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Modified Newtonian dynamics at all astrophysical scales /Angus, Garry William. January 2008 (has links)
Thesis (Ph.D.) - University of St Andrews, September 2008.
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Supersymmetry at pp,̄ pp and e⁺e⁻ colliders in light of WMAP measurements of the dark matter density of the universeKrupovnickas, Tadas. Baer, Howard A. January 2004 (has links)
Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Howard Baer, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed Sept. 24, 2004). Includes bibliographical references.
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From supermassive black holes to supersymmetric dark matterKoushiappas, Savvas Michael, January 2004 (has links)
Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xxi, 172 p.; also includes graphics (some col.) Includes bibliographical references (p. 162-172). Available online via OhioLINK's ETD Center
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High-energy neutrino fluxes from supermassive dark matter /Crotty, Patrick R. January 2002 (has links)
Thesis (Ph. D.)--University of Chicago, Departments of Physics, June 2002. / Includes bibliographical references. Also available on the Internet.
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Structure formation and the end of the cosmic dark agesAlvarez, Marcelo Alonso, January 1900 (has links) (PDF)
Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.
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Numerical simulations of galaxy formation in a cosmological context /Gardner, Jeffrey P. January 2000 (has links)
Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (p. 156-167).
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Energia escura acoplada /Otalora Patiño, Giovanni. January 2010 (has links)
Orientador: Rogério Rosenfeld / Banca: Alberto Vasquez Saa / Banca: Bruto Max Pimentel Escobar / Resumo: Na última década várias observações indicam que o universo está expandindo aceleradamente. Essa expansão acelerada pode ser explicada em um universo composto de 70% de energia escura e 30% de matéria (25% de matéria escura e 5% de matéria bariônica). A energia escura proporciona a pressão negativa necessária para produzir a aceleração em grandes escalas. Nesse trabalho faz-se uma revisão do modelo de um campo escalar como fonte da energia escura, conhecido genericamente como modelo de quintessência. Estuda-se o modelo de quintessência acoplada à matéria escura / Abstract: In the previous decade many observations indicate that the universe is accelerating. This rapid expansion can be explained in an universe made up of 70% of dark energy and 30% of matter (25% of dark matter and 5% of baryonic matter). The dark energy provides negative pressure to produce acceleration. In this work it is studied the model of Quintessence, a model of scalar field, as source of the dark energy. It is studied the model of Coupled Quintessence with dark matter / Mestre
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Development of xenon level instrumentation for the LZ dark matter detectorLiao, FengTing January 2017 (has links)
Galactical and cosmological evidence show that a quarter of the energy budget of our universe is made of collisionless, non-relativistic, and non-baryonic dark matter. Its potential coupling to standard model particles, however, has not yet been understood. One of the leading candidates - Weakly Interacting Massive Particles (WIMP) - allows the production of a dark matter relic density as observed today and couples to standard model particles at or below the weak scale. LUX-ZEPLIN (LZ) is a future tonne-scale two-phase xenon TPC aiming to detect WIMP recoils with xenon nuclei. The experiment will begin WIMP search data-taking in 2020 at the Sanford Underground Research Facility (SURF) in Lead, South Dakota and has a projected sensitivity of 3 × 10<sup>-48</sup> cm<sup>2</sup> or better in probing a 40 GeV/c<sup>2</sup> WIMP. The main observables of particle interactions in LZ are the primary scintillation (S1) and secondary scintillation (S2). However, optimising and achieving a stable S2 signal in such a tonne-scale TPC is non-trivial. Effects from the structural design of the S2 production region (top-corner structure), TPC tilt, and the xenon circulation system requires precise monitoring of the liquid surface. Such monitoring is achieved by the capacitive liquid level sensors developed within this thesis. The sensors are strategically placed to ensure that nonuniformity of the S2 signal due to the effects can be understood and corrected. In this thesis, the development of a monitoring system designed to optimise the quality of the S2 signal, based on the capacitive level sensors is discussed. A design of the electronics scheme based on a differential measurement allows femtofarad precision measurement of sensor's capacitance at picofarad level, even in the presence of cable capacitance at nanofarad level. A systematic study of the response of such a sensor to LXe and the application of the precision level sensors to two-phase TPC was carried out. Findings of intrinsic influences from LXe artefacts and LXe dielectric constant variation with its saturated temperature are identified; the result on the application of the sensors contributes to the designs of LZ circulation and the top-corner region. The final LZ level sensors show an artefact-free liquid level measurement and a 12 μm precision in measuring liquid nitrogen level (projection for LXe: ∼ 9 μm) over a 20 mm measurement range.
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Dark matter in a 'Z IND. 3'-symmetry extension of the Standard modelKoerich, Luan Vinícius [UNESP] 28 August 2015 (has links) (PDF)
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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
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The Local Group and its dwarf galaxy members in the standard model of cosmologyFattahi, Azadeh 18 September 2017 (has links)
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
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