In this thesis we construct new supergravity solutions representing continuous distributions of D3, M2, and M5-branes. These solutions are completely specified by the harmonic function H , which is determined by solving 12H=0 in carefully chosen coordinate systems with SO( n) x SO(D⊥ - n) symmetry. Afterwards, we calculate the corresponding charge distributions using a generalized Gauss's law type argument. These solutions are asymtoptically AdS in the near horizon limit.

STACEE (Solar Tower Atmospheric Cerenkov Effect Experiment) is a ground-based gamma-ray telescope. Using a large array of mirrors from a solar heliostat facility to capture Cerenkov light from gamma-ray showers in the atmosphere, STACEE plans to lower the threshold available to ground-based gamma-ray telescopes. Determining the threshold of STACEE is reliant upon understanding the components of the telescope. The photomultiplier tubes used to convert the Cerenkov light to electronic signals need to be carefully characterized as a part of this process. We describe a method to determine the gain of the photomultiplier tubes using an uncalibrated light source. Using a statistical model, the output distribution of a photomultiplier tube with a fixed-amplitude, pulsed light source can be used to determine the gain.

The prescription of R. M. Wald for determining a thermodynamic first law for stationary, axisymmetric, asymptotically flat black holes in general theories of gravity is applied to the effective Lagrangian for the bosonic sector of low-energy heterotic super-string theory. It is found that the presence of the gauge fields necessitates an alteration of the prescription. Specifically, the Lie derivatives with respect to the Killing vector of the gauge fields are non-vanishing. This introduces new terms which ensure gauge-invariance of the final result in a natural way.

Particle production is examined within the context of brane cosmology. Non-perturbative formalisms are reviewed and employed to calculate particle number (or the energy density associated with such particles) produced in dynamical spacetimes arising from various brane configurations. Specifically, reheating from tachyon condensation, the quantum instability of a class of S-brane spacetimes, and particle production on an orbiting brane-antibrane system are investigated.

The warped braneworld picture introduced by Randall and Sundrum provides new ways of solving long-standing problems in physics, like the gauge hierarchy problem. If the warp factor is different for the time and space components of the metric, new effects may arise. We concentrate on this possibility and show that the speed of gravity may differ from that of electromagnetism, while Lorentz invariance is preserved for the standard model fields. A charged black hole in a 5 dimensional bulk provides the necessary background. Its properties are studied in detail to ensure correct embedding of the brane. Computation of the speed of gravity in this setup is done both perturbatively and numerically. The results are compared with experimental bounds to constrain the parameters of our scenario.

Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2007. / Source: Dissertation Abstracts International, Volume: 68-07, Section: B, page: 4556. Adviser: V. Alan Kostelecky. Title from dissertation home page (viewed Apr. 22, 2008).

Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2007. / Adviser: V. Alan Kostelecky.

The steady, supersonic outflow from the Sun we call the solar wind was first posited in the 1950s and initial theories rightly linked the acceleration of the wind to the existence of the million-degree solar corona. Still today, the wind acceleration mechanisms and the coronal heating processes remain unsolved challenges in solar physics. In this work, I seek to answer a portion of the mystery by focusing on a particular acceleration process: Alfven waves launched by the motion of magnetic field footpoints in the photosphere. The entire corona is threaded with magnetic loops and flux tubes that open up into the heliosphere. I have sought a better understanding of the role these magnetic fields play in determining solar wind properties in open flux tubes. After an introduction of relevant material, I discuss my parameter study of magnetic field profiles and the statistical understanding we can draw from the resulting steady-state wind. In the chapter following, I describe how I extended this work to consider time dependence in the turbulent heating by Alfven waves in three dimensional simulations. The bursty nature of this heating led to a natural next step that expands my work to include not only the theoretical, but also a project to analyze observations of small network jets in the chromosphere and transition region, and the underlying photospheric magnetic field that forms thresholds in jet production. In summary, this work takes a broad look at the extent to which Alfven-wave-driven turbulent heating can explain measured solar wind properties and other observed phenomena. / Astronomy

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