**Basic
Info:**

Research:

In the broadest sense most of my research is driven by the desire to understand the fundamental nature of spacetime. I feel that the continuum model is an unphysical idealization, and I suspect that there are in fact only a finite number of degrees of freedom in any finite volume. It seems difficult to reconcile this hypothesis with local Lorentz invariance, and with ordinary unitary quantum theory (since the metric is dynamical, and in particular the volume of the universe is currently increasing). I hope these difficulties are hints, rather than signs that the idea is wrong. The question whether discreteness can be reconciled with the existence of Hawking radiation was one subject of much of my work from 1990 to 1999. The answer seems to be yes.

I am presently
pursuing several research strategies:

# observational consequences and constraints on Lorentz symmetry
violation that might presumably be induced by spacetime substructure, in

+ high energy astroparticle physics

+ gravitational theory with a preferred rest frame
field

# analogies with effective field theory of condensed matter
physics

# black hole (& more generally horizon) thermodynamics as a
possible guiding light

# construction of model discrete substitutes for quantum field
theory, with irregular microtopology flexible enough to allow creation
of degrees of freedom (as in cosmological expansion).

A list and links to my publications can be found in the Spires Database.

*Intermediate
Theoretical Methods: *Phys 374, Spring 2006* *

*Intro.
Mechanics: *Phys 171, Spring 2001,
Phys 171, Spring
2002,
Phys 171, Spring 2003

*Intro. Oscillations and Waves: *Phys 273, Fall 2000, Phys 273, Fall 2001, Phys 273, Fall 2002

*Quantum
Mechanics: *Syllabi, supplemental handouts, homework
sets, and exams for Quantum Mechanics I (Phys 622, Spring 1998,
Phys 622, Fall 1999)
and II (Phys 623, Fall
1997, Phys 623,
Fall 1998, Phys
623, Spring 2000) are available here as postscript files.

*Gravitation
Theory: *Phys 776, Spring 2003,
Phys 776, Spring 2005
(black hole thermodynamics)

Several files are
available
here:

A
Spacetime Primer (41 pages, pdf) consisting of incomplete notes on
introductory
concepts of general and special relativity (in that order), with the figures
now available;

Introductory
Lectures on Black Hole Thermodynamics (68 pages, postscript);

Black holes:
inside and out (3 pages, postscript), some notes for a talk to
beginning graduate
students.

*Foundations
and Frontiers of Physics: *graduate seminar
series

**Links:**

Gravitation theory group at UMD Group seminars

Last updated: *20
September 2005*