{"id":{"repo_id":"brazil-uff","oai_identifier":"oai:app.uff.br:1/17280"},"canonical_url":"https://search.dev.ndltd.org/etd/brazil-uff/oai:app.uff.br:1/17280","repository":{"repo_id":"brazil-uff","name":"Brazil UFF","base_url":"https://app.uff.br/oai/request"},"display":{"title":"Colapso gravitacional de fluido perfeito em espaços-tempos circularmente simétricos com auto-similaridade cinemática","abstract":"Perfect fluid with kinematic self-similarity is studied in 2 + 1 dimensional spacetimes with circular symmetry and various exact solutions to the Einstein field equations are given. These include all the solutions of dust and stiff perfect fluid with self-similarity of the first kind (homothetic) and all the solutions of perfect fluid with a linear equation of state and self-similarity of the zeroth and second kinds. It is found that some of these solutions represent gravitational collapse and the final state of the collapse can be either a black hole or a null singularity. It is also shown that one solution can have two different kinds of kinematic self-similarity. At last, linear perturbations of homothetic self-similar stiff fluid solutions are studied. It is found that, except for those with n = 1 and n = 3, none of them is stable and all have more than one unstable mode. Hence, none of these solutions can be critical, because, by definition, a critical solution has one and only one unstable mode.","abstract_html":"Perfect fluid with kinematic self-similarity is studied in 2 + 1 dimensional spacetimes with circular symmetry and various exact solutions to the Einstein field equations are given. These include all the solutions of dust and stiff perfect fluid with self-similarity of the first kind (homothetic) and all the solutions of perfect fluid with a linear equation of state and self-similarity of the zeroth and second kinds. It is found that some of these solutions represent gravitational collapse and the final state of the collapse can be either a black hole or a null singularity. It is also shown that one solution can have two different kinds of kinematic self-similarity. At last, linear perturbations of homothetic self-similar stiff fluid solutions are studied. It is found that, except for those with n = 1 and n = 3, none of them is stable and all have more than one unstable mode. Hence, none of these solutions can be critical, because, by definition, a critical solution has one and only one unstable mode.","abstract_has_math":false,"creators":["Miguelote, Alexandre Yasuda"],"institution":"Programa de Pós-graduação em Física","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":null,"date_issued":"","date_published":null,"updated_at":"2026-07-27T19:00:38Z","subjects":["Gravitação","Relatividade geral","Colapso gravitacional","Simetria circular","Auto-similaridade","Fenômenos críticos"],"languages":["por"],"rights":["Acesso Aberto"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://app.uff.br/riuff/handle/1/17280","outbound_label":"Repository record","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Miguelote, Alexandre Yasuda"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2021-03-10T19:10:36Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2021-03-10T19:10:36Z","2009-11-19"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["Física"]},{"key":"dc:type","label":"Dc Type","values":["Tese","Teses"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Gravitação","Relatividade geral","Colapso gravitacional","Simetria circular","Auto-similaridade","Fenômenos críticos"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["por"]},{"key":"dc:rights","label":"Dc Rights","values":["Acesso Aberto"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://app.uff.br/riuff/handle/1/17280"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Perfect fluid with kinematic self-similarity is studied in 2 + 1 dimensional spacetimes with circular symmetry and various exact solutions to the Einstein field equations are given. These include all the solutions of dust and stiff perfect fluid with self-similarity of the first kind (homothetic) and all the solutions of perfect fluid with a linear equation of state and self-similarity of the zeroth and second kinds. It is found that some of these solutions represent gravitational collapse and the final state of the collapse can be either a black hole or a null singularity. It is also shown that one solution can have two different kinds of kinematic self-similarity. At last, linear perturbations of homothetic self-similar stiff fluid solutions are studied. It is found that, except for those with n = 1 and n = 3, none of them is stable and all have more than one unstable mode. Hence, none of these solutions can be critical, because, by definition, a critical solution has one and only one unstable mode.","Fluido perfeito com auto-similaridade cinemática é estudado em espaçostempos 2 + 1 dimensionais com simetria circular e várias soluções exatas das equações de campo de Einstein são dadas. Estas incluem todas as soluções de poeira e fluido perfeito rígido com auto-similaridade do primeiro tipo (homotética) e todas as soluções de fluido perfeito com uma equação de estado linear e auto-similaridade do tipo de ordem zero e do segundo tipo. Viu-se que algumas destas soluções representam colapso gravitacional e o estado final do colapso pode ser ou um buraco negro ou uma singularidade nula. Mostrou-se também que uma solução pode ter dois tipos diferentes de auto-similaridade cinemática. Por fim, perturbações lineares de soluções auto-similares homotéticas são estudadas. Notou-se que, exceto para aquelas com n = 1 e n = 3, nenhuma delas é estável e todas possuem mais de um modo instável. Portanto, nenhuma destas soluções pode ser crítica, já que, por definição uma solução crítica possui um e somente um modo instável."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Colapso gravitacional de fluido perfeito em espaços-tempos circularmente simétricos com auto-similaridade cinemática"]}]}],"canonical_facts":{"dc:creator":["Miguelote, Alexandre Yasuda"],"dc:date.accessioned":["2021-03-10T19:10:36Z"],"dc:date.available":["2021-03-10T19:10:36Z","2009-11-19"],"dc:description.abstract":["Perfect fluid with kinematic self-similarity is studied in 2 + 1 dimensional spacetimes with circular symmetry and various exact solutions to the Einstein field equations are given. These include all the solutions of dust and stiff perfect fluid with self-similarity of the first kind (homothetic) and all the solutions of perfect fluid with a linear equation of state and self-similarity of the zeroth and second kinds. It is found that some of these solutions represent gravitational collapse and the final state of the collapse can be either a black hole or a null singularity. It is also shown that one solution can have two different kinds of kinematic self-similarity. At last, linear perturbations of homothetic self-similar stiff fluid solutions are studied. It is found that, except for those with n = 1 and n = 3, none of them is stable and all have more than one unstable mode. Hence, none of these solutions can be critical, because, by definition, a critical solution has one and only one unstable mode.","Fluido perfeito com auto-similaridade cinemática é estudado em espaçostempos 2 + 1 dimensionais com simetria circular e várias soluções exatas das equações de campo de Einstein são dadas. Estas incluem todas as soluções de poeira e fluido perfeito rígido com auto-similaridade do primeiro tipo (homotética) e todas as soluções de fluido perfeito com uma equação de estado linear e auto-similaridade do tipo de ordem zero e do segundo tipo. Viu-se que algumas destas soluções representam colapso gravitacional e o estado final do colapso pode ser ou um buraco negro ou uma singularidade nula. Mostrou-se também que uma solução pode ter dois tipos diferentes de auto-similaridade cinemática. Por fim, perturbações lineares de soluções auto-similares homotéticas são estudadas. Notou-se que, exceto para aquelas com n = 1 e n = 3, nenhuma delas é estável e todas possuem mais de um modo instável. Portanto, nenhuma destas soluções pode ser crítica, já que, por definição uma solução crítica possui um e somente um modo instável."],"dc:format":["application/pdf"],"dc:identifier.uri":["https://app.uff.br/riuff/handle/1/17280"],"dc:language":["por"],"dc:publisher.department":["Física"],"dc:rights":["Acesso Aberto"],"dc:subject":["Gravitação","Relatividade geral","Colapso gravitacional","Simetria circular","Auto-similaridade","Fenômenos críticos"],"dc:title":["Colapso gravitacional de fluido perfeito em espaços-tempos circularmente simétricos com auto-similaridade cinemática"],"dc:type":["Tese","Teses"]},"updated_at":"2026-07-27T19:00:38Z"}