Physics Commons^™

The Design And Construction Of A Green Laser And Fabry-Perot Cavity System For Jefferson Lab's Hall A Compton Polarimeter, Abdurahim Rakhman

Physics - Dissertations

A high finesse Fabry-Perot cavity with a frequency doubled green laser (CW, 532 nm) have been built and installed in Hall A of Jefferson Lab for high precision Compton polarimetry project in spring of 2010. It provides a high intensity circularly polarized photon target for measuring the polarization of electron beam with energies from 1.0 GeV to 11.0 GeV in a nondestructive manner. The IR beam (CW, 1064 nm) from a Ytterbium doped fiber laser amplifier seeded by a Nd:YAG narrow linewidth NPRO laser is frequency doubled in by a single-pass Periodically Poled Lithium Niobate (PPMgLN) crystal. The maximum achieved …

Characterization Of Enhanced Interferometric Gravitational Wave Detectors And Studies Of Numeric Simulations For Compact-Binary Coalescences, Larne Pekowsky

Physics - Dissertations

Gravitational waves are a consequence of the general theory of relativity. Direct detection of such waves will provide a wealth of information about physics, astronomy, and cosmology. A worldwide effort is currently underway to make the first direct detection of gravitational waves. The global network of detectors includes the Laser Interferometer Gravitational-wave Observatory (LIGO), which recently completed its sixth science run.

A particularly promising source of gravitational waves is a binary system consisting of two neutron stars and/or black holes. As the objects orbit each other they emit gravitational radiation, lose energy, and spiral inwards. This produces a characteristic ``chirp'' …

Searching For Gravitational Waves From Compact Binary Coalescence Using Ligo And Virgo Data, Collin Capano

Physics - Dissertations

This thesis describes current efforts to search for gravitational waves from compact binary coalescences (CBCs) by the LIGO Scientific Collaboration (LSC) and the Virgo Collaboration. We briefly review the physics of gravitational-wave emission and detection, describing how gravitational waves are emitted from "inspiraling" compact stellar mass objects and how the LSC and Virgo try to detect them using interferometers. Next we review the data-analysis principles used to search for potential signals in the detectors' noise. These principles are employed by ``ihope," which is the data-analysis pipeline used to search for CBCs. We describe each step in this pipeline and discuss …

Interacting Stochastic Processes: From Viciousness To Caging To Force Chains, Shiliyang Xu

Physics - Dissertations

This thesis documents a quest to develop and study several novel interacting stochastic processes. As for the first example, we generalize a system of vicious random walkers in which the only interaction between any two random walkers is that when they intersect, both walkers are annihilated. We define a system of N vicious accelerating walkers with each walker undergoing random acceleration and compute the survival probability distribution for this system. We also define and study a system of N vicious Levy flights in which any two Levy flights crossing one another annihilate each other. The average mean-squared displacement of a …

Higher Derivative Gravitational Systems And Ghost Fields, Michele Fontanini

Physics - Dissertations

Effective Field Theory (EFT) is one of the most powerful theoretical tools in the hands of cosmologists, it allows them to come up with testable effective descriptions of the universe even when a fundamental theory is missing. EFT though, is not the only possible answer for pushing our knowledge beyond the limits of what has already been established. Applying EFT and other alternative methods has become an important part of a cosmologist’s work, particularly in the last few years when a vast plethora of extensions of the Standard Model of Cosmology has been proposed and needs to be tested against …

Topics In Cosmic Acceleration And Braneworlds, Eric J. West

Physics - Dissertations

Cosmic acceleration has come to be a standard, and perhaps required, ingredient in our current understanding of the universe. In the early universe, under the name of inflation, a phase of accelerated expansion is used to solve many problems with the standard Hot Big Bang cosmology. In the late universe, cosmic acceleration seems to best explain a wide variety of observations. In both cases, we lack a complete theory of what drives cosmic acceleration. In this thesis I discuss some open issues in our understanding of cosmic acceleration, both in the early and late universe.

Supersymmetric Yang-Mills Theories On The Lattice, Anosh Joseph

Physics - Dissertations

This dissertation reviews the formulation of twisted supersymmetric Yang--Mills (SYM) theories in the continuum and also on the lattice. We focus on the maximally supersymmetric twisted SYM theories in four and two dimensions. The one-loop renormalization of the lattice four-dimensional SYM theory is investigated. We also study the thermal phase structure of the maximally supersymmetric SYM in two dimensions and possible black hole transitions in its dual gravitational theory, using numerical simulations of the lattice theory.

Bioenergetics And Dynamics Of Ciliary Responses And Systems Biology Of Phototaxis In Chlamydomonas Reinhardtii, Suphatra Adulrattananuwat

Physics - Dissertations

The goal of this dissertation is to understand how a eukaryotic cell makes decisions. Chlamydomonas reinhardtii, a biciliated unicellular green alga, is used as our model organism. This organism has the ability to track the light using its photoreceptor called rhodopsin, which overlays the eyespot. The organism makes decisions to swim toward, away from, perpendicular to or to ignore the light using its slender arm-like structures called cilia. It can integrate several external inputs such as ion concentration and light intensity, and then process this information to adjust the steering of its cilia corresponding to its environment. We investigated how …

Morphology And Mechanics Of The Actin Cytoskeleton, David Aaron Quint

Physics - Dissertations

Contained in this thesis is the quest to model the growth, form and mechanics of part of the cellular cytoskeleton known as the lamellipodium. The cellular cytoskeleton is made of filamentous proteins, such as F-actin, and provides for structural support for the cell. Lamellipodia are extensions of the cellular cytoskeleton at the leading edge of a crawling cell generated so that the cell can extend, and thereby move in a particular direction. In the first two chapters, we focus on morphological characteristics of lamellipodia formation, which is, in part, shaped by branched filament nucleation via the branching protein Arp2/3. For …