Searching for the Lowest Metallicity Galaxies in Our Local Universe

Hsyu, Tiffany ProQuest Dissertations & Theses University of Cali 2020 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Observational determinations of the primordial light element abundances produced during Big Bang Nucleosynthesis (BBN) provide an important test on our current understanding of the Universe and the Standard Model due to their sensitivities to two parameters at the time of BBN: the baryon density and the expansion rate of the Universe. The primordial helium-4 abundance is particularly sensitive to the latter, which is partly driven by the number of effective neutrino species. In this thesis, I present a new observational survey to discover near-pristine environments in our local Universe whose properties can be used to determine the latest value of the primordial 4He abundance.I first describe the details of our observational survey, which uses photometry from the Sloan Digital Sky Survey (SDSS) to identify candidate metal-poor galaxies. We use the Kast spectrograph on the Shane 3m telescope at Lick Observatory to obtain confirmation spectroscopy and follow up on a subset of these systems using LRIS and NIRSPEC/NIRES at Keck Observatory, which we name the Primordial Helium Legacy Experiment with Keck (PHLEK) survey. The high S/N optical and near-infrared (NIR) spectroscopy of the PHLEK sample enable a direct measurement of the electron temperature for the oxygen abundance and the detection of a suite of HeI lines for the helium abundance.Our survey results include the discovery of the Little Cub, one of the lowest-metallicity star-forming galaxies currently known. The Little Cub has a gas phase oxygen abundance about a twentieth solar metallicity and is a testament to the success in picking out metal-poor systems from photometry alone.Finally, I describe our code yMCMC, which uses the Markov Chain Monte Carlo (MCMC) technique to explore an 8-dimensional parameter space and solve for the parameters that best describe our observations. We supplement our PHLEK sample with SDSS spectroscopy and existing low-metallicity systems in the literature. Using systems well-modelled by yMCMC, we make an extrapolation to the primordial helium number abundance ratio, finding yP=0.0805+/-0.0017. When combined with the existing primordial deuterium abundance, this places constraints on the baryon-to-photon ratio and effective number of neutrino species in agreement with the Standard Model.

Kant's System of Moral Law

Biondi, Zachary ProQuest Dissertations & Theses University of Cali 2022 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Immanuel Kant’s Groundwork for the Metaphysics of Morals has a surprisingly simple aim: to identify the Categorical Imperative, the single principle of morality. Yet Kant never directly says what the principle is. It is a scandal of Kant scholarship. One statement is the Formula of Universal Law: “act only according to that maxim whereby you can at the same time will that it should become a universal law.” Shortly after, in a different formulation of the principle (called the Formula of Humanity), Kant says that you should “act in such a way that you treat humanity [...] always at the same time as an end and never simply as a means.” The book includes as many as five or six other formulations, all of which are somehow the Categorical Imperative.There is a natural puzzle: given that Kant presents his single moral principle in a variety of formulations, how do they all relate to each other? Any reading of the text demands an answer to this question. Literature tends to revolve around issues of equivalence and priority among formulations. The majority of scholars, including John Rawls, Paul Guyer, and Onora O’Neill, believe that the formulations are equivalent: the formulations either yield the same results when applied to cases or can be derived from each other. Scholars also wonder whether some formulations are more important than others. For example, is the Formula of Universal Law the Categorical Imperative, while the others are subsidiary?Fortunately, in some neglected and abstract passages, Kant discusses the relation among the formulas directly. In the Groundwork (p. 4:436), he says that the Formula of Universal Law highlights 1) the form of the law, 2) the Formula of Humanity the matter, and 3) most enigmatically, that there is a “complete determination” of laws in a possible kingdom of ends. Kant is invoking terms from the Critique of Pure Reason, an earlier work not directly about ethics. My dissertation uses a new reading of the terms in the Critique of Pure Reason to inform a new reading of the Categorical Imperative and Groundwork as a whole. On this approach, issues like equivalence and priority fall away and new, more productive readings of Kant’s argument emerge. In my view, the best way to solve an enduring problem in the scholarship on Kant’s ethics is to look outside his ethics.Chapter One uses Kant’s theory of matter and form to frame a new reading of the first two formulas in the Groundwork, the Formula of Universal Law and the Formula of Humanity. The chapter begins by discussing the influence of Aristotelian hylomorphism on Kant’s language, epistemology, and metaphysics. I look at the first Critique and Lectures to develop Kant’s picture of form and matter. With this picture, it becomes clear that the first two formulations are about two distinct but inseparable concepts. When Kant talks about universality, he is highlighting the formal or structural features of the Categorical Imperative. It is a law—universal, general, and necessary. ‘Do not lie’ is a principle that holds for everyone. The formulation about humanity as an “end” supplies its matter or content. The law is about humanity—a rational nature with value or worth. Lying involves communication among rational beings. My reading has implications for freedom or autonomy, the concept at the core of Kant’s philosophy. Hylomorphic language indicates that the matter and form combine. An autonomous will is one that wills universal laws that have itself as content. A good will, then, has a hylomorphic structure: it is a combination of matter and form. Kant uses the relation between the first two formulas to make this point. Understanding the relation among the formulations turns out to be the same as understanding how we are free.Chapters Two and Three analyze Kant’s claims about complete determination and possibility, the third point in the 4:436 passage. Chapter Two focuses entirely on theoretical philosophy. Kant discusses complete determination in the Ideal of Pure Reason, the last chapter of the Transcendental Dialectic in the Critique of Pure Reason. He makes an intricate and compressed argument that possibility is grounded in reality, specifically God as a rational ideal. By considering Kant’s theories of modality, reason, and concepts, I show that the primary function of complete determination is to lead to this ideal. For Kant, the faculty of reason assumes that all concepts are derived from some maximally real and completely determined being, the titular ideal of pure reason. The chapter provides a new reading of the argument, including a discussion of Kant’s mention of refinement (lauterung), which has gone overlooked by scholars. It also traces the development of the argument from pre-critical works like The Only Possible Argument in Support of a Demonstration of the Existence of God and Negative Magnitudes.Chapter Three, the culmination of the dissertation, applies the reading of the Ideal of Pure Reason to the Groundwork. It begins with a treatment of Kant’s theory of reason and concept of system. With a third formula of the moral law, the Formula of the Kingdom of Ends, Kant is showing that practical reason utilizes systematic thinking. Morality is not a list of isolated principles but includes interrelation and interdependence among them. The Formula of the Kingdom of Ends and reference to complete determination emphasize this. Chapter Three provides a reading of the Kingdom of Ends, why systematicity is essential to it, and what a complete determination of moral laws would be. For Kant, practical reason assumes that all possible moral principles are derived from a single ideal that supplies their content. The reference to complete determination leads the reader to see that a version of the argument from the first Critique Ideal of Pure Reason is assumed in the Groundwork. The chapter details the argument and explores how it solves a longstanding problem in Kant’s scholarship, namely, the source of the positive content of the law. The answer is an ideal that makes systematic practical cognition possible.The central claim of the dissertation is that the relation among the formulas is best understood through the theories of hylomorphism, modality, and reason implicit throughout the Groundwork. A possible law, like ‘Do not lie’, is a type of hylomorphic composite: the matter of rational nature under the form of universality. But reason treats morality as necessarily systematic. The individual laws are a plurality that is unified under the form of system. The Groundwork uses a sequence of formulas to identify the moral law as a single system. And if the law is a complete system, it cannot be stated in a single formula. The reading that the Categorical Imperative and Groundwork must be understood as parts of Kant’s philosophical system provides responses to many objections to his moral theory. It also portrays the theory as a commentary on figures in the history of philosophy—from Aristotle and Plato to Leibniz and Rousseau. In the end, this is how Kant wanted his system to be read: as one part of a larger whole.

Experimental Investigations of Convective Turbulence in Planetary Cores

Hawkins, Emily Kate ProQuest Dissertations & Theses University of Cali 2020 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The magnetic fields of planets and other bodies are created and sustained due to the turbulent motions of an internal fluid layer, a process known as dynamo action. Forward models are required to characterize the dynamics of rotating convective turbulence driving dynamo action due to the inability to obtain direct measurements of the internal fluid layers of planetary bodies. The characteristic flow velocities and length scales of dynamo systems remain poorly constrained due to the difficulty of modeling realistic planetary core conditions. Thus, the goal of this dissertation is to explore these key properties of core-style convection. To do so, I have conducted novel experiments aimed to better quantify the features of quasi- geostrophic turbulence using the UCLA large-scale rotating convection device, ‘NoMag’.I have completed a systematic study to simultaneously measure the heat transfer and bulk velocities of different rotating convective regimes at some of the most extreme laboratory conditions possible to date. The study of heat transfer is employed in most forward models of core-style convection. In laboratory experiments in particular, due to the relative difficulty of collecting velocity measurements, those of heat transfer alone are assessed, the dynamics of which are assumed to describe the the bulk velocity dynamics of the system. On the contrary, I utilize laser doppler velocimetry to obtain measurements of bulk velocities concurrently with the collection of temperature measurements for the characterization of system heat transfer. I find that heat transfer behavior is consistent with the results of past studies and is largely controlled by boundary layer dynamics. I further find that velocity behaviors do not directly coincide with heat transfer behaviors in the parameter space studied. Instead, I show that a dynamical flow regime of quasi-geostrophic turbulence relevant to core flows is robustly reached, suggesting that it is possible to access realistic bulk dynamics in models that remain far from planetary core conditions.Using the results of this study, I estimate the characteristic length scales of the flows of each experiment. These estimates from my data are compared with length scale estimates of numerous numerical models of planetary core convection. I conclude from this meta-analysis of forwards models that all evidence to date suggests that the theorized characteristic length scales of planetary dynamo systems co-scale with one another and are thus non-separable.In two other studies that comprise the remainder of this dissertation, I further examine the applicability of laboratory models towards planetary settings. An experimental study on the influence of centrifugal buoyancy on rotating convection in water and in liquid metal was completed, where results agree with the recent numerical work of Horn and Aurnou (2018). It is found that the transition from Coriolis to centrifugally dominated convection depends on the strength of the centrifugal buoyancy relative to the gravitational buoyancy and the geometry of the cylinder in which experiments are conducted. These results are useful to ensure that the regime of rotating convection explored in a given experiment is relevant to planetary core flows, i.e. not centrifugally dominated. Separately, I conducted a series of spin up experiments with well-established theory to calibrate the NoMag apparatus and its measuring components. Further, the results from spin up experiments conducted with rough boundaries might have geophysical implications for the possible viscous coupling at Earth’s core mantle boundary, as well as turbulent mixing in the global ocean.The results of the studies presented in this dissertation clarify the relevance of long theorized and poorly tested dynamic length and velocity scalings of planetary core flows. Flows that are quasi-geostrophically turbulent are robustly observed in the laboratory data collected in this dissertation. The need for next generation models of planetary core flows is motivated by the results of the work herein. In particular, studies in which the characteristic length scales of core-style flows are directly quantified will undoubtedly enhance ourunderstanding of the multi-scale turbulent physics driving planetary dynamo systems.

Dowling Set Partitions, and Positional Marked Patterns

Thamrongpairoj, Sittipong ProQuest Dissertations & Theses University of Cali 2019 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This dissertation consists of two parts. First, we define and study positional marked patterns. A positional marked pattern τ is a permutation where one of elements in τ is underlined. Given a permutation σ, we say that σi is τ-match at position i if τ occurs in σ in such a way that σi plays the role of the underlined element in the occurrence. We let pmpτ(σ) denote the number of position i which σ is τ-match. This defines a new class of statistics on permutations, where we study such statistics and prove a number of results. In particular, we prove that two positional marked patterns (1)23 and (1)32 give rise to two statistics that have the same distribution. The equidistibution phenomenon also occurs in other several pairs of patterns like 1(2)3 and 1(3)2, which we prove in this dissertation. The second part of the dissertation focuses on the Whitney numbers of Dowling lattices. In the papers [2, 3], Benoumhani defined two polynomials Fm,n,1(x) and Fm,n,2(x). Then, he defined Am(n,k) and Bm(n,k) to be the polynomials satisfying Fm,n,1(x) = Σk=0. n Am(n,k)x. (n-k)(x+1). k and Fm,n,2(x) = Σk=0. n Bm(n,k)x. (n-k)(x+1). k. In this dissertation, we give a combinatorial interpretation of coefficients of Am+1(n,k) and prove a symmetry of the coefficients, namely Am+1(n,k)|m. s = Am+1(n,n-k)|m. (n-s). We also give a combinatorial interpretation of Bm+1(n,k), prove that Bm+1(n,n-1) is a polynomial in m with non-negative integer coefficients, and prove that Bm+1(n,n-2) is a polynomial in m with non-negative integer coefficients except for the coefficient of m. (n-1) which is -(n-1) for n >=6.

The Analytic Structure of Scattering Amplitudes in N = 4 Super-Yang-Mills Theory

Litsey, Sean Christopher ProQuest Dissertations & Theses University of Cali 2016 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

We begin the dissertation in Chapter 1 with a discussion of tree-level amplitudes in Yang-. Mills theories. The DDM and BCJ decompositions of the amplitudes are described and. related to one another by the introduction of a transformation matrix. This is related to the. Kleiss-Kuijf and BCJ amplitude identities, and we conjecture a connection to the existence. of a BCJ representation via a condition on the generalized inverse of that matrix. Under. two widely-believed assumptions, this relationship is proved. Switching gears somewhat, we introduce the RSVW formulation of the amplitude, and the extension of BCJ-like features to residues of the RSVW integrand is proposed. Using the previously proven connection of BCJ representations to the generalized inverse condition, this extension is validated, including a version of gravitational double copy. The remainder of the dissertation involves an analysis of the analytic properties of loop. amplitudes in N = 4 super-Yang-Mills theory. Chapter 2 contains a review of the planar case, including an exposition of dual variables and momentum twistors, dual conformal symmetry, and their implications for the amplitude. After defining the integrand and on-shell diagrams, we explain the crucial properties that the amplitude has no poles at infinite momentum and that its leading singularities are dual-conformally-invariant cross ratios, and can therefore be normalized to unity. We define the concept of a dlog form, and show that it is a feature of the planar integrand as well. This leads to the definition of a pure integrand basis. The proceeding setup is connected to the amplituhedron formulation, and we put forward the hypothesis that the amplitude is determined by zero conditions. Chapter 3 contains the primary computations of the dissertation. This chapter treats. amplitudes in fully nonplanar N = 4 super-Yang-Mills, analyzing the conjecture that they. follow the pattern of having no poles at infinity, can be written in dlog form, and can. be decomposed into a pure integrand basis, with each basis element having unit leading. singularity. Through explicit calculation, we show that this is true for the two-loop fourpoint. three-loop four-point, and two-loop five-point amplitudes, and discuss the features of. each case. We then discuss the zero condition hypothesis, showing explicitly that it holds for the two-loop four-particle amplitude, and showing the set of conditions that fix the amplitude in the three-loop four-particle and two-loop five-particle cases without explicitly performing the fixing. This concludes the body of the dissertation. Two appendices complete the dissertation. Appendix B includes an in-depth discussion of. dlog forms, including purely mathematical examples and a discussion of their appearance in one-loop amplitudes. Finally, Appendix C redoes portions of the analysis of Chapter 3 for the two- and three-loop four-particle amplitudes, but gives representations that are not in a pure integrand basis. Instead diagram symmetry is imposed on the basis elements, and diagrams that lack maximal cuts are pushed into maximal-cut diagrams. This gives representations closer in spirit to the previously-constructed representations of these amplitudes, such as the BCJ representations. It also highlights the role of color Jacobi identities and the freedom in the amplitude representation they can generate, and contains an explicit discussion of these features that is unpublished elsewhere.

Lorentz boosted frame simulation technique in Particle-in-cell methods

Yu, Peicheng ProQuest Dissertations & Theses University of Cali 2016 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

In this dissertation, we systematically explore the use of a simulation method for modeling laser wakefield acceleration (LWFA) using the particle-in-cell (PIC) method, called the Lorentz boosted frame technique. In the lab frame the plasma length is typically four orders of magnitude larger than the laser pulse length. Using this technique, simulations are performed in a Lorentz boosted frame in which the plasma length, which is Lorentz contracted, and the laser length, which is Lorentz expanded, are now comparable. This technique has the potential to reduce the computational needs of a LWFA simulation by more than four orders of magnitude, and is useful if there is no or negligible reflection of the laser in the lab frame. To realize the potential of Lorentz boosted frame simulations for LWFA, the first obstacle to overcome is a robust and violent numerical instability, called the Numerical Cerenkov Instability (NCI), that leads to unphysical energy exchange between relativistically drifting particles and their radiation. This leads to unphysical noise that dwarfs the real physical processes. In this dissertation, we first present a theoretical analysis of this instability, and show that the NCI comes from the unphysical coupling of the electromagnetic (EM) modes and Langmuir modes (both main and aliasing) of the relativistically drifting plasma. We then discuss the methods to eliminate them. However, the use of FFTs can lead to parallel scalability issues when there are many more cells along the drifting direction than in the transverse direction(s). We then describe an algorithm that has the potential to address this issue by using a higher order finite difference operator for the derivative in the plasma drifting direction, while using the standard second order operators in the transverse direction(s). The NCI for this algorithm is analyzed, and it is shown that the NCI can be eliminated using the same strategies that were used for the hybrid FFT/Finite Difference solver. This scheme also requires a current correction and filtering which require FFTs. However, we show that in this case the FFTs can be done locally on each parallel partition. We also describe how the use of the hybrid FFT/Finite Difference or the hybrid higher order finite difference/second order finite difference methods permit combining the Lorentz boosted frame simulation technique with another "speed up" technique, called the quasi-3D algorithm, to gain unprecedented speed up for the LWFA simulations. In the quasi-3D algorithm the fields and currents are defined on an r--z PIC grid and expanded in azimuthal harmonics. The expansion is truncated with only a few modes so it has similar computational needs of a 2D r--z PIC code. We show that NCI has similar properties in r--z as in z-x slab geometry and show that the same strategies for eliminating the NCI in Cartesian geometry can be effective for the quasi-3D algorithm leading to the possibility of unprecedented speed up. We also describe a new code called UPIC-EMMA that is based on fully spectral (FFT) solver. The new code includes implementation of a moving antenna that can launch lasers in the boosted frame. We also describe how the new hybrid algorithms were implemented into OSIRIS. Examples of LWFA using the boosted frame using both UPIC-EMMA and OSIRIS are given, including the comparisons against the lab frame results. We also describe how to efficiently obtain the boosted frame simulations data that are needed to generate the transformed lab frame data, as well as how to use a moving window in the boosted frame. The NCI is also a major issue for modeling relativistic shocks with PIC algorithm. In relativistic shock simulations two counter-propagating plasmas drifting at relativistic speeds are colliding against each other. We show that the strategies for eliminating the NCI developed in this dissertation are enabling such simulations being run for much longer simulation times, which should open a path for major advances in relativistic shock research. (Abstract shortened by ProQuest.).

Prototyping the Developer Experience for Data Science Practitioners and Instructors

Kross, Sean Michael ProQuest Dissertations & Theses University of Cali 2022 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Data science encompasses the most prominent collection of methods for creating scientific knowledge in the 21st century. Currently, data scientists must navigate a wide-ranging and often incoherent ecosystem of tools, in addition to organizing sociotechnical interactions with colleagues across many fields of expertise.This predicament motivates my thesis: The elements of data science work that are based in human expertise and social relationships must be integrated into existing programming workflows to create the developer experience that data scientists require to be successful.This dissertation supports my thesis by presenting three empirical studies and two tools. First, I investigated how professional data scientists teach novices about data science focused programming workflows, including how to adapt software development tools to their work, how to navigate the full depth of the stack of technologies that data science relies on, and how to use their tools to help communicate their findings. Then I explored how a team of academic data scientists repurposed the tools from their everyday data science work to create a data science course designed to reach traditionally underrepresented groups in computing. Finally, I examined how consulting data scientists interact with their clients, how their working relationships take them beyond well-characterized programming-oriented cycles, and how they achieve success by integrating designerly work into their data analysis process.These studies inspired me to develop two tools: 1. Datamations animates each step in a data analysis pipeline via transitions that show how rows, columns, and cells move within a data frame. 2. Tidy Data Tutor creates step-by-step interactive illustrations for a data analysis pipeline, so that every individual cell can be tracked.The main research findings of this dissertation are that data scientists adapt software engineering tools to fit into their own workflows, and that data scientists must communicate the uncertainty that they face in their work to novices. Additionally, this dissertation found that several nested cycles are required for data scientists to achieve success in collaboration with their colleagues. Finally, my prototype tools showed that animations and illustrations derived from data wrangling code can help convey a clearer understanding of data analysis pipelines.

Performing Possibilities: Trans-Healing in Activist Performance

Winget, Anna Renee ProQuest Dissertations & Theses University of Cali 2019 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

I argue that healing performances are an important site of activist practice and urge performance-based healing (including applied theatre, dramatherapy, and social justice theatre) to engage in decolonizing critiques and methods, integrating performances of healing and activism. By studying the work of transgender artists of color and analyzing their healing intentions and methods in activist performances, I theorize the possibilities of change incited by the performances-both utopic social change and individual healing for audience members and performers. As this project formulates it, trans-healing is a term I utilize to address the particular needs and experiences of people who self-identify as trans to heal themselves and their queer and trans communities. "Trans-healing" does not suggest that trans identity or trans people need healing, but rather, that society does. Three case studies are presented to examine the possibilities of trans-healing in performance. To open even the possibility of trans-healing, it is important to recognize all the artists in this dissertation as cultural and knowledge producers who perform a valuable labor. I examine Sri Lankan-American queer trans solo performer, D'Lo, arguing that performing in a trans temporality, alchemizing tragedy into comedy, and "transing" tradition can yield trans-healing possibilities for the performer and audience members. In the case of the group, Living Mythologies, consisting of five multi-ethnic trans and intersex femmes of color, I argue that their performance opens an Anzalduan borderland space where tensions between dis/ease and healing, death and life perform activism and healing possibilities. Through decolonial projects such as resisting colonial closures, reclaiming mythological figures, and rebuilding a community space through a "hermeneutics of love" (Sandoval) that centralizes (and thus reframes) the narratives of trans people of color, Living Mythologies performs a trans-healing. Finally, I argue that the South Asian American (former) spoken word duo, DarkMatter, performs possibilities of decolonizing the neoliberal university. I refer to their workshop/ performance as a "pedagogy of failure" (LeMaster), finding the theoretical site of "failure" in the context of the neoliberal university, useful for threading important connections among healing, performance, pedagogy, and decolonial activism.

The Undiscovered CO: Charting the Molecular Gas of the Early Universe

Keating, Garrett Kent ProQuest Dissertations & Theses University of Cali 2016 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Molecular gas, observed through tracers such as CO rotational transitions, is a vital component of galactic evolution and star formation. Recent detections of the CO molecule in massive galaxies at high redshift have demonstrated its existence in the early Universe, and have motivated its use as a means of exploring large-scale structure and as a probe of galaxy evolution in the early Universe. But many questions about molecular gas and the evolution of galaxies in the early Universe still remain: its distribution at high redshift understood is so poorly that theoretical models of the mean abundance of CO for the first several billion years of cosmic history span orders of magnitude. Direct detection of molecular gas in galaxies at these redshifts have only found the largest and most luminous of galaxies in the early Universe, whereas the bulk of the molecular gas is expected to be in the unseen masses of smaller galaxies. While difficult to detect individually, these smaller galaxies are likely detectable as an integrated ensemble with the technique of ''intensity mapping". This technique, similar to those employed by HI epoch of reionization experiments, utilizes measurements of different 3D Fourier modes to construct a power spectrum. In this thesis, I present results from the CO Power Spectrum Survey (COPSS), an intensity mapping experiment performed with the Sunyaev Zel'dovich Array (SZA). I present power spectrum constraints from of the first and second phase of this project, utilizing an archival dataset (covering 44 fields in 1400 hours observing time) and a 5000-hour observing campaign (covering 19 fields) with the SZA. With these data, we are capable of observing CO(1-0) emission arising from z = 2.3{-}3.3, surveying a volume of more than ten million cubic megaparsecs. With this measurement, we place the first-ever constraints on the CO autocorrelation power spectrum, and place constraints on the CO(1-0) galaxy luminosity function and the cosmic molecular gas density at z ∼ 3. I also present a series of simulations designed to probe the impact of cosmic variance, continuum foregrounds, and systematic errors on our measurement with the SZA. I will also present simulations designed to probe the challenges that will face intensity mapping experiments with the Yuan-Tseh Lee Array (YTLA). Finally, I will present some preliminary work on CO(3-2) and [CII] intensity mapping experiments.

Computing Maximally Supersymmetric Scattering Amplitudes

Stankowicz, James Michael, Jr ProQuest Dissertations & Theses University of Cali 2016 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This dissertation reviews work in computing N = 4 super-Yang--Mills (sYM) and N = 8 maximally supersymmetric gravity (mSUGRA) scattering amplitudes in D = 4 spacetime dimensions in novel ways. After a brief introduction and overview in Ch. 1, the various techniques used to construct amplitudes in the remainder of the dissertation are discussed in Ch. 2. This includes several new concepts such as d log and pure integrand bases, as well as how to construct the amplitude using exactly one kinematic point where it vanishes. Also included in this chapter is an outline of the Mathematica package on shell diagrams and numerics.m (osdn) that was developed for the computations herein. The rest of the dissertation is devoted to explicit examples. In Ch. 3, the starting point is tree-level sYM amplitudes that have integral representations with residues that obey amplitude relations. These residues are shown to have corresponding residue numerators that allow a double copy prescription that results in mSUGRA residues. In Ch. 4, the two-loop four-point sYM amplitude is constructed in several ways, showcasing many of the techniques of Ch. 2; this includes an example of how to use osdn. The two-loop five-point amplitude is also presented in a pure integrand representation with comments on how it was constructed from one homogeneous cut of the amplitude. On-going work on the two-loop n-point amplitude is presented at the end of Ch. 4. In Ch. 5, the three-loop four-point amplitude is presented in the d log representation and in the pure integrand representation. In Ch. 6, there are several examples of four- through seven-loop planar diagrams that illustrate how considerations of the singularity structure of the amplitude underpin dual-conformal invariance. Taken with the previous examples, this is additional evidence that the structure known to exist in the planar sector extends to the full theory. At the end of this chapter is a proof that all mSUGRA amplitudes have a pole at infinity for (L ≥ 4)-loops. Finally in Ch. 7, the current status of ultraviolet divergences in the five-loop four-point mSUGRA amplitude is addressed. This includes a discussion of ongoing work aimed at resolving the mSUGRA finiteness question. The following Mathematica scripts are submitted with this dissertation: • on shell diagrams and numerics.m with dependencies: -- all_trees *.m -- external_kinematics_*_point.m -- rational_external_*_point.m where "*" is a wild-card string of any set of characters of any length -- either an integer or a number spelled out.