Academic literature on the topic 'Dark Matter Models'

I review the construction of simplified models for dark matter searches. After discussing the philosophy and some simple examples, I turn the attention to the aspect of the theoretical consistency and to the implications of the necessary extensions of these models.

Dark matter and dark energy are used as two important concepts in cosmology to explain some of the observed phenomena in the universe. Dark matter is one of the most dominant constituents of the Universe, and it influences the structural formation of the Universe through gravity, including the formation and evolution of galaxies, clusters, and the large-scale structure of the Universe. Dark energy is believed to be one of the causes of the accelerated expansion of the Universe, and its presence explains the observed phenomenon of the accelerating rate of expansion of the Universe. Although their existence has not been directly observed, people understand through the study of the structure and evolution of the universe that they play an important role in the universe. This paper first introduces the background knowledge of dark matter and its related properties and explains the reasons why three types of models, namely WIMP, axion, and sterile neutrino, are candidates for dark matter in the light of existing observations. The paper then discusses the relevant properties of dark energy and analyses the mainstream dark energy models. For the cosmological constant mode, the fine-tuning problem and cosmic coincidence problem it faces are analysed in detail. The evolution of the dark energy equation of state from the past >-1 to the present <-1 is then explained, and this is used to introduce the scalar field model involving dynamic, the Chaplygin gas model, the holographic dark energy model, and the interacting dark energy model.

We analyze and review cosmological models in which the dynamics of a single scalar field accounts for a unified description of the Dark Matter and Dark Energy sectors, dubbed Unified Dark Matter (UDM) models. In this framework, we consider the general Lagrangian of -essence, which allows to find solutions around which the scalar field describes the desired mixture of Dark Matter and Dark Energy. We also discuss static and spherically symmetric solutions of Einstein's equations for a scalar field with noncanonical kinetic term, in connection with galactic halo rotation curves.

Revealing the nature of the dark matter is among the most puzzling issues of today particle physics, astrophysics and cosmology. Given the striking evidences for dark matter at all astrophysical scales, starting from galactic and going to cosmological scales, a widespread and well motivated assumption on the nature of the dark matter is that it is made by a new particle that extends the Standard Models of Particle Physics. Indirect detection of dark matter, which annihilates in over-dense regions like the galactic centre, is an important probe of a possible dark matter interaction with the Standard Model particles. It could provide insights both to the underlying production mechanism of dark matter in the early Universe, on the annihilation properties at present time in galactic halos and on the underlying particle physics model. In this master thesis project we will focus on simplified leptophilic models for dark matter. These models feature an massive boson, called for instance Z', and a Dirac dark matter candidate, that complement the Standard Model of particle physics. We will study the annihilation of dark matter into leptons, focusing in particular on neutrino lines and box-shaped energy spectra. These tow signals are smoking gun signature to discover the dark matter properties. We will perform a numerical analysis using the dark matter software MadDM to predict the expected flux from the galactic centre, by performing scans in the model parameter space. We will implement the constrains from the Fermi-LAT telescope and the XENON1T experiment. Finally we will use the predictions of those models to assess the reach of the future KM3NeT neutrino telescope.

Una enorme quantità di evidenze sperimentali sulla esistenza di una forma di materia non luminosa nell'Universo, si sono accumulate nel corso di circa un secolo. Chiarire la sua natura è diventata una delle sfide più eccitanti ed urgenti negli sforzi per capire il nostro Universo. In questo lavoro presento uno studio su un approccio per scoprire la Materia Oscura interpretata come particella elementare e sulla possibilità di produrla e rilevarla negli acceleratori. Nella parte introduttiva presento una breve storia delle evidenze astrofisiche e astronomiche che hanno portato alla ipotesi della esistenza di Materia Oscura. Assumendo che la Materia Oscura sia costituita da una particella elementare ulteriore a quelle predette dal Modello Standard, delineo poi i tre principali metodi di rilevazione utilizzati attualmente per identificarla. Nella seconda parte discuto come si possono costruire teorie nelle quali sia possibile interpretare le ricerche attuali ed i risultati corrispondenti. Eseguo un confronto tra approcci diversi, partendo da modelli completi fino a quelli che utilizzano teorie di campo effettive. In particolare, discuto i loro lati positivi e negativi, motivando l'utilizzo di uno schema intermedio, il cosiddetto approccio con modelli semplificati, caratterizzati da un numero limitato di nuovi stati e parametri e che supera le limitazioni intrinseche delle teorie effettive nel contesto delle ricerche negli acceleratori. Nell'ultima parte fornisco una esaustiva classificazione dei modelli semplificati nel canale t, che non sono ancora stati analizzati sistematicamente nella letteratura. Per ciascuno di essi presento un possibile completamento UV e i segnali più promettenti ad LHC. Per questa ragione tutti i modelli considerati sono stati implementati in strumenti Monte Carlo, validati nel confronto con risultati analitici, studiati in dettaglio e resi pronti per un rilascio pubblico per la comunità fenomenologica e sperimentale di LHC.

We investigate models of composite dark matter in which the dark matter candidate arises naturally as an accidentally stable bound state of a confining dynamics and with observable signatures in a wide variety of experiments. In the first part of the thesis we introduce and explore a new class of models with dark fermions in the adjoint repre- sentation of the confining gauge group. The low energy dynamics and the cosmological history are peculiar and provide a dark matter candidate with properties much different from that of a canonical WIMP. The dark matter is heavy but has a large interaction range and can be tested primarily with indirect searches. In the second part of the thesis we classify and study models of composite dark matter with a strongly interacting chiral dark sector, in which all the mass scales are generated dynamically. In this case the candidate is a SM singlet dark pion with a thermal abundance whose low energy phenomenology can be thoroughly studied through chiral lagrangian techniques. We present an analysis of the low energy phenomenology, compute the radiatively generated masses of the light states and study the cosmological history of the model. The presence of partner states interacting with the SM offers the opportunity to test the model at colliders. In the last part of the thesis we present the phenomenological signatures of the models previously introduced and determine the current bounds. In doing so we also present a strategy to derive a limit on the lifetime of dark matter particles in generic models of particle dark matter from the observation of the 21 cm cosmological signal.

At present, the best model for the Universe as a whole is given by the so called ``Hot Big Bang'', which describes an expanding universe in which the density and temperature of matter and radiation are followed in time. The value of the parameters characterizing the observed universe is summarized by the concordance $\Lambda$CDM model, where CDM stands for Cold Dark Matter (the main matter component), and $\Lambda$ is the cosmological constant (some kind of unknown energy, with an anti-gravitational effect). According to this model, the universe is spatially flat (i.e. the density parameter $\Omega$ equals one), and 75\% of its energy balance is assigned to dark energy, about 20\% to dark matter and about 5\% to ordinary (baryonic) matter; the expansion speed assumes a value $H_{0}=70.5$ Km/s/Mpc (the Hubble parameter). The present dissertation focuses on the distribution of dark matter into virialized structures, called dark matter haloes. According to structure formation theory, cosmic structures originates from the amplification of quantum fluctuations during an early stage of accelerated expansion (cosmic inflation); these perturbations grow by self-gravity until they collapse and originate virialized structures. In the linear regime (when fluctuations are small), this process is well understood by the Jeans' theory. The non linear regime is much harder to describe; erlier attempts assumed a simple spherical simmetry, where the collapse is driven only by the internal density (e.g. Peebles, 1980); more recently (White \& Silk 1979; Bond \& Myers 1996) this hypothesis has been relaxed, and a more complex model was proposed in which proto-structures are described by triaxial ellipsoids, governed by their internal density and shape. Using the results coming from the dynamical analysis of the spherical collapse, and exploiting the statistical ``excursion sets formalism'', it is possible to obtain analytical information about the mass distribution of dark matter haloes. In this approach, for each particle in the universe, the trajectory describing the density evolution of a sphere of matter built around that particle is modeled as a random walk as a function of the mass $M$ within that sphere. When a trajectory crosses some pre-defined threshold, one assumes that a virialized structure of mass $M$ has formed. By considering all the particles in the universe one obtains analytical forms for the global mass function, and for the progenitor and descendant mass functions. From these it is possible to calculate other quantities, like the (instantaneous and integrated) rates of creation and destruction of dark matter haloes. In the 1990's the ellipsoidal collapse was first tried in order to find a better match with numerical simulations. However, partly due to the analytical complexity of the model, until now one can still not find in the literature analytical forms for e.g. the descendant and merger rate distributions (see Table \ref{tab:scec}). The main goal of this work is to provide such expressions for a number of statistics related to the mass distributions of dark matter haloes, striving to obtain simple and accurate formulas. In order to do so, we start from the statistical considerations by Sheth, Mo e Tormen (2001), who introduced the dynamical effects of the ellipsoidal collapse into the excursion sets formalism just by modifying the shape of the density threshold. Sheth and Tormen (2002) further suggested an new expression for the ellipsoidal global mass function, using a Taylor expansion series for the barrier: this expression allows one to also derive analytical formulas for the conditional mass functions. We obtain a set of models changing the order of this Taylor expansion, and considering the normalization of the distribution as a free parameter; we then compare these equations with the results of the cosmological simulation Gif2 (Gao et al. 2004) and, in some cases, with the Millennium Simulation (Springel et al. 2005). For the global and conditional mass functions the match between models and simulations is estimated using a $\chi ^2$-method. For the merger rates we compare the results qualitatively, whereas for the creation rates we only derived analytical results. We especially focus on the cases providing the simplest analytical expressions: the zero-order and the infinite-orders Taylor series. In the last part of the dissertation we propose a new statistical method that can overcome two inconvenients of $\chi ^2$-methods: (i) data binning and (ii) neglect of field particles (dust) in simulations. Concerning point (i), different bin-sizes can lead to small differences in the $\chi ^2$-results. As for point (ii), particles that are not bound to haloes are usually considered only for computing the normalization. By using a maximum likelihood analysis we can treat unbinned data, as well as take into account dust in the determination of the best parameters of the mass function. Our tests are performed by comparing a two-parameter mass function with results of Monte Carlo simulations. Our work naturally settles within the systematic search of analytical expressions associated to the ellipsoidal collapse of dark matter haloes. Since haloes are thought to be the sites where baryons can condense and form stars, galaxies and other luminous objects, the expression we derive can be used for a number of applications, ranging from unveiling the nature of dark matter through self-annihilation, to the understanding of the mechanisms leading to galaxy formation. Furthermore, the description of galaxy evolution requires knowledge on the hosting haloes: semi-analytical models of galaxy formation depend on the global mass function of the dark matter haloes, and the corrisponding merger-trees are based on the progenitor mass functions. The rates of creation and destruction are useful to compute the abundances of objects like Active Galactic Nuclei (AGNs) and Super Massive Black Holes (SMBHs). Many other examples can be found in the literature for the use of dark matter distributions in studies of galaxy formation. The structure of the dissertation is as follows: {\bf Chapters 1} justifies the need of dark matter. In {\bf Chapters 2} we present the concordance cosmological model, its geometry and thermal history. We also introduce the linear and non-linear models for the formation of dark matter haloes. {\bf Chapter 3} describes the excursion sets approach in the framework of the spherical collapse. The extension of this method to the ellipsoidal collapse is given in {\bf Chapter 4}, where the firsts analytical results are derived. In {\bf Chapter 5} we compare our analytical predictions to a number of results from numerical simulations. {\bf Chapter 6} is devoted to the new maximum likelihood tests with unbinned data and dust particles. We finally draw our {\bf Conclusions}, followed by one {\bf Appendix} where the numerical simulations are described.
La miglior descrizione dell'Universo, di cui si dispone al momento, è il modello del ``Big Bang Caldo'', che contempla un universo in espansione nel quale viene seguita l'evoluzione temporale della densità e della temperatura della materia e della radiazione. I parametri che caratterizzano l'Universo osservato sono riassunti in un modello chiamato $\Lambda$CDM di concordanza: CDM sta per Cold Dark Matter (la componente dominante della materia), e $\Lambda$ è la costante cosmologica (una sorta di energia oscura, con effetto anti-gravitazionale). Secondo questo modello, l'universo è spazialmente piatto (cioè il parametro di densità $\Omega$ è uguale a uno), e il $75\%$ del suo bilancio energetico è assegnato all'energia oscura, circa il $20\%$ alla materia oscura e circa il $5\%$ alla materia ordinaria (barioni); la velocità dell'espansione assume il valore $70.5$ Km/s/Mpc (parametro di Hubble). Questa tesi si sofferma sulla distribuzione della materia oscura in strutture virializzate, chiamate aloni di materia oscura. Secondo la teoria di formazione delle strutture, le strutture cosmiche hanno origine dall'amplificazione di fluttuazione quantistiche durante un periodo iniziale di espansione accelerata (inflazione cosmica); queste perturbazioni crescono per effetto dell'autogravità fino al collasso, creando delle strutture virializzate. Durante il regime lineare (quando le fluttuazioni sono piccole), questo processo è ben descritto dalla teoria di Jeans. Il regime non lineare è molto più difficile da descrivere; i primi tentativi assumono una simmetria sferica, per la quale il collasso è descritto solo dalla densità interna (es. Peebles, 1980); più recentemente (White \& Silk 1979; Bond \& Myers 1996) questa ipotesi è stata rilassata, ed è stato proposto un modello più complesso nel quale le protostrutture sono descritte da ellissoidi triassiali, regolati dalla loro densità interna e dalla loro forma. Utilizzando i risultati ottenuti dall'analisi dinamica del collasso sferico e sfruttando il formalismo statistico degli ``excursion set'', è possibile ottenere informazioni analitiche in merito alla distribuzione di massa degli aloni di materia oscura. In questo approccio, per ogni particella nell'universo, la traiettoria che descrive l'evoluzione della densità della sfera di materia costruita attorno a quella particella viene modellata come un cammino browniano come funzione della massa $M$ all'interno della sfera. Quando una traiettoria interseca una pre-definita soglia, si assume che venga a formarsi una struttura virializzata di massa $M$. Considerando tutte le particelle dell'universo, si ottengono forme analitiche per la funzione di massa globale, e per le funzioni di massa dei progenitori e dei figli. Da queste, è possibile calcolare altre quantità, come i tassi di creazione e distruzione (istantanei e integrati). Negli anni '90, il collasso ellissoidale è stato utilizzato per trovare un miglior accordo con le simulazioni numeriche. Tuttavia, in parte a causa della complessità analitica del modello, fino ad ora non è stato ancora possibile trovare in letteratura forme analitiche per esempio per la funzione dei figli o per i tassi di distruzione (vedi Tabella \ref{tab:scec}). l'obiettivo principale di questo lavoro è di fornire tali espressioni per una serie di funzioni legate alle distribuzione di massa degli aloni di materia oscura, aspirando ad ottenere delle formule semplici ed accurate. Per farlo, siamo partiti dalle considerazioni statistiche di Sheth, Mo e Tormen (2001) che introducono gli effetti dinamici del collasso ellissoidale nel formalismo excursion sets, modificando la forma della soglia di densità. Sheth e Tormen (2002), inoltre, propongono una nuova espressione per la funzione di massa globale ellissoidale, usando uno sviluppo in serie di Taylor per la barriera: questa espressione permette di derivare forme analitiche anche per le funzioni di massa condizionali. Abbiamo ottenuto un set di modelli cambiando l'ordine di questo sviluppo di Taylo, e considerando la normalizzazione delle distribuzioni come un parametro libero; abbiamo poi confrontato queste equazioni con i risultati della simulazione cosmologica Gif2 (Gao et al. 2004) e, in alcuni casi, con la Millennium Simulation (Springel et al. 2005). Per le funzioni di massa globale e condizionali, l'accordo tra modelli e simulazioni è stimato usando un metodo $\chi ^2$. Per i merger rates abbiamo confronti qualitativi, mentre per i tassi di creazione abbiamo derivato le sole equazioni analitiche. Ci siamo soffermati specialmente sui casi che forniscono le espressioni analiticamente più semplici: le serie di Taylor con zero ordini e con infiniti ordini. Nell'ultima parte della tesi, proponiamo un nuovo metodo statistico che può scartare gli inconvenienti dei metodi $\chi ^2$: (i) la divisione in intervalli dei dati e (ii) il trascurare le particelle di campo (polvere) delle simulazioni. Per quanto riguarda il punto (i), differenti ampiezze degli internalli di massa possono portare a piccole differenze nei risultati del $\chi^2$. Il punto (ii) si riferisce al fatto che le particelle che non sono legate in aloni sono di solito considerate solo per il calcolo della normalizzazione. Usando un'analisi di massima verosimiglianza, possiamo trattare dati non raggruppati in intervalli e considerare la polvere nella determinazione dei parametri migliori per la funzione di massa. I nostri tests sono condotti confrontando una funzione di massa a due parametri con i risultati di simulazioni Monte Carlo. Il nostro lavoro si inserisce naturalmente nella ricerca sistematica delle espressioni analitiche associate al collasso ellissoidale degli aloni di materia oscura. Poichè si pensa che gli aloni siano i siti ove i barioni possono concentrarsi e formare stelle, galassie ed altri oggetti luminosi, le espressioni che otteniamo possono essere usate in varie applicazioni, dallo svelare la natura della materia oscura attraverso l'auto annichilazione, fino alla comprensione dei meccanismi che portano alla formazione galattica. Inoltre, la descrizione dell'evoluzione galattica richiede la conoscenza dell'alone correlato: i modelli semi-analitici di formazione galattica dipendono dalla funzione di massa globale degli aloni di materia oscura, e i corrispondenti merger-trees sono basati sulle funzioni di massa dei progenitori. I tassi di creazione e distruzione sono utili per calcolare le abbondanze di oggetti come Nuclei Galattici Attivi (AGN) e Buchi Neri Super Massicci (SMBH). Altri esempi dell'utilizzo delle distribuzioni della materia oscura in studi di formazione galattica si possono trovare copiosi in letteratura.\\ L'elaborato si articola in questo modo: il {\bf Capitoli 1} giustifica la necessità della materia oscura. Nel {\bf Capitolo 2} presentiamo il modello cosmologico di concordanza, la sua geometria e la storia termica. Inoltre, introduciamo i modelli, lineare e non lineare, di formazione degli aloni di materia oscura. Il {\bf Capitolo 3} descrive l'approccio degli excursion sets nel contesto del collasso sferico. L'estensione di questo metodo al collasso ellissoidale è proposto nel {\bf Capitolo 4}, ove vengono esposti i primi risultati analitici. Nel {\bf Capitolo 5} confrontiamo le nostre predizioni analitiche con i risultati di due simulazioni numeriche. Il {\bf Capitolo 6} è dedicato all'esposizione dei test di un nuovo metodo di massima verosimiglianza con l'utilizzo di dati non raggruppati in intervalli e con le particelle di polvere. Infine tracciamo le nostre {\bf Conclusioni}, seguite da un'{\bf Appendice} ove sono descritte le simulazioni numeriche.

La teoría científica de más éxito hoy en día, sobre el origen y la evolución del universo, es conocida como el modelo estándar del Big Bang, el cual es una de las construcciones intelectuales más ambiciosas de la humanidad. Se basa en dos ramas bien consolidadas de la física teórica, a saber, la teoría de la Relatividad General y el Modelo Estándar de la física de partículas, y es capaz de hacer predicciones sólidas, como la expansión del universo, la existencia del fondo de radiación de microondas y las abundancias relativas de los elementos ligeros. Algunas de las predicciones teóricas ya han sido confirmadas por observaciones muy precisas.
Según la cosmología estándar del Big Bang, el universo primitivo consistía en un plasma muy caliente y denso que se expandió y se enfrió continuamente hasta el presente, dando paso a una serie de transiciones de fase cosmológicas, donde las teorías que describen el universo en cada fase son distintas. Dado que las energías del universo primitivo fueron mucho más altas que las alcanzadas en experimentos terrestres, el estudio del universo primitivo podría ofrecernos importantes informaciones sobre nuevas interacciones y nuevas partículas, abriendo nuevas direcciones para la extensión del Modelo Estándar de la física de partículas.
Como ya he mencionado anteriormente, durante la expansión del universo ocurrieron varias transiciones de fase que dejaron su huella sobre el estado presente del universo. Las observaciones sugieren que durante una de estas transiciones de fase, el universo primitivo sufrió un periodo de expansión acelerada, conocido como inflación. Aunque no forma parte de la cosmología estándar, la inflación es capaz de solucionar de una manera simple y elegante casi todos los problemas relacionados con el modelo estándar del Big Bang, y debería tenerse en cuenta en cualquier extensión posible de la teoría. Las observaciones también revelan la existencia de dos formas de energía desconocidas, a saber, materia oscura y energía oscura. La materia oscura es una forma de materia no relativista y no bariónica, que solamente puede ser detectada indirectamente, mediante su interacción con la materia normal. La energía oscura es un tipo de sustancia con presión negativa, que empezó a dominar recientemente y que es la causa de la aceleración de la expansión del universo.
En esta tesis doctoral presento varios modelos originales propuestos para resolver algunos de los problemas de la cosmología estándar, como posibles extensiones del modelo del Big Bang. Algunos de estos modelos introducen nuevas simetrías y partículas con el fin de explicar la inflación y la energía oscura y/o la materia oscura en una descripción unificada. Uno de los modelos es propuesto para explicar la energía oscura del universo, a través de un nuevo campo escalar que oscila en un potencial.
The most successful scientific theory today about the origin and evolution of the universe is known as the standard Big Bang model, which is one of the most ambitious intellectual constructions of the humanity. It is based on two consolidated branches of theoretical physics, namely, the theory of General Relativity and the Standard Model of particle physics, and is able to make robust predictions, such as the expansion of the universe, the existence of the cosmic microwave background radiation and the relative primordial abundance of light elements. Some of the theoretical predictions have already been confirmed by very precise observations.
According to the standard Big Bang cosmology, the early universe consisted of a very hot and dense plasma that continuously expanded and cooled up to the present, giving place to a series of cosmological phase transitions, where the theories describing the universe in each phase are different. Given that the energies of the early universe were much higher than those reached in terrestrial experiments, the study of the early universe might give us important information about new interactions and new particles, opening new directions for extending the Standard Model of particle physics.
As already mentioned above, during the expansion of the universe, different phase transitions occurred, which left their imprint on the present state of the universe. Observations suggest that during a very early phase transition the universe suffered a stage of accelerated expansion, known as inflation. Although inflation is not included in the standard cosmology, it is able to solve in a simple and elegant manner almost all of the shortcomings related to the standard Big Bang model, and should be taken into account in any possible extension of the theory. Observations also reveal evidence of the existence of two unknown forms of energy, i.e., dark matter and dark energy. Dark matter is a form of non-relativistic and non-baryonic matter, which can only be detected indirectly, by its gravitational interactions with normal matter. Dark energy is a kind of substance with negative pressure, which started to dominate recently and causes the accelerated expansion of the universe.
In this PhD Thesis, I present a few original models proposed to solve some of the shortcomings of the standard cosmology, as possible extensions of the Big Bang model. Some of these models introduce new symmetries and particles in order to explain inflation and dark energy and/or dark matter in a unified description. One of the models is proposed for explaining the dark energy of the universe, by means of a new scalar field oscillating in a potential.
The most successful scientific theory today about the origin and evolution of the universe is known as the standard Big Bang model, which is one of the most ambitious intellectual constructions of the humanity. It is based on two consolidated branches of theoretical physics, namely, the theory of General Relativity and the Standard Model of particle physics, and is able to make robust predictions, such as the expansion of the universe, the existence of the cosmic microwave background radiation and the relative primordial abundance of light elements. Some of the theoretical predictions have already been confirmed by very precise observations.
According to the standard Big Bang cosmology, the early universe consisted of a very hot and dense plasma that continuously expanded and cooled up to the present, giving place to a series of cosmological phase transitions, where the theories describing the universe in each phase are different. Given that the energies of the early universe were much higher than those reached in terrestrial experiments, the study of the early universe might give us important information about new interactions and new particles, opening new directions for extending the Standard Model of particle physics.
As already mentioned above, during the expansion of the universe, different phase transitions occurred, which left their imprint on the present state of the universe. Observations suggest that during a very early phase transition the universe suffered a stage of accelerated expansion, known as inflation. Although inflation is not included in the standard cosmology, it is able to solve in a simple and elegant manner almost all of the shortcomings related to the standard Big Bang model, and should be taken into account in any possible extension of the theory. Observations also reveal evidence of the existence of two unknown forms of energy, i.e., dark matter and dark energy. Dark matter is a form of non-relativistic and non-baryonic matter, which can only be detected indirectly, by its gravitational interactions with normal matter. Dark energy is a kind of substance with negative pressure, which started to dominate recently and causes the accelerated expansion of the universe.
In this PhD Thesis, I present a few original models proposed to solve some of the shortcomings of the standard cosmology, as possible extensions of the Big Bang model. Some of these models introduce new symmetries and particles in order to explain inflation and dark energy and/or dark matter in a unified description. One of the models is proposed for explaining the dark energy of the universe, by means of a new scalar field oscillating in a potential.

In this thesis we go beyond the standard cosmological LCDM model and study the effect of an interaction between dark matter and dark energy. Although the LCDM model provides good agreement with observations, it faces severe challenges from a theoretical point of view. In order to solve such problems, we first consider an alternative model where both dark matter and dark energy are described by fluids with a phenomenological interaction given by a combination of their energy densities. In addition to this model, we propose a more realistic one based on a Lagrangian density with a Yukawa-type interaction. To constrain the cosmological parameters we use recent cosmological data, the CMB measurements made by the Planck satellite, as well as BAO, SNIa, H0 and Lookback time measurements.
Nesta tese vamos além do modelo cosmológico padrão, o LCDM, e estudamos o efeito de uma interação entre a matéria e a energia escuras. Embora o modelo LCDM esteja de acordo com as observações, ele sofre sérios problemas teóricos. Com o objetivo de resolver tais problemas, nós primeiro consideramos um modelo alternativo, onde ambas, a matéria e a energia escuras, são descritas por fluidos com uma interação fenomenológica dada como uma combinação das densidades de energia. Além desse modelo, propomos um modelo mais realista baseado em uma densidade Lagrangiana com uma interação tipo Yukawa. Para vincular os parâmetros cosmológicos usamos dados cosmológicos recentes como as medidas da CMB feitas pelo satélite Planck, bem como medidas de BAO, SNIa, H0 e Lookback time.

In this thesis we studied dark matter models with strong self-interactions, typically known as self-interacting dark matter (SIDM). This kind of models constitute a promising solution to the tension between small scale structure observations and predictions assuming the standard case of collisionless cold dark matter (CDM) while keeping the success of the standard cosmological model, LambdaCDM, at large scales. The presence of strong self-interactions can increase the dark matter capture and annihilation in astrophysical objects like our sun, enhancing the potential of indirect detection signals. We used the high energy neutrinos produced by such annihilations to probe SIDM models. We established strong constraints on SIDM with velocity independent cross section by comparing the expected neutrino signal with the results of the IceCube-79 dark matter search. Also, we determined the sensitivity for the IceCube-DeepCore and PINGU detectors for SIDM with a velocity dependent self-interacting cross section (vdSIDM). Most of its relevant parameter space can be tested with the three years of data already collected by IceCube-DeepCore, complementing results from direct detection experiments and other indirect detection studies.
Nesta tese investigamos modelos de matéria escura com auto-interações fortes, conhecidos tipicamente como matéria escura auto-interagente (SIDM). Este tipo de modelos constituem uma solução promissora à tensão entre as observações de estrutura a pequena escala e as previsões assumindo o caso padrão de matéria escura fria não colisional (CDM), enquanto se mantêm o sucesso do modelo cosmológico padrão, LambdaCDM, a grandes escalas. A presença de auto-interações fortes podem aumentar a captura e a aniquilação da matéria escura em objetos astrofísicos como o nosso sol, aumentando o potencial de sinais de detecção indireta. Usamos o sinal de neutrinos de alta energia produzidos por essas aniquilações para explorar modelos de SIDM. Estabelecemos fortes vínculos em modelos de SIDM com seção de auto-interação independente da velocidade comparando o sinal de neutrinos esperado com os resultados de busca de matéria escura do IceCube-79. Também, determinamos a sensibilidade dos detectores IceCube-DeepCore e PINGU para modelos de SIDM com uma seção de auto-interação dependente da velocidade (vdSIDM). A maior parte do espaço de parâmetros de interesse pode ser testado com os três anos de dados já coletados pelo IceCube-DeepCore, complementando os resultados de experimentos de detecção direta e outras an análises de detecção indireta.

This thesis explores topics related to the formation and development of the large-scale structure in the Universe, with the focus being to compute properties of the evolved non-linear density field in an approximate way. The first three chapters form an introduction: Chapter 1 contains the theoretical basis of modern cosmology, Chapter 2 discusses the role of N-body simulations in the study of structure formation and Chapter 3 considers the phenomenological halo model. In Chapter 4 a novel method of computing the matter power spectrum is developed. This method uses the halo model directly to make accurate predictions for the matter spectrum. This is achieved by fitting parameters of the model to spectra from accurate simulations. The final predictions are good to 5% up to k = 10 hMpc-1 across a range of cosmological models at z = 0, however accuracy degrades at higher redshift and at quasi-linear scales. Chapter 5 is dedicated to a new method of rescaling a halo catalogue that has previously been generated from a simulation of a specific cosmological model to a different model; a gross rescaling of the simulation box size and redshift label takes place, then individual halo positions are modified in accord with the large scale displacement field and their internal structure is altered. The final power spectrum of haloes can be matched at the 5% level up to k = 1 hMpc-1, as can the spectrum of particles within haloes reconstituted directly from the rescaled catalogues. Chapter 6 applies the methods of the previous two chapters to modified gravity models. This is done in as general a way possible but tests are restricted to f(R) type models, which have a scale-dependent linear growth rate as well as having 'chameleon screening' - by which modifications to gravity are screened within some haloes. Taking these effects into account leads to predictions of the matter spectrum at the 5% level and rescaled halo distributions that are accurate to 5% in both real and redshift space. For the spectrum of halo particles it is demonstrated that accurate results may be obtained by taking the enhanced gravity in some haloes into account.

The monograph examines a wide range of problems related to the origin and development of the Universe. An overview of the history of the study of astronomy from Stone Age observatories to modern space telescopes is given. The theories of the origin of the Universe are analyzed, evidence of the Big Bang, the expansion of the Universe, the cosmic effects of dark energy and dark matter are given. The origin and causes of the existence of planets, stars, nebulae, galaxies and other cosmic bodies in the Universe are considered. A large place is given to the analysis of the origin and development of the Solar system. The origin and functioning of the Sun, planets and other objects located in its gravitational field are considered. Among the planets of the Solar System, the greatest attention is paid to the Earth and the analysis of the factors that ensured the emergence and maintenance of various forms of life on it. For a wide range of readers interested in the origin and evolution of the universe. It can be useful for students, postgraduates and teachers of physics and mathematics universities.