Massive gravity is an extension of general relativity where the graviton, which mediates gravitational interactions, has a non-vanishing mass. The first steps towards formulating a theory of massive gravity were made by Fierz and Pauli in 1939, but it took another 70 years until a consistent theory of massive gravity was written down. This thesis investigates the phenomenological implications of this theory, when applied to cosmology. In particular, we look at cosmic expansion histories, structure formation, integrated Sachs-Wolfe effect and weak lensing, and put constraints on the allowed parameter range of the theory. This is done by using data from supernovae, the cosmic microwave background, baryonic acoustic oscillations, galaxy and quasar maps and galactic lensing. The theory is shown to yield both cosmic expansion histories, galactic lensing and an integrated Sachs-Wolfe effect consistent with observations. For the structure formation, however, we show that for certain parameters of the theory there exists a tension between consistency relations for the background and stability properties of the perturbations. We also show that a background expansion equivalent to that of general relativity does not necessarily mean that the perturbations have to evolve in the same way. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Manuscript. Paper 6: Manuscript.</p>

The observation of solar and atmospheric neutrino oscillations place bounds on the mass differences. However, these probes are insensitive to the absolute mass. To date, cosmology has provided the best bounds on the total neutrino mass. These bounds are based on a degenerate mass model. With the increasing precision of cosmological data, we investigate the effect of the neutrino mass hierarchy. The precision of the parameter estimates stems from precise observations of the cosmic microwave background. However, the effect of neutrino mass hierarchy on this observation is smaller than the cosmic variance. Therefore, we rely on the measurement of the matter power spectrum for hierarchy effects. We propose the use of importance sampling rather than the commonly used Markov chain Monte Carlo. Importance sampling takes advantage of the microwave background's statistical insensitivity to hierarchy. We present forecasted bounds due to Planck and the proposed CMBPol. We also discuss the needed precision for future galaxy surveys in detecting the effect of neutrino mass hierarchy. / text

Due to their violent stellar winds, ionising radiation and famous deaths as supernovae, massive stars play a key role in galactic evolution. A complete understanding of these objects has been hindered by both their rarity and by the relatively limited volume of the Universe that is accessible with existing facilities. Addressing the first of these limiting factors, the VLT-FLAMES Tarantula Survey (VFTS) has drawn from the 30 Doradus region an unprecedented sample of over 800 O and B-type stars. The survey is beginning to uncover a wide range of global properties such as the region’s binary fraction of massive stars and their dynamics, whilst also looking in detail at some of its more fascinating objects. This thesis documents the reduction of the VFTS data set, whilst also describing the analysis for one of the serendipitous discoveries: the massive binary R139. This high-mass binary will provide an excellent future calibration point for stellar models, in part as it seems to defy certain expectations about its evolution. Outwith the VFTS, a search for binary companions around a trio of B-type supergiants is presented. These stars are surrounded by nebulae that closely resemble the triple-ring structure associated with the poorly-understood SN1987A. Do these stars share a similar evolutionary fate? While strong evidence is found for periodic pulsations in one of the stars, there appears to be no indication of a short-period binary companion suggested in the literature. Gathering observations from a wide range of environments builds a fuller picture of massive stars, but the samples remain somewhat limited. The coming generation of extremely large telescopes will open new regions for studies like the VFTS. Fully utilising these remarkable telescopes will require many new technologies, and this thesis presents one such development project. For adaptive-optics corrected, multi-object instruments it will be necessary to position small pick-off mirrors in the telescope’s focal plane to select the sub-fields on the sky. This could be most efficiently achieved if the mirrors were self-propelled, which has led to a miniature robot project called MAPS - the Micro Autonomous Positioning System. A number of robots have been built with a footprint of only 30 x 30mm. These wirelessly-controlled robots draw their power from the floor on which they operate and have shown the potential to be positioned to an accuracy of tens of microns. This thesis details much of the early design work and testing of the robots, and also the development of the camera imaging system used to determine the position of the robots. The MAPS project is ongoing and a number of the potential future tests, and avenues for new research, are discussed. This is a thesis that brings together an area of active astronomical research with cutting-edge technological development, highlighting how tomorrow’s telescopes will be an essential tool to answer some of today’s most puzzling research questions

The architecture of cellular networks has been undergoing an extraordinarily fast evolution in the last years to keep up with the ever increasing user demands for wireless data and services. Motivated by a search for a breakthrough in network capacity, the paradigm of heterogeneous networks (HetNets) has become prominent in modern cellular systems, where carefully deployed macrocells coexist with layers of irregularly deployed cells of reduced coverage sizes. Users can thus be offloaded from the macrocell and the capacity of the network increases. However, universal frequency reuse is usually employed to maximize capacity gains, thereby introducing the fundamental problem of inter-cell interference (ICI) in the network caused by the sharing of the spectrum among the different tiers of the HetNet. The objective of this PhD thesis is to provide analysis and mitigation techniques for the fundamental problem of interference in heterogeneous cellular networks. First, the interference of a two-tier network is modeled and analyzed by making use of spatial statistics tools that allow the reconstruction of complete coverage maps. A correlation analysis is then performed by deriving a spatial coverage cross-tier correlation function. Second, a novel architecture design is proposed to minimize interference in HetNets whose base stations may be equipped with very large antenna arrays, another key technology of future wireless systems. Then, we present interference mitigation techniques for different types of small cells, namely picocells and femtocells. In the third contribution of this thesis, we analyze the case of clustered deployments by proposing and comparing techniques suitable for this scenario. Fourth, we tackle the case of femtocell deployments by analyzing the degrading effect of interference and proposing new mitigation methods. Fifth, we introduce femtorelays, a novel small cell access technology that combats interference in femtocell networks and provides higher backhaul capacity.

Stuttgart, Univ., Diss., 2001.

Dusty star forming galaxies (DSFGs), characterized by their far-infrared (far-IR) emission, undergo the largest starbursts in the Universe, contributing to the majority of the cosmic star formation rate density at z = 1−4. The Herschel Space Observatory for the first time was able observe the full far-IR dust emission for a large population of high-redshift DSFGs, thereby accurately measuring their star formation rates. With gravitational lensing, we are able to surpass the Herschel confusion limit and probe intrinsically less luminous and therefore more normal star-forming galaxies. With this goal in mind, we have conducted a large Herschel survey, the Herschel Lensing Survey, of the cores of almost 600 massive galaxy clusters, where the effects of gravitational lensing are the strongest. In this thesis, I present follow-up studies of gravitationally lensed Herschel-detected DSFGs by utilizing multi-wavelength data from optical to radio. Specifically, I characterize the star forming properties of gravitationally lensed DSFGs by using these three subsamples: (1) A gravitationally lensed DSFG galaxy at z = 0.6 in one of the most massive galaxy clusters, Abell S1063 (at z = 0.3), (2) One of the brightest sources in HLS, which is a system of two strongly gravitationally lensed galaxies, one at z = 2.0 (optically faint gravitational arc) and the other at z = 4.7 (triply-imaged galaxy), (3) A sample of the brightest sources in HLS at z = 1−4, in which we detect rest-frame optical nebular emission lines (e.g. Hα, Hβ, [OIII]λλ4959,5007) by utilizing near-IR spectroscopy. The main results from these studies are as follows: (1) In the cluster-lensed DSFG at z = 0.6, discovered in the core of Abell S1063, we identify a luminous (SFR = 10 M⊙/yr) giant (D~1 kpc) HII region similar to those typically found at higher redshift (z~2). We show that the HII region is embedded in a rotating disk and likely formed in isolation, rather than through galaxy interaction, which is observed in local galaxies. We can use this source as a nearby laboratory for star forming regions at z ~ 2, in which more detailed follow-up of this source can help us to understand their origin/properties. (2) We discovered that one of the brightest sources in HLS is a blend of two cluster-lensed DSFGs, one at z = 2.0 (an optically faint arc) and the other at z = 4.7 (triply-imaged galaxy), implying that a sample of bright Herschel sources may have such multiplicity. In the z = 2.0 arc, the sub-arcsecond clumps detected in the SMA image surprisingly do not correspond to the clumps in the JVLA CO(1-0) image. When investigating the CO(1-0) velocity structure, there is a substantial amount of molecular gas (likely a molecular wind/outflow) we find that we find is not associated with star formation. This suggests that the CO morphology in DSFGs could be strongly influenced by molecular outflows resulting in the over-prediction of the amount of the molecular gas available for star formation. In the z = 2.0 arc, we also constrain αCO~4. While this value is normal for galaxies like the Milky Way, it is quite unusual for ULIRGs. This hints that the physical conditions may be much different in the arc from other ULIRGs, which usually have αCO ≈ 0.8.(3) We successfully detect rest-frame optical emission lines in 8 gravitationally lensed DSFGs at z = 1−4 using ground-based near-IR spectroscopy with Keck, LBT and Magellan. The luminosities of these lines are substantially less than what the far-IR derived star formation rates predict, suggesting that these DSFGs have large dust attenuations. The difference in the star formation rates is a factor of 30 x (AV= 4), which is larger than previously reported for DSFGs at z > 1. One galaxy (z = 1.5) in the sample showed the largest suppression with a factor of 550x (AV = 7), which is similar to local ULIRGs. Future prospects: Herschel provided a glimpse into the star formation of DSFGs, but only the brightest at z > 2 could be studied in detail without gravitational lensing. ALMA will revolutionize the study of DSFGs with its high spatial resolution submm/mm imaging of their dust continuum and molecular gas, and it will begin to unravel their physical properties. In order to detect nebular emission lines in fainter higher redshift sources, 20-30 meter class telescopes, with next generation near-IR spectrographs, will be necessary. JWST will play a significant role as it will target rest-frame optical nebular emission lines in DSFGs unobtainable from the ground as well as weaker Hydrogen series lines (such as Paschen and Brackett series) to better understand their instantaneous star formation and dust attenuation.

MOTL/O embodies the MOTL paradigm and models organizational adaptation. We report progress on developing computational tools for systematically altering organizational components. This adds a novel dimension to MOTL (Hexmoor, et.al., 2008). This extension is necessary to allow communities of agents or robots to reconfigure their organizational structure in response to changes in the environment. Traditional approach of a hierarchical command and control (C2) structure is ineffective (Alberts & Hayes, 2003). Recently, an edge organization has been proposed as a more suitable alternative Command and control structure in the current information age, due to its empowerment of the edge members, better shared awareness among all the members in the organization, interoperability and most importantly, agility and adaptability to dynamic situations (Chang, 2005). We will explore principled mechanisms for converting a hierarchical organization to an edge type organization. Other than structural differences, organizations differ in information flow network and information sharing strategies. We move toward a solution for organizational adaptation. Beyond current project, many other types of organizational adaptation are possible and require much further research that we anticipate for our future work. This task will lay the foundation for automatic organizational adaptation. This report begins by outlining related work and background in section 2. In section 3 we

Graphs are commonly selected as a model of scientific information: graphs can successfully represent imprecise, uncertain, noisy data; and graph theory has a well-developed mathematical apparatus forming a solid and sound foundation for graph research. Design and experimental confirmation of new, scalable, and practical analytics for massive graphs have been actively researched for decades. Our work concentrates on developing new accurate and efficient algorithms that calculate the most influential nodes and communities in an arbitrary graph. Our algorithms for graph decomposition into families of most influential communities compute influential communities faster and using smaller memory footprint than existing algorithms for the problem. Our algorithms solving the problem of influence maximization in large graphs use much smaller memory than the existing state-of-the-art algorithms while providing solutions with equal accuracy. Our main contribution is designing data structures and algorithms that drastically cut the memory footprint and scale up the computation of influential communities and nodes to massive modern graphs. The algorithms and their implementations can efficiently handle networks of billions of edges using a single consumer-grade machine. These claims are supported by extensive experiments on large real-world graphs of different types. / Graduate

Orientador: Sebastião Gomes de Carvalho / Banca: Antenor Zanardo / Banca: João Batista Moreschi / Resumo: A mineralização sulfetada de Ni-Cu-Co (PGE), associado a rochas komatiíticas, da Jazida de Fortaleza de Minas, no sudoeste do Estado de Minas Gerais é tido como de origem magmática, porém processos pós-magmáticos modificaram substancialmente a distribuição original, estrutura, textura, mineralogia e química dos minérios. Estão presentes três importantes tipos de minérios sulfetados mobilizados: brecha, formação ferrífera bandada (BIF) e minério maciço hidrotermal. O último, é o objeto de estudo desta pesquisa. O minério maciço hidrotermal está associado a zonas de falhas transversais tardias, de direção NE-SW e N-S que cortam as rochas hospedeiras, e são perpendiculares a principal zona de cisalhamento que contém o principal corpo de minério. O minério maciço hidrotermal é formado por uma matriz oxi-sulfetada, constituída por pirrotita, pentlandita, calcopirita, pirita, violarita e magnetita, contendo minerais da série cobaltita-gersdorffita, minerais do grupo da platina, minerais da série linneita-polidymita, siegenita, além de carbonatos e quartzo. Os minerais do grupo da platina ocorrem disseminados por todo minério, associados a fases silicáticas hidratadas, inclusos em grãos de magnetita e minerais da série cobaltita-gersdorffita, no contato entre o minério e as rochas encaixantes. Próximo ao contato, são observados típicas feições de alteração hidrotermal do tipo talco-carbonato-clorita-sulfeto. Ao final do evento tectono-metamórfico, durante o Neo Proterozóico, que atuou na área em condições de baixa a alta temperatura (fácies xisto verde), foram produzidas diversas soluções hidrotermais que afetaram as rochas encaixantes nas proximidades do corpo de minério, bem como do próprio minério, originando um novo tipo de minério, aqui designado como minério maciço hidrotermal. / Abstract: The komatiite-associated Ni-Cu-Co (PGE) sulphide mineralization at Fortaleza de Minas, southwestern of Minas Gerais state is believed to have a magmatic origin, but a number of post-magmatic processes significantly modified the original distribution, structure, texture, mineralogy and chemistry of the ores. Three important types of mobilized sulphide are present: breccia, banded iron formation (BIF) and hydrothermal massive ore. The last is the object of study of this research. The hydrothermal massive ore are associated to the late transversal fault zones, of N-S and NE-SW direction that cut host rocks, and are perpendicular to the principal shear zone that comprise the main ore body. The hydrothermal massive ore is formed by a massive oxi-sulphated matrix, consisted of pyrrhotite, pentlandite, chalcopyrite, pyrite, violarite and magnetite, comprising cobaltite-gersdorffite minerals series, platinum-group minerals, linnaete-polydymite minerals series, siegenite, besides carbonates and quartz. The platinum-group minerals occur disseminated over the entire ore, associated to hydrated siliceous phases, and enclosed in magnetite grains and cobaltite-gersdorffite mineral series, in the contact between the ore and enclosing rocks. Next to this contact, are observed typical hydrothermal alteration features as talc-carbonate-chlorite-sulphide. In the end of the tectonic-metamorphic event, during the Neo Proterozoic, that actuated in the area in conditions of low to medium temperatures (greenschist facies), were produced a number of hydrothermal solutions that affected enclosing rocks next to the ore body as well as the proper ore, generating a new type of ore, here designated as hydrothermal massive ore. / Mestre

Orientador: Orlando Luis Goulart Peres / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-05T23:57:09Z (GMT). No. of bitstreams: 1 Gratieri_DiegoRossi_M.pdf: 1187066 bytes, checksum: ff3152f17c81f69ea53b5fdcfd2357be (MD5) Previous issue date: 2006 / Resumo: Neste trabalho buscamos entender o fenômeno de oscilações de neutrinos e como exemplo tentamos descrever os dados dos neutrinos atmosféricos Nossa motivação principal é descrever o excesso de eventos do tipo neutrino eletrônico encontrado nos dados do detector SuperKamiokande (SK)a baixas energias quando comparados com o formalismo de oscilação de sabores de neutrinos em duas gerações,o qual resolve o problema da assimetria up-down para os neutrinos atmosféricos do tipo muônico. Para isso generalizamos o modelo de oscilação de sabores para três gerações de neutrinos, abrindo dessa forma a possibilidade de oscilação entre o neutrino eletrônico e os demais sabores.Obtemos uma solução semianalítica para o problema nos valendo dos limites impostos pela fenomenologia de neutrinos para os parâmetros de oscilação,diferenças quadráticas de massas e ângulos de mistura. Além disso levamos em conta os efeitos de matéria atuando sobre o neutrino eletrônico quando este cruza o interior terrestre e tem seu padrão de oscilação alterado / Abstract: In this work we try to understand the phenomena of neutrino oscillations,and use this to describe more precisely the atmospheric neutrino data.Our main motivation is to describe the excess of events of electron-neutrino type found in the SuperKamiokande results at low energies when compared with the predictions of the two-generation neutrino oscillation which solves the problem of the up-down muon neutrino asymmetry very successfully To do this we generalize the oscillationmodel from two to three neutrino flavors,opening the possibility of oscillation between the electron neutrino type and the others.Then we obtain a semi-analytic solution of the three flavors problem using the neutrino phenomenological limits on oscillation parameters,squared masses differences and mixing angles.We also take into account matter effects on the electronic neutrino when it crosses the Earth and has it ¿s oscillation pattern changed. / Mestrado / Física das Particulas Elementares e Campos / Mestre em Física