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Thesis (Ph. D.)--University of Wisconsin--Madison, 1960. / Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 62-65).

archives@tulane.edu / The multiplicity-free subgroups (strong Gelfand subgroups) of wreath products are investigated. Various useful reduction arguments are presented. In particular, for any finite group G and its normal subgroup K, if G/K is isomorphic to a cyclic group and its order is a multiplicity free integer, then (G,K) is a strong Gelfand pair. Furthermore, we classify all multiplicity-free subgroups of Z/p wreath S_n when n>6. Along the way, we derive various decomposition formulas from some special subgroups of Z/p wreath S_n when n>6. / 1 / Yiyang She

<p> This thesis gives basic properties of the newly defined topological properties local paracompactness and strong local paracompactness. An example is given to show that they do not coincide in T2 spaces; another example is given of a strongly locally paracompact T2 space which is neither locally compact nor paracompact. The existence of a one point paracompactification analagous to the Aleksandrov one point compactification is constructed and proved for strongly locally paracompact T2 spaces. Also considered are conditions under which these two properties are preserved under closed maps and heredity.</p> / Thesis / Master of Science (MSc)

Inaug. _ Diss.: Philosophische Fakultät I: Zürich: 1974. Bibliogr. p. 147-150.

Made available in DSpace on 2014-06-12T15:52:47Z (GMT). No. of bitstreams: 2 arquivo4748_1.pdf: 788444 bytes, checksum: bf529ae650fd6acfbf8f43c0335c33fd (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2003 / Lewitzka, Steffen; José Guerra Barreto de Queiroz, Ruy. Contributions to the investigations of Lascar strong types in simple theories. 2003. Tese (Doutorado). Programa de Pós-Graduação em Ciência da Computação, Universidade Federal de Pernambuco, Recife, 2003.

Unusual and challenging ionization processes take place when an atom or molecule is placed in the presence of a super intense, ultra short laser field. One such process is the ionization and subsequent return of an electron to the ionic core. The electron carries with it the energy it has absorbed from the laser field and this energy drives different atomic phenomena such as high harmonic generation or multiple ionization. The mechanism of the electron return is often referred to as the “three-step” model. In this model, an electron is first ionized at the peak amplitude of the laser field. Once ionized, a change in the direction of the laser field forces the electron to return to the parent ion and causes a subsequent recollision. The purpose of this thesis is to examine in great detail the recollision process, its mechanisms, and its dependence on physical parameters (such as laser intensity and ellipticity) for a number of physically interesting scenarios.

We study the abundance of substructure in the matter density near galaxies using ALMA Science Verification observations of the strong lensing system SDP. 81. We present a method to measure the abundance of subhalos around galaxies using interferometric observations of gravitational lenses. Using simulated ALMA observations we explore the effects of various systematics, including antenna phase errors and source priors, and show how such errors may be measured or marginalized. We apply our formalism to ALMA observations of SDP. 81. We find evidence for the presence of a M = 10(8.96 +/- 0.12)M(circle dot) subhalo near one of the images, with a significance of 6.9 sigma in a joint fit to data from bands 6 and 7; the effect of the subhalo is also detected in both bands individually. We also derive constraints on the abundance of dark matter (DM) subhalos down to M similar to 2 x 10(7) M-circle dot, pushing down to the mass regime of the smallest detected satellites in the Local Group, where there are significant discrepancies between the observed population of luminous galaxies and predicted DM subhalos. We find hints of additional substructure, warranting further study using the full SDP. 81 data set (including, for example, the spectroscopic imaging of the lensed carbon monoxide emission). We compare the results of this search to the predictions of Lambda CDM halos, and find that given current uncertainties in the host halo properties of SDP. 81, our measurements of substructure are consistent with theoretical expectations. Observations of larger samples of gravitational lenses with ALMA should be able to improve the constraints on the abundance of galactic substructure.

The General theory of Relativity (GR) brought gravity into accord with the principles of locality and relativity. Since its discovery it has been preeminent, recognized as the most accurate description of gravity on the many scales where it has been tested. During this period, seemingly radical predictions like the existence of black holes and the expansion of the Universe have been verified and testify to the great leap of insight that GR represented in our understanding of space and time. However not all precision observations of astrophysical systems have yielded easily to interpretation within GR, and with the discovery of cosmic acceleration, there is genuine concern that General Relativity may be incomplete when describing the Universe on the largest sizes imaginable. In this uncertainty, many theoretical models have been proposed. In this thesis we shall first outline the motivation behind a certain subset of these models and the known issues that arise in interpreting these models as alternative theories of gravity. Then focus on one variety of theory the f(R) modifications to gravity. Demonstrating that many of the known instabilities have a common origin and that they are avoided when treating these theories via perturbative constraints. In the second part of this work we examine the astrophysical impact of modifications to gravity, first in the case of high mass neutron stars, then subsequently on corrections to the line profile of neutral hydrogen from violations of the equivalence principle. Finally we explore the phenomenology of modifications to gravity that produce late-Universe acceleration. In particular, what solutions are allowed and what range of accelerations are predicted as a result. Furthermore we explore how a correction to gravity at large scales would impact the growth and evolution of cosmological perturbations.

Thesis (Th. D.)--Concordia Seminary, 1986. / Includes bibliographical references (leaves 246-264).