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The cold dark matter (CDM) paradigm underlying the standard <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5CLambda" />CDM model of cosmology is successful on large scales but faces potential problems on small scales partly related to a seeming overproduction of dwarf galaxies. This could be alleviated in exotic dark matter models that suppresses small-scale structure formation. One such attractive model is known as fuzzy dark matter (FDM). FDM positsthat dark matter is composed of ultra-light bosons with masses <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?m_%7B%5Crm%20FDM%7D%20%5Csim%2010%5E%7B-22%7D" /> eV. With such light particle masses, quantum effects become important. More specifically, a pressure-like term appears in the equations of motion that counteracts gravitational collapse on small scales. Because small galaxies form first in CDM, it follows that the early history ot galaxy formation predicted by FDM should be markedly different. One novel way to probe this effect would be to use the 21 cm line of hydrogen which acts as a sensitive probe of the epoch of reionization (EoR) and Cosmic Dawn — when the first galactic sources of X-rays started to reheat theintergalactic medium (IGM). In this thesis, the evolution of the 21 cm signal have been simulated for both CDM and FDM. These simulations indicate that the fluctuationsin the 21 cm signal amenable to future observations are extremely weak (<img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Cll" /> 1 mK) — and probably unobservable — for FDM at high redshifts <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?z%20%5Csim%2015-16" /> compared to CDM (which tend to yield signals with amplitudes <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Cgg" /> 1 mK). This is mainly due to the delayed galaxy formation in FDM resulting in delayed Lyman-<img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Calpha" /> coupling of the 21 cm spin temperature to the kinetic temperature of the IGM. A robust prediction from all FDM scenarios explored in this thesis is that any detection of a signal at <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?z%20%5Csim%2015-16" /> would rule out interesting particle masses for FDM, and would be evidence for CDM-like structure formation. Future work that properly models ionization fluctuations during the EoR could also yield strong predictions at lower redshifts.

abstract: The Universe transitioned from a state of neutral hydrogen (HI) shortly after recombination to its present day ionized state, but this transition, the Epoch of Reionization (EoR), has been poorly constrained by observational data. Estimates place the EoR between redshifts 6 < z <13 (330-770 Myr). The interaction of the 21 cm hyperfine ground state emission/absorption-line of HI with the cosmic microwave background (CMB) and the radiation from the first luminous sources in the universe can be used to extract cosmological information about the EoR. Theorists have created global redshifted 21 cm EoR models of this interaction that predict the temperature perturbations to the CMB in the form of a sky-averaged difference temperature, Tb. The difficulty in measuring Tb is that it is predicted to be on the order of 20 to 100 mK, while the sky foreground is dominated by synchrotron radiation that is 105 times brighter. The challenge is to subtract the much brighter foreground radiation without subtracting the Tb signal and can only be done when the data has small error levels. The Experiment to Detect the Global EoR Signature (EDGES) is an effort to measure Tb with a single wide field-of-view well-calibrated antenna. This dissertation focuses on reducing systematic errors by quantifying the impact of the chromatic nature of the antenna’s beam directivity and by measuring the variability of the spectral index of the radio sky foreground. The chromatic beam study quantified the superior qualities of the rectangular blade-shaped antenna and led to its adoption over the previously used fourpoint-shaped antenna and determined that a 5 term polynomial was optimum for removing the foreground. The spectral index, β, of the sky was measured, using 211 nights of data, to be −2.60 > β > −2.62 in lower LST regions, increasing to −2.50 near the Galactic plane. This matched simulated results using the Guzm´an et al. (2011) sky map (∆β < 0.05) and demonstrated the exceptional stability of the EDGES instrument. Lastly, an EoR model by Kaurov & Gnedin (2016) was shown to be inconsistent with measured EDGES data at a significance level of 1.9. / Dissertation/Thesis / Doctoral Dissertation Astrophysics and Astronomy 2017

One method that can be used to identify the dynamic origin and specific parent bodies of Earth crossing meteoroids is the determination of the meteoroids’ orbital evolution. In this study, a Python-based program using the REBOUND software integration package to integrate meteoroid orbits backwards in time is developed. The program uses data from meteor observations made by the Swedish Allsky Meteor Network, and traces the distance and relative velocity between the meteoroid orbit and the orbits of selected parent body candidates backwards in time. The measure of these orbital differences is known as dissimilarity. The model is used to successfully reproduce the evolution of the Southworth-Hawkins dissimilarity criterion of the Annama meteorite and plausible parent body candidate 2014 UR116 presented by Trigo-Rodríguez et al (2015), as well as to determine plausible parent body associations of several meteors observed by the Swedish Allsky Meteor Network. Plausible parent bodies are presented in two new meteor cases, one of which confirms the parent body of the Geminid meteor shower. The model is concluded to be sufficiently accurate to motivate further use for meteoroid orbit integration purposes, and suggestions for future improvements are made. A new plausible parent body candidate for the Annama H5 meteorite is identified; the asteroid 2017 UZ44. In the case of one meteor event previously identified as a Perseid, the verification of the parent body is not successful using the developed model. In this case, no parent body candidate is found. Possible reasons for this are discussed. Moreover, the observational accuracy is found to be crucial if the program is to be used to study the meteor events observed by the network in detail, as the orbit has to be very well-constrained. / En metod som kan användas för att identifiera moderkroppar till meteoroider som äntrar jordens atmosfär är analys av meteoroidbanornas utveckling över tid. I denna studie har ett Python-baserat program som använder det numeriska integrationspaketet REBOUND för att följa meteoroidbanors utveckling över tid tagits fram. Programmet använder data från meteorobservationer som genomförts av det svenska meteornätverket Swedish Allsky Meteor Network och följer meteoroidbanors banutveckling i jämförelse med potentiella moderkroppars banutveckling över tid. För jämförelsen används Southworth-Hawkins-kriteriet. Modellen används för att framgångsrikt reproducera resultat presenterade av Trigo-Rodríguez et al (2015) genom att följa Annama-meteoritens banutveckling jämfört med banutvecklingen hos den möjliga moderkropp som presenteras i studien, asteroiden 2014 UR116. Modellen används också för att hitta möjliga moderkroppar för flertalet meteorer som observerats av det svenska meteornätverket. Möjliga moderkroppar presenteras i två fall, varav ett bekräftar moderkroppen för meteorregnet Geminiderna. Modellen verkar vara tillräckligt bra för att motivera användning vid integration av meteoroidbanor i syfte att identifiera moderkroppar genom att jämföra banornas utveckling över tid. En ny möjlig moderkropp presenteras för Annama-meteoriten; asteroiden 2017 UZ44. I ett fall har en meteor som observerats av det svenska meteornätverket tidigare klassificerats som en Perseid, men beräkningar genomförda med modellen framtagen i denna studie kan inte bekräfta resultatet. I detta fall återfinns ingen möjlig moderkropp för den specifika meteoren. Möjliga anledningar till detta diskuteras. Slutligen dras slutsatsen att mätosäkerheten i meteorobservationerna är vital för att meteoroidens bana ska vara tillräckligt välbestämd för att användas i syfte att analysera meteoroidbanornas utveckling över tid och hitta möjliga moderkroppar.

The Gaia space telescope is dedicated to monitor the sky, collect data and create the most precise 3D map consisting of more than 1.7 billion objects in the Milky Way. At the same time, the Radial Velocity Spectrometer (RVS) will collect spectra for ~150 million stars in the wavelength range 847 to 874 nm. This wave range is selected because it coincides with G-and K-type star energy-distribution peaks, as well as containing the strong Ca II infrared triplet lines (λ =8498, 8542, 8662 Å). The aim of this thesis is to create a grid of synthetic spectra in RVS wavelength range which later when compared to the real spectra can be used to determine the chemical composition of the star as well as precise atmospheric parameters. Calculations consist of 198 spectra ranging in effective temperature from Teff =4500 K to 7000 K with various steps, surface gravity log g = 2.5 to 4.5 with the step of 0.5and metallicities [M/H] = −0.5, 0.0 and 0.5 relative to the Solar composition. For calculations MARCS atmosphere models [3], a line list extracted from the VALD3 database [6] and the software SME [7] was used. Spectra calculations were conducted in both classical LTE and refined non-LTE modes for the line formation of calcium.

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Orientador: Saulo Henrique Pereira / Banca: Elias Leite Mendonça / Banca: Luiz Cleber Tavares de Brito / Resumo: O campo espinorial ELKO associado às partículas de matéria de spin 1/2 e dimensão de massa 1, construídos em um conjunto completo de autoespinores de helicidade dual do operador conjugação de carga, é um canditado a descrever a matéria escura. Devido a sua natureza, possui diversas aplicações cosmológicas. Neste trabalho, o estudo de tais espinores é realizado sob universo de Friedmann-Robertson-Walker plano, homogênio e isotrópico. À luz da Teoria Quântica de Campos em Espaços-Tempo Curvos, com as transformações de Bogoliubov, obteve-se a densidade de partículas criadas em uma métrica modelo de regime assintóticamente plano no passado e no futuro, permitindo-se comparar com soluções exatas presentes na literatura para produção de partículas escalares e férmions de Dirac. Discute- se, também, a compatibilidade do fenômeno de criação de partículas provenientes da Teoria Quântica de Campos em Espaço Curvos com os estudos de Prigogine para descrição deste fenômeno à escala cosmológica, considerando-se um universo termodinamicamente aberto / Abstract: The ELKO spinor field associated with spin 1/2 particles and mass dimension 1, con- structed on a complete set of dual helicity eigenspinors of the charge conjugation operator, is a candidate for describing dark matter. Due to its nature, it has several cosmological applications. In this work, the study of such spinors is performed under a homogenous and isotropic Friedmann-Robertson-Walker universe. In the light of the Quantum Field Theory in Curved Space-Time, with the Bogoliubov transformations, we obtained the density of particles created in a model of asymptotically plane metric in the past and in the future, allowing to compare with exact solutions present in the literature for the production of scalar particles and Dirac fermions. It is also discussed the compatibility of the phenomenon of particle creation from the Quantum Field Theory in Curved Space with the studies of Prigogine to describe this phenomenon at the cosmological scale, considering a thermodynamically open universe / Mestre

Orientador: Horatiu Stefan Nastase / Banca: Robert Brandenberger / Banca: Rogério Rosenfeld / Banca: Nathan Jacob Berkovits / Banca: Luis Raul Weber Abramo / Resumo: Nesta tese a Teoria das Perturbações Cosmológicas é revisada e três tópicos originais, incluídos neste grande ramo da cosmologia teórica, são apresentados. Começamos introduzindo e deduzindo as fórmulas necessárias partindo de primeiros princípios no capítulo 2. Em seguida, no capítulo 3, estudamos em detalhe Teorias Quânticas de Campos em de Sitter que contêm correntes de spin alto. Mostramos que a existência de correntes de spin alto - mesmo em teorias com interação - pode colocar mais vínculos na função de n-pontos, tornando a teoria assintoticamente gaussiana no futuro longínquo. Este resultado pode ser interpretado como o análogo do teorema de ColemanMandula para o espaço-tempo de de Sitter. O capítulo 4 é dedicado a modelos inflacionários conformes com o campo de Higgs fazendo o papel de Inflaton. Modelos com simetria de Weyl e com simetria SO(1, 1) para valores altos da energia são construídos. Verificamos quais as condições necessárias para que se obtenha um valor arbitrário para a razão escalar tensorial, parâmetro que mede a intensidade de ondas gravitacionais primordiais em um dado modelo. Introduzimos também um acoplamento diferente do valor conforme para a interação do campo escalar com o tensor de curvatura. Isto quebra a simetria de Weyl, mas verificamos que existe um forte atrator na direção da linha de Starobinsky. No último capítulo, aplicamos o efeito do 'back reaction' dos modos com comprimentos de onda longo (maiores que o raio de Hubble) em alguns modelos inflacionários e no cenário Ekpyrótico. Checamos se este efeito pode prevenir a inflação eterna nas regiões onde efeitos estocásticos são importantes nestes modelos. Alguns apêndices, com cálculos detalhados, são incluídos no final / Abstract: In this thesis the Theory of Cosmological Perturbations is reviewed and three original topics, that are part of this huge branch of theoretical cosmology, are presented. We start by reviewing and deducing the needed formulas from first principles in chapter 2. After it, in chapter 3, we study in detail Quantum Field Theories in de Sitter spacetime that contain Higher Spin currents. We show that the existence of Higher Spin currents - even in the interacting case - can put further constraints on the n-point function, making it asymptotically gaussian in the far future. This result can be interpreted as the analog of Coleman-Mandula theorem for de Sitter spacetime. Chapter 4 is devoted to conformal inflationary models with the Higgs field playing the role of the Inflaton field. We construct models with a Weyl symmetry and a SO(1, 1) symmetry at high energies. It is verified what are the conditions to get an arbitrary value for the tensor to scalar ratio, which measures the amplitude of primordial gravitational waves in a given model. Also, we introduce a coupling, different from the conformal one, for the scalar field and the curvature tensor. This breaks the Weyl symmetry but we verify that there is a strong attractor towards the Starobinsky line. In the last chapter, we apply the back-reaction effect of long wavelength modes (modes with wavelength bigger than the Hubble radius) in some inflationary models and in the Ekpyrotic scenario. We check if this effect could prevent eternal inflation in the region where stochastic effects are important for these models. Some appendices, with detailed calculations, are also included in the end / Doutor

abstract: I combine, compare, and contrast the results from two different numerical techniques (grid vs. particle methods) studying multi-scale processes in galaxy and structure formation. I produce a method for recreating identical initial conditions for one method from those of the other, and explore methodologies necessary for making these two methods as consistent as possible. With this, I first study the impact of streaming velocities of baryons with respect to dark matter, present at the epoch of reionization, on the ability for small halos to accrete gas at high redshift. With the inclusion of this stream velocity, I find the central density profile of halos is reduced, overall gas condensation is delayed, and infer a delay in the inevitable creation of stars. I then combine the two numerical methods to study starburst outflows as they interact with satellite halos. This process leads to shocks catalyzing the formation of molecular coolants that lead to bursts in star formation, a process that is better captured in grid methods. The resultant clumps of stars are removed from their initial dark matter halo, resemble precursors to modern-day globular clusters, and their formation may be observable with upcoming telescopes. Finally, I perform two simulation suites, comparing each numerical method's ability to model the impact of energetic feedback from accreting black holes at the core of giant clusters. With these comparisons I show that black hole feedback can maintain a hot diffuse medium while limiting the amount of gas that can condense into the interstellar medium, reducing the central star formation by up to an order of magnitude. / Dissertation/Thesis / Doctoral Dissertation Astrophysics 2014

Apresentamos neste trabalho uma generalização da teoria de perturbações cosmológicas para o caso de universos homogêneos e anisotrópicos, caracterizados por um espaço-tempo do tipo Bianchi I. Como aplicação da teoria, investigamos as conseqüências de uma fase inflacionária e anisotrópica do universo dos pontos de vista clássico e quântico. Após uma discussão da evolução do espaço-tempo de fundo nós quantizamos os modos perturbativos para, em seguida, construir o espectro de potências das perturbações de curvatura e de ondas gravitacionais do fim da inflação. Nossos resultados mostram que as principais características de uma fase anisotrópica primordial do universo são: (1) dependência direcional dos espectros de potências, (2) acoplamento entre as perturbações de curvatura e as ondas gravitacionais e (3) espectros distintos para as diferentes polarizações das ondas gravitacionais em grandes escalas cosmológicas. Todos esses efeitos são importantes apenas em grandes escalas cosmológicas e, localmente, recuperamos a teoria isotrópica de perturbações cosmológicas. Nossos resultados dependem de uma escala característica que pode, embora não seja estritamente necessário, ser ajustada a alguma escala observável. / In this work we generalize the standard theory of cosmological perturbations to the case of homogeneous and anisotropic universes described by a Bianchi I spacetime metric. As an application of this theory we investigate the predictions of an inflationary anisotropic phase, both at the classical and quantum level. After discussing the evolution of the background spacetime, we solve and quantize the perturbation equations in order to predict the power spectra of the curvature perturbations and gravity waves at the end of inflation. Our results show that the main features of an early anisotropic phase are: (1) a dependence of the spectra on the direction of the modes, (2) a coupling between curvature perturbations and gravity waves, and (3) the fact that the two gravity waves polarisations do not share the same spectrum on large scales. All these effects are significant only on large scales and die out on small scales where isotropy is recovered. Finally, our results depend on a characteristic scale that can, but a priori does not have to, be tuned to some observable scale.