Na última década, o extraordinário progresso nas observações astronômicas (distâncias com supernovas (SNe Ia), espectros de potência da matéria e da radiação cósmica de fundo (RCF), determinação do brilho de aglomerados de galáxias, etc.) aliado com importantes desenvolvimentos teóricos, transformaram a Cosmologia numa das fronteiras mais excitantes da ciência contemporânea. Nesta tese, diferentes testes observacionais são utilizados para vincular alguns cenários cosmológicos acelerados (com e sem energia escura), todos eles definidos no contexto teórico da Relatividade Geral. Inicialmente, para uma grande classe de modelos com decaimento do vácuo, investigamos os vínculos provenientes da existência de objetos velhos em altos redshifts. No modelo de Chen e Wu generalizado, encontramos que o limite para o parâmetro livre descrevendo a taxa do decaimento do vácuo é 0,21 < n < 0,81. Este resultado descarta o modelo de Chen e Wu original (n=2) e também o modelo de concordância cósmica, LCDM (n=0). Além disso, quando incluímos o fluido bariônico em nossa análise do modelo de Wang e Meng, obtemos para seu parâmetro livre um limite inferior, epsilon > 0,231, um valor em desacordo com estimativas independentes baseadas em SNe Ia, RCF e o brilho de Raios-X de aglomerados. Propusemos também um teste estatístico com base nas idades estimadas para uma amostra de 13 galáxias velhas em altos redshifts. Através de uma análise conjunta envolvendo as idades das galáxias e as oscilações acústicas dos bárions (BAO), vinculamos o valor da constante de Hubble no contexto do modelo LCDM plano. Considerando um tempo de incubação adotado por diferentes autores, obtemos h=0,71±0,04 (1 sigma), um resultado de acordo com observações independentes baseadas em Cefeidas (obtidas com o Hubble Space Telescope) e outras estimativas mais recentes. Outro resultado interessante foi obtido através de uma análise termodinâmica para uma classe de modelos com interação no setor escuro (matéria escura-energia escura). Contrariamente ao que se pensava até então, encontramos que a termodinâmica permite que a matéria escura decaia em energia escura, contanto que ao menos uma das componentes possua um potencial químico não-nulo. Como complemento, mostramos que, para um termo de interação específico, dados de SNe Ia, BAO e RCF favorecem o decaimento da matéria escura com ~ 93% de confiança estatística. Investigamos também o comportamento do redshift de transição em diferentes cosmologias, com e sem energia escura, e mostramos que essa quantidade pode ter uma variação extrema dependendo do modelo cosmológico subjacente. Finalmente, discutimos também um novo modelo cosmológico cuja aceleração em baixos redshifts é determinada pela criação de partículas da matéria escura fria. O modelo representa uma redução do setor escuro, isto é, não tem energia escura, contém apenas um parâmetro livre e satisfaz os vínculos de Supernovas do tipo Ia tão bem quanto o modelo LCDM padrão. / In the last decade, the extraordinary progress of the astronomical observations (distances with supernovas, matter and cosmic background radiation (CBR) power spectrum, X-ray surface brightness of galaxy clusters, etc) associated with important theoretical developments turned Cosmology one of the most exciting frontiers of contemporary science. In this thesis, different observational tests are used to constrain several cosmological accelerating scenarios (with and without dark energy), all of them defined in the theoretical framework of General Relativity. Initially, for a large class of decaying vacuum models, we investigate the constraints provided by the existence of old high redshift objects. In the model proposed by Chen and Wu, we find that the limit for the free parameter describing the decay rate of the vacuum fluid is 0.21 < n < 0.81. This result ruled out the original Chen and Wu model (n = 2) and also the cosmic concordance model, LCDM (n = 0). Further, when we include the baryonic fluid in our analysis of the Wang and Meng model, we find for its free parameter a lower bound, epsilon > 0.231, a value in disagreement with independent estimates based on SNe Ia, CMB (shift parameter) and the X-ray surface brightness of galaxy clusters. We also propose a new cosmological statistical test based on the estimated ages of 13 old high redshift galaxies. By performing a joint analysis involving the ages of the galaxies and the baryon acoustic oscillations (BAO) probe, we constrain the value of the Hubble parameter in the context of the flat LCDM model. For an incubation time adopted by different authors, we find h = 0.71 ± 0.04 (1 sigma), a result in agreement with independent observations based on Cepheids (obtained with the Hubble Space Telescope) and other recent estimations. Another interesting result has been derived from a thermodynamic analysis for a class of models endowed with interaction in the dark sector (dark matter and dark energy). In contrast with some results appearing in the literature, we show that the decaying of cold dark matter into dark energy is not forbidden by thermodynamics, provided that the chemical potential of one component is different from zero. As a complement, we also show (for a specific term describing the interaction) that this kind of decaying is favored by SNe Ia, BAO and CMB data with ~ 93% of statistical confidence. We also investigate in detail the behavior of the transition redshift for different cosmologies (with and without dark energy). It is found that such a quantity may have an extreme variation that depends on the underlying cosmological model. Finally, we also discuss a new cosmological model whose acceleration at low redshifts is determined by the creation of cold dark matter particles. The model represents a reduction of the dark sector, that is, it has no dark energy, contains only one free parameter and satisfies the Supernovae type Ia constraints with the same precision of the standard LCDM model.

In this project we study chameleon theories in cosmic voids. We investigate the field profile of the chameleon field as well as the fifth force in voids by numerically solving the equations of motion for chameleon fields. The possibility of an analytical approximation for voids is also studied, the well known thin and thick-shell regimes are studied and both are deemed unsuitable for use in cosmic voids. We develop an alternative approximation which is tested against the numerically solved field profile. The agreement between the numerical solution and the analytical approximation is generally poor and the disagreement is likely due in part to the fact that the chameleon field doesn't reach it's equilibrium value inside the void.

La prochaine génération d’instruments pour l'observation de la polarisation du fond diffus cosmologique est particulièrement exigeante en termes de nombre de détecteurs, de qualité de la mesure et d'efficacité de remplissage du plan focal. De plus, pour détecter les modes-B de polarisation provenant de l’inflation, il faut observer le ciel avec plusieurs bandes de fréquence afin de soustraire les avant-plans. Dans ce contexte, les détecteurs à inductance cinétique (KIDs) représentent une technologie très prometteuse en raison de leur grand facteur de multiplexage et de leur facilité de réalisation, tandis que le couplage avec une antenne peut fournir des solutions multi-bandes et double-polarisation dans un design compacte. Les KIDs à éléments localisés (LEKID) couplé à une antenne développé dans cette thèse sont sensibles à la polarisation avec deux sous-bandes à 140 GHz et 160 GHz chacune avec une bande passante de 10%. L'architecture proposée utilise une antenne à fente excitée par une ligne microruban et deux filtres passe-bande vers deux résonateurs. Ces derniers sont couplés capacitivement avec l'antenne et comprennent une ligne microruban en Aluminium comme absorbeur. Cette architecture est particulièrement simple à fabriquer, sans via et ne nécessite que de deux niveaux de métallisation. La transition ne nécessite aucun dépôt de diélectrique au-dessus du résonateur, évitant ainsi les limitations de toute source de bruit due au substrat non-monocristallin (TLS). En outre, la même technique de couplage peut être appliquée à de nombreux types d'antennes excitées par une ligne microruban, ce qui permet de s'adapter aux filtres passe-bande. / Next generation telescopes for observing the Cosmic Microwave Background are demanding in terms of number of detectors and focal plane area filling efficiency. Moreover, foreground reduction in B-Mode polarimetry requires sky observation with multiple frequency bands. In this context KIDs are promising technology because of their large multiplexing rate, while antenna coupling can provide multi-band and dual-polarization solutions in compact design. The proposed polarization sensitive antenna-coupled LEKID is operating at 140 GHz and 160 GHz with a bandwidth of almost 10% for each sub-band. The design involves a microstrip excited slot antenna and two open-stub band-pass filters to direct the signal toward two resonators. These are lumped elements capacitively coupled to the antenna and include an Aluminium strip as absorber. The architecture proposed is particularly simple to fabricate, via-less and only involves two metallization levels. The transition doesn't require any dielectric deposition above the resonator, thus preventing limitations from any source of noise due to non-monocrystalline substrate (TLS). Furthermore, the same coupling technique can be applied to many types of microstrip excited antennas, which allow to accommodate band-pass filters.

Dans les dernières décennies, un modèlecosmologique, dénommé “modèle ACDM” ,a émergé et plusieurs observations ont montréqu’il est consistant avec les données. Toutefois, ilsexistent des problèmes encore ouverts ; en particuliernous ne connaissons pas la cause de l’accélérationobservée de l’expansion de l’Univers. De nombreuxmodèles alternatifs ont été proposés.Cette thèse traite d’une approche pour contraindreles alternatives au modèle ACDM dénommée “EffectiveTheory of Dark Energy”. Elle s’applique àtoutes les théories où un seul degré de liberté scalaireest ajouté aux deux degrés de liberté de la RelativitéGénérale. Ces théories sont appelées “théoriestenseur-scalaire”.Le chapitre 1 résume la plus générale classe de théoriestenseur-scalaire viables actuellement connue.Le chapitre 2 introduit la théorie efficace de l’énergienoire. L’inclusion dans la théorie efficace descouplages généraux entre le secteur gravitationnelle(métrique et champ scalaire) et la matière est décritdans le chapitre 3. Ceci inclut aussi la possibilitéque différentes espèces interagissent de façondifférente avec la gravité. La possibilité d’analyseren détail la stabilité de la théorie est explicité dansle chapitre 4.Un objectif de cette thèse est aussi l’investigationdes effets observables des déviations du modèleLCDM. Le chapitre 5 considère la possibilité d’uneinteraction entre la matière noire et l’énergie noire.Ce chapitre étudie les effets d’une telle interactionet, plus généralement, analyse la capacité des observationsfutures à imposer des contraintes sur lesparamètres libres de la théorie efficace. Le chapitre 6 se concentre sur les effets observationnels de lathéorie “ beyond-Horndeski” , en démontrant quedans ce théorie il existe un melange cinétique entrela matière et le champ scalaire. Ce melange donnelieu à un effets particuliers: l’affaiblissement de lagravité aux échelles des grands structures. / In the last decades, a cosmological model that fits observations through a vast range of scales emerged. It goes under the name of ACDM. However, there are still challenging questions that remain unanswered by this model, such as what causes the observed accelerated expansion of the universe. Hence, many alternative models have been proposed. This thesis concerns an approach to test such models known as “Effective Theory of Dark Energy” . It applies to all models where general relativity is modified by adding a single scalar degree of freedom, called “ scalar-tensor theories”. In Chapter 1 I introduce the most general classof such theories currently known. In Chapter 2, I resume the Effective theory of dark energy. The inclusion of a general coupling between matter and the gravitational sector is the subject of Chapter 3. Chapter 4 analyses in details the stability of different classes of theories.Another goal of the thesis is to study the observable effects of deviations from ACDM. In Chapter5, I consider the possibility of an interaction between dark matter and dark energy and I analyse the constraining power of future surveys on the free parameters of the theory. Chapter 6 focuses on the observational effects of theories where a kinetic mixing between matter and the scalar field exists.This gives a peculiar effect, namely the weakening of gravity at large scale structure scales.

Le fond diffus infrarouge est la contribution de toutes les galaxies infrarouges intégrée sur toute l’histoire de l’Univers. Il émet entre 8 et 1000 µm et à un pic vers 200 µm. On résout une large fraction de ce fond dans l’infrarouge proche mais seule une petite fraction l’est dans l’infrarouge moyen et lointain à cause de la confusion. Les sources les plus faibles sont perdues dans le bruit de confusion. Cela forme des fluctuations de brillance, les anisotropies du fond diffus infrarouge. L’étude de ces fluctuations permet l’étude des galaxies sous le seuil de détection, donc des galaxies les plus faibles. Grâce au spectre de puissance on peut mesurer la puissance conte- nue dans ces fluctuations en fonction de l’échelle spatiale. Cette mesure contient, entre autre, le regroupement des galaxies infrarouges. Dans un premier temps, j’ai isolé du spectre de puissance d’une carte infrarouge, le spectre de puissance dû uniquement aux galaxies infrarouges. En effet, aux grandes échelles spatiales, il est contaminé par l’émission des cirrus Galactiques. Ces cirrus sont des nuages d’hydrogène neutre, tracés par la raie à 21 cm. J’ai donc utilisé des données à 21 cm pour estimer l’émission infrarouge de ces cirrus pour ensuite la soustraire aux cartes infrarouge à 100 et 160 µm. Cela m’a aussi permis de faire une mesure précise du niveau absolu du fond diffus infrarouge à ces longueurs d’onde. Afin d’analyser ces spectres de puissances, j’ai mis en place un modèle de regroupement des galaxies infrarouges reliant un modèle d’évolution des galaxies infrarouge reproduisant les données existantes dont celles d’Herschel et un modèle de halo. C’est un modèle complétement paramétré ce qui permet l’étude des dégénérescences de ces paramètres. J’en ai aussi tiré des mesures physiques et leur évolution avec la longueur d’onde. De plus, j’ai ajusté les données existantes de 100 à 1380 µm. Grâce au modèle on peut déterminer les contributions en redshift à chaque longueur d’onde. Les courtes longueurs d’onde tracent les bas redshifts alors que les grandes longueurs d’onde tracent les hauts redshifts. Cependant la contribution des bas redshifts est loin d’être négligeable à ces longueurs d’onde. Afin de déterminer l’évolution du regroupement avec le redshift des cartes des anisotropies du fond diffus infrarouge sont nécessaires. Je vais expliciter une méthode de séparation de composantes dédiée à cela. / The Cosmic Infrared Background is the contribution of all infrared galaxies integrated on the history of the Universe. It emits between 8 and 1000 um with a peak around 200 um. A large fraction of this background is resolved into sources in the near infrared but only a tiny fraction is in the mid and far infrared because of confusion. The least luminous sources are lost in the confusion noise which forms brightness fluctuations, the anisotropies of the cosmic infrared background. The study of these fluctuations enables the study of the galaxies below the detection threshold, thus the less luminous galaxies. Thanks to the power spectrum we can measure the power contained in these fluctuations as a function of the scale. This measure contains, among others, the clustering of the infrared galaxies. First, I have isolated from the power spectrum of an infrared map, the power spectrum only due to infrared galaxies. Indeed, at large spatial scales, it is contaminated by the emission of Galactic cirrus. These cirrus are clouds of neutral hydrogen traced by the 21 cm line. Therefore, I made use of data at 21 cm to estimate the infrared emission of these cirrus that I have then subtracted from infrared maps at 100 and 160 um.This has also enabled me to compute the absolute level of the cosmic infrared background at these wavelengths. In order to analyse these power spectra, I developped a model of clustering of infrared galaxies. To do so I linked a model of evolution of galaxies that reproduces very well existing data including those of Herschel and a halo model. This is a fully parametric model that enables the study of the degeneracies of these parameters. I was also able to study the evolution with the wavelength of several physical measures. Furthermore, I fitted data from 100 um to 1380 um. Thanks to that model, I can determine the redshift distribution at each wavelength. Short wavelength probe small redshifts whereas long wavelength probe high redshifts. However the contribution of small redshift is far from being negligeable at long wavelength. As a long term purpose of determining the evolution of the clustering if the infrared galaxies, maps of the anisotropies of the cosmic infrared background are needed. I will then detail a component separation method dedicated to this problem.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22028号 / 理博第4532号 / 新制||理||1651(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 向山 信治, 准教授 Antonio De Felice, 教授 鶴 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

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Uncovering the nature of dark matter is one of the most pressing problems in 21st century cosmology. Despite overwhelming evidence that dark matter exists and vigorous experimental efforts to detect it, dark matter has evaded detection and its fundamental nature remains shrouded in mystery. Indirect dark matter detection experiments search for Standard Model byproducts of dark matter annihilation or decay. At low energies, cosmic antideuterons provide an especially clean dark matter signature, since the production of low-energy antideuterons from conventional astrophysical processes is highly suppressed. The General Antiparticle Spectrometer (GAPS) is an Antarctic balloon experiment designed to search for low-energy cosmic antinuclei as signatures of dark matter. GAPS is optimized to detect low-energy antideuterons, as well as to provide unprecedented sensitivity to low-energy antiprotons and antihelium nuclei. GAPS uses a novel approach to detect antinuclei, based on the formation, decay, and annihilation of exotic atoms. At least three GAPS long-duration balloon (LDB) flights are planned, with the first launch date anticipated for December 2022. The core of the GAPS instrument is a particle tracker, comprised of >1000 lithium-drifted silicon (Si(Li)) detectors, that provides particle tracking and X-ray spectroscopy capabilities. In order to preserve the long-term performance of the tracker, the Si(Li) detectors require a surface passivation coating to protect against environmental contamination. In this thesis, I cover four main areas of my research: prototype Si(Li) detector fabrication and performance evaluation; development of a surface passivation technique to ensure the long-term stability of GAPS flight detectors; calculation of the GAPS antihelium sensitivity using particle tracking; and prediction of the antihelium exotic atom X-ray energies and yields for future identification studies. I discuss the prototype fabrication work that was carried out at Columbia, which led to the successful mass-production of large-area Si(Li) detectors for the GAPS LDB flights. I report the research and development of a surface passivation method to protect the GAPS flight detectors from environmental contamination. I then describe the calibration scheme for the GAPS Si(Li) detectors, and a simulation study that I conducted to disentangle the contribution of Compton scattering and intrinsic detector performance on the observed spectra. I then move on to discuss the simulation studies used to determine the performance capabilities of GAPS. I describe the benchmarking of the hadronic annihilation products in antinucleus-nucleus annihilations in Geant4. I review the exotic atom cascade model used to determine the X-rays produced by antiprotonic and antideuteronic exotic atoms, and discuss my work extending this model to describe the de-excitation of antihelium exotic atoms. Finally, I present the first GAPS antihelium nuclei sensitivity study, based on full instrument simulation, event reconstruction, and realistic atmospheric influence simulations.

No description available.

An extensive survey of extragalactic objects with accurate distances is difficult to perform. Distance at that scale is commonly found with redshift and most easily identified with spectroscopic observations, which are time intensive. This is especially a concern when surveying for the elusive, possibly non-existent dwarf galaxies in the centers of voids, whose light would be so faint that a spectroscopic survey to find them would be unreasonably time consuming. Photometric methods to calculate redshift could provide a much quicker way to find distance, but the photometric methods used thus far are characterized by large errors that make them unusable for research on nearby voids. I have been testing two photometric redshift methods that have been recently developed: the Gaussian filter method and the ramp filters method. The Gaussian filter method isolates objects that have emission within the bandpass of the Gaussian filters. Spectroscopic follow-up observations of objects observed with the Gaussian filter method confirmed that 41.9% of the objects identified by the method actually had emission lines within the bandpass of the filters, which is more than a random sampling where only 7% of galaxies had emission within that wavelength range. Assuming that all the lines identified were Hα, the photometric redshift calculated from the Gaussian filter observations had an error of 945 km/s (or 430 km/s by excluding one outlier). Ramp filter observations of objects with SDSS redshifts provided a way to identify redshift with an error of 641.8 km/s. These errors are about an order of magnitude less than other redshift methods. These methods show promise for uses in observational cosmology, specifically extragalactic survey work and searching for void galaxies.