Univ., Diss., 2004--Mainz

University, Diss., 2005--Heidelberg.

Made available in DSpace on 2018-08-01T22:29:32Z (GMT). No. of bitstreams: 1 tese_4557_.pdf: 3091584 bytes, checksum: f3f8012b211cf4052797c2a8cbf07695 (MD5) Previous issue date: 2010-08-09 / Esta dissertação é dedicada à investigação sobre a natureza da matéria e da energia escura no Universo através da técnica que utiliza observações a explosões de supernovae do tipo Ia como indicadoras de distâncias, usada no -fim do séc. XX para detectar a aceleração da expansão do Universo. Desde então alguns projetos voltados à observação de supernovae foram executados e tornaram públicos os seus dados, que são usados neste trabalho para a estimativa de parâmetros e comparação de modelos cosmológicos. O objetivo deste trabalho é de estudar a capacidade do teste cosmolgico feito com os dados das distâncias às supernovae tipo Ia e a sua resposta a diferentes modelos cosmológicos e parâmetros livres. Para isto foi feito uma revisão do modelo padrão da Cosmologia e das evidências que apontam para a presença da matéria e da energia escuras, seguida de um estudo sobre o fenômeno das supernovae tipo Ia em seus aspectos observacionais e astrofísicos, que permitem a construção das técnicas de calibração de suas magnitudes e a estimativa de suas distâncias. Antes de seguir para a análise cosmológica introduz-se a ferramenta apropriada que é a estatística bayesiana, estudada aqui apenas em suas ferramentas e aplicações mais elementares. E por último aplicamos estas ferramentas às amostras de dados de supernovae tipo Ia disponíveis na literatura conhecidas como Gold, SNLS, Essence e Constitution, para estudar alguns modelos cosmológicos de interesse, a começar pelo próprio modelo de concordância CDM e a parametrização wCDM que testa a consistência da suposição wX = -1 para a energia escura. Em seguida testamos dois modelos de energia do vácuo dinâmica (t) e por último um caso especial de quartessência, o Gás de Chaplygin generalisado. Os resultados mostram que os dados das supernovae usados isoladamente dão resultados bem menos expressivos do que os encontrados na literatura onde são usados em conjunto com outras evidências. Duas das amostras de dados incluindo a mais atual dão origem a resultados que apresentam irregularidades inesperadas, que apontam para a existência de fatores ainda não controlados pelas técnicas de calibração da supernovae. Ambos os resultados indicam que o teste cosmológico baseados nas distância às supernovae Ia ainda passará por um outro salto de qualidade num futuro próximo.

Orientadores: Marcelo Moraes Guzzo, Renata Zukanovich Funchal / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-06T18:49:31Z (GMT). No. of bitstreams: 1 SanchezVega_BruceLehmann_M.pdf: 867356 bytes, checksum: 7ef0ed6b2a81cab96ae23751d7ad2efa (MD5) Previous issue date: 2006 / Resumo: Neste trabalho estudamos os decaimentos não radiativos de neutrinos de Majorana, via bósons sem massa, no vácuo e na matéria. Os acoplamentos considerados entre os neutrinos e os bósons foram de tipo escalar ou pseudoescalar. Em particular estudamos os processos n i ® nj + c e n i ® n j + c (onde c representa o campo escalar ou pseudoescalar). No vácuo, calculamos as taxas efetivas na ordem mais baixa da teoria de perturbações usando o formalismo convencional para neutrinos de Majorana. Calculamos estas mesmas taxas para o caso da matéria usando o formalismo de helicidade de dois componentes introduzido em [P. Mannheim, Phys. Rev. D. 37, 1935 (1988)] para uma teoria geral (n, m), onde se tem n campos que pertencem a isodubletos de SUL(2) (neutrinos ativos) e m campos isosingletos de SUL(2) (neutrinos estéreis). Decaimentos de neutrinos com tempos de vida relativamentes longos podem ser provados, em principio, através de observações de neutrinos relíquias de supernovas. Portanto, calculamos o uxo de antineutrinos ne relíquias de supernovas que chegam à terra considerando simultaneamente as oscilações e os decaimentos dos neutrinos mencionados anteriormente / Abstract: In this work we study nonradiative decays of Majorona neutrinos, via massless bosons, in vacuum and matter. The considerate couplings between the neutrinos and the bosons were scalar and pseudoscalar. In particular we study the processes n i ® nj + c e n i ® n j + c (where is either scalar or pseudoscalar field). In vacuum, we calculate effective rates in the lowest order of the perturbation theory using the conventional formalism for Majorana neutrinos. We calculate the same rates in the matter case using the two-component helicity formalism introduced in [P. Mannheim, Phys. Rev. D. 37, 1935 (1988)] for a general theory, where there are neutrino fields belong to SUL(2) isodoublets (active neutrinos) and neutrino fields belong to SUL(2) isosinglets (sterile neutrinos). Neutrino decays of relatively long lifetimes could be proved, in principle, through of supernova relic neutrino (SRN) observations. Therefore, we calculate the antineutrinos ux of SRN that arrive to the Earth simultaneously considering both neutrino oscillations and the previously mentioned neutrino decays / Mestrado / Física das Particulas Elementares e Campos / Mestre em Física

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21573号 / 理博第4480号 / 新制||理||1643(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 前田 啓一, 准教授 上田 佳宏, 教授 嶺重 慎 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22242号 / 理博第4556号 / 新制||理||1654(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 中家 剛, 准教授 WENDELL Roger, 教授 鶴 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18079号 / 理博第3957号 / 新制||理||1570(附属図書館) / 30937 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 嶺重 慎, 准教授 前田 啓一, 教授 長田 哲也 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Studying the properties of newborn neutron stars is a complicated matter since they cannot be directly observed. Neutron stars are born when some massive stars go supernova (SN), where the expelled material from the explosion goes on to shield the young neutron star from our view by absorbing its radiation. To estimate properties such as their flux, luminosity and magnetic field strength, upper limits can be found by modeling the emission and absorption and then performing spectral fitting. The assumptions made when modeling can cause the results to differ, this thesis investigates which parameters in the model have the most impact by analysing an X-ray observation of SN 1909A. The varied model parameters are the photon index of the neutron star emission, the density of the SN ejecta, and the composition of the ejecta material. The density can vary depending on the line of sight since SN explosions are asymmetrical, and it is found that this parameter carries most significance, with maximal result variations of about 55% for most ejecta compositions. The least significant parameter is the assumed photon index of the emission from the neutron star, this is found to only cause maximal variations of around 24%. Furthermore, the upper limits on the total luminosity computed by assuming different model parameters, differ by a factor 2.5 at most. The minimum upper limit to the total luminosity of the neutron star of SN 1909A is found to be L_min = 3.6 * 10^6 L⊙ and the corresponding relation between its rotational period and magnetic field is B < 1.88 * 10^20 P^2 G s^-1.

Nous présentons ici une nouvelle étude du reste de supernova G78.2 +2.1 basée sur les plus récentes données du Relevé Canadien du Plan Galactique (RCPG ou CGPS en anglais). Suite à une soustraction du rayonnement thermique à l'aide d'une corrélation entre le continu radio à 1420 MHz (CGPS) et le continu en infrarouge à 60^m, une analyse de l'indice spectral de température nous donne (3 — 2,75 pour le reste de supernova (RSN), soit une valeur de 0,2 supérieure à celle obtenue lors de travaux antérieurs. De plus, une très grande variation de cet indice est observée sur l'ensemble de l'objet mais plus spécifiquement dans la partie ouest de G78.2 +2.1. Également, l'analyse de l'hydrogène neutre (HI) a permis de mettre en évidence des structures que l'on pense être associées au reste de supernova. / We present a new study of the supernova remnant G78.2 +2.1 made with recent data from the Canadian Galactic Plane Survey (CGPS). A thermal correlation constructed from the radio (1420MHz) and infrared (60 //m) images allowed us to subtract the thermal emission from the original image. A spectral index analysis yields a value of temperature spectral index 0 = 2, 75 for the supernova remnant, or 0,2 over the value found in previous works. Furthermore, many variations of the spectral index are observed over the whole object, specifically in the western part of G78.2 +2.1. An analysis of the HI data allowed us to find structures that we argue are associated with the super nova remnant.

Multi-messenger astronomy began when a massive star underwent core collapse in a neighboring dwarf galaxy, whose light and neutrinos reached Earth in 1987. Supernova 1987A was observed optically but was also observed through roughly two dozen neutrinos. Modern instruments have the ability to measure electromagnetic signatures in more wavelengths and detect many more neutrinos from a nearby core-collapse supernova, providing insight into an astrophysical phenomena that is not yet fully understood. In this dissertation, we discuss predictions for future core-collapse supernova signals and the nuclear and particle interactions that produce them. We focus on several different aspects related to both typical and rare supernovae. The diffuse supernova neutrino background (DSNB) - the isotropic background of ~10 MeV neutrinos from all past supernovae - is one such signal that does not rely on a local event for neutrino detection. We update several aspects of theoretical DSNB modeling by (i) using simulation data to better understand neutrino emission spectra as a function of time, (ii) collating recent star formation rate measurements to infer the rate of core collapse in the cosmos, and (iii) performing a signal vs. background analysis of state-of-the-art neutrino experiments. We find that the DSNB is likely to be detected in the next two decades, but large uncertainty on the average neutrino emission spectra combined with unclear treatment of background events prevents a precise timeline. We also discuss the signatures from rare supernovae driven by magnetorotational engines called protomagnetars. We find that outflows from these central engines can produce pions through inelastic np interactions, resulting in ~0.1 - 10 GeV neutrinos that are detectable for galactic supernovae. We also find that these outflows can synthesize heavier nuclei than traditional supernovae through the `weak r-process.' We compare the nucleosynthesis in supernova outflows to that in compact object mergers and find that mergers are more conducive for creating the heaviest nuclei. We also predict the detection rates of another kind of transient called kilonovae that are powered by the decay of unstable nuclei. Finally, these protomagnetar systems may be able to accelerate nuclei in relativistic jets. If these jets are beamed toward us, the gamma ray lines from the decays of unstable nuclei can be boosted to high energies and are detectable from extragalactic distances. / Doctor of Philosophy / Supernovae are one of the most well studied astronomical phenomena because of how broadly they connect to different fields of physics. This kind of event can be bright enough to be seen visually and has been observed and documented for centuries. Its name derives from nova stella - Latin for `new star' - but supernovae occur as the final stages of a star's life. Core-collapse supernovae are an important subclass that occur for stars several times more massive than our own sun. There is a long history of core-collapse supernova observation - from the naked eye to modern optical telescopes - but only one has ever been observed using a particle other than light. SN1987A was a nearby core-collapse supernova that occurred in 1987 and emitted a large burst of rarely interacting particles known as neutrinos along with its usual optical emission. Only two dozen neutrinos were detected during this event, but nearby core-collapse supernovae are rare and astronomers have been eager for another one. With today's modern neutrino detectors, a nearby core-collapse supernova would yield thousands of neutrino events which would help astronomers learn about the internal physics occurring during the collapse, which an optical signal cannot do. In this dissertation, we study the ways in which light and neutrinos can teach us more about core-collapse supernovae. We cover another way to observe supernova neutrinos without waiting for one nearby to occur by predicting the signal from the `diffuse supernova neutrino background.' This is a background of supernova neutrinos that constantly surrounds us, but interacts extremely infrequently, so kiloton-mass detectors are needed to detect this background. Measuring this will also shed light on how stars evolve over a galaxy's history. There are additional subclasses of core-collapse supernovae that give rise to the usual optical and neutrino signal but may also populate the universe with heavy elements, produce higher energy light, and emit higher energy neutrinos. This class is even rarer but are systematically more energetic and are powered internally by objects called `protomagnetars.' We study models of these rare, energetic supernovae and make predictions for each of these signals - heavy elements, high energy light, and high energy neutrinos - to help answer outstanding questions in astrophysics and make predictions for events not yet seen.