MANE (MCNP ACE from NJOY & ENDF), a code for generating continuous energy cross sections at arbitrary temperatures, was created. Cross sections were evaluated using NJOY99 such that they would agree with the cross sections provided by MCNP5. The MANE cross sections were found to be in very good agreement with those provided by MCNP5 with some minor exceptions caused by round-off errors and some differences in the unresolved resonance region. Differences in the resonance region are caused by differences in the random number generator used to start the cross section calculations. The MANE cross sections were verified against the MCNP5 cross sections in five unique MCNP configurations: an 8.7% enriched MOX fuel pin cell, a UO₂ assembly (controlled and uncontrolled), a MOX assembly, and a whole core configuration containing the 3 assemblies. In each of these cases, eigenvalue and tally density results were found to be in very good agreement with one another.

The study of scattering amplitudes beyond one loop is necessary for precision phenomenology for the Large Hadron Collider and may also provide deeper insights into the theoretical foundations of quantum field theory. In this thesis we develop a new method for computing two-loop amplitudes, based on unitarity rather than Feynman diagrams. In this approach, the two-loop amplitude is first expanded in a linearly independent basis of integrals. The process dependence thereby resides in the coefficients of the integrals. These expansion coefficients are then the object of calculation. Our main results include explicit formulas for a subset of the integral coefficients, expressing them as products of tree-level amplitudes integrated over specific contours in the complex plane. We give a general selection principle for determining these contours. This principle is then applied to obtain the coefficients of integrals with the topology of a double box. We show that, for four-particle scattering, each double-box integral in the two-loop basis is associated with a uniquely defined complex contour, referred to as its master contour. We provide a classification of the solutions to setting all propagators of the general double-box integral on-shell. Depending on the number of external momenta at the vertices of the graph, these solutions are given as a chain of pointwise intersecting Riemann spheres, or a torus. This classification is needed to define master contours for amplitudes with arbitrary multiplicities. We point out that a basis of two-loop integrals with as many infrared finite elements as possible allows substantial technical simplications, in terms of obtaining the coefficients of the integrals, as well as for the analytic evaluation of the integrals themselves. We compute two such integrals at four points, obtaining remarkably compact expressions. Finally, we provide a check on a recently developed recursion relation for the all-loop integrand of the amplitudes of N=4 supersymmetric Yang-Mills theory, examining the two-loop six-gluon MHV amplitude and finding agreement. The validity of the approach to two-loop amplitudes developed in this thesis extends to all four-dimensional gauge theories, in particular QCD. The approach is suited for obtaining compact analytical expressions as well as for numerical implementations.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (M.S.)--University of Nevada, Reno, 2007. / "May, 2007." Includes bibliographical references (leaves 128-129). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2008]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.

Thesis (M.S.)--Ohio University, August, 1998. / Title from PDF t.p.

Thesis (M.S.)--Ohio University, August, 1998. / Title from PDF t.p.

Thesis(M.S.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.

Thesis (Ph.D.)--University of Tennessee Health Science Center, 2007. / Title from title page screen (viewed on July 17, 2008). Research advisor: Atul J. Shukla, Ph.D. Document formatted into pages (ix, 146 p. : ill.). Vita. Abstract. Includes bibliographical references (p. 137-146).

Thesis (doctoral)--Universität Bonn, 1986. / Includes bibliographical references (p. 121-124).

Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: 1 l. at end.