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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
171

Effect of Curvature Squared Corrections to Gravitational Action on Viscosity-to-Entropy Ratio of the Dual Gauge Theory

Petrov, Pavel January 2012 (has links)
In this thesis we study the properties of strongly-coupled large-N conformal field theories (CFT’s) using AdS/CFT correspondence. Chapter 1 serves as an introduction. In Chapter 2 we study the shear viscosity of strongly-coupled large-N conformal field theories. We find that it is affected by \(R^2\) corrections to the AdS action and present an example of 4D theory in which the the conjectured universal lower bound on viscosity-to-entropy ratio \(\eta/s > 1/4 \pi\) is violated by 1/N corrections. This fact proves that there is no universal lower bound of \(1/4 \pi\) on viscosity-to-entropy ratio and may be relevant for the studies of QCD quark-gluon plasma for which this ratio is experimentally found to be close to \(1/4 \pi\). In Chapter 3 we study the formation of the electron star in 4D AdS space. We show that in a gravity theory with charged fermions a layer of charged fermion fluid may form at a finite distance from the charged black hole. We show that these “electron stars” are candidate gravity duals for strongly interacting fermion systems at finite density and finite temperature. Entropy density for such systems scales as \(s \sim T^{2/z}\) at low temperatures as expected from IR criticality of electron stars solutions. / Physics
172

Nonparametric Statistics on Manifolds With Applications to Shape Spaces

Bhattacharya, Abhishek January 2008 (has links)
This thesis presents certain recent methodologies and some new results for the statistical analysis of probability distributions on non-Euclidean manifolds. The notions of Frechet mean and variation as measures of center and spread are introduced and their properties are discussed. The sample estimates from a random sample are shown to be consistent under fairly broad conditions. Depending on the choice of distance on the manifold, intrinsic and extrinsic statistical analyses are carried out. In both cases, sufficient conditions are derived for the uniqueness of the population means and for the asymptotic normality of the sample estimates. Analytic expressions for the parameters in the asymptotic distributions are derived. The manifolds of particular interest in this thesis are the shape spaces of k-ads. The statistical analysis tools developed on general manifolds are applied to the spaces of direct similarity shapes, planar shapes, reflection similarity shapes, affine shapes and projective shapes. Two-sample nonparametric tests are constructed to compare the mean shapes and variation in shapes for two random samples. The samples in consideration can be either independent of each other or be the outcome of a matched pair experiment. The testing procedures are based on the asymptotic distribution of the test statistics, or on nonparametric bootstrap methods suitably constructed. Real life examples are included to illustrate the theory.
173

Social Asymmetries in Online Personal Ads in Japanese: Discursive Construction of Desirable Personae, Bodies, and Practices

Sato, Tetsuya January 2008 (has links)
The Internet is increasingly becoming a key medium through which people establish social contacts and form interpersonal relationships. In particular, online dating websites are gaining popularity and rapidly expanding around the world. This study explores the discourse that constitutes the practices of the deai-kee-saito 'encounter-oriented sites' in Japanese, as observed in three major personal ad websites, namely 1) Ekisaito furenzu 'Excite Friends', 2) Match.com, and 3) Yahoo!Japan paasonaruzu 'Yahoo!Japan Personals'. It focuses on the ways that self-advertisers express their socio-sexual desires and describe their ideal partners and relationships, and analyzes them with respect to the reproduction of social asymmetries.More specifically, it examines the discursive construction of the kinds of personae (personality characteristics) and bodies (physical features) that advertisers aged 20-29 wish in their future partners, as well as the kinds of practices (activities and actions) they wish to engage in with their partners, what they wish to do for their partners, and/or wish the partners to do for them in their envisioned interactions. Out of the 1200 ads collected from these websites, a total of 463 ads are identified as target-gender-explicit and analyzed at lexical, morphosyntactic, phrasal, clausal, sentential and discourse levels. It pays close attention to the linguistic resources utilized in the articulation of socio-sexual desires and desirability, and the textual formation of the addresser(advertiser)-addressee(ad reader) relationships, including adjectives, nouns, verbal phrases, person references, desideratives, conditionals, and the formula yoroshiku/o-negai shimasu 'Thank you in advance'. It also analyzes para-linguistic resources, such as emoticons, symbols, and unique use of hiragana/katakana syllabaries. These discursive processes involve prioritization, or hierarchization, of personal attributes and consequently of the owners of those attributes. It argues that socio-sexual desirability is reflective of the hegemonic ideologies of gender and sexuality in today's Japanese-speaking communities.In addition, it examines explicit and implicit language related to race, class, and similar constructs. It also investigates the functions of style-shift that advertisers use in expressing desire. This study shows that individuals' 'innocuous' expression of socio-sexual desires through personal ads is a locus for the reproduction and contestation of the hegemonic order of gender, sexuality, race and class.
174

Fragment Mass Distributions in Neutron-Induced Fission of 232Th and 238U from 10 to 60 MeV

Simutkin, Vasily January 2010 (has links)
Since its discovery, the phenomenon of nuclear fission is the object of extensive theoretical and experimental studies. However, we are still far from a complete understanding of the fission process. Nuclear theory can satisfactorily explain the process of neutron-induced fission at thermal neutron energies, but it meets problems at high neutron energies. However, new applications are nowadays developed involving neutron-induced fission in this energy domain. An example of such an application is accelerator-driven systems (ADS) which are dedicated to transmutation of highly radioactive nuclear waste. Conceptual studies of ADS require new nuclear data on neutron-induced reactions within a wide incident energy range. Along with structural, spallation target and other materials, data on neutron-induced fission are especially required for two nuclides, 232Th and 238U. At present, however, there are no published neutron-induced fission yield data for either 232Th or 238U at energies above 20 MeV. In this thesis, I present measurements of fission fragment mass yields at neutron energies from 10 to 60 MeV for 232Th and 238U. The experiment was done at the Louvain-la-Neuve quasi-monoenergetic neutron beam facility. A multi-section Frisch-gridded ionization chamber was used as the fission fragment detector. The fission fragment mass yields were measured at peak neutron energies of 33, 45, and 60 MeV. In addition, data for the neutron-energy intervals 9-11, 16-18, and 24-26 MeV were also extracted from the low-energy tail. The measurement results show that the symmetric fission component increases with incident neutron energy for both uranium and thorium, but it is more enhanced for thorium. The uranium results were compared to the only existing set of experimental data for neutron energies above 20 MeV. Reasonable agreement was found. However, our data show a lower symmetric fission component. For thorium, the present data are the first above 20 MeV. Model calculations with the TALYS code have also been done. This code is based on the multi-modal random neck-rupture model extended for higher excitation energies. We included a phenomenological model into the code and achieved a good description of our experimental results. / Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 723
175

AdS/CFT, Black Holes, And Fuzzballs

Zadeh, Aida 09 January 2014 (has links)
In this thesis we investigate two different aspects of the AdS/CFT correspondence. We first investigate the holographic AdS/CMT correspondence. Gravitational backgrounds in d+2 dimensions have been proposed as holographic duals to Lifshitz-like theories describing critical phenomena in d+1 dimensions with critical exponent z>1. We numerically explore a dilaton-Einstein-Maxwell model admitting such backgrounds as solutions. We show how to embed these solutions into AdS space for a range of values of z and d. We next investigate the AdS3/CFT2 correspondence and focus on the microscopic CFT description of the D1-D5 system on T^4*S_1. In the context of the fuzzball programme, we investigate deforming the CFT away from the orbifold point and study lifting of the low-lying string states. We start by considering general 2D orbifold CFTs of the form M^N/S_N, with M a target space manifold and S_N the symmetric group. The Lunin-Mathur covering space technique provides a way to compute correlators in these orbifold theories, and we generalize this technique in two ways. First, we consider excitations of twist operators by modes of fields that are not twisted by that operator, and show how to account for these excitations when computing correlation functions in the covering space. Second, we consider non-twist sector operators and show how to include the effects of these insertions in the covering space. Using the generalization of the Lunin-Mathur symmetric orbifold technology and conformal perturbation theory, we initiate a program to compute the anomalous dimensions of low-lying string states in the D1-D5 superconformal field theory. Our method entails finding four-point functions involving a string operator O of interest and the deformation operator, taking coincidence limits to identify which other operators mix with O, subtracting conformal families of these operators, and computing their mixing coefficients. We find evidence of operator mixing at first order in the deformation parameter, which means that the string state acquires an anomalous dimension. After diagonalization this will mean that anomalous dimensions of some string states in the D1-D5 SCFT must decrease away from the orbifold point while others increase. Finally, we summarize our results and discuss some future directions of research.
176

AdS/CFT, Black Holes, And Fuzzballs

Zadeh, Aida 09 January 2014 (has links)
In this thesis we investigate two different aspects of the AdS/CFT correspondence. We first investigate the holographic AdS/CMT correspondence. Gravitational backgrounds in d+2 dimensions have been proposed as holographic duals to Lifshitz-like theories describing critical phenomena in d+1 dimensions with critical exponent z>1. We numerically explore a dilaton-Einstein-Maxwell model admitting such backgrounds as solutions. We show how to embed these solutions into AdS space for a range of values of z and d. We next investigate the AdS3/CFT2 correspondence and focus on the microscopic CFT description of the D1-D5 system on T^4*S_1. In the context of the fuzzball programme, we investigate deforming the CFT away from the orbifold point and study lifting of the low-lying string states. We start by considering general 2D orbifold CFTs of the form M^N/S_N, with M a target space manifold and S_N the symmetric group. The Lunin-Mathur covering space technique provides a way to compute correlators in these orbifold theories, and we generalize this technique in two ways. First, we consider excitations of twist operators by modes of fields that are not twisted by that operator, and show how to account for these excitations when computing correlation functions in the covering space. Second, we consider non-twist sector operators and show how to include the effects of these insertions in the covering space. Using the generalization of the Lunin-Mathur symmetric orbifold technology and conformal perturbation theory, we initiate a program to compute the anomalous dimensions of low-lying string states in the D1-D5 superconformal field theory. Our method entails finding four-point functions involving a string operator O of interest and the deformation operator, taking coincidence limits to identify which other operators mix with O, subtracting conformal families of these operators, and computing their mixing coefficients. We find evidence of operator mixing at first order in the deformation parameter, which means that the string state acquires an anomalous dimension. After diagonalization this will mean that anomalous dimensions of some string states in the D1-D5 SCFT must decrease away from the orbifold point while others increase. Finally, we summarize our results and discuss some future directions of research.
177

En studie över förekomsten av genuttryck för enzym i biosyntesen av malarialäkemedlet artemisinin hos Artemisia vulgaris och Artemisia absinthium

Svensson, Alexandra January 2014 (has links)
Malaria är en farlig tropiksjukdom orsakad av parasiten Plasmodium som vållar många dödsfall varje år. Sedan några år tillbaka rekommenderar Världshälsoorganisationen (WHO) användandet av artemisinin och dess derivat för behandlandet av malaria. Artemisinin syntetiseras normalt i växten Artemisia annua i lågt utbyte. På grund av det låga utbytet är läkemedlet väldigt dyrt. Då parasiten blivit resistent mot de flesta malarialäkemedel är artemisinin ett viktigt preparat i kampen mot malaria. Forskning pågår för att hitta nya eller effektivare metoder för framställning av substansen då en oro finns att produktionen från A. annua inte kommer kunna möta kraven från läkemedelsindustrin. En av teorierna är ifall andra växter inom Artemisia-släktet kan syntetisera artemisinin då flera växter uppvisat helande effekter vid andra sjukdomar. I denna studie undersöktes det ifall växterna A. vulgaris och A. absinthium från Artemisia-släktet skulle kunna syntetisera artemisinin. Med hjälp av molekylärbiologiska tekniker isolerades genetiskt material ifrån växterna. Materialet granskades efter ribonukleinsyra (RNA)- och deoxiribonukleinsyra (DNA) -sekvenser för funktionella enzym som katalyserar reaktioner i artemisinins biosyntes. Ifall generna uttrycks för dessa enzym kan eventuellt artemisinin bildas. Växterna hämtades från Revsudden, Sverige och genetiskt material isolerades. Förekomsten av genuttryck för fem viktiga enzym i artemisinins biosyntes undersöktes med Polymerase Chain Reaction (PCR). Resultatet blev att växterna hade genuttryck för två respektive tre av de fem enzymen. Detta pekar mot att varken A. vulgaris eller A. absinthium kan syntetisera artemisinin då de saknade några viktiga nyckelenzym i syntesen. Trots att en tidigare studie indikerar närvaro av artemisinin i dessa växter kan slutsatsen dras att A. vulgaris och A. absinthium inte kan bilda artemisinin. / Malaria is a tropical disease that accounts for the death of many people annually and is caused by a parasite called Plasmodium. The World Health Organization (WHO) recommends artemisinin and its derivates for malaria treatment. Artemisinin is synthesized generally in Artemisia annua in small amounts. The artemisinin-treatment is very expensive due to the small amounts produced in the plant. Since the parasite has developed resistance towards many antimalarial drugs, artemisinin is an important drug against malaria. Research to find alternative methods for artemisinin-production has begun because there is a great concern that artemisinin-production at current rate will not meet the demand from the pharmaceutical industry. Some speculate if artemisinin can be synthesized in other plants from the Artemisia-genus since many plants have shown healing properties towards other diseases. In this study, we investigated if A. vulgaris and A. absinthium could produce artemisinin. Using molecular biology techniques, genetic material was isolated from the plants. Ribonucleotide (RNA)- and deoxyribonucleotide (DNA)- sequences which encode important enzymes in the artemisinin biosynthesis were examined. In case all the genes were expressed, artemisinin may be synthesized. The plants were picked on Revsudden, Sweden and genetic material was isolated. The presence of gene expression of five important enzymes in the artemisinin biosynthesis was investigated by Polymerase Chain Reaction (PCR). The results showed that the plants had gene expression of two respectively three of the five enzymes. Due to the fact that the plants need all five enzymes to synthesize artemisinin, even though a recent study has shown presence of artemisinin in these plants, this study concludes that artemisinin cannot be synthesized in A. vulgaris and A. absinthium.
178

„Google” paieškos „AdWords” skelbimų efektyvumo vertinimas / Assessing the effectiveness of „Google“ search engine „AdWords” ads

Lukošiūtė, Edita 05 June 2014 (has links)
Darbe yra analizuojamas „Google“ paieškos „AdWords“ skelbimų efektyvumas. Dėl didėjančios informacinių technologijų svarbos, dauguma vartotojų ieškosi informacijos apie produktus ir paslaugas bei perka juos internetu. Todėl reklamos kūrėjams tampa ypač aktualus efektyvių paieškos sistemos skelbimų kūrimo klausimas. Darbo tikslas – remiantis moksliniais reklamos efektyvumo vertinimo šaltiniais ir „Google“ paieškos „AdWords“ skelbimų efektyvumo vertinimo rezultatais, pateikti bendrą „AdWords“ skelbimų efektyvumo vertinimo ir skelbimų efektyvumo didinimo modelius. Magistro baigiamąjį darbą sudaro trys pagrindinės dalys. Pirmojoje, teorinėje dalyje, yra analizuojami skirtingų autorių požiūriai į reklamos efektyvumo vertinimą, yra pateikiami „Google“ paieškos „AdWords“ skelbimų vertinimo ypatumai. Analitinėje baigiamojo darbo dalyje yra atliekamas pasirinktų „Google“ paieškos „AdWords“ reklaminių kampanijų skelbimų efektyvumo vertinimas. Trečiojoje dalyje yra pateikiamas „Google“ paieškos „AdWords“ skelbimų efektyvumo vertinimo ir efektyvumo didinimo modeliai bei pateikiamos skelbimų efektyvumo didinimo priemonės. / The paper analyzes the effectiveness of „Google“ search engine „AdWords“ ads. Due to the growing importance of information technology , most users search for information about products and services and buy them online. Therefore the issue of ads effectiveness has become extremely important to every advertiser. The objective of this paper is to present general model of „Google“ search engine „AdWords“ ads effectiveness measurement and opportunities of ads effectiveness improvement, scientific resources of advertising effectiveness assessment and results of case analysis. Master's thesis consists of three main parts. In the first, theoretical part of the work introduces analysis, comparison of different authors approaches to the advertising activities performance by finding out methods and indicators, which assess the effectiveness of the ads. The analytical part is based on case study which analyzes effectiveness of particular „Google“ search engine „AdWords“ campaigns. The third part is intended for the model, which shows how to measure effectiveness of the „Google“ search engine „AdWords“ ads, and oppurtinities of ads effectiveness improvement.
179

Spins and Giants : Fundamental Excitations in Weakly and  Strongly Coupled ABJM Theory

Ohlsson Sax, Olof January 2011 (has links)
The discovery of integrability on both sides of the duality between planar N=4 super Yang-Mills theory and free type IIB string theory in AdS5 × S5 has lead to great progress in our understanding of the AdS/CFT correspondence. Similar integrable structures also appear in the more recent three-dimensional superconformal N=6 Chern-Simons-matter theory constructed by Aharony, Bergman, Jafferis and Maldacena (ABJM), as well as in its gravity dual, type IIA string theory on AdS4 × CP3. However, new interesting complications arise in the AdS4/CFT3 duality. In the conjectured all-loop Bethe equations by Gromov and Vieira the dispersion relation of the magnons has a non-trivial coupling dependence which is parametrized by a function that is only known to the leading order at weak and strong coupling. In the first part of this thesis I discuss our calculations of the next-to-leading correction to this function at weak coupling. We compute this function from four-loop Feynman diagrams in the SU(2) × SU(2) sector of the ABJM model. As a consistency check we have performed the calculation both in a component formalism and using superspace techniques. At strong coupling the fundamental excitations of the integrable model are the giant magnons. The topic of the second part of this thesis is the spectrum of these giant magnons in CP3. Furthermore, I discuss our analyses of the finite-size corrections beyond the asymptotic Bethe ansatz. At weak coupling we have computed the leading four-loop wrapping diagrams in the ABJM model. At the strong coupling side of the duality I discuss our results for the exponentially suppressed finite-size corrections to the energy of giant magnons.
180

Applications of the gauge/gravity duality

Probst, Jonas January 2017 (has links)
This thesis investigates applications of the gauge/gravity duality to strongly coupled quantum field theories. After a review of the duality and of correlators and transport in quantum systems, we present our results on second-order non-conformal hydrodynamics. We derive new Kubo formulae for five second-order transport coefficients in non-conformal relativistic fluids. We then apply these Kubo formulae to a class of non-conformal holographic fluids at infinite coupling. We find strong evidence that the Haack-Yarom identity, known to relate second-order coefficients in conformal holographic fluids at infinite coupling, continues to hold in holographic fluids without conformal symmetry: Within our class of models, we prove that it still holds when leading non-conformal corrections are taken into account, and we show numerically that it is also obeyed beyond leading order. This provides further evidence that the identity may be a universal feature of strongly coupled fluids. Next, we present our results on magnetic spin impurities in strongly correlated systems. We build a holographic two-impurity Kondo model, identifying the inter-impurity interaction as double-trace deformation. Our numerical results for the phase diagram suggest a quantum phase transition between a trivial phase with uncorrelated spins and no Kondo screening, and a non-trivial phase with anti-ferromagnetic correlations and simultaneous Kondo screening. Computing the spectrum in the single-impurity case, we observe Fano resonances, which at low temperatures we identify with the Kondo resonance.

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