In the following thesis, I will conduct a thermodynamic analysis of the Taub-NUT spacetime in various dimensions, as well as show uses for Taub-NUT and other Hyper-Kahler spacetimes. <br /><br /> Thermodynamic analysis (by which I mean the calculation of the entropy and other thermodynamic quantities, and the analysis of these quantities) has in the past been done by use of background subtraction. The recent derivation of the (A)dS/CFT correspondences from String theory has allowed for easier and quicker analysis. I will use Taub-NUT space as a template to test these correspondences against the standard thermodynamic calculations (via the N&ouml;ether method), with (in the Taub-NUT-dS case especially) some very interesting results. <br /><br /> There is also interest in obtaining metrics in eleven dimensions that can be reduced down to ten dimensional string theory metrics. Taub-NUT and other Hyper-Kahler metrics already possess the form to easily facilitate the Kaluza-Klein reduction, and embedding such metrics into eleven dimensional metrics containing M2 or M5 branes produces metrics with interesting Dp-brane results.

In the first part of this thesis we study baryonic U(1) symmetries dual to Betti multiplets in the AdS_4/CFT_3 correspondence for M2 branes at Calabi-Yau four-fold singularities. Such short multiplets originate from the Kaluza-Klein compactification of eleven-dimensional supergravity on the corresponding Sasaki-Einstein seven-manifolds. Analysis of the boundary conditions for vector fields in AdS_4 allows for a choice where wrapped M5 brane states carrying non-zero charge under such symmetries can be considered. We begin by focusing on isolated toric singularities without vanishing six-cycles, which we classify, and propose for them field theory duals. We then study in detail the cone over the well-known Sasaki-Einstein space Q^111, which is a U(1) fibration over CP^1 x CP^1 x CP^1. The boundary conditions considered are dual to a CFT where the gauge group is U(1)^2 x SU(N)^4. We find agreement between the spectrum of gauge-invariant baryonic-type operators in this theory and M5 branes wrapping five-cycles in the Q^111 space. Moreover, the physics of vacua in which these symmetries are spontaneously broken precisely matches a dual gravity analysis involving resolutions of the singularity, where we are able to match condensates of the baryonic operators, Goldstone bosons and global strings. We then study the implications of turning on a closed three-form with non-zero periods through torsion three cycles in the Sasaki-Einstein manifold. This three-form, otherwise known as torsion G-flux, non-trivially affects the supergravity dual of Higgsing, and we show that the supergravity and field theory analyses precisely match in an example based on the Sasaki-Einstein manifold Y^1,2(CP^2), which is a S^3 bundle over CP^2. We then explain how the choice of M-theory circle in the background can result in exotic renormalization group flows in the dual field theory, and study this in detail for the Sasaki-Einstein manifold Y^1,2(CP^2). We also argue more generally that theories where the resolutions have six-cycles are expected to receive non-perturbative corrections from M5 brane instantons. We give a general formula relating the instanton action to normalizable harmonic two-forms, and compute it explicitly for the Sasaki-Einstein Q^222 example, which is a Z_2 orbifold of Q^111 in which the free Z_2 quotient is along the R-symmetry U(1) fibre. The holographic interpretation of such instantons is currently unclear. In the second part of this thesis we study the breaking of baryonic symmetries in the AdS_5/CFT_4 correspondence for D3 branes at Calabi-Yau three-fold singularities. This leads, for particular vacuum expectation values, to the emergence of non-anomalous baryonic symmetries during the renormalization group flow. We identify these vacuum expectation values with critical values of the NS-NS B-field moduli in the dual supergravity backgrounds. We study in detail the C^3/Z_3 orbifold theory and the dual supergravity backgrounds that correspond to the breaking of the emerging baryonic symmetries, and identify the expected Goldstone bosons and global strings in the infra-red. In doing so we confirm the claim that the emerging symmetries are indeed non-anomalous baryonic symmetries.

The discovery of integrability in planar N=4 super Yang-Mills and ABJM has enabled a precise study of AdS/CFT. In the past decade integrability has been successfully applied to the spectrum of anomalous dimensions, which can now be obtained at any value of the coupling. However, in order to solve conformal field theories one also needs to understand their structure constants. Recently, there has been great progress in this direction with the all-loop proposal of Basso, Komatsu and Vieira. But there is still much to understand, as it is not yet possible to use that formalism to find structure constants of short operators at strong coupling. It is important to study wrapping corrections and resum them as the TBA did for the spectrum. It is also crucial to obtain perturbative data that can be used to check if the all-loop proposal is correct or if there are new structures that need to be unveiled. In this thesis we compute several structure constants of short operators at strong coupling, including the structure constant of Konishi with half-BPS operators. Still at strong coupling, we find a relation between the building blocks of superstring amplitudes and the tensor structures allowed by conformal symmetry. We also consider the case of extremal correlation functions and the relation of their poles to mixing with double-trace operators. We also study three-point functions at weak coupling. We take the OPE limit in a four-point function of half-BPS operators in order to shed some light on the structure of five-loop wrapping corrections of the Hexagon form factors. Finally, we take the first steps in the generalization of the Hexagon programme to other theories. We find the non-extremal setup in ABJM and the residual symmetry that it preserves, which we use to fix the two-particle form factor and constrain the four-particle hexagon. Finally, we find that the Watson equations hint at a dressing phase that needs to be further investigated.

Påträngande och störande annonser har blivit alltmer vanligt på internet vilket har medfört att konsumenter fått en alltmer negativ inställning till online-annonser. Därmed har användningen av mjukvaror för blockering av annonser på senare tid blivit alltmer vanligt. Detta har medfört minskningar i reklamintäkter för företag som använder sig av webbaserad marknadsföring, vilket har lagt för handen att de måste anpassa sina online-annonser till konsumenten för att kunna hålla verksamheten lönsam. Syftet med denna studie är att undersöka vilken typ av online-annonser som används för att nå ut till användare på internet på ett mindre påträngande och irriterande sätt samt vilken inställning de har till annonsblockerare. Uppsatsen har en triangulär ansats i form av kvalitativa semi-strukturerade intervjuer som stärks och jämförs med en kvantitativ enkätundersökning. Av slutsatsen framkommer det att native advertising är det mest effektfulla annonsformatet för att nå ut till konsumenter på ett mer accepterat sätt. Samtidigt börjar fler företag som använder sig av online-annonser att införa betalväggar på sina hemsidor där konsumenter på internet tvingas stänga av sin annonsblockerare, bli nekade innehållet eller betala för att få tillgång till det. / Intrusive and annoying ads have become increasingly common on the internet, which has led to that consumers have a more negative attitude to online ads. Thus, using softwares for blocking ads have lately become more common. This has led to reductions in advertising revenues for companies that use web-based marketing which have forced them to customize their ads to the consumers in order to keep the business profitable.     The aim of this paper is to examine what type of online ads that is used to reach out to internet users in a less intrusive way and to see their opinion about adblockers. From a consumer perspective the study examines the view of the consumer on this development and if they fulfil their purpose. The thesis has a triangular approach with semi-structured interviews that is strengthened and compared with a quantitative questionnaire. The conclusion of the research have showed that native advertising is the most effective ad format to reach out to consumers in a more acceptable manner. At the same time more companies that are using online ads choose to introduce paywalls on their webpages where consumers on the internet are forced to deactivate their adblockers, to be denied the content or to pay to gain access to it.

The most general AdS$_5 imes Y$ solutions of type IIB string theory that are AdS/CFT dual to superconformal field theories in four dimensions can be fruitfully described in the language of generalized geometry, a powerful hybrid of complex and symplectic geometry. We show that the cone over the compact five-manifold $Y$ is generalized Calabi-Yau and carries a generalized holomorphic Killing vector field $xi$, dual to the R-symmetry. Remarkably, this cone always admits a symplectic structure, which descends to a contact structure on $Y$, with $xi$ as Reeb vector field. Moreover, the contact volumes of $Y$, which can be computed by localization, encode essential properties of the dual CFT, such as the central charge and the conformal dimensions of BPS operators corresponding to wrapped D3-branes. We then define a notion of ``generalized Sasakian geometry'', which can be characterized by a simple differential system of three symplectic forms on a four-dimensional transverse space. The correct Reeb vector field for an AdS$_5$ solution within a given family of generalized Sasakian manifolds can be determined---without the need of the explicit metric---by a variational procedure. The relevant functional to minimize is the type IIB supergravity action restricted to the space of generalized Sasakian manifolds, which turns out to be just the contact volume. We conjecture that this contact volume is equal to the inverse of the trial central charge whose maximization determines the R-symmetry of the dual superconformal field theory. The power of this volume minimization is illustrated by the calculation of the contact volumes for a new infinite family of solutions, in perfect agreement with the results of $a$-maximization in the dual mass-deformed generalized conifold theories.

Recent trends and developments in the fields of Big Data, Machine Learning, and Artificial Intelligence are completely transforming the way brands are engaging and communicating with their audience, allowing more personalized communications than ever. With the spread of social networking sites, such as Facebook, YouTube or Instagram a new opportunity arises for companies to connect to their consumers. However, since social media personalization implies the collection and analysis of highly personal data, consumers may develop negative reactions, attitudes or perceptions towards personalized advertising. Research covers extensively issues such as privacy concerns, invasiveness, forced exposure or irritation, which can lead to advertising avoidance. Though understanding the user perspective is crucial, the topic advertising avoidance in the context of personalization, especially in social media environments, hasn’t been discussed at great length. The purpose of this thesis is to understand how YouTube users experience personalized advertising while using the platform. The empirical findings of this thesis contribute to the ongoing research on personalized advertising within a social media setting. In addition, by understanding what can influence personalized ad avoidance on YouTube and describing how consumers express ad avoidance on the platform, this thesis aims to nurture a deeper understanding of the phenomenon. This study is based on an interpretative, abductive as well as a qualitative research design. It uses semi-structured interviews to explore the views, experiences, beliefs, and motivations of individual participants as well as focus groups that can leverage group dynamics to generate new qualitative data. The results of this thesis show that YouTube users experience ad avoidance in relationship with personalized ads for several reasons linked to prior negative attitudes, perceived goal impediment or ad irritation. The analysis of the findings revealed that users can experience cognitive, affective and behavioral ad avoidance as presented in the literature, but a theoretical model which can perfectly explain the phenomena of personalized ad avoidance on social media is currently not existent. While some antecedents claimed by the previously mentioned theoretical frameworks were also visible in the study, additional aspects may have an impact on how consumers experience personalized advertising avoidance in the social media environment, and more specifically on YouTube.

In a radio frequency (RF) system, the front-end of a radio receiver consists of an active antenna arrangement with a conducting mode antenna along with an active circuit. This arrangement helps avoid losses and SNR degradation due to the use of a coaxial cable. The active circuit is essentially an impedance matching network and a low noise amplification (LNA) stage. The input impedance of the antenna is always different from the source impedance required to be presented at the LNA input for maximum power gain and this gives rise to undesired reflections at the antenna-LNA junction. This necessitates a matching network that provides the impedance matching between the antenna and the LNA at a central frequency (CF). From the Friis formula it is seen that the total noise figure (NF) of the system is dependent on the noise figure and gain of the first stage. So, by having an LNA that provides a high gain (typically &gt;15 dB) which inserts minimum possible noise (desirably &lt; 1 dB), the overall noise figure of the system can be maintained low. The LNA amplifies the signal to a suitable power level that will enable the subsequent demodulation and decoding stages to efficiently recover the original signal. The antenna and the LNA can be matched with each other in two possible ways. The first approach is the traditional method followed in RF engineering where in both the antenna and LNA are matched to 50 W terminations and connected to each other. In this classical method, the antenna and LNA are matched to 50 W at the CF and does not take into account the matching at other frequencies in the operation range. The second approach employs a co-design method to match the antenna and LNA without a matching network or with minimum possible components for matching. This is accomplished by varying one or more parameters of either the antenna or LNA to control the impedances and ultimately achieve a matching over a substantial range of frequencies instead at the CF alone. The co-design method is shown to provide higher gain and a lower NF with reduced number of components, cost and size as compared to the classical method. The thesis work presented here is a study, design and manufacturing of an antenna-LNA module for a wide frequency range of 1.7 GHz – 2.7 GHz to explore the gain and NF improvements in the co-design approach. Planar micro strip patch antennas and GaAs E-pHEMT transistor based LNA’s are designed and the matching and co-design are simulated to test the gain and NF improvements. Furthermore, fully functional prototypes are developed with Roger R04360 substrate and the results from simulations and actual measurements are compared and discussed.

In advertising, the target has traditionally been aimed towards the product’s advantages.Today the trend is that the advertisers want to create a restless and unsatisfied consumer. Theconsumer on her part is not trying to achieve a goal with her consumption, but experiences theconsumption itself as a goal. Because of this the consumer demands a fast and variedselection.In order to sell their products the companies must create a non-existent need amongst theconsumers. Therefore it is very common in advertising today to use emotions instead ofinformation to attract the customers. Fashion ads are often created to form an emotion withthe consumer. It is also very important to make ads that the target group can identify with.The advertisers often try to achieve this by using models with positive qualities that theconsumer can look up to. Because of this we see a tendency that today’s fashion ads are verysimilar and can be hard to separate from each other.In our paper we want to go deeper into marketing communication as a subject by examininghow the receiver is affected by the message in magazine ads. To reach our aim we haveinvestigated, described and analyzed the fashion ads of today to see if they are built by similarcomponents and whether they attract the target group. Our chosen target group is womenbetween 20 and 30 years old. We have decided to have a hermeneutic way of interpretationand an inductive reasoning. To enlighten our problem areas we have chosen to conduct aqualitative study consisting of personal interviews where the objects were asked to make astatement about three fashion ads. We also conducted a quantitative analysis of the ad contentin three fashion magazines. In our theoretical frame of reference we have used marketingliterature. The paper therefore consists of both primary and secondary data.The conclusion of our studies is that our target group mostly perceives fashion ads aspositive, but they do not to a great extent identify themselves with them. They want ads to benatural and that the model is presented in a trustworthy environment regarding the productsthat are in the picture. It is hard for the consumers to separate the ads from each other andconnect them to a specific brand. The women in our target group require that the ads consistof more information, mostly regarding price and store location. Our analysis of content showsthat fashion ads today is similar in imagery and existing elements. The most prominentfeatures are female models and homepage addresses. / <p>Program: Textilekonomutbildningen</p><p>Uppsatsnivå: C</p>

Orientador: Vilson Tonin Zanchin / Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Física, 2011

General relativity, one of the pillars of our understanding of the universe, has been a remarkably successful theory. It has stood the test of time for more than 100 years and has passed all experimental tests so far. Most recently, the LIGO collaboration made the first-ever direct detection of gravitational waves, confirming a long-standing prediction of general relativity. Despite this, several fundamental mathematical questions remain unanswered, many of which relate to the global existence and the stability of solutions to Einstein's equations. This thesis presents our efforts to use numerical relativity to investigate some of these questions. We present a complete picture of the end points of black ring instabilities in five dimensions. Fat rings collapse to Myers-Perry black holes. For intermediate rings, we discover a previously unknown instability that stretches the ring without changing its thickness and causes it to collapse to a Myers-Perry black hole. Most importantly, however, we find that for very thin rings, the Gregory-Laflamme instability dominates and causes the ring to break. This provides the first concrete evidence that in higher dimensions, the weak cosmic censorship conjecture may be violated even in asymptotically flat spacetimes. For Myers-Perry black holes, we investigate instabilities in five and six dimensions. In six dimensions, we demonstrate that both axisymmetric and non-axisymmetric instabilities can cause the black hole to pinch off, and we study the approach to the naked singularity in detail. Another question that has attracted intense interest recently is the instability of anti-de Sitter space. In this thesis, we explore how breaking spherical symmetry in gravitational collapse in anti-de Sitter space affects black hole formation. These findings were made possible by our new open source general relativity code, GRChombo, whose adaptive mesh capabilities allow accurate simulations of phenomena in which new length scales are produced dynamically. In this thesis, we describe GRChombo in detail, and analyse its performance on the latest supercomputers. Furthermore, we outline numerical advances that were necessary for simulating higher dimensional black holes stably and efficiently.