. Ambrosetti et al., J. Chem. Phys. 2014, 140, 18A508], in which the long-range correlation energy is computed from a model system of coupled quantum harmonic oscillators. In this work, we seek to extend the applicability of the MBD model by developing the analytical gradients necessary to compute MBD corrections to ionic forces, unit-cell stresses, phonon modes, and self-consistent updates to the Kohn-Sham potential. We include all implicit coordinate dependencies arising from charge density partitioning, as we find that neglecting these terms leads to unacceptably large relative errors in the MBD forces. Such errors would impact the predictive nature of ab initio molecular dynamics simulations employing MBD. We develop a new efficient implementation of the MBD correlation energy and forces within the Quantum ESPRESSO software package and rigorously test its numerical stability and convergence properties for condensed phase simulations. Additionally, we re-parameterize the MBD model for use with a wide variety of generalized gradient approximation exchange-correlation functionals. We demonstrate the efficiency and accuracy of these MBD gradient corrections for optimizations of isolated dispersively bound molecular systems, as well as representative condensed phase systems including adsorbed hydrocarbons, layered materials, and hydrogen-bonded crystals. Where highly accurate reference geometries are available, we find the DFT+MBD method significantly improves the predicted structures of these systems and consistently outperforms popular pairwise-additive DFT-D dispersion corrections. Though significant work remains in the benchmarking and testing of these contributions to the MBD model, we are optimistic that these methodological developments will enable many exciting discoveries of beyond-pairwise dispersive effects in organic materials.
Physics

The ability to conduct in-flight, absolute radiometric calibrations of ocean color sensors will determine their usefulness in the decade to come. On-board calibration systems are often integrated into the overall design of such sensors and have claimed uncertainty levels below 5%. Independent means of system calibration are needed to confirm that the sensor is accurately calibrated. Vicarious (i.e. ground-referencing) methods are an attractive way to conduct this verification. This research describes the development of in-flight, absolute radiometric calibration methods which reference dark (i.e. low-reflectance) sites. The high sensitivity of ocean color sensors results in saturation over bright surfaces. Low-reflectance targets, such as water bodies, are therefore required for their vicarious calibration. Sensitivity analyses of the reflectance-based and radiance-based techniques, when applied to a water target, are performed. Uncertainties in atmospheric parameters, surface reflectance measurements, and instrument characterization are evaluated for calibrations of a representative ocean color sensor. For a viewing geometry near the sun glint region, reflectance-based uncertainties range between 1.6% and 2.3% for visible and near-IR wavelengths; radiance-based uncertainties range between 6.8% and 20.5%. These studies indicate that better characterization of aerosol parameters is desired and that radiometer pointing accuracy must be improved to make the radiance-based method useful. The uncertainty estimates are evaluated using data from a field campaign at Lake Tahoe in June, 1995. This lake is located on the California-Nevada border and has optical characteristics similar to oceanic waters. Aircraft-based radiance data and surface measurements of water reflectance are used to calibrate visible and near infrared bands of the Airborne Visible/InfraRed Imaging Spectrometer (AVIRIS). The vicariously-derived calibration coefficients are compared to those obtained from a preflight calibration of AVIRIS. The results agree at the 0.3-7.7% level for the reflectance-based technique, which is within the believed method uncertainties. Finally, as a consequence of this research, the testing and refinement of radiative transfer codes applicable to oceanic environments is accomplished. These modifications lead to an improvement in the prediction of top-of-atmosphere radiances over water targets.

Frisch grid ionization chambers are commonly used experimental tools for charged particle spectroscopy. In the ideal Frisch grid chamber the anode pulse height is independent of where inside the sensitive volume the charge has been created. This ideal cannot be realized because of imperfect shielding of the anode by the grid. The effect of the imperfect shielding is generally referred to as grid inefficiency. For accurate energy determination the anode pulse height needs to be corrected for this.

At present two opposing explanation for grid inefficiency exist. The first explanation suggests that there is a reduction of the anode pulse height. This is said to arise from positive ions inducing charge on the anode as the electrons are collected. The second explanation suggests that there is a too large anode signal. The addition to the anode signal is said to arise from the drift of electrons.

In this thesis the concept of grid inefficiency is investigated by means of wave form digitization. The use of digital signal processing makes it possible to maintain information on the drift of electrons. This information is lost in charged particle spectroscopy experiments using electronic signal processing networks.

A series of experiments is described in this thesis. The first experiment was performed to find good measuring conditions for the following experiments. For this purpose the drift velocity of electrons was measured in two chamber filling gases, P-10 and CF4. The measured drift velocities are presented for the two gases. Finally, P-10 was chosen as filling gas for the following experiments.

In the second experiment the grid inefficiency was measured for two different types of shielding electrodes. The method of determining the grid inefficiency is based on the analysis of the shape of digitized charge signals. The measured values are shown to be in good agreement with calculated values.

In the final experiment the effects of grid inefficiency on alpha particle spectroscopy is investigated. It is shown how the correction for grid inefficiency by the two existing models yield equivalent results for energy determination. An attempt to separate the two models is also presented indicating that there is in fact a reduction of the anode pulse height because of grid inefficiency. The thesis is concluded with a theoretical discussion of the anode pulse shape. There grid inefficiency is explained by the drift of electrons. It is shown in this section how explaining grid inefficiency by the drift of electrons should yield the same result as explaining it by the effect of positive ions.

Base rivalry arises at replication of monotonous DNA – sequences. Irreparable mutations can arise by tunnel processes if the developed energy is high enough. The tunnel probability depends not only on the base rivalry energy but also depends on the temperature of surroundings. The tunnel probability diminishes with decreasing temperature. The cytoplasm viscosity increases in the long term with decreasing temperature. The length of the monotonous sequence in which happens an irreparable mutation (caused by base rivalry) then will be larger than at higher temperatures. This means that the possible distribution variety of all base components on the given matrix will diminish; therefore the probability increases that one base component which possesses the necessary energy, comes into the certain monotonous sequence to provoke a tunnel process. These different temperature dependences are the subject of the following examinations; they lead to the equation (32) which is valid for coming off of an irreparable mutation which is caused by base rivalry. Because of the dependence between temperature change and mutating sequence length from s1 to s1+1 (expressed in this equation), there result informations about evolution, and informations about mutation of DNA – viruses. The calculations are performed with very small DNA fragments so called residual fragments.

Holonomy in nonrelativistic quantum mechanics is examined in the context of the adiabatic theorem. This theorem is proven for sufficiently regular unbounded hamiltoni-ans. Then, simplifying to matrix hamiltonians, it is proven that the adiabatic theorem defines a connection on vector bundles constructed out of eigenspaces of the hamiltonian. Similar degeneracy regions, the natural base spaces for these bundles, are defined in terms of stratifications for the spaces of complex, hermitian matrices and real, symmetric matrices. The algebraic topology of similar degeneracy regions is studied in detail, and the results are used to classify and calculate all possible adiabatic phases for time-reversal invariant matrix hamiltonians in terms of the relevant topological data. It is shown how vector bundles may be used to impose transversality on the helicity vector of a photon. This is used to give a calculation, which is consistent with transversality, of quantum adiabatic phase for photons in a coiled optical fibre. As an additional application, the importance of quantum adiabatic in the dynamical Jahn-Teller effect is briefly explained. An introduction is given to some important aspects of algebraic topology, which are used herein. Moreover, a number of mathematical results for flag manifolds are obtained. These results are applied to quantum adiabatic holonomy.
Science, Faculty of
Physics and Astronomy, Department of
Graduate

The use and optimisation of integration grid techniques to generate next-to-leading order predictions of jet cross-sections, independent of parton distribution functions, was investigated. Such methods were found to provide an accurate approximation to a standard Monte-Carlo simulation (within 1%) and enable collider data to be readily included in global PDF fitting procedures. However, the benefit of including inclusive-jet cross-section data from ATLAS in global fits is only significant if the jet energy scale (JES) can be constrained to ~1% at high pT. Uncertainties in the theoretical prediction of the inclusive-jet cross-section such as PDFs and fixed-order (scale) uncertainties were studied and compared with experimental errors arising from jet energy resolution and absolute scale. These uncertainties were then considered in the context of a quark compositeness search where a sensitivity to a compositeness scale of Lambda<10TeV can be achieved with 10 inverse femtobarns of data, if the jet energy scale can be constrained to ~1%. An analysis using dijet angular distributions found a similar sensitivity without the dependence on the jet energy scale. A potential method of evaluating the stability of the jet energy scale out to high pT by `bootstrapping' the calibration at low pT by the use of multi-jet events was also investigated. This suggests that a calorimeter non-linearity can be detected for jets with pT>500GeV at ~1.5%/500GeV (i.e. a 1.5% change in JES over 500GeV in pT). An investigation of inner-detector commissioning issues associated with the ATLAS Semiconductor Tracker (SCT), including a review of `noisy' modules on the SCT Barrel (from May 2007) was carried out. In addition a tool for DCS monitoring within the online monitoring framework was developed and tested during the M5 and M6 commissioning weeks. Finally, a method of assessing the track reconstruction efficiency by track-insertion was considered for the particular case of minimum bias events.

With the advent of reasoning problems in dynamic environments, there is an increasing need for automated reasoning systems to automatically adapt to unexpected changes in representations. In particular, the automation of the evolution of their ontologies needs to be enhanced without substantially sacrificing expressivity in the underlying representation. Revision of beliefs is not enough, as adding to or removing from beliefs does not change the underlying formal language. General reasoning systems employed in such environments should also address situations in which the language for representing knowledge is not shared among the involved entities, e.g., the ontologies in a multi-ontology environment or the agents in a multi-agent environment. Our techniques involve diagnosis of faults in existing, possibly heterogeneous, ontologies and then resolution of these faults by manipulating the signature and/or the axioms. This thesis describes the design, development and evaluation of GALILEO (Guided Analysis of Logical Inconsistencies Lead to Evolution of Ontologies), a system designed to detect conflicts in highly expressive ontologies and resolve the detected conflicts by performing appropriate repair operations. The integrated mechanism that handles ontology evolution is able to distinguish between various types of conflicts, each corresponding to a unique kind of ontological fault. We apply and develop our techniques in the domain of Physics. This an excellent domain because many of its seminal advances can be seen as examples of ontology evolution, i.e. changing the way that physicists perceive the world, and case studies are well documented – unlike many other domains. Our research covers analysing a wide ranging development set of case studies and evaluating the performance of the system on a test set. Because the formal representations of most of the case studies are non-trivial and the underlying logic has a high degree of expressivity, we face some tricky technical challenges, including dealing with the potentially large number of choices in diagnosis and repair. In order to enhance the practicality and the manageability of the ontology evolution process, GALILEO incorporates the functionality of generating physically meaningful diagnoses and repairs and, as a result, narrowing the search space to a manageable size.

This dissertation has three parts. In "Quantum Entanglement, Bohmian Mechanics, and Humean Supervenience," I defend David Lewis's metaphysical doctrine of Humean supervenience, and traditional metaphysical reductionism more generally, against an alleged holistic threat encapsulated in the non-separability argument from quantum entanglement. I argue that, contrary to popular belief, realism about quantum mechanics is compatible with Humean reductionism.
Philosophy

Inspired by the recast of the quantum mechanics in a toposical framework, we develop a contextual quantum mechanics via the geometric mathematics to propose a quantum contextuality adaptable in every topos. The contextuality adopted corresponds to the belief that the quantum world must only be seen from the classical viewpoints à la Bohr consequently putting forth the notion of a context, while retaining a realist understanding. Mathematically, the cardinal object is a spectral Stone bundle Σ → B (between stably-compact locales) permitting a treatment of the kinematics, fibre by fibre and fully point-free. In leading naturally to a new notion of points, the geometricity permits to understand those of the base space B as the contexts C — the commutative C*–algebras of a incommutative C*–algebras — and those of the spectral locale Σ as the couples (C, ψ), with ψ a state of the system from the perspective of such a C. The contexts are furnished with a natural order, the aggregation order which is installed as the specialization on B and Σ thanks to (one part of) the Priestley's duality adapted geometrically as well as to the effectuality of the lax descent of the Stone bundles along the perfect maps.

During the twentieth century, particle physics developed into a cornerstone of modern physics, culminating in the Standard Model. Even though this theory has proved to be of extraordinary power, it is still incomplete in several respects. It is our aim in this bachelor thesis to discuss some possible theories beyond the Standard Model, the main focus being on Grand Unified Theories, while also taking a look at attempts of further unication via discrete family symmetry. At the heart of all these theories lies the concept of local gauge invariance, which is introduced as a fundamental principle, followed by an overview of the Standard Model itself. No theory has so far managed to unify all elementary particles and their interactions, but some interesting features are highlighted. We also give a hint at some possible paths to go in the future in the quest for a unication in particle physics.
Under 1900-talet utvecklades partikelfysiken till en av de fundamentala teorierna inom fysiken, och kom att sammanfattas i den s.k. Standardmodellen. Även om denna modell rönt exceptionella framgånger vad gäller beskrivningen av elementarpartiklar och deras växelverkan, är den fortfarande ofullständig på flera sätt. Syftet med denna kandidatuppsats är att diskutera möjliga teorier bortom Standardmodellen såsom Storförenande Teorier och diskreta familjesymmetrier vars avsikt är att koppla samman de tre familjerna av fermioner i Standardmodellen. Men först introduceras idén om lokal gaugeinvarians, vilken ligger till grund for dessa teorier, varpå en översikt av Standardmodellen följer. Ingen teori har ännu lyckats ge en helt tillfredsställande bild av elementarpartiklar och deras interaktion, men en del intressanta egenskaper hos föreslagna teorier belyses i denna uppsats. Slutligen ges en del spekulativa förslag på väger att gå i framtida försök till föreningar inom partikelfysiken.