This Thesis is concerned with three particular aspects of extended cosmic strings and domain walls in cosmology: their dynamics, gravitation and interaction with a black hole. In Chapter 3, we study the dynamics of an abelian-Higgs cosmic string. We find its equations of motion from an effective action and compare, for three test trajectories, the resulting motion with that observed in the Nambu-Gotō approximation. We also present a general argument showing that the corrected motion of any string is generically antirigid. We pursue the investigation of the dynamics of topological defects in Chapter 5, where we find (from integrability conditions rather than an effective action) the effective equations governing the motion of a gravitating curved domain wall. In Chapter 4 we investigate the spacetime of a gravitating domain wall in a theory with a general potential V(ɸ). We show that, depending on the gravitational coupling e of the scalar ɸ, all nontrivial solutions fall into two categories interpretable as describing respectively domain wall and false vacuum-de Sitter solutions. Wall solutions cannot exist beyond a value (^4)(_3)ɛmax, and vacuum-de Sitter solutions are unstable to decaying into wall solutions below ɛmax at ɛmax we observe a phase transition between the two types of solution. We finally specialize for the Goldstone and sine-Gordon potentials. In Chapter 6 we consider a Nielsen-Olesen vortex whose axis passes through the centre of an extremal Reissner-Nordstr0m black hole. We examine in particular the existence of piercing and expelled solutions (where the string respectively does and does not penetrate the black hole's horizon) and determine that while thin strings penetrate the horizon — and therefore can be genuinely called hair — thick strings are expelled; the two kinds of solution are separated by a phase transition.

A 'Subject Indexing Language' (SIL) is an artificial language used for formulating names of subjects. Although classificationists have sought for universals in many fields of study such as, philosophy, biology, general systems theory, etc., the search for a deep structure of SILs formally began with Ranganathan's idea of 'absolute syntax' and was brought to the present by G. Bhattacharyya and D. Austin. Whereas Bhattacharyya's deep structure of SIL is primarily based on classificatory principles (parallel to 'absolute syntax'), the deep structure proposed by Austin has a linguistic connotation. The present study describes and compares two such deep structurebased SILs, viz., PRECIS (PREserved Context Index System) and DSIS (Deep Structure Indexing System), a recent computerized version of POPSI (POstulate-based Permuted Subject Indexing), developed by F. J. Devadason at Documentation Research and Training Centre, Bangalore, India. Both also belong to the category of SILs typified as 'string indexing' languages. The study involves: i) writing of a suitable DSIS index entry generation program, ii) using both PRECIS (in-house) and DSIS programs to index a collection of representative sample documents from the soft sciences, iii) analyzing and comparing their respective syntactic and semantic aspects in terms of both linguistic and classificatory principles, and iv) applying some measures of efficiency and effectiveness. It was realized that certain modifications in the existing DSIS string manipulation algorithms are necessary to make the program fully operational. Although, no attempts have been made to quantify the measures of effectiveness and efficiency as such, suggestions have been provided as to what these probably would be. Some indications of their searching difficulties for a prospective searcher have been put forward as well.

With the start of the age of the Large Hadron Collider (LHC) two challenges face theoreticians and computational physicists. The first is about understanding theories beyond the Standard Model and producing verifiable predictions that can be tested against what the LHC and subsequent machines would produce. The second is to improve computational methods so that the new experimental precision is matched by a theoretical one. But this improvement is also crucial for the detection of potential deviations from Standard Model predictions and possibly also finding the elusive Higgs. This work tries to address problems in both areas. In the first part we study the effects of adding tension in considering a black-hole on a brane. Such black-holes are predicted by some models as potential phenomena at the LHC. We calculate the effects of adding tension on observable quantities of black-holes, namely, quasinormal mode frequencies and Hawking radiation, and we show how this improves predictions. In the second part we investigate the computational problem of extending the Britto-Cachazo-Feng-Witten (BCFW) method to 1-loop level. The BCFW has been successfully used in recent years to compute scattering amplitudes at tree-level by suitably complex-shifting external momenta and reducing diagrams to simpler ones. In our investigation we establish that the BCFW can be extended to 1-loop, which means that 1-loop integrands can be treated as trees and can be broken down further into even simpler trees using the BCFW. We explicitly look at the effects of the shift for the lowest three n-point cases, but also demonstrate how the result extends to arbitrary n.

This thesis considers two different aspects of string theory, the tensionless limit of the string and supersymmetric sigma models with extended supersymmetry. First, the tensionless limit is used to find a IIB supergravity background generated by a tensionless string. The background has the characteristics of a gravitational shock-wave. Then, the quantization of the tensionless string in a pp-wave background is performed and the result is found to agree with what is obtained by taking a tensionless limit directly in the quantized theory of the tensile string. Hence, in the pp-wave background the tensionless limit commutes with quantization. Next, supersymmetric sigma models and the relation between extended world-sheet supersymmetry and target space geometry is studied. The sigma model with N=(2,2) extended supersymmetry is considered and the requirement on the target space to have a bi-Hermitean geometry is reviewed. The Hamiltonian formulation of the model is constructed and the target space is shown to have generalized Kähler geometry. The equivalence between bi-Hermitean geometry and generalized Kähler follows, in this context, from the equivalence between the Lagrangian- and Hamiltonian formulation of the sigma model. Then, T-duality in the Hamiltonian formulation of the sigma model is studied and the explicit T-duality transformation is constructed. It is shown that the transformation is a symplectomorphism, i.e. a generalization of a canonical transformation. Under certain assumptions, the amount of extended supersymmetry present in the sigma model is shown to be preserved under the T-duality transformation. Next, extended supersymmetry in a first order formulation of the sigma model is studied. By requiring N=(2,2) extended world-sheet supersymmetry an intriguing geometrical structure arises and in a special case generalized complex geometry is found to be contained in the new framework.

This thesis deals with different aspects of string and /p/-brane theories. One of the motivations for string theory is to unify the forces in nature and produce a quantum theory of gravity. /p/-branes and related objects arise in string theory and are related to a non-perturbative definition of the theory. The results of this thesis might help in understanding string theory better. The first part of the thesis introduces and discusses relevant topics for the second part of the thesis which consists of five papers. In the three first papers we develop and treat a perturbative approach to relativistic /p/-branes around stretched geometries. The unperturbed theory is described by a string- or particle-like theory. The theory is solved, within perturbation theory, by constructing successive canonical transformations which map the theory to the unperturbed one order by order. The result is used to define a quantum theory which requires for consistency d = 25 + p dimensions for the bosonic /p/-branes and d = 11 for the supermembrane. This is one of the first quantum results for extended objects beyond string theory and is a confirmation of the expectation of an eleven-dimensional quantum membrane. The two last papers deal with a gauged WZNW-approach to strings moving on non-trivial space-times. The groups used in the formulation of these models are connected to Hermitian symmetric spaces of non-compact type. We have found that the GKO-construction does not yield a unitary spectrum. We will show that there exists, however, a different approach, the BRST approach, which gives unitarity under certain conditions. This is the first example of a difference between the GKO- and BRST construction. This is one of the first proofs of unitarity of a string theory in a non-trivial non-compact space-time. Furthermore, new critical string theories in dimensions less then 26 or 10 is found for the bosonic and supersymmetric string, respectively.

Thesis (PhD)--Macquarie University, Division of Information and Communication Sciences, Department of Computing, 2008. / Thesis submitted for the joint institutional requirements for the double-badged degree of Doctor of Philosophy and Docteur de l'Université de Provence, Spécialité : Informatique. Includes bibliography (p. 229-240) and index.

The fuzzball model of a black hole is an attempt to resolve the many paradoxes and puzzles of black hole physics that have revealed themselves over the last century. These badly behaved solutions of general relativity have given physicists one of the few laboratories to test candidate quantum theories of gravity. Though little is known about exactly what lies beyond the event horizon, and what the ultimate fate of matter that falls in to a black hole is, we know a few intriguing and elegant semi-classical results that have kept physicists occupied. Among these are the known black hole entropy and the Hawking radiation process.

Made available in DSpace on 2015-05-14T12:52:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-05-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The present work is about the Orquestra Criança Cidadã (Child Citizen Orchestra), a nongovernmental organisation that assists children and youngsters aged 4 to 20 who live in the Coque neighbourhood in Recife, Pernambuco. The main purpose of this study is to understand the relationship between the music education received and the social inclusion of these children and youngsters. In order to fulfill this aim, case study method was chosen as the means of collecting data. The results revealed the influence of a social music education on the lives of these children and youngsters, especially regarding their personal relationships and their development as citizens. / Este trabalho teve o objetivo de compreender como se tece a relação entre formação musical e inclusão social de crianças e jovens do Projeto Orquestra Criança Cidadã, que atende crianças e jovens de quatro a vinte anos, oriundos da Comunidade do Coque em Recife, Pernambuco. A pesquisa foi realizada à luz dos conhecimentos de pesquisa qualitativa, tendo como método o estudo de caso e utilizando como instrumentos de coleta de dados a observação, entrevistas com alunos do Projeto e fontes documentais. A pesquisa revelou, para além de aspectos pedagógicos e organizacionais do Projeto, a formação musical social proporcionada a essas crianças e jovens, bem como o sentido dessa formação em suas vidas, principalmente em suas relações pessoais e em seu crescimento enquanto cidadãos.

Este trabalho realiza uma leitura, pautada nos fundamentos da contemporaneidade, sobre a Literatura de Cordel do século XXI, tomando como corpus a obra de Klévisson Viana, um dos expoentes do cordel nordestino nas últimas décadas. Para tratar de aspectos como a folkcomunicação e o diálogo entre literatura canônica e literatura popular, foi utilizado o embasamento teórico de Antoine Compagnon (2010), José Marques de Melo (2008), Márcia Abreu (1999) e Madalena Jorge Dine (1998). Já para tratar de questões como a performance e a ligação entre oralidade e escrita, foram aproveitadas as teorias advindas dos estudos de Paul Zumthor (2007), Idelette Muzart Fonseca dos Santos (1995), Ana Maria Galvão (2001) e Luís da Câmara Cascudo (2005). Este trabalho pretende, assim, construir uma interpretação abrangente sobre os temas, os personagens e as expressões que a linguagem do cordel mantém, mas também os que ela renova, de modo que certas ideologias e personagens tradicionais permanecem na identidade nordestina utilizando novas linguagens e novas poéticas. / This thesis carries out a reading, based on the principles of contemporaneity, of twenty-first century Cordel Literature (String Literature), taking as corpus the works of Klévisson Viana, who has been an exponent of Northeastern Cordel Literature in recent decades. To handle aspects such as folkcomunication and dialogue between canonical literature and popular literature, a theoretical basis supplied by the works of Antoine Compagnon (2010), José Marques de Melo (2008), Márcia Abreu (1999), and Magdalena Jorge Dine (1998) has been used. And to address issues such as performance and the connection between orality and writing , theories arising from the studies of Paul Zumthor (2007), Idelette Muzart Fonseca dos Santos (1995), Ana Maria Galvão (2001) and Luís da Câmara Cascudo (2005) have provided appropriate support. The work thus seeks to build a comprehensive interpretation of the themes, characters and expressions that Cordel (String Literature) language has maintained, but also the ones that it has renewed, in the sense that certain ideologies and traditional characters have remained in Northeastern identity by utilizing new languages and new poetics.

Este trabalho realiza uma leitura, pautada nos fundamentos da contemporaneidade, sobre a Literatura de Cordel do século XXI, tomando como corpus a obra de Klévisson Viana, um dos expoentes do cordel nordestino nas últimas décadas. Para tratar de aspectos como a folkcomunicação e o diálogo entre literatura canônica e literatura popular, foi utilizado o embasamento teórico de Antoine Compagnon (2010), José Marques de Melo (2008), Márcia Abreu (1999) e Madalena Jorge Dine (1998). Já para tratar de questões como a performance e a ligação entre oralidade e escrita, foram aproveitadas as teorias advindas dos estudos de Paul Zumthor (2007), Idelette Muzart Fonseca dos Santos (1995), Ana Maria Galvão (2001) e Luís da Câmara Cascudo (2005). Este trabalho pretende, assim, construir uma interpretação abrangente sobre os temas, os personagens e as expressões que a linguagem do cordel mantém, mas também os que ela renova, de modo que certas ideologias e personagens tradicionais permanecem na identidade nordestina utilizando novas linguagens e novas poéticas. / This thesis carries out a reading, based on the principles of contemporaneity, of twenty-first century Cordel Literature (String Literature), taking as corpus the works of Klévisson Viana, who has been an exponent of Northeastern Cordel Literature in recent decades. To handle aspects such as folkcomunication and dialogue between canonical literature and popular literature, a theoretical basis supplied by the works of Antoine Compagnon (2010), José Marques de Melo (2008), Márcia Abreu (1999), and Magdalena Jorge Dine (1998) has been used. And to address issues such as performance and the connection between orality and writing , theories arising from the studies of Paul Zumthor (2007), Idelette Muzart Fonseca dos Santos (1995), Ana Maria Galvão (2001) and Luís da Câmara Cascudo (2005) have provided appropriate support. The work thus seeks to build a comprehensive interpretation of the themes, characters and expressions that Cordel (String Literature) language has maintained, but also the ones that it has renewed, in the sense that certain ideologies and traditional characters have remained in Northeastern identity by utilizing new languages and new poetics.