50 research outputs found
Modified Chaplygin Gas and Solvable F-essence Cosmologies
The Modified Chaplygin Gas (MCG) model belongs to the class of a unified
models of dark energy and dark matter. In this paper, we have modeled MCG in
the framework of f-essence cosmology. By constructing an equation connecting
the MCG and the f-essence, we solve it to obtain explicitly the pressure and
energy density of MCG. As special cases, we obtain both positive and negative
pressure solutions for suitable choices of free parameters. We also calculate
the state parameter which describes the phantom crossing.Comment: 12 pages, (Invited Review), accepted for publication in "Astrophysics
and Space Science" DOI: 10.1007/s10509-011-0870-
Space-time evolution induced by spinor fields with canonical and non-canonical kinetic terms
We study spinor field theories as an origin to induce space-time evolution.
Self-interacting spinor fields with canonical and non-canonical kinetic terms
are considered in a Friedman-Robertson-Walker universe. The deceleration
parameter is calculated by solving the equation of motion and the Friedman
equation, simultaneously. It is shown that the spinor fields can accelerate and
decelerate the universe expansion. To construct realistic models we discuss the
contributions from the dynamical symmetry breaking.Comment: 16 pages, 19 figure
Processos condicionantes de alteraçÔes em variĂĄveis limnolĂłgicas: uma abordagem estatĂstica na Represa de SĂŁo Pedro, Juiz de Fora (MG)
RESUMO Os mananciais de abastecimento de ĂĄgua sĂŁo ativos ambientais que precisam da atenção de toda a sociedade. O monitoramento de variĂĄveis limnolĂłgicas possibilita inferir sobre as condiçÔes do recurso hĂdrico, alĂ©m de oferecer indicativos de toda a dinĂąmica natural ou antrĂłpica compreendida na bacia hidrogrĂĄfica. A precipitação Ă© um dos principais mecanismos atuantes nos parĂąmetros de qualidade de ĂĄgua, o que justifica sua relevĂąncia nesse tipo de anĂĄlise. O teste t de Student e a anĂĄlise fatorial/anĂĄlise de componentes principais constituĂram importantes ferramentas na interpretação dos dados limnolĂłgicos da captação da Represa de SĂŁo Pedro, Juiz de Fora, Minas Gerais. O teste t de Student possibilitou verificar quais parĂąmetros apresentaram variação sazonal estatisticamente significativa. JĂĄ os resultados da anĂĄlise fatorial/anĂĄlise de componentes principais apontaram as variĂĄveis mais relevantes na qualidade da ĂĄgua do manancial. A anĂĄlise conjunta dos resultados estatĂsticos definiu os processos condicionantes das alteraçÔes nas variĂĄveis estudadas, indicando o escoamento superficial como principal determinante das variĂĄveis que compĂ”em as componentes apĂłs rotação da matriz de componentes principais, Fator Varimax FV1 e FV4, e a contribuição orgĂąnica, nĂŁo associada Ă precipitação, como reflexo das variĂĄveis da FV2 e FV3
Highly-parallelized simulation of a pixelated LArTPC on a GPU
The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 10^3 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype
The DUNE far detector vertical drift technology. Technical design report
DUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals