Physics Commons^™

Direct Measurement Of The 114cd(��, ��)115cd Cross Section In The 1 Ev To 300 Kev Energy Range, Kofi Tutu Addo Assumin-Gyimah

Theses and Dissertations

The large thermal cross section of cadmium makes it ideal for many practical applications where screening of thermal neutrons is desired. For example, in non-destructive assay techniques, or for astrophysical studies of the s-process. All such applications require precise knowledge of the neutron-capture cross section on cadmium. Although there are some data on neutron-capture cross sections particularly at thermal energies and at energies relevant for astrophysics, there is very little data at most other energies. Further, the evaluated cross sections from the ENDF and JENDL databases disagree at high energies. Therefore, there is a critical need for precise knowledge of …

Dyonic Taub-Nut-Ads Space Phase Structure, Mohamed Tharwat

Theses and Dissertations

The Taub-NUT spacetime remains to hold many mysteries more than half a century after its discovery. The metric's controversy owes largely to the nut charge and the existence of Misner strings. Traditionally the metric is treated in the euclidean signature, this treatment hides the Misner strings. We treat the Taub-NUT spacetime with the Misner strings visible, not enforcing the time periodicity condition. We examine the phase structure belonging to three different horizon geometries. We deal with the hyperbolic, flat and spherical cases. We consider the stable phases, the phase transitions that exist between them, and find the preferable phases in …

Chasing Transients: Constructing Local Galaxy Catalogs For Electromagnetic Follow-Up Of Gravitational Wave Events, Chaoran Zhang

Theses and Dissertations

Gravitational waves (GWs) provide a new window for observing the universe which is not possible using traditional electromagnetic (EM) wave astronomy. The coalescence of compact object binaries, such as black holes (BHs) and neutron stars (NSs) generates “loud" GW signals that are detectable by the LIGO-Virgo-KAGRA (LVK) GW Observa- tory. If the binary contains at least one NS, there is a possibility that an observable EM counterpart will be launched during and/or after the merger. The first joint detection of GW radiation (GW170817) and its EM counterpart (AT 2017gfo) greatly extended our understanding of the universe in many fields, such …

Searching For Gravitational Wave Associations With High-Energy Astrophysical Transients, Brandon Joseph Piotrzkowski

Theses and Dissertations

Gravitational waves (GW) have become an invaluable tool in modern astronomy, especiallyin conjunction with other astronomical observations. GWs are created in highly dynamical systems such as compact binary coalescences (CBC) which are comprised of black holes and/or neutron stars. The Laser Interferometer Gravitational Wave Observatory (LIGO), Virgo Observatory, and KAGRA have now collectively identified almost a hundred of these events. GWs have also been predicted to come from core collapse supernovae. Both of these types of systems have been shown to produce other detectable transients, such as gamma- ray bursts (GRB) and neutrino bursts. Observations of the same astrophysical system …

Data-Driven Population Inference From Gravitational-Wave Sources And Electromagnetic Counterparts, Siddharth Mohite

Theses and Dissertations

Gravitational-wave (GW) astronomy has presented an unprecedented way to view the universe and study populations of astrophysical objects such as merging compact binaries containing black holes (BHs) and neutron stars (NSs). With the latest catalog of observations detected by the Advanced LIGO-Virgo detector network, recent analyses are placing interesting constraints on the population of BHs and NSs in these binaries. In particular, we are learning a great deal about how these binaries are distributed as a function of their masses. Another aspect of GW astronomy that has the potential to provide insights into fundamental physics is the multi-messenger follow up …

Gravitational Wave Timing Residual Models For Pulsar Timing Experiments, Casey Mcgrath

Theses and Dissertations

The ability to detect gravitational waves now gives scientists and astronomers a new way in which they can study the universe. So far, the scientific collaboration LIGO has been successful in detecting binary black hole and binary neutron star mergers. These types of sources produce gravitational waves with frequencies of the order hertz to millihertz. But there do exist other theoretical sources which would produce gravitational waves in different parts of the frequency spectrum. Of these are the theoretical mergers of supermassive black hole binaries (SMBHBs), which could occur upon the merging of two galaxies with supermassive black holes at …

Automated Identification Of Lines In Data From Gravitational Wave Detectors, Thomas A. Cruz

Theses and Dissertations

On the frontier of gravitational wave (GW) astronomy, the LIGO detectors record vast quantities of data that need to be analyzed constantly for rare and transient GW signals. A foundational problem in LIGO data analysis is the identification of spectral line features in the Power Spectral Density (PSD) of the data. Such line features correspond to high power terrestrial or instrumental signals that must be removed from the data before any search for GW signals can take place. In this study the method developed aims to automate the extraction of the frequencies and bandwidths of the lines, treated as sharp …

Enhanced Detection Efficiencies And Reduced False Alarms In Searching For Gravitational Waves From Core Collapse Supernovae, Gaukhar Nurbek

Theses and Dissertations

A supernova is a star that flares up very suddenly and then slowly returns to its former luminosity or, explodes violently with energy $10^{52}$ erg. There are stars which are 10 times or more massive than the Sun, which usually end their lives going supernova. When there is no longer enough fuel for the fusion process in the core of the star and inward gravitational pull of the star’s great mass takes place, the star starts to explode. A series of nuclear reactions starts taking place after the star begins shrinking due to gravity. In the final phase of this …

Searching For Optical Counterparts To Gravitational Waves, Richard Camuccio

Theses and Dissertations

The era of multi-messenger astronomy has begun. The coordinated activities of multiple, distinct observatories play a critical role in both responding to astrophysical transients and building a more comprehensive interpretation otherwise inaccessible to individual observations. The Transient Robotic Observatory of the South (TOROS) Collaboration has a global network of instruments capable of responding to several transient targets of opportunity. The purpose of this thesis is to demonstrate how optical observatories with small fields of view (degree) can follow up and observe astrophysical transients. TOROS facilities responded to three unique gravitational wave events during the second and third observational campaigns of …

Studies In Gravitational-Wave Astronomy And Tests Of General Relativity, Hong Qi

Theses and Dissertations

Modern astronomical data sets provide the opportunity to test our physical theories of the Universe at unprecedented levels of accuracy. This dissertation examines approaches to testing gravitational theories using a) observations of stars orbiting the center of the Milky Way; b) observations of the pulsations of Cepheid variable stars in dwarf galaxies; and c) gravitational-wave observations of compact binary mergers.

Observations of stars orbiting the center of the Milky Way have been used to infer the mass of the putative black hole that exists there. I discuss how well present and future measurements of stellar orbits can constrain the black …

Using An Astrophysical Model To Characterize Nuclear Dust, Anita N. Dunsmore

Theses and Dissertations

Dust clouds resulting from nuclear explosions are complex phenomena, and knowledge on how they form is lacking. Noting the similarities between supernovae and nuclear explosions led to the concept of modeling a nuclear dust cloud using a supernova simulation. MOCASSIN uses a Monte Carlo approach to model photons traveling through a dust cloud, allowing the cloud's characteristics to be discovered by comparing an observed spectrum to a calculated one and then changing input values to make the spectra match. Data files describing two nuclear fireballs of varying yields were created and analyzed using MOCASSIN, but yielded zero energy spectra. After …

Modeling Gravitational-Wave Sources For Pulsar Timing Arrays, Joseph Simon

Theses and Dissertations

The recent direct detections of gravitational waves (GWs) from merging black holes by the Laser Interferometer Gravitational-wave Observatory (LIGO) marks the beginning of the era of GW astronomy and promises to transform fundamental physics. In the coming years, there is hope for detections across the mass scale of binary black holes.

Pulsar Timing Arrays (PTAs) are galactic-scale low-frequency (nHz - $\mu$Hz) GW observatories, which aim to directly detect GWs from binary supermassive black holes (SMBHs) ($\gtrsim 10^{7} \msun$). The frequency and black hole mass range that PTAs are sensitive to is orders of magnitude different from those LIGO is observing, …

Galactic Outflows And Their Correlations With Galaxy Properties At 0.8 < Z < 1.6, Lindsey Whiting

Theses and Dissertations

Out

ows have been shown to be ubiquitous in galaxies between z = 1 and z=2,

and many models and observations have attempted to correlate the absorption line

properties of these out

ows with morphological characteristics of their host galaxies.

In this study, we examined the spectra of 71 galaxies with redshifts 1< z<2, paying

particular attention to the FeII and MgII absorption lines. We plotted the equivalent

width, velocity, and maximum velocity of the absorption features against various

physical properties of the galaxies, obtained from catalogues created by Skelton et

al., (2014) and van der Wel et al., (2012). We conrmed …

Monsters In The Dark: High Energy Signatures Of Black Hole Formation With Multimessenger Astronomy, Alexander L. Urban

Theses and Dissertations

When two compact objects inspiral and violently merge it is a rare cosmic event, producing fantastically “luminous” gravitational wave emission. It is also fleeting, staying in the Laser Interferometer Gravitational-wave Observatory’s (LIGO) sensitive band only for somewhere between tenths of a second and several tens of minutes. However, when there is at least one neutron star, disk formation during the merger may power a slew of potentially detectable electromagnetic counterparts, such as short gamma-ray bursts (GRBs), afterglows, and kilonovae. These explosions span the full electromagnetic spectrum and are expected within seconds, hours or days of the merger event. To learn …

Improvements To The Two-Point In Situ Method For Measurement Of The Room Constant And Sound Power In Semi-Reverberant Rooms, Zachary R. Jensen

Theses and Dissertations

The two-point in situ method is a technique for measuring the room constant of a semi-reverberant room and the sound power of a source in that room simultaneously using two measurement positions. Using a reference directivity source, where the directivity factor along any given axis of the source has been measured, one is able to use the Hopkins-Stryker equation to measure both the room constant and the sound power level of another source rather simply. Using both numerical and experimental data, it was found that by using generalized energy density (GED) as a measurement quantity, the results were more accurate …

Development, Evaluation, And Validation Of A High-Resolution Directivity Measurement System For Played Musical Instruments, K Joshua Bodon

Theses and Dissertations

A high-resolution directivity measurement system at Brigham Young University has been renovated and upgraded. Acoustical treatments have been installed on the microphone array, professional-grade audio hardware and cabling have been utilized, and user-friendly MATLAB processing and plotting codes have been developed. The directivities of 16 played musical instruments and several loudspeakers have been measured by the system, processed, and plotted. Using loudspeakers as simulated musicians, a comprehensive analysis was completed to validate the system and understand its error bounds. A comparison and evaluation of repeated-capture to single-capture spherical systems was made to demonstrate the high level of detail provided by …

Construction Of A 408 Nm Laser System For Use In Ion Interferometry, Lawrence Archibald

Theses and Dissertations

This work reports on the construction of a 408 nm laser system designed to drive stimulated Raman transitions between the F = 4 and F = 5 2 S 1/2 states of 87 Sr + using the 2 P 3/2 state as the intermediate state. This laser system will be used as part of a 87 Sr + ion interferometer. This work also includes a discussion of relevant theory describing the interaction of the ions and laser, along with a calculation of the transition rates as a function of laser power and detuning.

Comparing Theory And Experiment For Analyte Transport In The First Vacuum Stage Of The Inductively Coupled Plasma Mass Spectrometer, Matthew R. Zachreson

Theses and Dissertations

The inductively coupled plasma mass spectrometer (ICP-MS) has been used in laboratories for many years. The majority of the improvements to the instrument have been done empirically through trial and error. A few fluid models have been made, which have given a general description of the flow through the mass spectrometer interface. However, due to long mean free path effects and other factors, it is very difficult to simulate the flow details well enough to predict how changing the interface design will change the formation of the ion beam. Towards this end, Spencer et al. developed FENIX, a direct simulation …

A Feasibility Study Of Photometric Reverberation Mapping With Meter-Class Telescopes, Carla June Carroll

Theses and Dissertations

For the past several decades, mass estimates for supermassive black holes hosted by active galactic nuclei (AGN) have been made with the reverberation mapping (RM) technique. This methodology has produced consistent results and has been used to establish several relations that link the characteristics of the host galaxy to the mass of the central black hole. Despite this success, there are less than 50 AGN with black hole masses derived from RM. This low number is generally attributed to the difficulties in coordinating large blocks of telescope time for making simultaneous photometric and spectroscopic observations. Spectroscopic observations also generally require …

Characterization Of Order-Disorder Phase Transition Temperature For Select Nanoparticles, Gregory J. Sutherland

Theses and Dissertations

A method was found for creating ordered nanoparticles whose size and theoretical order-disorder temperature are ideal for study in the TEM. Specifically FePt, NiPt, FeNiPt and AuCu nanoparticles were studied. We were able to show how a nanoparticle's size affects its order-disorder temperature (Tod). When the particles were around 6 nm in diameter there was a shift downward of the Tod of 10-15 percent compared to the bulk. While particles around 10 nm in diameter experienced a downward shift of 0-6 percent compared to the bulk. One can approximate that particles less than 10-15 nm in diameter would show significant …

Gravitational Waves From Rotating Neutron Stars And Compact Binary Systems, Leslie Wade

Theses and Dissertations

It is widely anticipated that the first direct detections of gravitational waves will be made by advanced gravitational-wave detectors, such as the two Laser Interferometer Gravitational-wave Observatories (LIGO) and the Virgo interferometer. In preparation for the advanced detector era, I have worked on both detection and post-detection efforts involving two gravitational wave sources: isolated rotating neutron stars (NSs) and compact binary coalescences (CBCs). My dissertation includes three main research projects: 1) a population synthesis study assessing the detectability of isolated NSs, 2) a CBC search for intermediate-mass black-hole binaries (IMBHBs), and 3) new methods for directly measuring the neutron-star (NS) …

Gravitational-Wave Science With The Laser Interferometer Gravitational-Wave Observatory, Madeline Wade

Theses and Dissertations

Gravitational-waves, as predicted by Einstein’s theory of general relativity, are oscillations of spacetime caused by the motion of masses. Although not yet directly detected, there is strong evidence for the existence of gravitational-waves. Detectable gravitational waves will come from dramatic astrophysical events, such as supernova explosions and collisions of black holes. The Laser Interferometer Gravitational-wave Observatory (LIGO) is a network of detectors designed to make the first direct detection of gravitational waves. The upgraded version of LIGO, Advanced LIGO (aLIGO), will offer a dramatic improvement in sensitivity that will virtually guarantee detections.

Gravitational-wave detections will not only illuminate mysterious astrophysical …

Self-Force On Accelerated Particles, Thomas Michael Linz

Theses and Dissertations

The likelihood that gravitational waves from stellar-size black holes spiraling into a supermassive black hole would be detectable by a space based gravitational wave observatory has spurred the interest in studying the extreme mass-ratio inspiral (EMRI) problem and black hole perturbation theory (BHP). In this approach, the smaller black hole is treated as a point particle and its trajectory deviates from a geodesic due to the interaction with its own field. This interaction is known as the gravitational self-force, and it includes both a damping force, commonly known as radiation reaction, as well as a conservative force. The computation of …

Topics In Broadband Gravitational-Wave Astronomy, Sydney Joanne Chamberlin

Theses and Dissertations

The direct detection of gravitational waves promises to open a new observational window onto the universe, and a number of large scale efforts are underway worldwide to make such a detection a reality. In this work, we attack some of the current problems in gravitational-wave detection over a wide range of frequencies.

In the first part of this work, low frequency gravitational-wave detection is considered using pulsar timing arrays (PTAs). PTAs are a promising tool for probing the universe through gravitational radiation. Supermassive black hole binaries (SMBHBs), cosmic strings, relic gravitational waves from inflation, and first order phase transitions in …

Radio Emission Toward Regions Of Massive Star Formation In The Large Magellanic Cloud, Adam Johanson

Theses and Dissertations

Four regions of massive star formation in the Large Magellanic Cloud (LMC) were observed for water and methanol maser emission and radio continuum emission. A total of 42 radio detections were made including 27 new radio sources, four water masers, and eight compact HII regions. The lobes of a radio galaxy were resolved for the first time, and the host galaxy identified. Seven sources were associated with known massive young stellar objects (YSOs). A multi-wavelength analysis using both the infrared and radio spectrum was used to characterize the sources. Mid-infrared color-magnitude selection criteria for ultracompact HII (UCHII) regions in the …

Simulations Of Electron Trajectories In An Intense Laser Focus For Photon Scattering Experiments, Grayson J. Tarbox

Theses and Dissertations

An experiment currently underway at BYU is designed to test whether the size of a free electron wave packet affects the character of scattered radiation. Using a semi-classical argument wherein the wave packet is treated as a diffuse charge distribution, one would expect strong suppression of radiation in the direction perpendicular to the propagating field as the wave packet grows in size to be comparable to the wavelength of the driving field. If one disallows the interaction of the wave packet with itself, as is the case when calculating the rate of emission using QED, then regardless of size, the …

Algebraic Semi-Classical Model For Reaction Dynamics, Tim Glenn Wendler

Theses and Dissertations

We use an algebraic method to model the molecular collision dynamics of a collinear triatomic system. Beginning with a forced oscillator, we develop a mathematical framework upon which inelastic and reactive collisions are modeled. The model is considered algebraic because it takes advantage of the properties of a Lie algebra in the derivation of a time-evolution operator. The time-evolution operator is shown to generate both phase-space and quantum dynamics of a forced oscillator simultaneously. The model is considered semi-classical because only the molecule's internal degrees-of-freedom are quantized. The relative translation between the colliding atom and molecule in an exchange reaction …

Searching For Gravitational Waves Using Pulsar Timing Arrays, Justin Ellis

Theses and Dissertations

Gravitational Waves (GWs) are tiny ripples in the fabric of spacetime predicted by Einstein's theory of General Relativity. Pulsar timing arrays (PTAs) offer a unique opportunity to detect low frequency GWs in the near future. Such a detection would be complementary to both LISA and LIGO GW efforts. In this frequency band, the expected source of GWs are Supermassive Black Hole Binaries (SMBHBs) that will most likely form an ensemble creating a stochastic GW background with possibly a few nearby/massive sources that will be individually resolvable. A direct detection of GWs will open a new window into the fields of …

Towards Stronger Coulomb Coupling In An Ultracold Neutral Plasma, Mary Elizabeth Lyon

Theses and Dissertations

Ultracold neutral plasmas are created by photoionizing laser-cooled atoms in a magneto-optical trap (MOT). Due to their large electrical potential energies and comparatively small kinetic energies, ultracold plasmas fall into a regime of plasma systems which are called “strongly coupled.” A priority in the field of ultracold plasmas is to generate plasmas with higher values of the strong coupling parameter Γ, which is given as the ratio of the nearest-neighbor Coulomb potential energy to the average kinetic energy. The equilibrium strong coupling in ultracold plasmas is limited by the ultrafast relaxation of the ions due to spatial disorder in the …

Investigation Of A New Method Of Estimating Acoustic Intensity And Its Application To Rocket Noise, Benjamin Young Christensen

Theses and Dissertations

An alternative pressure-sensor based method for estimating the acoustic intensity, the phase and amplitude gradient estimation (PAGE) method, is presented. This method is similar to the finite-difference p-p (FD) method, in which the intensity is estimated from pressure measurements made using an array of closely spaced microphones. The PAGE method uses the same hardware as the FD method, but does not suffer from the frequency-dependent bias inherent to the FD method. Detailed derivations of the new method and the traditional FD method are presented. Both methods are then compared using two acoustic fields: a plane wave and a three monopole …