The role of hydroelectricity in the Swedish energy system is increasing rapidly as the share of renewable energy sources in the country grows. Meanwhile, the dams are under current revision as ecology and safety requirements has changed since most of them were built. The need for research regarding the Swedish hydroelectric dams is higher than ever.  Historically, such research has been made through measurements in physical laboratory models – scaled down several times to reasonable sizes. However, these models become problematic in cases of very shallow waters. Distorted scaling allows the flows to keep necessary depths to remain representative for the prototype flows, however, research on such distorted flows are quite limited and moreover limited to models with completely free surface flows.  In this study the effects of distortion upon physical as well as numerical measurements of water depths and velocities are analyzed for a dam with a tunnel outlet at the bottom. Measurements were made in a distorted physical model with a distortion ratio of 3, the values of which were later compared to measurements conducted in an earlier study of the same dam in an undistorted model. Furthermore, results of numerical simulations for both the earlier mentioned scales as well as measurements in two models with distortion ratios of 2 and 4 were added to the comparison.  The purpose of the study is to widen the knowledge of distorted models and flows, as well as the knowledge of which situations CFD can perform satisfactory results and not. Numerically conducted values seem to match physical ones well, whereas the differences increased rapidly following an increased distortion ratio. Initially a goal of the study was to find a suitable distortion-ratio to obtain differences of a maximum of 10%, however, as the study came to show consistently much larger differences than that regarding water depths, the question of why these large differences occur rose to become the more significant one. The leading theory of why the differences increase as the distortion ratio becomes greater is that of the decreased utilization of the cross-sectional tunnel area, which leads to higher velocities and thereby higher tunnel resistance.

In recent decades, spinor-helicity formalism has gained popularity as a useful tool for studyingscattering amplitudes in four dimensions. This formalism has been extended to higher dimensions,but there is still much work to be done around its application. This thesis explores a new approachto extending the spinor-helicity formalism to ten dimensions by breaking the Lorentz symmetryinto two five-dimensional subspaces. We use this approach to express the ten-dimensional dynamical variables in terms of five-dimensional spinor helicities. We divide the polarization vectorsinto a direct sum of two massive polarization vectors, each living in five dimensions. We thenapply this new spinor-helicity formalism in ten dimensions to construct the YM, SYM, and higherderivative amplitudes. The results obtained in this thesis suggest that this approach may providea promising avenue for extending the spinor-helicity formalism relevant to SYM, supergravity, andsuperstring theory.

The use of exhaled breath analysis in assessing the health status of human individuals is an intriguing concept that has attracted more and more attention during recent years. Although detection of species in breath can, to a certain extent, be made by both electrochemical and mass spectrometric techniques, these do not always provide sufficient sensitivity, selectivity and speed. Due to the development of new laser sources in the (MIR) wavelength region, absorption spectrometry (AS) has shown such good performance that MIR-AS techniques start to become more viable alternatives to breath analysis. Of the large number of species exhaled  (major species, which are in %-concentrations, e.g. H2O and CO2, minor species, which exist in ppm concentrations, e.g. CO and CH4, and trace species, which exist in low or sup-ppb concentrations), some are more important than others, such as Carbonyl Sulfide, Ethane, Ethylene and Formaldehyde, since they are important biomarkers for various diseases e.g. chronic respiratory diseases, acute lung transplant rejection, UV-radiation damage of the skin and gastro-esophageal/breast cancer. The present thesis consists of a compilation and analysis of possible transitions primarily in the 3-4 µm region that can be used for detecting such species by MIR-AS techniques.

<p>Godkänd; 1994; 20070410 (ysko)</p>

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No description available.

This thesis reviews the theory of group extensions, gerbes and twisted K-theory. Application to anomalies in gauge theory is briefly discussed. The main results are presented in two appended scientific papers. In the first paper we establish, by construction, a criterion for when an infinite dimensional abelian Lie algebra extension corresponds to a Lie group extension. In the second paper we introduce the fractional loop group L_qG, construct highest weight modules for the Lie algebra and discuss an application to twisted K-theory on G. / QC 20101111

The Yang-Mills gauge theories play prominent role in modern high energy physics and the direct non-perturbative calculations present the main challenge in the field.Two dimensional gauge theories provide a nice playground where it is possible to carry out exact computations and at the same time some non-trivial phenomena canbe studied. This thesis is devoted to review and summarize a core portion of the quantum version of this field, accompanying the reader through the technicalities that one can encounter during the first approach to the subject.The thesis starts with a brief introduction to the subject and a brief review of the literature, the first two chapters are then spent on the computation of the partition functions over the simplest surfaces, i.e. disk and cylinder, using different formalisms.In chapter 4 there is presented the generalization of the procedure in order to find the general partition function that can be applied over any orientable surface (not necessarily closed). Interesting observables in this theory are the so called Wilson loops, chapter 5 contains the definition and a presentation of the non-intersecting ones over closed surfaces. In the end some of these encountered formulae have been applied to U(1) and SU(N) groups, i.e. we derived some partition functions of Maxwell theory and quantum chromodynamics over non-trivial surfaces and we gave the tools to explore more complex cases. The appendices contain one a brief review of the mathematics, the other all the step by step computations performed during the proofs.

ΛCDM cosmology is described in terms of general relativity and the Robertson-Walker metric. The evolution of the observable universe, currently dominated by dark energy (Λ) and cold dark matter (CDM), is presented in terms of its thermal history. CDM is extended to include an inflation epoch that accelerates the early expansion rate to near exponential levels. It is shown that inflation solves several problems in CDM and produces perturbations in the metric that lead to the observed anisotropies in the Cosmic Microwave Background and the formation of large scale cosmological structures. Various theories of inflation are explored. Predictions of inflation theories are compared to observations published by the Planck Collaboration. The paper concludes with an examination of “𝜶-attractor” theories of inflation based on a modified form of gravity.

The concept of faster than light travel in general relativity is examined, starting with a review of the Alcubierre metric. This spacetime, although incredible in its implications, has certain unavoidable problems which are discussed in detail. It is demonstrated that in order to describe faster than light travel without any ambiguities, a coordinate independent description is much more convenient. An alternative method of describing superluminal travel is then proposed, which has similarities to the Krasnikov tube.