<p>The overall goal of this diploma work is to produce a design of a 5 GHz radio frontend using Agilent Advanced Design System (ADS) and then build a working prototype. Using this prototype to determine if RF circuits at 5 GHz can be successfully produced using distributed components on a laminate substrate. </p><p>The design process for the radio front-end consists of two stages. In the first stage the distributed components are designed and simulated, and in the second stage all components are merged into a PCB. This PCB is then manufactured and assembled. All measurements on the radio front-end and the test components are made using a network analyser, in order to measure the S-parameters. </p><p>This diploma work has resulted in a functional design and prototype, which has proved that designing systems for 5 GHz on a laminate substrate is possible but by no means trivial.</p>

<p>For the first time in the history of physics we stand in front of a theory that might actually serve as a unification of it all - string theory. It provides a self-consistent framework for gravity and quantum mechanics, which naturally incorporates matter and gauge interactions of the type seen in the standard model. Unfortunately, at the moment we do not know of any principle that selects the vacuum of the theory, so predictions about our four-dimensional world are still absent. However, the introduction of extended objects opens up an intricate new arena of physics, which is non-trivial and challenging to map out, even at a basic level.</p><p>A key concept of quantum gravity is holography; this is realised in string theory by the AdS/CFT correspondence, which relates string theory to a field theory living in a lower dimensional space. In this thesis we discuss two limits of the correspondence, namely the BMN limit, giving rise to a plane wave geometry, and the tensionless limit, exhibiting massless higher spin interactions. We also study a limit of string theory in a background electric field, where the theory is described by open strings and positively wound closed strings only.</p><p>We begin with a brief review of the theory, focusing on an intuitive understanding of the basic aspects and serving as an introduction to the papers. In the first paper we calculate, from two different points of view, scattering amplitudes in the non-commutative open string limit. In the second paper we obtain the quadratic scalar field contributions to the stress-energy tensor in the minimal bosonic higher spin gauge theory in four dimensions. In the last paper we propose a way to avoid fermion doubling when discretizing the string in the BMN limit.</p>

<p>One of the still big problems in the Standard Model of particle physics is the problem of confinement. Quarks or other coloured particles have never been observed in isolation. Quarks are only observed in colour neutral bound states. The strong interactions are described using a Yang-Mills theory. These type of theories exhibits asymptotic freedom, i.e. the coupling is weak at high energies. This means that the theory is perturbative at high energies only. Understanding quark confinement requires knowledge of the non perturbative regime. One attempt has been to identify the proper order parameters for describing the low energy limit and then to write down effective actions in terms of these order parameters. We discuss one possible scenario for confinement and the effective models constructed with this as inspiration. Further we discuss solitons in these models and their properties.</p><p>Yang-Mills theory has also become important in the context of string theory. According to the AdS/CFT correspondence string theory in AdS₅×S⁵ is dual to four dimensional Yang-Mills with four supersymmetries. The duality relate the non perturbative regime of one of the theories to the perturbative regime of the other. This makes it in general hard to test this conjecture. For a special type of solutions it is however possible to use a perturbative expansion in both theories. We discuss this type of solutions and in particular we discuss a method, the Bethe ansatz, to find the solutions on the gauge theory side.</p>

For the first time in the history of physics we stand in front of a theory that might actually serve as a unification of it all - string theory. It provides a self-consistent framework for gravity and quantum mechanics, which naturally incorporates matter and gauge interactions of the type seen in the standard model. Unfortunately, at the moment we do not know of any principle that selects the vacuum of the theory, so predictions about our four-dimensional world are still absent. However, the introduction of extended objects opens up an intricate new arena of physics, which is non-trivial and challenging to map out, even at a basic level. A key concept of quantum gravity is holography; this is realised in string theory by the AdS/CFT correspondence, which relates string theory to a field theory living in a lower dimensional space. In this thesis we discuss two limits of the correspondence, namely the BMN limit, giving rise to a plane wave geometry, and the tensionless limit, exhibiting massless higher spin interactions. We also study a limit of string theory in a background electric field, where the theory is described by open strings and positively wound closed strings only. We begin with a brief review of the theory, focusing on an intuitive understanding of the basic aspects and serving as an introduction to the papers. In the first paper we calculate, from two different points of view, scattering amplitudes in the non-commutative open string limit. In the second paper we obtain the quadratic scalar field contributions to the stress-energy tensor in the minimal bosonic higher spin gauge theory in four dimensions. In the last paper we propose a way to avoid fermion doubling when discretizing the string in the BMN limit.

One of the still big problems in the Standard Model of particle physics is the problem of confinement. Quarks or other coloured particles have never been observed in isolation. Quarks are only observed in colour neutral bound states. The strong interactions are described using a Yang-Mills theory. These type of theories exhibits asymptotic freedom, i.e. the coupling is weak at high energies. This means that the theory is perturbative at high energies only. Understanding quark confinement requires knowledge of the non perturbative regime. One attempt has been to identify the proper order parameters for describing the low energy limit and then to write down effective actions in terms of these order parameters. We discuss one possible scenario for confinement and the effective models constructed with this as inspiration. Further we discuss solitons in these models and their properties. Yang-Mills theory has also become important in the context of string theory. According to the AdS/CFT correspondence string theory in AdS5×S5 is dual to four dimensional Yang-Mills with four supersymmetries. The duality relate the non perturbative regime of one of the theories to the perturbative regime of the other. This makes it in general hard to test this conjecture. For a special type of solutions it is however possible to use a perturbative expansion in both theories. We discuss this type of solutions and in particular we discuss a method, the Bethe ansatz, to find the solutions on the gauge theory side.

Cette thèse est consacrée à l'étude de systèmes quantiques intégrables tels des chaînes de spins, des théories de champs à 1+1 dimensions, et la dualité AdS/CFT. Cette dualité AdS/CFT est une conjecture, émise à la fin du siècle dernier, qui relie notamment le régime non-perturbatif d'une théorie de jauge superconforme (nommée N =4 super Yang- Mills) au régime perturbatif d'une théorie de cordes dans un espace à 10 dimensions (de géométrie AdS5×S5). Ce manuscrit explore les similarités entre des chaînes de spins intégrables et des théories de champs intégrables, tels Super Yang Mills. Il commence par une étude ap- profondie des chaînes de spins intégrables pour y construire explicitement un "flot de Bäcklund" et des "opérateurs Q" polynômiaux, qui permettent de diagonaliser le Hamil- tonien. Des théories de champs intégrables sont ensuite étudiées et des "fonctions Q" sont obtenues, qui sont l'analogue des opérateurs Q construits pour les chaînes de spins. Il apparaît que de nombreuses informations sont contenue dans les propriétés analytiques des fonctions Q. Cela permet d'aboutir, dans le cadre de l'ansatz de Bethe thermody- namique, à un nombre fini d'équations non-linéaires intégrales qui encode le spectre des niveaux d'énergie de la théorie considérée (en taille finie). Ce système d'équations est équivalent au système infini d'équations, connu sous le nom de système Y, qui dans le cas de la dualité AdS/CFT avait été conjecturé assez récemment.

Using the AdS/CFT correspondence, we study the anisotropic transport properties of both supersymmetric and non-supersymmetric matter fields on (2+1)-dimensional defects coupled to a (3+1)-dimensional N=4 SYM "heat bath". We address on the one hand the purely conformal defect where the only non-vanishing background field that we turn on is a "topological", parameter parametrizing the impact on the bulk. On the other hand we also address the case of a finite external background magnetic field, finite net charge density and finite mass. We find in the purely conformal limit that the system possesses a conduction threshold given by the wave number of the perturbation and that the charge transport arises from a quasiparticle spectrum which is consistent with an intuitive picture where the defect acquires a finite width in the direction of the SYM bulk. We also examine finite-coupling modifications arising from higher derivative interactions in the probe brane action. In the case of finite density, mass and magnetic field, our results generalize the conformal case. We discover at high frequencies a spectrum of quasiparticle resonances due to the magnetic field and finite density and at small frequencies a Drude-like expansion around the DC limit. Both of these regimes display many generic features and some features that we attribute to strong coupling, such as a minimum DC conductivity and an unusual behavior of the "cyclotron" and plasmon frequencies, which become correlated to the resonances found in the conformal case. We further study the hydrodynamic regime and the relaxation properties, in which the system displays a set of different possible transitions to the collisionless regime. The mass dependence can be cast in two regimes: a generic relativistic behavior dominated by the UV and a non-linear hydrodynamic behavior dominated by the IR. In the massless case, we also extend earlier results to find an interesting duality under the transformation of the conductivity and the exchange of density and magnetic field. Furthermore, we look at the thermodynamics and the phase diagram, which reproduces general features found earlier in 3+1 dimensional systems and demonstrates stability in the relevant phase.

The overall goal of this diploma work is to produce a design of a 5 GHz radio frontend using Agilent Advanced Design System (ADS) and then build a working prototype. Using this prototype to determine if RF circuits at 5 GHz can be successfully produced using distributed components on a laminate substrate. The design process for the radio front-end consists of two stages. In the first stage the distributed components are designed and simulated, and in the second stage all components are merged into a PCB. This PCB is then manufactured and assembled. All measurements on the radio front-end and the test components are made using a network analyser, in order to measure the S-parameters. This diploma work has resulted in a functional design and prototype, which has proved that designing systems for 5 GHz on a laminate substrate is possible but by no means trivial.

Using the AdS/CFT correspondence, we study the anisotropic transport properties of both supersymmetric and non-supersymmetric matter fields on (2+1)-dimensional defects coupled to a (3+1)-dimensional N=4 SYM "heat bath". We address on the one hand the purely conformal defect where the only non-vanishing background field that we turn on is a "topological", parameter parametrizing the impact on the bulk. On the other hand we also address the case of a finite external background magnetic field, finite net charge density and finite mass. We find in the purely conformal limit that the system possesses a conduction threshold given by the wave number of the perturbation and that the charge transport arises from a quasiparticle spectrum which is consistent with an intuitive picture where the defect acquires a finite width in the direction of the SYM bulk. We also examine finite-coupling modifications arising from higher derivative interactions in the probe brane action. In the case of finite density, mass and magnetic field, our results generalize the conformal case. We discover at high frequencies a spectrum of quasiparticle resonances due to the magnetic field and finite density and at small frequencies a Drude-like expansion around the DC limit. Both of these regimes display many generic features and some features that we attribute to strong coupling, such as a minimum DC conductivity and an unusual behavior of the "cyclotron" and plasmon frequencies, which become correlated to the resonances found in the conformal case. We further study the hydrodynamic regime and the relaxation properties, in which the system displays a set of different possible transitions to the collisionless regime. The mass dependence can be cast in two regimes: a generic relativistic behavior dominated by the UV and a non-linear hydrodynamic behavior dominated by the IR. In the massless case, we also extend earlier results to find an interesting duality under the transformation of the conductivity and the exchange of density and magnetic field. Furthermore, we look at the thermodynamics and the phase diagram, which reproduces general features found earlier in 3+1 dimensional systems and demonstrates stability in the relevant phase.

There have been a lot of researches done on political parties and their characteristics in the modern world concerning marketing and communication. This thesis seeks to tap into a new area within this subject by asking a main research question: How could political parties use exposure in newspapers as a marketing tool to raise opinion numbers? The theories that has been applied to the thesis consists of findings within several areas; political science, philosophy and psychology. However, emphasize has been to apply it to the area of business administration by connecting it to consumer/voting behavior to explain how through the complexity of exposure and choice forms a voter into voting. The thesis consist of data concerning opinion numbers spanning over ten years, January 2000 – December 2009, as well as the total number of articles that has been published in four of Sweden’s largest newspapers. Both data sources are to be considered reliable, which is important since the entire thesis consists of secondary data.