Made available in DSpace on 2018-07-27T18:26:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-08-28. Added 1 bitstream(s) on 2018-07-27T18:30:43Z : No. of bitstreams: 1 000876019.pdf: 830419 bytes, checksum: d04b4fc0f1ac3688428cce3a07901b9e (MD5) / A matéria escura é responsável por cerca de 85% de toda a matéria do universo. Sabe-se que ela possui um longo tempo de vida, que é neutra e interage com a matéria comum apenas gravitacionalmente. Muitos modelos foram aventados para descrever as possíveis partículas de matéria escura, muitos deles baseados em extensões do modelo padrão para partículas elementares. Em particular, há os modelos de partículas massivas interativas por força forte, os SIMPs, que estendem o modelo padrão com um setor escalar extra contendo todas as partículas de matéria escura, cuja estabilidade é garantida por uma simetria discreta, a qual respeitam. Essa simetria também estende as possível interações entre as partículas de matéria escura para além da usual auto-aniquilação de pares e do contexto do problema de Lee-Weinberg, descrito pelas partículas massivas interagentes por força fraca, os WIMPs. Neste trabalho postulamos a existência de um setor escalar com uma simetria discreta 'Z IND. 3'; consequente de uma quebra de simetria U(1)DM global. Esta simetria permite que processos de semi-aniquilação e aniquilação 3 SETA 2 também ocorram, além do usual processo de auto-aniquilação. Estudaremos esses três cenários, encontrando as soluções das equações de Boltzmann e comparando suas respectivas abundâncias com o resultado observacional, para podermos avaliar nosso modelo. Começaremos por revisar importantes conceitos da cosmologia padrão e por apresentar o modelo. Então revisaremos as soluções numéricas para as equações, e apresentaremos nossos próprios resultados para soluções semi-analíticas dos processos de semianiquilação e de aniquilação 3 'SETA' 2. Concluiremos por apresentar nossos próprios resultados para a solução da equação de Boltzmann para o processo 3 'SETA' 2 usando uma seção de choque que é dependente da temperatura, calculada com o pacote CalcHEP / Dark matter accounts for approximately 85% of all the matter in the universe. It is known to have a long lifetime, to be neutral and to interact with ordinary matter almost only gravitationally. There have been several models to suggest possible particles for the dark matter, many of them relying on extensions to the standard model of elementary particles. In particular, there are SIMP (strongly-interacting massive particles) models, which extend the standard model by an extra scalar sector containing the dark-matter particles, whose stability is provided by a discrete symmetry. This symmetry also extends the possible interactions between the dark-matter particles to beyond the usual pair annihilation and Lee-Weinberg scenario described by the WIMP (weakly-interacting massive particles) models. In our study, we postulate the existence of an extended dark sector with a 'Z IND. 3' discrete symmetry, which is the consequence of a global U(1)DM symmetry breaking. This symmetry allows the semi-annihilation and 3 'SETA' 2 annihilation processes to take place, besides the usual self-annihilation process. We will study each of these three scenarios, solving the respective Boltzmann equations and comparing the correspondent relic abundance to the observed one, in order to verify the liability of each of them. We will start by reviewing important aspects of standard cosmology and presenting our model. Then we will review the numerical solutions for the equations, and present our own results for semi-analytical solutions to the semi- and 3 'SETA' 2 annihilation processes. We will end by presenting our own results on solving the 3 'SETA' 2 Boltzmann equation for a temperature-dependent cross-section, calculated with the CalcHEP package

Orientador: Rogério Rosenfeld / Banca: Ruben Aldrovandi / Banca: Luís Raul Weber Abramo / Resumo: Nos últimos anos diversas evidências acumularam-se indicando que o universo é plano e dominado por alguma forma de energia escura, cuja pressão negativa está atualmente fazendo com que ele esteja em expansão acelerada. Vários modelos têm sido propostos para a energia escura, entre os quais destacam-se os modelos de quintessência, nos quais essa energia é modelada por um campo escalar. Neste trabalho analisamos alguns vínculos observacionais nos modelos de quintessência com potenciais exponenciais, e obtivemos limites para o espaço de parâmetros desses modelos no caso em que a quintessência está desacoplada dos demais componentes do universo e no caso em que ela está acoplada à partícula de matéria escura. No caso desacoplado, estudamos as soluções do tipo scaling, e mostramos que nesse regime, o único em que a quintessência exponencial desacoplada apresenta soluções cosmologicamente realísticas, esses modelos não podem ser considerados menos naturais que os demais potenciais de quintessência. Obtivemos ainda que o caso acoplado, assim como o desacoplado, também não resolve o problema da coincidência cósmica, e que a idade do universo nestes modelos é consideravelmente maior que no caso desacoplado, de modo que os limites na idade podem ser úteis para distinguir observacionalmente entre as quintessências acoplada e desacoplada / Abstract: During the last years many evidences are indicating that the universe is flat and dominated by some form of dark energy, whose negative pressure is currently driving its accelerated expansion. A plenty of models have been proposed, with special attention to the quintessence models, in which the dark energy is modelled by a scalar field. In this work we have analysed some observational constraints in the quintessence models with exponential potentials, and we have put limits on the parameter space in both coupled and uncoupled cases. In the uncoupled case, we have studied the scaling Solutions, and we have showed that in this regime, that is the only one in which the exponential uncoupled quintessence presents realistic Solutions, such models can not be considered less natural than others quintessence potentials. We have also obtained that in the case in which the quintessence is coupled to dark matter the cosmic coincidence problem can not be solved, and that the age for coupled models is considerably higher than the age for non-coupled models, in such a way that limits on the age can be useful in distinguishing between coupled and non-coupled models. / Mestre

Orientador: Rogério Rosenfeld / Banca: Reuven Opher / Banca: Ioav Waga / Banca: Ruben Aldrovandi / Banca: José Ademir Sales de Lima / Resumo: Investigamos a formação, em larga escala, de estruturas no Universo, na presença da energia escura. Sua influência sobre o crescimento de perturbações cosmológicas é exercida tanto através do efeito sobre a taxa de expansão do fundo cósmico homogêneo, quanto de suas próprias flutuações de densidade de energia. Para calcularmos a taxa de formação de aglomerados de galáxias, empregamos uma generalização do formalismo de colapso esférico para a inclusão de fluidos com pressão. Um importante efeito de flutuações de energia escura associados a halos de matéria escura é a indução de halos de energia escura, que reprimem o crescimento de estruturas quando temos equações de estado não phantom; por outro lado, quando temos equações de estado phantom, são gerados vazios de energia escura, aumentando o crescimento de estruturas de matéria. Outro importante efeito ocorre quando consideramos a possibilidade da energia escura mudar sua equação de estado quando há grandes variações de sua densidade no interior dos halos em relação ao fundo homogêneo. O grande número de parametrizações da energia escura que foram obtidos com dados, de supernovas Ia são sensíveis apenas até desvios para o vermelho de ordem um. Mostramos que as parametrizações produzem assinaturas distintas na formação de aglomerados com o uso do formalismo de Press-Schechter. Portanto, futuras observações de aglomerados galácticos podem prover vínculos importantes no comportamento da energia escura durante a evolução do Universo / Abstract: We investigate large scale structure formation in universe with dark energy presence. The dark energy influence on cosmological perturbation growth is exerted both through its effect on the expansion rate of background, and through its own density fluctuation as well. To compute the rate of formation of massive objects we employed the spherical collapse formalism, which was generalized to include fluids with pressure. An important effect caused by fluctuations in dark energy associated with dark matter halos is the induction of dark energy halos damping the growth of structures when the equations of state are non-phantom; on the other hand, phantom models generate dark energy voids, enhancing the growth of matter halos. Other important effect occurs when we consider the possibility of dark energy changing its equation of state when there are large differences between densities in the background and in the halos. The large number of dark energy parametrizations obtained with supernova Ia data are only sensitive to redshifts up to order one. We show these parametrizations produce distinguishable signatures in cluster formation using the Press-Schechter formalism. Therefore, future observations of galaxy clusters can provide important constraints on the behavior of dark energy in the course of universe evolution / Doutor

Photoallergic compounds cause an allergy when applied to the skin and the skin is then exposed to light. Photoallergy is connected with the ability of the allergen to bind to the skin. This thesis describes much basic photochemistry of several photoallergens and has explained any differences in that photochemistry when on surfaces and in the presence of H.S.A.

According to the current cosmological paradigm, ``Lambda Cold Dark Matter'' (LambdaCDM), only ~20% of the gravitating matter in the universe is made up of ordinary (i.e. baryonic) matter, while the rest consists of invisible dark matter (DM) particles, which existence can be inferred from their gravitational influence on baryonic matter and light. Despite the large success of the LambdaCDM model in explaining the large scale structure of the Universe and the conditions of the early Universe, there has been debate on whether this model can fully explain the observations of low mass (dwarf) galaxies. The Local Group (LG), which hosts most of the known dwarf galaxies, is a unique laboratory to test the predictions of the LambdaCDM model on small scales. I analyze the kinematics of LG members, including the Milky~Way-Andromeda (MW-M31) pair and dwarf galaxies, in order to constrain the mass of the LG. I construct samples of LG analogs from large cosmological N-body simulations, according to the following kinematics constraints: (a) the separation and relative velocity of the MW-M31 pair; (b) the receding velocity of dwarf galaxies in the outskirts of the LG. I find that these constraints yield a median total mass of 2*10^{12} solar masses for the MW and M31, but with a large uncertainty. Based on the mass and the kinematics constraints, I select twelve LG candidates for the APOSTLE simulations project. The APOSTLE project consists of high-resolution cosmological hydrodynamical simulations of the LG candidates, using the EAGLE galaxy formation model. I show that dwarf satellites of MW and M31 analogs in APOSTLE are in good agreement with observations, in terms of number, luminosity and kinematics. There have been tensions between the observed masses of LG dwarf spheroidals and the predictions of N-body simulations within the LambdaCDM framework; simulations tend to over-predict the mass of dwarfs. This problem is known as the ``too-big-to-fail'' problem. I find that the enclosed mass within the half-light radii of Galactic classical dwarf spheroidals, is in excellent agreement with the simulated satellites in APOSTLE, and that there is no too-big-to-fail problem in APOSTLE simulations. A few factors contribute in solving the problem: (a) the mass of haloes in hydrodynamical simulations are lower compared to their N-body counterparts; (b) stellar mass-halo mass relation in APOSTLE is different than the ones used to argue for the too-big-to-fail problem; (c) number of massive satellites correlates with the virial mass of the host, i.e. MW analogs with virial masses above ~ 3*10^{12} solar masses would have faced too-big-to-fail problems; (d) uncertainties in observations were underestimated in previous works. Stellar mass-halo mass relation in APOSTLE predicts that all isolated dwarf galaxies should live in haloes with maximum circular velocity (V_max) above 20 km/s. Satellite galaxies, however, can inhabit lower mass haloes due to tidal stripping which removes mass from the inner regions of satellites as they orbit their hosts. I examine all satellites of the MW and M31, and find that many of them live in haloes less massive than V_max=20 km/s. I additionally show that the low mass population is following a different trend in stellar mass-size relation compared to the rest of the satellites or field dwarfs. I use stellar mass-halo mass relation of APOSTLE field galaxies, along with tidal stripping trajectories derived in Penarrubia et al., in order to predict the properties of the progenitors of the LG satellites. According to this prediction, some satellites have lost a significant amount of dark matter as well as stellar mass. Cra~II, And~XIX, XXI, and XXV have lost 99 per-cent of their stellar mass in the past. I show that the mass discrepancy-acceleration relation of dwarf galaxies in the LG is at odds with MOdified Newtonian Dynamics (MOND) predictions, whereas tidal stripping can explain the observations very well. I compare observed velocity dispersion of LG satellites with the predicted values by MOND. The observations and MOND predictions are inconsistent, in particular in the regime of ultra faint dwarf galaxies. / Graduate

The Dark Valley Period and its resultant Asia Pacific War remains an open question in Japan; this era is consistently revisited in both public debates over textbooks and state apology as well as in popular culture and literature. The discussion of the Dark Valley Period and the conflicts it generated also exists within manga, a widely consumed media, and has shifted genres multiple times in the decades following the Japanese surrender. Some genres, such as early senki-mono, portrayed the war as a heroic, although ultimately futile, action undertaken by self-sacrificing youth. Semiautobiographical works, such as those created by the late manga artist Mizuki Shigeru, countered this narrative by showing the war as brutal, senseless, and useless. Often, the popularity or decline of a genre skewed closely to the general attitude concerning the wartime period. Due to its wide-scale consumption by youth, manga has the potential to both represent and forward shifts in public perception. Additionally, historical revisionists and anti-Article 9 proponents have shifted their discourse into manga in order to appeal to and influence a younger audience. This strategy is further strengthened by previous genre works, such as the Space Battleship Yamato series, which reframed the Dark Valley Period and the Asia Pacific War in a positive light indirectly through their narrative. This dissertation posits that the discussion has recently shifted into shōnen/seinen fantasy manga and that this discussion reflects a level of sympathy with revisionist historians that would normally cause a public backlash against the series in question if this sympathy was not masked by genre.

Philosophiae Doctor - PhD / The matter power spectrum is key to understanding the growth of large-scale structure in the Universe. Upcoming surveys of galaxies in the optical and HI will probe increasingly large scales, approaching and even exceeding the Hubble scale at the survey redshifts. On these cosmological scales, surveys can in principle provide the best constraints on dark energy (DE) and modified gravity models and will be able to test general relativity itself. However, in order to realise the potential of these surveys, we need to ensure that we are using a correct analysis, i.e. a general relativistic analysis, on cosmological scales. There are two fundamental issues underlying the general relativistic (GR) analysis. Firstly, we need to correctly identify the galaxy overdensity that is observed on the past light cone. Secondly, we need to account for all the distortions arising from observing on the past light cone, including redshift distortions (with all general relativistic effects included) and volume distortions. These general elativistic effects appear in the angular power spectra of matter in redshift space. We compute these quantities, taking into account all general relativistic large-scale effects, and including the important contributions from redshift space distortions and lensing convergence. This is done for self-consistent models of DE, known as ‘quintessence’, which have only been very recently treated in the GR approach. Particularly, we focus mainly on computing the predictions (i.e. the power spectra) that need to be confronted with future data. Hence we compute the GR angular power spectra, correcting the 3D Newtonian calculation for several quintessence models. We also compute the observed 3D power spectra for interacting DE (which until now have not previously been studied in the GR approach) – in which dark matter and DE exchange energy and momentum. Interaction in the dark sector can lead to large-scale deviations in the power spectrum, similar to GR effects or modified gravity. For the quintessence case, we found that the DE perturbations make only a small contribution on the largest scales, and a negligible contribution on smaller scales. Ironically, the DE perturbations remove the false boost of large-scale power that arises if we impose the (unphysical) assumption that the DE perturbations vanish. However, for the interacting DE (IDE) case, we found that if relativistic effects are ignored, i.e. if they are not subtracted in order to isolate the IDE effects, the imprint of IDE will be incorrectly identified – which could lead to a bias in constraints on IDE, on horizon scales. Moreover, we found that on super-Hubble scales, GR corrections in the observed galaxy power spectrum are able to distinguish a homogeneous DE (being one whose density perturbation in comoving gauge vanishes) from the concordance model (and from a clustering DE) – at low redshifts and for high magnification bias. Whereas the matter power spectrum is incapable of distinguishing a homogeneous DE from the concordance model. We also found that GR effects become enhanced with decreasing magnification bias, and with increasing redshift.

The topic of this thesis is the study of the vertical structure of the disk galaxies and their dark matter halos through theoretical modeling and numerical calculations. The basic theoretical model of the galactic disk used involves gravitationally-coupled stars and gas under the force-field of a dark matter halo; the disk is rotationally-supported in the plane and pressure-supported perpendicular to the plane of the galaxy. The first part of the thesis involves evaluating the vertical structure of stars and gas in normal as well as dwarf spiral galaxies. The second part of the thesis deals with probing the dark matter halo density profiles of disk galaxies using both the observed rotation curve and the H i scale height data. Following is the layout of the thesis. Chapter 1 gives a general introduction to the topic of vertical structure of spiral galaxies and their dark matter halos, followed by a broad overview of the theoretical development of the topic and ends with highlighting the motivation and challenges met in this thesis. Chapters 2 & 3 deal with the vertical structure of stars and gas in galaxies, Chapters 4-6 focus on obtaining the dark matter halo density profiles of disk galaxies from the observed rotation curve and the H i scale height data whereas Chapter 7 is devoted to the summary of results and future research plans. Vertical structure of stars and gas in galaxies The vertical thickness of the stars and the gas, namely atomic hydrogen (H i) and molecular hydrogen (H2) in a spiral galaxy, is crucial in regulating the disk dynamics close to the mid-plane, especially in the inner galaxy. However, measuring it observationally is not in general practicable due to the limitations of astronomical observations, and often impossible as in the case of face-on galaxies. Therefore, it is imperative to develop a theoretical model of the galaxy which can predict the thickness of the disk components by using as input parameters the physical quantities, which are more observationally-amenable compared to the disk thickness. The vertical thickness of the disk components is determined by a trade-off between the upward kinetic pressure and the net downward gravitational pull of the galaxy. The fraction of the disk mass due to the stars is an order of magnitude higher than that of the gas in ordinary spiral galaxies, and therefore the gas contribution to the disk gravity is ignored in general. We have developed a multi-component model of gravitationally-coupled stars, HI and H2 subjected to the force-field of an external dark matter halo, and conclusively demonstrated the importance of the inclusion of gas gravity in explaining the steep vertical stellar distribution observed in galaxies. These apart, this model does not implicitly assume a flat rotation curve for the galaxy and therefore is applicable in general to obtain the thickness of stars and gas in dwarfs (with linearly rising rotation curves) as well as in ordinary spirals. In Chapter 2, we investigate the origin of the steep vertical stellar distribution in the Galactic disk. One of the direct fall outs of our above model of the galaxy, which incor¬porates the self-gravity of the gas unlike the earlier theoretical models, lies in explaining the long-standing puzzle of the steep vertical stellar density distribution of the disk galax¬ies near the mid-plane. Over the past two decades, observations revealed that the vertical density distribution of stars in galaxies near the mid-plane is substantially steeper than the sech2 function that is expected for a self-gravitating system of stars under isothermal ap¬proximation. However, the physical origin for this has not been explained so far. We have clearly demonstrated that the inclusion of the self-gravity of the gas in the dynamical model of the Galaxy solves the problem even under the purview of isothermal approximation for the disk components. Being a low dispersion component, the gas resides closer to the mid¬plane compared to the stars, and forms a thin, compact layer near the mid-plane, thereby strongly governing the local disk dynamics. This novel idea, highlighting the significance of gas gravity has produced substantial impact on the field and triggered research activities by other groups in related areas of disk dynamics. The strong effect of the gas gravity on the vertical density profile of the stellar disk indicates that it should also bear its imprint on the Milky way thick disk, as the epoch of its formation 109 years ago is marked by a value of gas fraction, almost an order of magnitude higher than its present day value. Interest-ingly, the findings of the upcoming Gaia mission can be harnessed to verify this theoretical prediction. It may also hold the clue as to the reason behind the absence of thick disk in superthin galaxies. In Chapter 3, we use the same model to theoretically determine the H i vertical scale heights in the dwarf galaxies: DDO 154, Ho II, IC 2574 & NGC 2366 for which most of the necessary input parameters are available from observations. We stress the fact that the observational determination of the gas thickness in these dwarf irregulars is not viable. Nevertheless, it is important to estimate it theoretically as it plays a crucial role in calculating the star-formation activities and other related phenomena. However, two vital aspects have to be taken care of while modeling these dwarf galaxies. Firstly, the mass fraction in gas in these galaxies is comparable to that of the stars, and hence the gas gravity cannot be ignored on any account unlike in the case of large spirals. Secondly, dwarf galaxies have a rising rotation curve over most of the disk unlike the flat rotation curves of ordinary spirals. Both these factors have been considered in developing our model of the dwarf galaxies. We find that three out of the four galaxies studied show a flaring of their H i disks with increasing radius, by a factor of a few within several disk scale lengths. The fourth galaxy (Ho II) has a thick H1 disk throughout. A comparison of the size distribution of H1 holes in the four sample galaxies reveals that of the 20 type 3 holes, all have radii that are in agreement with them being still fully contained within the gas layer. Probing the dark matter halo profiles of disk galaxies The next part of the thesis involves the dynamical study of the shapes and density profiles of galactic dark matter halos using observational constraints on our theoretical model of a spiral galaxy. The density distribution of the dark matter halo is generally modeled using the observed rotation curve of the spiral galaxies. The rotational velocity at any radius is determined by the radial component of the net gravitational force of the galaxy, which, however, is weakly dependent on the shape of the dark matter halo. Therefore, one cannot trace the dark matter halo shape by the observed rotation curve alone. The vertical thickness of the stars and gas, on the other hand, is strongly dependent on the flattening of the dark matter halo, and therefore the observed gas thickness can be used as a diagnostic to probe the halo shape. In this thesis, we have used the double constraints of the rotation curve and the H i thickness data to obtain the best-fit values of the core density, core radius and the vertical-to-planar axis ratio (or flattening) of the dark matter halos of our largest nearby galaxy Andromeda (or M31), a low-surface brightness (LSB) superthin galaxy UGC 7321 and to study the dark matter halo shape of our Galaxy. In Chapter 4, we study the dark matter halo of M31 or Andromeda, the largest nearby galaxy to the Milky Way. We find that M31 has a highly flattened isothermal dark matter halo with the vertical-to-horizontal axis ratio equal to 0.4, which interestingly lies at the most oblate end of the halo shapes found in cosmological simulations. This indicates that either M31 is a unusual galaxy, or the simulations need to include additional physics, such as the effect of the baryons, that can affect the shape of the halo. This is quite a remarkable result as it challenges the popular practice of assuming a spherical dark matter halo in the dynamical modeling of the galaxy In Chapter 5, we have applied this technique to the superthin galaxy UGC 7321. Su¬perthins are somewhat the “extreme” objects in the local Universe because of their high gas fraction and absence of a thick disk component. It is interesting to analyze their so-called extreme characteristics in the light of the physical mechanisms which determined them to understand better the properties of ordinary spirals. We find that UGC 7321 has a spher¬ical isothermal halo, with a core radius almost equal to the disk scale length. This reveals that the dark matter dominates the dynamics of this galaxy at all radii, including the inner parts of the galaxy. This is unlike the case for the large spiral galaxies, where the core radius is typically about 3-4 disk scale lengths. Interestingly, the best-fit halo core density and the core radius are consistent, with deviations of a few percent, with the dark matter fundamental plane correlations, which depict the systematic properties of the dark matter halo in late-type and dwarf spheroidal galaxies. This apart, a high value of the gas velocity dispersion is required to get a better fit to the H i scale height data, although the superthin nature of the stellar disk implies a dynamically cold dynamic galactic disk. However, it explains the low star-formation rates in these galaxies since the Toomre Q criterion (Q < 1) for instability is less likely to be satisfied, and hence the disk is liable to be more stable to star formation. In Chapter 6, we investigate the shape of the dark matter halo in the outer Galaxy. We find that the halo is prolate, with the vertical-to-planar axis ratio monotonically increasing to 2.0 at 24 kpc, or 8 radial disk scale lengths. The resulting prolate-shaped halo can explain several long-standing puzzles in galactic dynamics, for example, it permits long-lived warps thus explaining their ubiquitous nature. It also imposes novel constraints on the galaxy formation models. Finally, in Chapter 7, the thesis is concluded with a summary of the main results and a brief discussion of the scope for future work.

Degradation in visibility is often introduced to images captured in poor weather conditions, such as fog or haze. In this paper, a fusion-based transmission estimation method is introduced to adaptively combine two different transmission models. Specifically, the new fusion weighting scheme and the atmospheric light computed from the Gaussian-based dark channel method improves the estimation of the locations of the light sources. To reduce the flickering effect introduced during the process of frame-based dehazing, a flicker-free module is formulated to alleviate the impacts. The system assessments show this approach is capable of superior defogging and dehazing performance, compared to the state-of-the-art methods, both quantitatively and qualitatively

Orientador: Rogério Rosendeld / Co-orientador: Nicolás Bernal / Banca: Ricardo D'Elia Matheus / Banca: Renata Zukanovich Funchal / Resumo: A matéria escura é responsável por cerca de 85% de toda a matéria do universo. Sabe-se que ela possui um longo tempo de vida, que é neutra e interage com a matéria comum apenas gravitacionalmente. Muitos modelos foram aventados para descrever as possíveis partículas de matéria escura, muitos deles baseados em extensões do modelo padrão para partículas elementares. Em particular, há os modelos de partículas massivas interativas por força forte, os SIMPs, que estendem o modelo padrão com um setor escalar extra contendo todas as partículas de matéria escura, cuja estabilidade é garantida por uma simetria discreta, a qual respeitam. Essa simetria também estende as possível interações entre as partículas de matéria escura para além da usual auto-aniquilação de pares e do contexto do problema de Lee-Weinberg, descrito pelas partículas massivas interagentes por força fraca, os WIMPs. Neste trabalho postulamos a existência de um setor escalar com uma simetria discreta 'Z IND. 3'; consequente de uma quebra de simetria U(1)DM global. Esta simetria permite que processos de semi-aniquilação e aniquilação 3 "SETA" 2 também ocorram, além do usual processo de auto-aniquilação. Estudaremos esses três cenários, encontrando as soluções das equações de Boltzmann e comparando suas respectivas abundâncias com o resultado observacional, para podermos avaliar nosso modelo. Começaremos por revisar importantes conceitos da cosmologia padrão e por apresentar o modelo. Então revisaremos as soluções numéricas para as equações, e apresentaremos nossos próprios resultados para soluções semi-analíticas dos processos de semianiquilação e de aniquilação 3 'SETA' 2. Concluiremos por apresentar nossos próprios resultados para a solução da equação de Boltzmann para o processo 3 'SETA' 2 usando uma seção de choque que é dependente da temperatura, calculada com o pacote CalcHEP / Abstract: Dark matter accounts for approximately 85% of all the matter in the universe. It is known to have a long lifetime, to be neutral and to interact with ordinary matter almost only gravitationally. There have been several models to suggest possible particles for the dark matter, many of them relying on extensions to the standard model of elementary particles. In particular, there are SIMP (strongly-interacting massive particles) models, which extend the standard model by an extra scalar sector containing the dark-matter particles, whose stability is provided by a discrete symmetry. This symmetry also extends the possible interactions between the dark-matter particles to beyond the usual pair annihilation and Lee-Weinberg scenario described by the WIMP (weakly-interacting massive particles) models. In our study, we postulate the existence of an extended dark sector with a 'Z IND. 3' discrete symmetry, which is the consequence of a global U(1)DM symmetry breaking. This symmetry allows the semi-annihilation and 3 'SETA' 2 annihilation processes to take place, besides the usual self-annihilation process. We will study each of these three scenarios, solving the respective Boltzmann equations and comparing the correspondent relic abundance to the observed one, in order to verify the liability of each of them. We will start by reviewing important aspects of standard cosmology and presenting our model. Then we will review the numerical solutions for the equations, and present our own results for semi-analytical solutions to the semi- and 3 'SETA' 2 annihilation processes. We will end by presenting our own results on solving the 3 'SETA' 2 Boltzmann equation for a temperature-dependent cross-section, calculated with the CalcHEP package / Mestre