VictorJuiz/thesis huggingface dataset:
No Negative Modes About the Axionic Wormhole Instanton
Keywords:  Department of Physics
axion
instanton
wormhole
Thesis

The axion is a hypothetical elementary particle originally proposed as a solution to the strong CP problem. Because the axion is associated with a pseudo-scalar field instead of a scalar field, it has a nontrivial instanton solution, which has the form of a spherically symmetric wormhole. We examine the perturbations about this instanton using a scalar-vector-tensor decomposition. The vector modes are pure gauge, and therefore may be directly integrated. We compute the action for the tensor modes and the spectrum is shown to be non-negative. We obtain the action of the scalar modes using a transformation from the known action of a scalar field coupled to gravity. The scalar mode spectrum is also shown to be non-negative, so the axionic wormhole instanton has no negative modes. This discourages the interpretation of this instanton as a decay rate, and instead supports the Coleman interpretation of this instanton as showing that the ground state is a superposition of many-universe states.
Non-Abelian Lefschetz hyperplane theorems [electronic resource]
Keywords: Mathematics.

Let X be a smooth variety over the complex numbers, and let D be an ample divisor in X. For which spaces Y does every map from D to Y extend uniquely to a map X to Y? Our main result, proved via positive characteristic methods, is the following: if dim(X) > 2, Y is smooth, the cotangent bundle of Y is nef, and dim(Y) < dim(D), every such map extends. Taking Y to be the classifying space of a finite group BG, the moduli space of pointed curves M_g, n, the moduli space of principally polarized Abelian varieties A_g, certain period domains, and various other moduli spaces, one obtains many new and classical Lefschetz hyperplane theorems. We also prove many other such extension theorems, and develop general techniques for recognizing spaces Y for which these sorts of Lefschetz theorems hold.
Nonlytic spread of a naked virus [electronic resource]
Keywords: Microbiology and Immunology.

How do viruses spread from cell to cell? Enveloped viruses acquire their surrounding membranes by budding either through the plasma membrane or an internal membrane of infected cells. Thus, a newly budded enveloped virus finds itself either in the extracellular milieu or in a lumenal compartment from which it can exit the cell by conventional secretion. On the other hand, naked viruses such as poliovirus lack an external membrane. They are simply protein-nucleic acid complexes within the cytoplasm or nucleus of the infected cell, and thus would seem to have no other exit route than cell lysis. Poliovirus is a lytic virus, although a few examples of apparently nonlytic spread have been documented. Real demonstration of nonlytic spread for poliovirus or any other cytoplasmic constituent requires demonstration that a small amount of lysis in the cellular population is not responsible for the release of cytosolic material. The work in this thesis has demonstrated, for the first time, definitive nonlytic cell-to-cell spread of poliovirus. We have also shown a link between this type of spread and components of a conserved pathway called autophagy. Chapter 1 contains a review of the cell biology of poliovirus infection that has led to the hypothesis for nonlytic spread. In Chapter 2, we describe the time-lapse microscopy setup used to monitor real time cell-to-cell spread of poliovirus and some of the unique early observations of how the virus spreads. In Chapter 3, we dive into the role the autophagy pathway or its components play on the spread of poliovirus. Chapter 4 moves to the mouse model of poliomyelitis where we investigate how perturbing the autophagy pathway affects the pathogenesis of poliovirus. In Chapter 5, we demonstrate nonlytic spread of poliovirus in tissue culture and begin to dissect the mechanism for this type of spread. Finally, in Chapter 6, we draw conclusions about the possible role of nonlytic spread in the life cycle of poliovirus and why studying the role of autophagy in acute viral infections may be important.
Nonproliferation Sanctions: Taking the "Profit out of Proliferation?"
Keywords: nonproliferation sanctions
Center for International Security and Cooperation
Interschool Honors Program in International Security Studies
Thesis

How do sanctions impact national decisions to go nuclear? Sanctions have emerged as a frequently employed tool of statecraft and as a go-to tool in U.S. nonproliferation policy. However, the outcomes of proliferation and nonproliferation in cases of sanction imposition beg a closer examination of their efficacy- when and how are sanctions effective?
This thesis finds that the efficacy of nonproliferation sanctions depends on their ability to impact domestic politics and change the calculus in the nuclear decision-making process. The causal mechanisms behind national decisions to go nuclear reveal that the efficacy of sanctions depends on domestic political conditions. These conditions include regime type, the structure of the economy, and domestic political coalitions.
In order to understand the causal mechanisms of sanctions, this thesis examines the empirical evidence of nonproliferation sanctions imposition. The cases are divided into two categories: North Korea, Pakistan, and India constitute the proliferation outcome cases, and South Africa, Argentina, Brazil, and Libya constitute the nonproliferation outcome cases. By analyzing the causal mechanisms of sanctions and applying the relevant theoretical frameworks of sanction efficacy in these cases, this thesis gleans insights on the conditions that render sanctions effective in dissuading states from proliferation. Ultimately, this thesis seeks to understand how sanctions can be effectively maximized as a tool of nonproliferation policy and to contribute to the literature on nonproliferation sanctions.
Norms, Latinos, and political attitudes in the United States [electronic resource]
Keywords: Political Science.

This dissertation investigates the that role norms play in structuring attitudes toward Latinos and immigrants in the United States, and on a variety of policies. Norms are defined as standards of conduct dictated by a person's identity. While previous research does focus on the role of cultural integration in structuring attitudes, this project takes the next step by breaking down the category of cultural integration into two primary components, norms of propriety (p-norms) and norms of culture (c-norms). P-norms are related to "good" behavior, where "good" refers to actions associated with an upstanding member of society, such as seeking or retaining employment and following the law. C-norms are markers of American cultural identity. Speaking Spanish and flying a Mexican flag are examples of c-norm violations. Survey experiments are used to compare and contrast the effects of violating p- and c-norms on attitudes toward immigrants, Latinos, and on policy stances. Respondents react negatively to p- and c-norm violations by Latinos and immigrants. Even when respondents are primed to view Latinos and immigrants as upstanding members of society (p-norm followers), c-norm violations negatively impact respondents' assessments of Latinos and immigrants. Moreover, the perception of Latinos as norm violators is related to support for restrictive immigration policies and English language laws. Norms are pervasive and targeting them for inquiry brings into view the societal structure of opposition to immigration. Additionally, this research uncovers the conditions under which norms matter more or less. Ideology greatly influences the lens by which people view norm violations by Latinos and immigrants, and the perceptions people hold about groups.
Novel low-cost tools for science, diagnostics, and education [electronic resource]
Keywords: Mechanical Engineering.

Scientific research and discovery have played a crucial role in the development of modern society. The technological innovations of the past few centuries offer multifarious benefits that many of us enjoy every day; yet, nearly half the world's population lives in poverty with inadequate resources to serve their basic needs. The methods, technologies, and tools engineered for the developed world often do not translate well as solutions for the idiosyncratic needs of developing regions. Accordingly, this thesis work aims to expand the impact of available funding by exploring the design space of "frugal science", or science practiced in a context of limited resources. My frugal innovations target simultaneous optimization of performance, cost, and scalability. The Foldscope, a
Numerical investigation of breaking internal waves on slopes [electronic resource] : dynamics, energetics, and transport
Keywords: Civil and Environmental Engineering.

Over the past fifty years, advancements in ocean instrumentation have led to fascinating observations of internal waves propagating, shoaling, and breaking in the coastal ocean. These observations have shown that breaking internal waves are likely important contributors to transport and mixing in coastal ecosystems, as well as to turbulent dissipation and mixing in the global ocean energy budget. However, much of the physics of internal waves, especially the process of breaking on slopes, remains poorly understood. Due to the limited spatial and temporal resolution of field observations in the ocean, many idealized laboratory and numerical experiments have also been used study internal waves. The primary goal of this dissertation is to use high-resolution, laboratory-scale numerical simulations to increase the current understanding of breaking internal waves on slopes. I take advantage of high-performance, parallel computing to resolve turbulent effects using direct numerical simulations (DNS), and focus on three specific aspects of internal wave breaking: dynamics, energetics, and transport.
Numerical investigations of turbulent duct flows using wall-modeled large-eddy simulation [electronic resource]
Keywords: Aeronautics and Astronautics.

The challenges posed by shock wave-turbulent boundary layer interactions (STBLIs) remain one of the primary considerations in the design and operation of air-breathing hypersonic vehicles. The internal flow within the isolator of a scramjet engine involves a series of coupled STBLIs. In order to study these phenomena, the interaction of a turbulent boundary layer with a shock train in a constant area duct (STCAD) is used as a model problem. Calculations of a STCAD are performed using wall-modeled Large-Eddy Simulation (WMLES). This approach reduces the computational cost of a simulation by modeling the inner portion of the boundary layer and thereby enables the calculation of high Reynolds number flows. The equilibrium formulation of the wall-model, which neglects the pressure gradient and convective terms in the thin boundary layer equations (TBLEs), is evaluated for a class of flows where the non-equilibrium characteristics are primarily exhibited outside of the wall-modeled region. Several modifications to the framework of the WMLES are also developed and tested in order to improve predictions for turbulent, non-circular duct flows. Results from calculations of a STCAD at lower Reynolds number are compared with previous wall-resolved LES investigations to establish confidence in the approach. The WMLES is then applied to a STCAD at the higher Reynolds number conditions from experiments where wall-resolved calculations were prohibitively expensive. A parameter study related to the physical characteristics of the interaction is performed to address the uncertainty created by the lack of experimental data with respect to the side wall boundary layers. The equilibrium WMLES is shown to provide accurate predictions in comparison with the experimental data measured in the spanwise center plane. The physics of the STCAD are shown to be strongly dependent on the three-dimensional confinement of the mean flow by the boundary layer as well as the pressure ratio across the interaction. Further studies explore the effects that the side wall boundary layers and variations in the Reynolds number have on the properties of the interaction. An investigation into the potential applicability of a reduced-order model to predict the general trends exhibited by the three-dimensional STCAD is also conducted.
Numerical optimization and modeling techniques for power system operations and planning [electronic resource]
Keywords: Electrical Engineering.

In modern societies, electricity is ubiquitous and its availability and reliability are often taken for granted. However, the reality is that these properties rely on the proper operation of one of man's most complex creations: electric power grids. These systems transport electric energy across wide geographical regions from places where it is produced to places where it is consumed. They do so in many cases with virtually no storage. To ensure an efficient and reliable operation of these complex machines, numerical optimization algorithms are applied at almost every level of the operations and planning spectrum. For example, they are used for planning network expansions, scheduling generators, adjusting control devices, determining system state, computing security margins, and for many other crucial tasks. However, many of the algorithms currently used by system operators and planners are based on heuristics and have severe limitations. For example, common power flow algorithms, which are used for scenario analysis, typically fail to provide useful system information in the absence of accurate estimates of system state. Optimal power flow algorithms, which are used for planning system adjustments, typically use inadequate techniques for handling discrete variables and identifying key control actions. Security assessment algorithms typically require expensive system simulations that prevent frequent security analyses. These deficiencies may compromise system performance as grids become more complex, variable and unpredictable, and are operated closer to their limits. In this work, modeling and numerical optimization techniques are explored for overcoming many of the limitations associated with the algorithms used for scenario analysis, planning and control, and online security assessment. The proposed techniques have been tested on mid to large-scale real power networks obtained from South American, North American, and European electric institutions. The results demonstrate the potential benefits of the proposed techniques for improving the tools used by operators and planners for maintaining system reliability and efficiency.
Numerical solution of jump-diffusion stochastic differential equations [electronic resource]
Keywords: Management Science and Engineering.

Jump-diffusion processes are widely used in finance, economics, and other areas. They serve as models for asset, commodity and energy prices, interest and exchange rates, and the timing of corporate and sovereign defaults. The distributions of jump-diffusions are rarely analytically tractable, so Monte Carlo simulation methods are often used to treat the pricing, risk management, and statistical estimation problems arising in applications of jump-diffusion models. The first chapter is based on a paper that is joint work with Yexiang Wei. The chapter develops, analyzes and tests a discretization scheme for jump-diffusion processes with general state-dependent drift, volatility, jump intensity, and jump size. The scheme allows for an unbounded jump intensity, a feature of many standard jump-diffusion models in finance, economics, and other disciplines. It constructs the jump times as time-changed Poisson arrival times, and generates the process between the jump epochs using Euler discretization. Under technical conditions on the coefficient functions of the jump-diffusion, the convergence of the discretization error is proved to be of weak order arbitrarily close to one. The second chapter develops, analyzes and tests several methods for improving the computational efficiency of simulating jump-diffusions. The methods are applicable to simulation algorithms that discretize the Brownian component while using a standard Poisson process to generate the jump times, and whose weak order of convergence for the discretization error is known. We propose variance reduction methods based on nested simulation and antithetic variates, as well as methods for improving the efficiency of Richardson extrapolation techniques. We also investigate simulation efficiency improvements based on multilevel Monte Carlo methods. Numerical experiments demonstrate the methods give significant improvements to simulation efficiency.
Numerical studies of cuprate high-temperature superconductors [electronic resource]
Keywords: Physics.

Strongly correlated electron systems exhibit a panoply of fascinating phases, such as antiferromagnetism, charge order, and unconventional superconductivity, that compete or cooperate with one another. Yet the intertwined degrees of freedom that create this complexity also obscure the underlying mechanisms, so that numerous experimental and theoretical studies have been brought to bear on these materials. This thesis provides a window on the field from the perspective of phenomenological and microscopic studies of the cuprates and nickelates. The first part presents a phenomenological model of strongly coupled orders that explains recent time-resolved x-ray diffraction experiments on the nickelates. The new experimental technique enables us to disentangle degrees of freedom that are intertwined in thermal equilibrium, motivating a need for theoretical developments. Our time-dependent Ginzburg-Landau theory facilitates an understanding of how coupled orders behave when driven out of equilibrium. The second part of the thesis explores numerical simulations of microscopic models to answer open questions in the cuprates. A comparison of spin and charge susceptibilities computed in the single-band Hubbard model via determinant quantum Monte Carlo (DQMC) to those calculated using the random phase approximation (RPA) elucidates how electronic correlations evolve throughout the phase diagram. Combined DQMC and exact diagonalization (ED) studies of the three-orbital Hubbard model systematically evaluate broken-symmetry states that have been proposed to explain the pseudogap regime. Thus the use of complementary techniques, both analytical and computational, sheds light on different ordered phases and excitations in strongly correlated systems and points the way to further studies.
The olympian economic alternative from Ancient Greece [electronic resource] : a convivial model without market exchange or state coordination
Keywords: Classics.

The ancient economy in classical studies of the last two centuries has generated great interest and enthusiasm as well as intense debate and controversy. In recent years, prevailing modes of analysis under the rubrics of "new institutionalism" and "cultural poetics" have prompted scholars to explore economic issues with either data or text. Making a U-turn from the latest precedents, my dissertation apprehends economic matters in the framework of large culture-stories that combine ideas and practice through an interplay among discourse, power, and identity. Based on such conceptualization, I argue that three distinct culture-stories shaped, overall, the economy of ancient Greece and, not the least, of Classical Athens, where most evidence has survived. Against this picture, my research focuses on Olympianism, the culture-story that envisions human society without market and state institutions, in contrast to Polisism and the market system, the other two contenders. Building upon a sacred metaphysics, Olympianism promoted and put into practice two fundamental principles: ecumenicism--the potential for all social categories to become worthy religious subjects, and conviviality--the desire for the individual and the community to coalesce in a state of mutual thriving and celebration. In some instances, however, these ideals coexisted with yet were contradicted by the acceptance of violence committed against women, slaves, and non-kin. Nevertheless, the core of Olympian values—as much as it failed to eliminate the contemporaneous sentiments of misogyny, slavery, and imperialism—manifested itself strongly in the evidence for the ancient economy, particularly with regard to property and labor. After demonstrating the economic paradigms of kleros/commons and homo faber, my study concludes that the convivial model of Olympianism thwarted the process of commodification as well as the rise of concomitant state institutions which lie at the heart of the market system and Polisism. Overall, the economy of fifth-century Athens was fractured by distinctive visions of who we are and what we ought to become, a predicament that still reverberates today.
"On a scale beyond all previous conceptions" [electronic resource] : plastics and the preservation of modernity
Keywords: History.

We enjoy exceptional material prosperity, but its form make many of us anxious. Modern material culture appears unsustainable. And, nothing seems to epitomize this better than the proliferation of plastic. America pumps over 100 billion pounds of it into the market each year, and we have already produced more plastic in the twenty-first century than during the entirety of the twentieth. Derived mostly from fossil fuels and mostly immune from degradation, it is not surprising that many people consider plastic to symbolize unsustainability. Yet, the development of synthetic materials represents our grandparents' and great-grandparents' response to resource anxieties of their own. A hundred years ago, conservationists recognized that America's economy was overexploiting forests, fur from Canada, ivory from Africa, whale oil from the Antarctic, gutta percha from Indonesia, shellac from India, and countless other commodity feedstocks. It was in this historical context that the economic and ecological value of synthetic materials was first vindicated. Plastic's potential to relieve pressure on traditional material resources was solidified when America's burgeoning car culture compelled engineers to crack apart the hydrocarbons of crude oil to fuel more powerful internal combustion. That process produced the unsaturated hydrocarbons like ethylene that became the feedstocks of the most successful plastics. Amid material shortages of the Second World War, these new synthetics were so important that the U.S. government invested $3.5 billion into their production--$1.5 billion more than the Manhattan Project. To satisfy consumer demands of baby boomers, the Truman Administration declared that petroleum-derived materials were critical, and within a single generation America produced a greater volume of plastics that that of steel, copper, and aluminum combined. Even during the oil shocks of the 1970s, the World Watch Institute advocated for plastics given their relative energy efficiency. Plastics have functioned as a sort of get-out-of-jail-free card, sustaining our materials culture as it grew beyond the bounds of traditional natural resources. Undoubtedly, petroleum-derived plastics exacerbated certain forms of unsustainability by enabling more wasteful consumption and by deepening our reliance on petroleum. But that is only one part of the history of plastics, which is not confined to petroleum. Plastics were originally engineered from cellulose and other biological molecules, and bio-based plastics producers can capitalize on the economic and ecological benefits established by petroleum-based plastics. The complexity and scale of our economy depend on plastics. And, contrary to popular assumptions and most historiography, the history of synthetic materials I illuminate in my dissertation shows that important aspects of sustainability depend on plastics too.