Physics Commons^™

Gravitational Wave Production Through Decay Of The Inflaton Into Intermediary Fields During Slow Roll Inflation, Jessica Lauren Cook

Open Access Dissertations

This dissertation looks for possible observable signals of tensor metric perturbations sourced during slow roll inflation from decay of the inflaton field into other intermediary fields. We focus on two main scenarios, one of explosive production of intermediary fields for a short period during inflation and another of prolonged production of vectors due to a derivative coupling of the vectors with the inflaton field. We only find a possible observable signal of tensor perturbations in the second case.

Conditional Gaussian Fluctuations And Refined Asymptotics Of The Spin In The Phase-Coexistence Region, Jingran Li

Open Access Dissertations

In this dissertation four results are presented on the fluctuations of the spin per site around the thermodynamic magnetization in the mean-field Blume-Capel model, a basic model in statistical mechanics. The first two results refine the main theorem in a 2010 paper by R. S. Ellis, J. Machta, and P. T. Otto published in Annals of Applied Probability 20 (2010) 2118-2161. This paper provides the first rigorous confirmation of the statistical mechanical theory of finite-size scaling for a mean-field model. The first main result studies the asymptotics of the centered, finite-size magnetization, giving its precise rate of convergence to 0 …

Replica Exchange Monte Carlo Simulations Of The Ising Spin Glass: Static And Dynamic Properties, Burcu Yucesoy

Open Access Dissertations

Spin glasses have been the subject of intense study and considerable controversy for decades, and the low-temperature phase of short-range spin glasses is still poorly understood. Our main goal is to improve our understanding in this area and find an answer to the following question: Are there only a single pair or a countable infinity of pure states in the low temperature phase of the EA spin glass? To that aim we first start by introducing spin glasses and provide a brief history of their research, then proceed to describe our method of simulation, the parallel tempering Monte Carlo algorithm. …

Charge Transport Studies Of Proton And Ion Conducting Materials, Craig William Versek

Open Access Dissertations

The development of a high-throughput impedance spectroscopy instrumentation platform for conductivity characterization of ion transport materials is outlined. Collaborative studies using this system are summarized. Charge conduction mechanisms and conductivity data for small molecule proton conducting liquids, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, and select mixtures of these compounds are documented. Furthermore, proton diffusivity measurements using a Pulse Field Gradient Nuclear Magnetic Resonance (PFG NMR) technique for imidazole and 1,2,3-triazole binary mixtures are compared. Studies of azole functionalized discotic and linear mesogens with conductivity, structural, and thermal characterizations are detailed.

The Effect Of Vesicle Shape, Line Tension, And Lateral Tension On Membrane-Binding Proteins, Jaime Bosart Hutchison

Open Access Dissertations

Model membranes allow for the exploration of complex biological phenomena with simple, controllable components. In this thesis we employ model membranes to determine the effect of vesicle properties such as line tension, lateral tension, and shape on membrane-binding proteins. We find that line tension at the boundary between domains in a phase separated vesicle can accumulate model membrane-binding proteins (green fluorescent protein with a histidine tag), and that those proteins can, in turn, alter vesicle shape. These results suggest that domains in biological membranes may enhance the local concentration of membrane-bound proteins and thus alter protein function. We also explore …

A Measurement Of The W/Z Cross Section Ratio As A Function Of Hadronic Activity With The Atlas Detector, Andrew Robert Meade

Open Access Dissertations

Hadronic collisions at the LHC at CERN probe particle interactions at the highest energy scale of any experiment to date. We present a research program measuring R_jet = &sigma_WBR(W&rarr&mu&nu) / (&sigma_ZBR(Z&rarr&mu&mu)) as a function of a number of hadronic variables. The measurements are performed with the ATLAS detector at the LHC, using the 2011 data set, consisting of 4.64 fb-1 of pp collisions at a center of mass energy of 7 TeV. This measurement is a robust way to test the Standard Model and the modeling of perturbative QCD, and is sensitive to a wide …

Investigations Of Surface-Tension Effects Due To Small-Scale Complex Boundaries, Jiansheng Feng

Open Access Dissertations

The earliest man-made irrigation systems in recorded history date back to the ancient Egypt and Mesopotamia era. After thousands of years of experience, exploration, and experimenting, mankind have learned how to construct canals and dams and use pipes and pumps to direct and control water flow, but till this day, there are still some behaviors of water and other simple fluids that surprise us. One such example is the lotus effect: a surface-tension effect which allows raindrops to roll freely on a lotus leaf as if they were drops of mercury. One of the key factors that determine how a …

Pattern Formation In Floating Sheets, Hunter King

Open Access Dissertations

This thesis presents a study of two basic modes of deformation of a thin sheet: wrinkling and crumpling, viewed primarily in the context of an elastic sheet confined by capillary forces on a drop of liquid.

First, it provides a brief conceptual background in the relevant physics of thin sheet mechanics and capillarity and introduces the general principles of wrinkling and crumpling.

The problem of confining a circular sheet on an increasingly curved spherical drop is presented as a vehicle to explore these principles. At finite curvature, the sheet is seen to wrinkle around its outer edge. At large confinement, …

Measuring Proton Spin Polarizabilities With Polarized Compton Scattering, Philippe Paul Martel

Open Access Dissertations

Polarized nuclear Compton scattering on a proton target provides a test of low energy QCD. The beam-target asymmetries of a circularly polarized Bremsstrahlung photon beam on a transversely polarized butanol target (&Sigma_2x) and on a longitudinally polarized butanol target (&Sigma_2z), and the beam asymmetry of a linearly polarized Bremsstrahlung beam on an unpolarized hydrogen target (&Sigma₃) are sensitive to the proton spin polarizabilities, third order terms in the energy expansion of the Compton scattering amplitude. This experiment consisted of the &Sigma_2x measurement, both just below and above two-pion threshold.

Quantum Corrections To The Gravitational Interaction Of Massless Particles, Thomas J. Blackburn Jr.

Open Access Dissertations

Donoghue's effective field theory of quantum gravity is extended to include the interaction of massless particles. The collinear divergences which accompany massless particles are examined first in the context of QED and then in quantum gravity. A result of Weinberg is extended to show how these divergences vanish in the case of gravity. The scattering cross section for hypothetical massless scalar particles is computed first, because it is simpler, and the results are then extended to photons. Some terms in the cross section are shown to correspond to the Aichelburg-Sexl metric surrounding a massless particle and to quantum corrections to …

Swelling And Folding As Mechanisms Of 3d Shape Formation In Thin Elastic Sheets, Marcelo A. Dias

Open Access Dissertations

We work with two different mechanisms to generate geometric frustration on thin elastic sheets; isotropic differential growth and folding. We describe how controlled growth and prescribing folding patterns are useful tools for designing three-dimensional objects from information printed in two dimensions. The first mechanism is inspired by the possibility to control shapes by swelling polymer films, where we propose a solution for the problem of shape formation by asking the question, ``what 2D metric should be prescribed to achieve a given 3D shape?'', namely the reverse problem. We choose two different types of initial configurations of sheets, disk-like with one …

Searches For Gravitational Waves From Binary Black Hole Coalescences With Ground-Based Laser Interferometers Across A Wide Parameter Space, Satyanarayan Ray Pitambar Mohapatra

Open Access Dissertations

This is an exciting time for Gravitational Wave (GW) theory and observations. From a theoretical standpoint, the grand-challenge problem of the full evolution of a Binary Black Hole (BBH) system has been solved numerically, and a variety of source simulations are made available steadfastly. On the observational side, the first generation of state-of-the-art GW detectors, LIGO and Virgo, have achieved their design goal, collected data and provided astrophysically meaningful limits. The second generation of detectors are expected to start running by 2015. Inspired by this zeitgeist, this thesis focuses on the detection of potential GW signatures from the coalescence of …

Parity Violation In Neutron Deuteron Scattering In Pionless Effective Field Theory, Jared James Vanasse

Open Access Dissertations

In this dissertation the parity violating neutron deuteron scattering amplitudes are calculated using pionless effective field theory to leading order. The five low energy parity violating constants present in pionless effective field theory are estimated by matching onto the "best" values for the parameters of the model by Desplanques, Donoghue, and Holstein (DDH). Using these estimates and the calculated amplitudes, predictions for the spin rotation of a neutron through a deuteron target are given with a value of 1.8×10-8 rad cm-1. Also given are the longitudinal analyzing power in neutron deuteron scattering with a polarized neutron yielding 2.2×10-8, and a …

Theory Of Interacting Polyelectrolytes Under Confinement, Alexander Eliseev

Open Access Dissertations

During my thesis work I have investigated the problem of polyelectrolyte characterization and in particular how to interpret the experimental data to obtain the mass and gyration radius of short polyelectrolytes. This is usually a challenging problem for experimentalists to deal with. For example, the interpretation of the static light scattering data to obtain the gyration radius becomes increasingly inaccurate as the size of the chain becomes very much smaller then the light wavelength. Also, the interpretation of membrane osmomometry data is complicated by the leakage of the solute of low molecular weight polymers and so forth. There are, however, …

Understanding Hard Interaction In Qcd And The Search For The Gluon Spin Contribution To The Spin Of The Proton, Amaresh Datta

Open Access Dissertations

In the following discourse unpolarized cross sections and double helicity asymmetries of single inclusive positive and negative charged hadrons at mid-rapidity from p + p collisions at p s = 62:4 GeV are presented. Measurements for the transverse momentum range 1:0 < pT < 4:5 GeV/c are done with PHENIX detector at Relativistic Heavy-Ion Collider (RHIC) and are consistent with calculations based on perturbative quantum chromodynamics (pQCD) at next-to-leading order (NLO) in the strong coupling constant, s. Resummed pQCD calculations including terms with next-to-leading log (NLL) accuracy, yielding reduced theoretical uncertainties, also agree with the data. The double helicity asymmetry, sensitive at leading order to the gluon polarization in a momentum fraction range of 0:05

Probing Novel Properties Of Nucleons And Nuclei Via Parity Violating Electron Scattering, Luis Rafael Mercado

Open Access Dissertations

This thesis reports on two experiments conducted by the HAPPEx (Hall A Proton Parity Experiment) collaboration at the Thomas Jefferson National Accelerator Facility. For both, the weak neutral current interaction (WNC, mediated by the Z0 boson) is used to probe novel properties of hadronic targets. The WNC interaction amplitude is extracted by measuring the parity-violating asymmetry in the elastic scattering of longitudinally polarized electrons off unpolarized target hadrons. HAPPEx-III, conducted in the Fall of 2009, used a liquid hydrogen target at a momentum transfer of Q² = 0.62 GeV². The measured asymmetry was used to set new …

Measurements Of Gravity Driven Granular Channel Flows, Kevin Facto

Open Access Dissertations

This dissertation presents experiments that studied two gravity driven granular channel flows. The first experiment used magnetic resonance imaging to measure the density and displacement distributions of poppy seeds flowing in a rough walled channel. Time-averaged measurements of normalized velocity and density showed little flow speed dependence. Instantaneous measurements, however, showed marked velocity dependence in the displacement distributions. There was evidence of aperiodic starting and stopping at lower flow speeds and the onset of density waves on a continuous flow at higher speeds. The second experiment measured forces in all three spatial directions at the boundary of a flow of …

Capillary Interactions Among Microparticles And Nanoparticles At Fluid Interfaces, Chuan Zeng

Open Access Dissertations

Particles can be adsorbed to liquid-fluid interface to minimize interfacial energy. The adsorbed particles interact in many ways. There has been a lot of theoretical predictions as well as experimental measurements of the interaction potential between particles confined at interfaces. Experimentally, we track multiple particles using optical microscope image processing of isolated pairs of particles and of more concentrated systems. Statistical methods were implemented to compute microparticle interaction forces from tracking data. The accuracy of different methods were tested with Monte Carlo simulation, which showed that care is needed to avoid artifacts. Our measurements confirmed the absence of significant pair-interactions …

Search For Contact Interactions With Dimuons At The Atlas Detector, Emily Thompson

Open Access Dissertations

The Standard Model has been very successful over the last few decades in its agreement with experimental evidence; however there are some remaining puzzles in our understanding of the Universe which have yet to be solved. Even if the Higgs boson and Super Symmetry are discovered, questions still arise, such as why Nature is primarily made of matter when antimatter should have been produced in equal amounts at the beginning of the Universe, why the fundamental particles have the mass hierarchy that they do, what the nature of dark matter is, or whether or not quarks and leptons are themselves …

Experiments And Simulations On Granular Gases, Hongqiang Wang

Open Access Dissertations

In this thesis we report experimental and simulation study of granular gases. As a non-equilibrium system composed of macroscopic particles, a granular gas often shows a picture similar to a molecular gas in that the system is dilute and particles interact with each other through instantaneous collisions. Unlike in molecular gases, the collisions are inelastic so that the interactions are a continuous sink of kinetic energy. The study of granular gases is not only of theoretical interest as an important example of non-equilibrium physics, but also of practical value since granular materials play an important role in many industrial processes …

Frontiers In Theoretical High Energy Physics: From Physics Beyond The Standard Model To Cosmology, Mohamed M. Anber

Open Access Dissertations

This dissertation is focused on three lines of work. In the first part, we consider aspects of holography and gauge/gravity duality in lower and higher dimensions. In particular, we study the duality for exact solutions localized on the Randal-Sundrum 2-branes. We also test if some holographic principles in general relativity can be generalized to include higher derivative theories of gravity; namely Lovelock gravity. In the second part we consider the role of pseudo Nambu-Goldstone bosons (pNGBs) in inflationary cosmology. Specifically, we construct an inflationary model using string theory axions, and use these pNGBs to produce the observed coherent magnetic field …

Self-Assembly Of Nanoparticles At Liquid-Liquid Interfaces, Kan Du

Open Access Dissertations

In this thesis, we studied the self-assembly of nanoparticles at liquid metal-water interfaces and oil-water interfaces. We demonstrated a simple approach to form nanostructured electronic devices by self-assembly of nanoparticles at liquid metal surfaces. In this approach, two liquid-metal droplets, which were coated with a monolayer of ligand-stabilized nanoparticles, were brought into contact. They did not coalesce but instead remained separated by the nanoparticles assembled at the interface. Devices formed by this method showed electron transport between droplets that was characteristic of the Coulomb blockade, where current was suppressed below a tunable threshold voltage because of the energy of charging …

Characterization And Interactions Of Ultrafast Surface Plasmon Pulses, Sibel Ebru Yalcin

Open Access Dissertations

Surface Plasmon Polaritons (SPPs) are considered to be attractive components for plasmonics and nanophotonic devices due to their sensitivity to interface changes, and their ability to guide and confine light beyond the diffraction limit. They have been utilized in SPP resonance sensors and near field imaging techniques and, more recently, SPP experiments to monitor and control ultrafast charge carrier and energy relaxation dynamics in thin films. In this thesis, we discuss excitation and propagation properties of ultrafast SPPs on thin extended metal films and SPP waveguide structures. In addition, localized and propagating surface plasmon interactions in functional plasmonic nanostructures will …

Hierarchical Multiple Bit Clusters And Patterned Media Enabled By Novel Nanofabrication Techniques - High Resolution Electron Beam Lithography And Block Polymer Self Assembly, Qijun Xiao

Open Access Dissertations

This thesis discusses the full scope of a project exploring the physics of hierarchical clusters of interacting nanomagnets. These clusters may be relevant for novel applications such as multilevel data storage devices. The work can be grouped into three main activities: micromagnetic simulation, fabrication and characterization of proof-ofconcept prototype devices, and efforts to scale down the structures by creating the hierarchical structures with the aid of diblock copolymer self assembly. Theoretical micromagnetic studies and simulations based on Landau-Lifshitz- Gilbert (LLG) equation were conducted on nanoscale single domain magnetic entities. For the simulated nanomagnet clusters with perpendicular uniaxial anisotropy, the simulation …

Rare Decays In Babar: Search For Decays Of The Neutral B Meson Into Two Leptons And Measurement Of Cp Asymmetry In Inclusive Radiative Decays Of The B Meson Into A Strange-Quark System, Emmanuele Salvati

Open Access Dissertations

No abstract provided.

Wrinkling, Folding, And Snapping Instabilities In Polymer Films, Douglas Peter Holmes

Open Access Dissertations

This work focuses on understanding deformation mechanisms and responsiveness associated with the wrinkling, folding, and snapping of thin polymer films. We demonstrated the use of elastic instabilities in confined regimes, such as the crumpling and snapping of surface attached sheets. We gained fundamental insight into a thin film's ability to localize strain. By taking advantage of geometric strain localization we were able to develop new strategies for responsive surfaces that will have a broad impact on adhesive, optical, and patterning applications. Using the rapid closure of the Venus flytrap's leafets as dictated by the onset of a snap instability as …

The Conformational Gymnastics Of The Escherichia Coli Seca Molecular Machine And Its Interactions With Signal Sequences, Jenny Lynn Maki

Open Access Dissertations

Protein secretion is a selective and regulated process that is essential in all organisms. In bacteria the preprotein translocase SecA, either free in the cytosol or associated with the SecYEG translocon, recognizes and binds most post-translational secretory proteins containing an N-terminal signal sequence. In Gram-negative bacteria, the molecular chaperone SecB binds many of the preproteins to keep them in a translocation-competent state. Subsequently, SecB delivers the preproteins to the translocon-associated SecA, which binds the signal sequence and also interacts with mature regions of the preprotein. After the preprotein/SecA/SecYEG complex has formed, the energy derived from ATP hydrolysis by SecA coupled …