Physical Sciences and Mathematics Commons^™

Classification Of Topological Defects In Cosmological Models, Abigail Swanson

Student Research Submissions

In nature, symmetries play an extremely significant role. Understanding the symmetries of a system can tell us important information and help us make predictions. However, these symmetries can break and form a new type of symmetry in the system. Most notably, this occurs when the system goes through a phase transition. Sometimes, a symmetry can break and produce a tear, known as a topological defect, in the system. These defects cannot be removed through a continuous transformation and can have major consequences on the system as a whole. It is helpful to know what type of defect is produced when …

Reheating Constraints To Palatini Coleman-Weinberg Inflation, Nilay Bostan

Turkish Journal of Physics

In this work, we examine the reheating constraints to symmetry-breaking mechanism, which is associated with Coleman-Weinberg inflation in the early universe. We consider the Coleman-Weinberg inflation potential, where the inflaton has a v ̸= 0 after inflation. Setting Treh = 105 GeV, we first show wreh dependency on ns , r , and N∗ for AV case. Then, we demonstrate the results of ns , r , N∗ , α = dns/d ln k for different reheating temperatures and compare the results with the latest BICEP/Keck data. We also present that ns −r and ns −N∗ planes and the effect …

Buzzard To Cardinal: Improved Mock Catalogs For Large Galaxy Surveys, Chun-Hao To, Joseph Derose, Risa H. Wechsler, Eli Rykoff, Hao-Yi Wu, Susmita Adhikari, Elisabeth Krause, Eduardo Rozo, David H. Weinberg

Physics Faculty Publications and Presentations

We present the Cardinal mock galaxy catalogs, a new version of the Buzzard simulation that has been updated to support ongoing and future cosmological surveys, including the Dark Energy Survey (DES), DESI, and LSST. These catalogs are based on a one-quarter sky simulation populated with galaxies out to a redshift of z = 2.35 to a depth of m_r = 27. Compared to the Buzzard mocks, the Cardinal mocks include an updated subhalo abundance matching model that considers orphan galaxies and includes mass-dependent scatter between galaxy luminosity and halo properties. This model can simultaneously fit galaxy clustering and group–galaxy …

Computing An Image Of Objects Hiding Behind A Black Hole, Shannon Harding

Honors Program Theses and Projects

Gravitational lensing is the bending of light rays around a black hole. The goal of this project was to produce a computer code that would model light rays coming from a grid of objects set behind a rotating black hole. Using these light rays, we produced an image illustrating how this background of objects would appear to an observer on Earth. This was done by creating a MATLAB code to model the paths of multiple light rays at a time. This code was then used to help check and correct a C++ code that produced an image. Over the semester, …

High-Performance Computing In Covariant Loop Quantum Gravity, Pietropaolo Frisoni

Electronic Thesis and Dissertation Repository

This Ph.D. thesis presents a compilation of the scientific papers I published over the last three years during my Ph.D. in loop quantum gravity (LQG). First, we comprehensively introduce spinfoam calculations with a practical pedagogical paper. We highlight LQG's unique features and mathematical formalism and emphasize the computational complexities associated with its calculations. The subsequent articles delve into specific aspects of employing high-performance computing (HPC) in LQG research. We discuss the results obtained by applying numerical methods to studying spinfoams' infrared divergences, or ``bubbles''. This research direction is crucial to define the continuum limit of LQG properly. We investigate the …

How Should Recent Creationists Respond To Dark Matter And Dark Energy?, Danny R. Faulkner

Proceedings of the International Conference on Creationism

Astronomers and cosmologists largely accept the reality of dark matter and dark energy. However, many recent creationists oppose both dark matter and dark energy, though it is not clear why. I propose a review of the evidence for dark matter and dark energy, a survey of creationists’ responses to both, and recommendations of how we ought to view dark matter and dark energy.

There are three lines of evidence for dark matter:

1. Rotation curves of spiral galaxies
2. Dispersion velocities of galaxy clusters
3. Gravitational lensing of distant galaxies and quasars by closer galaxy clusters

The evidence for dark matter goes back …

Exploring Non-Orientable Topology: Deriving The Poincaré Conjecture And Possibility Of Experimental Vindication With Liquid Crystal, Victor Christianto, Florentin Smarandache

Branch Mathematics and Statistics Faculty and Staff Publications

This review investigates the potential of non-orientable topology as a fundamental framework for understanding the Poincaré conjecture and its implications across various scientific disciplines. Integrating insights from Dokuchaev (2020), Rapoport, Christianto, Chandra, Smarandache (under review), and other pioneering works, this article explores the theoretical foundations linking non-orientable spaces to resolving the Poincaré conjecture and its broader implications in theoretical physics, geology, cosmology, and biology.

Tests Of General Relativity Through Searches For Lorentz And Cpt Symmetry Breaking, Kellie Ault

Doctoral Dissertations and Master's Theses

An effective field theory framework, the Standard Model Extension (SME), provides an agnostic, systematic test of General Relativity (GR) and its founding spacetime symmetries, Lorentz and CPT symmetry. Violating these symmetries may provide clues toward unifying the physics of the General Relativity and the Standard Model of particle physics. Part of this work involves the merge of theory, data analysis and experiments with gravitational wave (GW) signals from LIGO/Virgo/KAGRA (LVK) detectors. A modified dispersion relation derived from the SME of GWs is implemented into the LIGO Scientific Collaboration Algorithm Library Suite (LALSuite), where a joint Bayesian inference of the source …

Cosmological Vector Fields And Constraining The Neutrino Masses, Avery J. Tishue

Dartmouth College Ph.D Dissertations

In this thesis I explore two main topics: the role and consequences of cosmological vector fields, and new ideas for constraining fundamental physics with state-of-the-art experiments. These topics are disparate in content and technique but unified in their attempt to leverage novel approaches to better understand longstanding questions in cosmology. These questions, such as ``What is causing the universe to accelerate today?'' and ``What are the neutrino masses?'', underpin the modern cosmological paradigm. They play a key role in our understanding of cosmic history, the formation of structure, and the fate of our universe. Answers to or hints about these …

Cosmology, Lensing, And Modified Gravity With Gravitational Waves, Ignacio Magana Hernandez

Theses and Dissertations

Since the first detection of gravitational waves (GWs) from the merger of two stellar-mass black holes in 2015, the LIGO-Virgo-KAGRA (LVK) Collaboration has accumulated over 90 observations of mergers involving neutron stars and black holes. With the upcoming observing runs for the LVK network of GW detectors, many more binary mergers are expected to be detected. The increasing size of gravitational wave catalogs has enabled the study of their population, its cosmic expansion history, signatures of gravitational wave lensing, and how well these observations agree with general relativity. In this dissertation, I will discuss my contributions to gravitational wave cosmology. …

New Physics In The Age Of Precision Cosmology, Vivian I. Sabla

Dartmouth College Ph.D Dissertations

The Lambda-cold dark matter (LCDM) model has become the standard model of cosmology because of its ability to reproduce a vast array of cosmological observations, from the earliest moments of our Universe, to the current period of accelerated expansion, which it does with great accuracy. However, the success of this model only distracts from its inherent flaws and ambiguities. LCDM is purely phenomenological, providing no physical explanation for the nature of dark matter, responsible for the formation and evolution of large-scale structure, and giving an inconclusive explanation for dark energy, which drives the current period of accelerated expansion.

Furthermore, cracks …

The Camels Project: Public Data Release, Francisco Villaescusa-Navarro, Shy Genel, Daniel Anglés-Alcázar, Lucia A. Perez, Pablo Villanueva-Domingo, Digvijay Wadekar, Helen Shao, Faizan G. Mohammad, Sultan Hassan, Emily Moser, Erwin T. Lau, Luis Fernando Machado Poletti Valle, Andrina Nicola, Leander Thiele, Yongseok Jo, Oliver H.E. Philcox, Benjamin D. Oppenheimer, Megan Tillman, Chang Hoon Hahn, Neerav Kaushal, Et Al.

Michigan Tech Publications

The Cosmology and Astrophysics with Machine Learning Simulations (CAMELS) project was developed to combine cosmology with astrophysics through thousands of cosmological hydrodynamic simulations and machine learning. CAMELS contains 4233 cosmological simulations, 2049 N-body simulations, and 2184 state-of-the-art hydrodynamic simulations that sample a vast volume in parameter space. In this paper, we present the CAMELS public data release, describing the characteristics of the CAMELS simulations and a variety of data products generated from them, including halo, subhalo, galaxy, and void catalogs, power spectra, bispectra, Lyα spectra, probability distribution functions, halo radial profiles, and X-rays photon lists. We also release over 1000 …

Systematic Study Of Projection Biases In Weak Lensing Analysis, Prudhvi Raj Varma Chintalapati

Graduate Research Theses & Dissertations

The nature of Dark Energy is possibly one of the most fundamental questions in Physicstoday. Comprising 70% of the energy density of the Universe, and being responsible for the accelerated expansion of the Universe, this mysterious form of energy with negative pressure is challenging our current understanding of the fundamental laws of nature. Cosmological parameters like total relative matter Density Ωm, the normalization of power spectrum σ8 and their combination S8 = σ8 (Ωm/0.3)**0.5 are used to quantify our understanding of the evolution of the large-scale structure in the Universe and shed light on the accelerated expansion, caused by the …

Evolution Of Density And Velocity Perturbations In A Slowly Contracting Universe, Olivia R. Bitcon

Honors Undergraduate Theses

One focus of research in cosmology regards the growth of structure in the universe: how we end up with stars, galaxies, galaxy clusters, and large scale structure in a universe that appears homogeneous and isotropic on large scales. Using cosmological perturbation theory, we investigate the evolution of density and velocity perturbations corresponding to a universe that is slowly contracting (Ijjas and Steinhardt), testing with and comparing different values for the equation-of-state parameter. This allows for the comparison of the growth of large scale structure in scenarios including a matter-dominated expanding universe, a dark energy-dominated expanding universe, and now, an ekpyrotic …

Applications Of Digital Filters In Radio Astronomy, Joseph William Kania

Graduate Theses, Dissertations, and Problem Reports

The radio sky spans tens of orders of magnitude in length, density, and time.
In this thesis, using novel filtering techniques and two different telescopes,
we investigate two tracers of cosmic structure: Baryon Acoustic Oscillations
(BAOs) and Fast Radio Bursts (FRBs). BAOs formed as the universe cooled
after the Big Bang. BAOs provide a fiducial length scale of the universe
throughout cosmic time and thus can be used to understand how the universe
is evolving. FRBs are very bright, short timescale, bursts of as-yet unknown
origin which occur uniformly on the sky at a rate of a few thousand per …

Probability Distributions Of The Scalar Potential, Candace Mathews

Legacy Theses & Dissertations (2009 - 2024)

In the study of cosmological inflation, string theory and supersymmetry have motivated a wide range of possible inflationary models. These models can be parameterized by a scalar potential V, which is a function of N scalar fields, and determines cosmological parameters such as the vacuum stability and energy density. In principle, we can determine V through high energy physics, such as string theory. In practice, though we may not know the details of V we might have clues about a distribution of plausible V’s, which we can build statistics on to further analyze. The purpose of this thesis defense is …

Astrophysics, Cosmology And Particle Phenomenology At The Energy Frontier, Jorge Fernandez Soriano

Dissertations, Theses, and Capstone Projects

This dissertation consists of two parts, treating significantly separated fields. Each part consists on several chapters, each treating a somewhat isolated topic from the rest. In each chapter, I present some of the work developed during my passage through the graduate program, which has mostly been published elsewhere.

Part I – Cosmic Rays and Particle Physics

• Chapter 1: In this chapter we present an introduction to the topic of cosmic ray physics, with an special focus on the so-called ultra high energy cosmic rays: their potential origins, effects during their propagation between their sources and Earth, the different techniques used …

Einstein's Equations, Lagrangians For General Relativity, And Adm Formalism, Timothy Corbett

Student Research Submissions

Einstein’s equations describe the relation of spacetime curvature and present matter. We will consider the case of a Lorentzian manifold diffeomorphic to ℝ × Σ, where time t ∈ ℝ and the three-dimensional manifold Σ represents space. In a homogeneous and isotropic universe, the three-dimensional manifold Σ of the Lorentzian manifold has Riemann curvature tensor ⁽³⁾R = KI, where K is a constant and I is the 3 × 3 identity matrix. Space is flat when K = 0, spherical when K is positive, and hyperbolic when K is negative. In this paper, we will show models agreeing with …

Understanding The Physics Of Galaxy Clusters Out To Their Virial Radii And Beyond, Arnab Sarkar

Theses and Dissertations--Physics and Astronomy

In the hierarchical structure formation model, galaxy clusters grow and evolve via mergers and accretion from the surrounding cosmic web, leaving distinctive marks in the gas properties, metallicity, and dynamical state at the outskirts of clusters, which needs to be probed to better understand the growth of a cluster. I probed the gas properties of four nearby galaxy groups MKW4, Antlia, RXJ1159, and ESO3060170 out to their virial radii using deep Suzaku and mostly snapshot Chandra observations. I found the gas entropy profiles of MKW4 follow a power-law at its outskirts - as expected from purely gravitational structure formation model. …

Accretion Onto A Black Hole At The Center Of A Neutron Star: Nuclear Equations Of State, Sophia Christina Schnauck

Honors Projects

A recent re-examination of Bondi accretion (see Richards, Baumgarte and Shapiro (2021)) revealed that, for stiff equations of state (EOSs), steady-state accretion can only occur for accretion rates exceeding a certain minimum. To date, this result has been explored only for gamma-law equations of state. Instead, we consider accretion onto a small black hole residing at the center of a neutron star governed by a more realistic nuclear EOS. We generalize the relativistic Bondi solution for such EOSs, approximated by piecewise polytropes, and thereby obtain analytical expressions for the accretion rates which were reflected in our numerical simulations. After taking …

Perturbative Unitarity And Nec Violation In Genesis Cosmology, Yong Cai, Ji Xu, Shuai Zhao, Siyi Zhou

Physics Faculty Publications

Explorations of the violation of null energy condition (NEC) in cosmology could enrich our understanding of the very early universe and the related gravity theories. Although a fully stable NEC violation can be realized in the “beyond Horndeski” theory, it remains an open question whether a violation of the NEC is allowed by some fundamental properties of UV-complete theories or the consistency requirements of effective field theory (EFT). We investigate the tree-level perturbative unitarity for stable NEC violations in the contexts of both Galileon and “beyond Horndeski” genesis cosmology, in which the universe is asymptotically Minkowskian in the past. We …

Toward Deep Learning Emulators For Modeling The Large-Scale Structure Of The Universe, Neerav Kaushal

Dissertations, Master's Theses and Master's Reports

Multi-billion dollar cosmological surveys are being conducted almost every decade in today’s era of precision cosmology. These surveys scan vast swaths of sky and generate tons of observational data. In order to extract meaningful information from this data and test these observations against theory, rigorous theoretical predictions are needed. In the absence of an analytic method, cosmological simulations become the most widely used tool to provide these predictions in order to test against the observations. They can be used to study covariance matrices, generate mock galaxy catalogs and provide ready-to-use snapshots for detailed redshift analyses. But cosmological simulations of matter …

Wavelet Packet Power Spectrum Of The Sdss Lyman-Alpha Forest: A Tool For Large-Scale Structure Detection, Jason Pero

College of Science and Health Theses and Dissertations

One of the goals of astrophysics is to obtain a full understanding how the Universe is organized on large scales and how structure evolved. In this thesis we develop a method of detecting structure on Mpc scales by measuring the one-dimensional power spectrum of the transmitted ux in the Lyman- forest. The method is based on the wavelet packet transform (WPT), which has several advantages over the Fourier transform. This includes reduced noise, resulting in less data manipulation and scrubbing in the early stages of analysis. Another advantage is localization of outliers in the data, which allows the general trend …

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 …

Effective Computational Cosmology, Eva Nesbit

Dissertations - ALL

Effective Field Theories (EFTs) provide a unique framework in which to attempt to answer outstanding questions in cosmology (and all field of physics, for that matter). This work investigates how the use of both EFTs and computational tools can help us to advance our knowledge of how the universe evolved and formed over time. Specifically, we review the successful EFT of Inflation, the EFT of Dark Energy (EFTDE), and introduce the EFT of Reheating as a generalized model of particle formation after inflation. In this way, we show how effective EFTs are at quantifying physical phenomenology at many different energy …

Searching For The Global 21 Cm Cosmic Dawn Absorption Signal With The Long Wavelength Array, Christopher Dilullo

Physics & Astronomy ETDs

The redshifted 21 cm signal from neutral hydrogen offers one of the best observational probes of Cosmic Dawn and the Epoch of Reionization. This dissertation presents an effort to detect the redshifted 21 cm signal using the Long Wavelength Array station located on the Sevilleta National Wildlife Refuge in New Mexico, USA (LWA-SV). The major goal is to validate the potential detection reported by the EDGES collaboration. This measurement requires a dynamic range on the order of 10⁵ in order to disentangle the cosmological signal from the Galactic foregrounds. The beamforming capability of LWA-SV is novel to this search. …

Phenomenology Of Fermion Production During Axion Inflation, Michael Roberts

Doctoral Dissertations

We study the production of fermions through a derivative coupling to an axion inflaton and the effects of the produced fermions on the scalar and tensor metric perturbations. We show how such a coupling can arise naturally from supergravity with an axion-like field driving large-field inflation and small instanton-like corrections. We present analytic results for the scalar and tensor power spectra, and estimate the amplitude of the non-Gaussianties in the equilateral regime. The scalar spectrum is found to have a red-tilted spectral index, small non-Gaussianities, and can be dominant over the vacuum contribution. In contrast, the tensor power spectrum from …

Formation Of Supermassive Black Holes In The Early Universe, Arpan Das

Electronic Thesis and Dissertation Repository

The aim of the work presented in this thesis is to understand the formation and growth of the seeds of the supermassive black holes in early universe. Supermassive black holes (SMBH) with masses larger than 10⁸M_Sun have been observed when the Universe was only 800 Myr old. The formation and accretion history of the seeds of these supermassive black holes are a matter of debate. We consider the scenario of massive seed black hole formation which allows gas to directly collapse into a black hole (DCBH) of similar mass. Considering this scenario, we show that the mass …

Expanding The Frontiers Of Supernova Cosmology In Preparation For Next Generation Telescopes, Justin Roberts-Pierel

Theses and Dissertations

Supernova (SN) research has been the source of many astronomical discoveries over the past several decades, most prominently the accelerated expansion of the universe by so-called “dark energy” in 1998. Next generation surveys like the Vera C. Rubin Observatory and the Nancy G. Roman Space Telescope, in large part through traditional luminosity distance measurements with Type Ia supernovae (SNe Ia), are set to reveal more about the nature of dark energy this decade than at any time in history. The enormous SN Ia samples from Roman and Rubin mean cosmological inferences will no longer be limited by statistical uncertainties, …

All-Sky Search In Early O3 Ligo Data For Continuous Gravitational-Wave Signals From Unknown Neutron Stars In Binary Systems, R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, K. E. Ramirez, W. H. Wang

Physics and Astronomy Faculty Publications and Presentations

Rapidly spinning neutron stars are promising sources of continuous gravitational waves. Detecting such a signal would allow probing of the physical properties of matter under extreme conditions. A significant fraction of the known pulsar population belongs to binary systems. Searching for unknown neutron stars in binary systems requires specialized algorithms to address unknown orbital frequency modulations. We present a search for continuous gravitational waves emitted by neutron stars in binary systems in early data from the third observing run of the Advanced LIGO and Advanced Virgo detectors using the semicoherent, GPU-accelerated, BinarySkyHough pipeline. The search analyzes the most sensitive frequency …