Astrophysics and Astronomy Commons^™

Application Of Quantum Mechanical Techniques To Optical Waveguide Structures, Stuart Ward

Physics & Astronomy ETDs

The focus of this dissertation is on the application of supersymmetric quantum mechanics to the problem of microbending in optical waveguides and on the analysis of soliton decay due solely to quantum mechanical effects.

The techniques of supersymmetric quantum mechanics are applied to the equation of motion describing light propagation in an optical waveguide which is undergoing microbending. Based on these supersymmetric techniques, given a particular refractive index profile, one may derive a new refractive index profile which results in less loss due to the microbending -- the particular example of the monomial index profile is analyzed in detail. An …

Near- And Far- Field Optical Response Of Ensembles Of Nanostructures, Lauren Zundel

Physics & Astronomy ETDs

The ability of metallic nanostructures to support collective oscillations of their conduction electrons, known as surface plasmons, makes them attractive candidates for a wide range of applications in areas as diverse as cancer therapy, biosensing, and solar energy harvesting. These applications are especially promising for periodic arrays of nanostructures, which can support collective modes known as lattice resonances, and for nanostructures with extreme aspect ratios that give rise to enhanced light-matter interaction. In this Thesis, we employ a coupled dipole model to theoretically explore the lattice resonances supported by complex arrays of nanoparticles containing multiple nanoparticles per unit cell. We …

Spectroscopy Of Highly Charged Ions For Astrophysical And Laboratory Plasma Diagnostics, Yang Yang

All Dissertations

Electron beam ion traps (EBITs) are small-scale laboratory devices that create and trap highly charged ions (HCI) for spectroscopic studies. These devices create plasma conditions resembling astrophysical environments like stellar winds and supernova remnants, providing valuable insights into astrophysical plasma. Theoretical models for such systems require incorporating relativistic and quantum electrodynamics effects, making experimental studies of HCIs essential for benchmarking these theories.

Spectral analysis of astrophysical and laboratory plasma requires understanding the ionization balance. Accurate atomic data, including excitation, ionization, and recombination cross sections, along with precise knowledge of operating conditions such as electron beam density, electron beam energy, and …

Deuterium Escape On Photoevaporating Sub-Neptunes, Pin-Gao Gu, Howard Chen

Aerospace, Physics, and Space Science Faculty Publications

We investigate the evolution of the deuterium-to-hydrogen (D/H) mass ratio driven by EUV photoevaporation of hydrogen-rich atmospheres of close-in sub-Neptunes around solar-type stars. For the first time, the diffusion-limited approach in conjunction with energy-limited photoevaporation is considered in evaluating deuterium escape from evolving exoplanet H/He envelopes. We find that the planets with smaller initial gas envelopes and thus smaller sizes can lead to weaker atmospheric escape, which facilitates hydrogen–deuterium fractionation. Specifically, in our grid of simulations with a low envelope mass fraction of less than 0.005, a low-mass sub-Neptune (4–5 M⊕) at about 0.25–0.4 au or a high-mass sub-Neptune …

Core States Of Neutron Stars From Anatomizing Their Scaled Structure Equations, Bao-Jun Cai, Bao-An Li, Zen Zhang

Faculty Publications

Given an Equation of State (EOS) for neutron star (NS) matter, there is a unique mass–radius sequence characterized by a maximum mass MNS max at radius Rmax. We first show analytically that the MNS max and Rmax scale linearly with two different combinations of the NS central pressure Pc and energy densityεc, by dissecting perturbatively the dimension less Tolman–Oppenheimer–Volkoff (TOV) equations governing NS internal variables. The scaling relations are then verified via 87 widely used and rather diverse phenomenological as well as 17 microscopic NS EOSs with/without considering hadron–quark phase transitions and hyperons, by solving numerically the original TOV equations. …

Computational And Experimental Study On Undoped And Er-Doped Lithium Tantalate Nanofluorescent Probes, Mkhitar A. Hobosyan, Andrea Pelayo Carvajal, Bhupendra B. Srivastava, Tamanna Zakia, Mohammed Uddin, Karen S. Martirosyan, Eric Rodriguez, Kofi Nketia Ackaah-Gyasi, Nicholas Dimakis

Physics & Astronomy Faculty Publications

We present a combined density functional theory (DFT) and experimental work on lithium tantalate LiTaO3 (LT) and its Er-doped counterparts. We calculate the electronic and optical properties for both LT and LT:Er+3, with Er occupying either Li or Ta sites, at 4.167 mol%. The generalized gradient approximation (GGA) calculations show that the Er-4 f bands appear closer to the conduction band bottom and to the valance band top, for the first and second doped configurations, respectively. This agrees with changes in the imaginary part of the frequency dependent dielectric function between the doped configurations. There are striking differences between the …

Eclipses, Aaron Steinhauer

Myth and Science, 2023-24

This lesson includes a series of four slide sets designed to cover increasingly specific eclipse content. Specifically, the slide sets cover the phases of the moon, lunar eclipses, solar eclipses generally, and a specific set for information about Geneseo's April 8, 2024, total solar eclipse.

Simulating The Eccentricity Evolution Of Accreting Equal-Mass Binaries: Numerical Sensitivity To The Computational Domain Size And Grid Resolution, Zhongtian Hu

All Theses

With high resolution hydrodynamics simulations, we show that the optimal values of domain radius and grid resolution for the software Sailfish when simulating time-based eccentricity evolution of equal mass, non-circular accreting binaries in a circumbinary disk to be $r_{\rm out} \leq 15a$ and $\delta x / a \le 0.01 $. These values provide a useful guideline for optimizing the performance of simulation runs while maintaining scientific accuracy. Each artificial parameter is probed with 15 runs of 2000 orbits each.

Cosmic Diffuse Neutrino And Gamma-Ray Backgrounds In The Mev Regime, Ilukpitiye Samalka Anandagoda

All Dissertations

Cosmic Multi-Messenger backgrounds include relic diffuse components created in the early Universe and contributions from individual sources. In this dissertation, I present the work done in Anandagoda (2019); Anandagoda et al. (2020, 2023) where type Ia (SNe Ia) and core-collapse supernovae (CCSNe) contributions to the diffuse neutrino and gamma-ray backgrounds in the MeV regime are studied. These backgrounds are referred to as DSNB and DSGB respectively. Based on this work, the diffuse SN Ia background is ~10⁶ times lower (for electron antineutrinos) than the CCSN background making it negligible. The predicted DSNB electron antineutrino flux at earth in the …

Delving Deep: A Population Of Extremely Dusty Dwarfs Observed By Jwst, L. Bisigello, G. Gandolfi, A. Grazian, G. Rodighiero, L. Costantin, A. R. Cooray, A. Feltre, C. Gruppioni, N. P. Hathi, Benne W. Holwerda, A. M. Koekemoer, R. A. Lucas, J. A. Newman, P. G. Pérez-González, L. Y. A. Yung, A. De La Vega, P. Arrabal Haro, M. B. Bagley, M. Dickinson, S. L. Finkelstein, J. S. Kartaltepe, C. Papovich, N. Pirzkal, S. Wilkins

Faculty and Staff Scholarship

Aims. We take advantage of the NIRCam photometric observations available as part of the Cosmic Evolution Early Release Science survey (CEERS) to identify and analyse very red sources in an effort to discover very dusty star forming galaxies. Methods. We select red galaxies as objects with a S / N > 3 at 4.4 μm and a S / N < 2 in all JWST and HST filters at λ ≤ 2 μm, which corresponds to [ F 200 W ]−[ F 444 W ]> 1.2 considering CEERS depths. This selection is ideal to identify very dusty ( A V > 1 mag) galaxies with stellar masses between 10 6 and 10 10 M ⊙ at z < 5, more massive dusty galaxies at z = 5 − 18 and galaxies at z > 18 due to the Lyman absorption, independently of their dust …

Climatic Influences On Incipient Alteration In Mars-Relevant Ultramafic Soils, Anthony Feldman

UNLV Theses, Dissertations, Professional Papers, and Capstones

An ongoing debate exists around the nature of the climatic conditions present during the Noachian and early Hesperian periods (~4.1 to 3 Gyr ago) of Mars’ ancient history. The various theories put forward can reasonably be grouped into “warm and wet” vs “cold and icy” camps. Warm and wet approximates an Earth-like system with a relatively clement climate with significant liquid water present including potentially long-lived oceans. Cold and icy theories generally postulate thick ice sheets at high elevations with periodic warming events driving precipitation and the formation of river channels and leading to the formation of chemical alteration products. …

Magmatic Processes Leading To Compositional Diversity In The Mars Crust, Amanda Marie Ostwald

UNLV Theses, Dissertations, Professional Papers, and Capstones

The ancient Mars crust can yield insights into planet formation and evolution that Earth cannot. Direct investigation of the martian surface is limited to studies on meteorites and rover-obtained analyses. The nakhlites and chassignites, two classes of martian meteorites, are together the largest suite of martian meteorites derived from a single location on the surface. As such, they present a rare opportunity to study the Mars crust in detail using samples bearing a contextual relationship. Rover studies have found a surprising amount of compositional diversity in surface materials, the formation mechanisms of which are not well-constrained. This dissertation leverages meteorites …

Dataset Of Optical And Electronic Properties For Mos2-Graphene Vertical Heterostructures And Mos2-Graphene-Au Heterointerfaces, Sanju Gupta, Panagiota Pimenidou, Miguel Garcia, Shivanshi Das, Nicholas Dimakis

Physics & Astronomy Faculty Publications

The computational and experimental data presented in this paper refer to the research article "First-Principles Calculations Integrated with Experimental Optical and Electronic Properties for MoS2-graphene Heterostructures and MoS2-graphene-Au Heterointerfaces". The computational data includes structural information, electronic and optical properties, and data to calculate the work functions for various molybdenum disulfide and graphene heterostructures and their heterointerfaces with gold. The optical properties calculations include the frequency-dependent dielectric function, the refractive index, the reflectivity, the extinction coefficient, and the energy loss function. These properties were calculated using the independent particle approximation (IPA). As for the experimental optoelectronic properties, we measured photoluminescence spectra …

Open Data From The Third Observing Run Of Ligo, Virgo, Kagra, And Geo, R. Abbott, H. Abe, F. Acernese, Teviet Creighton, Mario C. Diaz, Francisco Llamas, Soma Mukherjee, Gaukhar Nurbek, Volker Quetschke, Wenhui Wang

Physics & Astronomy Faculty Publications

The global network of gravitational-wave observatories now includes five detectors, namely LIGO Hanford, LIGO Livingston, Virgo, KAGRA, and GEO 600. These detectors collected data during their third observing run, O3, composed of three phases: O3a starting in 2019 April and lasting six months, O3b starting in 2019 November and lasting five months, and O3GK starting in 2020 April and lasting two weeks. In this paper we describe these data and various other science products that can be freely accessed through the Gravitational Wave Open Science Center at https://gwosc.org. The main data set, consisting of the gravitational-wave strain time series …

Complexity Heliophysics: A [New] System Science That Transcends The Previous Boundaries Of Our Field, Ryan M. Mcgranaghan, Seebany Datta-Barua, Jeffrey Thayer, Joe Borovsky, Jay R. Johnson, Simon Wing, Dan Baker, Massimo Materassi

Faculty Publications

Synopsis

1. The 21st century is the time of complexity. We delineate it and its importance as necessary to solve ‘wicked problems.’

2. Inherently transdisciplinary, trans-scale, and interconnected to living systems, the solution to Heliophysics’ identity crisis and to unlock the next generation of scientific discovery may be to embrace complexity.

3. With the right foresight, direction, and incentive over the next ten years, Heliophysics can become a beacon for how all of society thinks about and does complexity science.

The Loneliest Galaxies In The Universe: A Gama And Galaxy Zoo Study On Void Galaxy Morphology, Lori E. Porter, Benne Holwerda, Sandor Kruk, Maritza Lara-López, Kevin A. Pimbblet, Christopher P A Henry, Sarah Casura, Lee S. Kelvin

Faculty and Staff Scholarship

The large-scale structure of the Universe is comprised of galaxy filaments, tendrils, and voids. The majority of the Universe’s volume is taken up by these voids, which exist as underdense, but not empty, regions. The galaxies found inside these voids are expected to be some of the most isolated objects in the Universe. This study, using the Galaxy and Mass Assembly (GAMA) and Galaxy Zoo surveys, aims to investigate basic physical properties and morphology of void galaxies versus field (filament and tendril) galaxies. We use void galaxies with stellar masses (⁠M∗" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; border: 0px; …

Advancing Our Understanding Of Martian Proton Aurora Through A Coordinated Multi-Model Comparison Campaign, Andrea C. G. Hughes, Michael Scott Chaffin, Edwin J. Mierkiewicz, Justin Deighan, Rebecca Jolitz, Esa Kallio, Guillaume Gronof, Valery I. Shematovich, Dmitry Bisikalo, Cyril L. Simon Wedlund, Jasper S. Halekas, Nicholas M. Schneider, Birgit Ritter, Zachary Girazian, Sonal Jain, Jean-Claude M. C. G´Erard, Bradley Michael Hegyi

Publications

Proton aurora are the most commonly observed yet least studied type of aurora at Mars. In order to better understand the physics and driving processes of Martian proton aurora, we undertake a multi-model comparison campaign. We compare results from four different proton/hydrogen precipitation models with unique abilities to represent Martian proton aurora: Jolitz model (3-D Monte Carlo), Kallio model (3-D Monte Carlo), Bisikalo/Shematovich et al. model (1-D kinetic Monte Carlo), and Gronoff et al. model (1-D kinetic). This campaign is divided into two steps: an inter-model comparison and a data-model comparison. The inter-model comparison entails modeling five different representative cases …

Connecting The Optical Regime To The X-Ray In Neutron Star Low Mass X-Ray Binaries, Alexander B. Igl

LSU Doctoral Dissertations

Using Rossi X-Ray Timing Explorer and Otto Struve Telescope data of low mass X-ray binaries (LMXBs) Cyg X-2 and Sco X-1, the optical regime’s relationship to the X-ray was investigated through several angles. Discrete cross correlations using the optical and X-ray data revealed evidence of reprocessing in both datasets. These were more consistently present in Sco X-1, where both small and obvious features were seen at less than 4 s of optical lag. The size of these lags makes it likely that most of the reprocessing is taking place on the accretion disk. Parameterization of the Z tracks led to …

It's All About Perspective, Erik Johnson

Natural Science Faculty

When we travel, we see obvious differences in the environment, such as terrain, wildlife, and climate. Our mostly spherical planet causes the sky to look different from different locations as well.

A Method For Calculating Lateral Surface Area Of Bistatic Radar Beam Overlap, James I. Murray, Fredrick A. Jenet

Physics & Astronomy Faculty Publications

It has been shown that bistatic radars using radio telescopes as receivers can be used to increase the sensitivity of orbital debris measurements over traditional terrestrial monostatic radar. A method to calculate the lateral surface area of a bistatic radar is needed to evaluate the efficacy of a proposed bistatic radar configuration for orbital debris measurements. For over three decades, models of the orbital debris (OD) environment in low Earth orbit (LEO) have been developed to assess the risk posed by OD to spacecraft. While terrestrial radar measures debris 3 mm and larger and in situ measurements provide data for …