arXiv subjects

Michael P. Ryan, Jr.

Publications and source records attributed to Michael P. Ryan, Jr..

4 recordsLinked to original sources

arXiv2004

The conformally invariant Laplace-Beltrami operator and factor ordering

In quantum mechanics the kinetic energy term for a single particle is usually written in the form of the Laplace-Beltrami operator. This operator is a factor ordering of the classical kinetic energy. We investigate other relatively simple factor orderings and show that the {\it only} other solution for a conformally flat metric is the conformally invariant Laplace-Beltrami operator. For non-conformally-flat metrics this type of factor ordering fails, by just one term, to give the conformally invariant Laplace-Beltrami operator.

quant-ph↗

arXiv2003

Generating Cosmological Solutions from Known Solutions

We consider three methods by which one can generate new cosmological models. Two of these are based on the Lorentzian structure of spacetime. In a Lorentzian manifold there can exist horizons that separate regions of spacetime that can be interpreted as cosmological models from others that have the character of ``black holes.'' A number of well known solutions of this type can be used to generate both known cosmological models and others that do not seem to have been recognized. Another method based on the Lorentzian character of spacetime is to simply interchange some space variable with time and try to restructure the metric to make a viable cosmology. A more broad-ranging method is the use of modern solution-generating techniques to construct new models. This method has been widely used to generate black hole solutions, but seems not to have been so widely used in cosmology. We will discuss examples of all three methods.

gr-qc↗

arXiv1997

On the Hamiltonian Formulation of Class B Bianchi Cosmological Models

The application of the divergence theorem in a non-coordinated basis is shown to lead to a corrected variational principle for Class B Bianchi cosmological models. This variational principle is used to construct a Hamiltonian formulation for diagonal and symmetric vacuum Class B models. [Note: This is an unpublished paper from 1984 that might be useful to anyone interested in Class B Bianchi models.]

gr-qc↗

arXiv1995

Minisuperspace Examples of Quantization Using Canonical Variables of the Ashtekar Type: Structure and Solutions

The Ashtekar variables have been use to find a number of exact solutions in quantum gravity and quantum cosmology. We investigate the origin of these solutions in the context of a number of canonical transformations (both complex and real) of the basic Hamiltonian variables of general relativity. We are able to present several new solutions in the minisuperspace (quantum cosmology) sector. The meaning of these solutions is then discussed.

gr-qc↗