Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Howard Baer, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed Jan 13, 2005). Includes bibliographical references.

We present results for the matrix elements relevant for proton decay in Grand Unified Theories (GUTs), using two methods. In the indirect method, we rely on an effective field theory description of proton decay, where we need to estimate two low energy constants. We then relate these low energy constants to the proton decay matrix elements using leading order chiral perturbation theory. In the direct method, we calculate the required matrix elements directly; this is computationally more expensive, but the calculation has no systematic error from the use of chiral perturbation theory. The calculations are performed with 2+1 flavors of domain wall fermions on lattices of size 163 × 32 and 243 × 64 with a fifth dimension of length 16. We work at fixed inverse lattice spacing, a−1 = 1.73(3) GeV, leading to physical volumes of (1.8 fm)3 and (2.7 fm)3 for the 163 × 32 and 243 × 64 lattices respectively. In the first four chapters we present the background theory. We start with a brief review of the standard model and the motivation for GUTs. We show that GUTs must lead to proton decay, and that the proton lifetime is an experimentally testable prediction which can be used to constrain GUT parameters, or rule out classes of GUT which predict a minimum lifetime shorter than the experimental minimum bound. We then review continuum and lattice QCD, including outlines of the lattice methods used to calculate the proton decay matrix elements. In the last three chapters we present the results and analysis. We calculate the nucleon and pion two–point correlation functions, and determine their ground state masses and amplitudes. These quantities will then be used to calculate the matrix elements using the indirect and direct methods outlined above. The matrix elements can then be combined with experimental bounds on the proton lifetime to bound parameters of individual GUTs.

During the twentieth century, particle physics developed into a cornerstone of modern physics, culminating in the Standard Model. Even though this theory has proved to be of extraordinary power, it is still incomplete in several respects. It is our aim in this bachelor thesis to discuss some possible theories beyond the Standard Model, the main focus being on Grand Unified Theories, while also taking a look at attempts of further unication via discrete family symmetry. At the heart of all these theories lies the concept of local gauge invariance, which is introduced as a fundamental principle, followed by an overview of the Standard Model itself. No theory has so far managed to unify all elementary particles and their interactions, but some interesting features are highlighted. We also give a hint at some possible paths to go in the future in the quest for a unication in particle physics. / Under 1900-talet utvecklades partikelfysiken till en av de fundamentala teorierna inom fysiken, och kom att sammanfattas i den s.k. Standardmodellen. Även om denna modell rönt exceptionella framgånger vad gäller beskrivningen av elementarpartiklar och deras växelverkan, är den fortfarande ofullständig på flera sätt. Syftet med denna kandidatuppsats är att diskutera möjliga teorier bortom Standardmodellen såsom Storförenande Teorier och diskreta familjesymmetrier vars avsikt är att koppla samman de tre familjerna av fermioner i Standardmodellen. Men först introduceras idén om lokal gaugeinvarians, vilken ligger till grund for dessa teorier, varpå en översikt av Standardmodellen följer. Ingen teori har ännu lyckats ge en helt tillfredsställande bild av elementarpartiklar och deras interaktion, men en del intressanta egenskaper hos föreslagna teorier belyses i denna uppsats. Slutligen ges en del spekulativa förslag på väger att gå i framtida försök till föreningar inom partikelfysiken.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1995. / Includes bibliographical references. / Microfiche. / xii, 148 leaves, bound ill. 29 cm

Thesis (Ph.D.)--Tufts University, 1999. / Director: W. Anthony Mann. Submitted to the Dept. of Physics. Includes bibliographical references (leaves 172-176). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (p. 134-138).

Thesis (M.S.)--Baylor University, 2006. / Includes bibliographical references (p. 115-123).

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Qaisar Shafi, Dept. of Physics & Astronomy. Includes bibliographical references.

Thesis (Ph. D.)--Northeastern University, 2008. / Title from title page (viewed March 9, 2009). Graduate School of Arts and Sciences, Dept. of Physics. Includes bibliographical references (p. 114-123).

Thesis (Ph. D.)--University of Notre Dame, 2008. / Thesis directed by Don Howard for the Graduate Program in History and Philosophy of Science. "April 2008." Includes bibliographical references (leaves 212-220).