Midwest gravity meeting

Comer Duncan
Bowling Green State University

The sixth annual Midwest Relativity Conference was held at Bowling Green State University in Bowling Green, Ohio on Nov. 1-2, 1996. There were about 50 participants, most of whom gave talks. Each talk was 15 minutes long. For the most part the topics covered fell into the following categories: 1) Numerical Relativity, 2) Mathematical Relativity, 3) Observational Topics, 4) Quantum Gravity, and 5) Alternative Theories of Relativity.

Numerical Relativity. There were quite a few talks which utilize numerical techniques, but several were more or less devoted to issues which center on the numerical implementation of Einstein's theory in two and three spatial dimensions, with and without matter. Beverly Berger discussed evolutions of symmetric cosmologies, showing the tracking of regions of large curvature using her symmetric code. David Garfinkle talked about a new symplectic algorithm for the evolution of mixmaster spacetimes which accurately evolves to late times. Jorge Pullin gave an overview of the successful 'close approximation' for colliding black holes and discussed its salient features and applications. Serge Droz discussed a numerical investigation of black hole interiors. Keith Lockitch reported on his investigations of how to numerically construct a family of asymptotically flat initial data sets which are axisymmetric and geodesically complete as counter-examples to the cosmic censorship conjecture. Comer Duncan gave a talk about a new hyperbolic solver for vacuum axisymmetric spacetimes which combines the Geroch manifold of trajectories approach with a symmetric hyperbolic form of Einstein's equations, and discussed a numerical implementation and tests on weak gravitational waves. Mark Miller reported his investigations into the utility of Regge Calculus for numerical relativity, focussing on issues of consistency and stability. Grant Mathews discussed his work on the appearance of instabilities in close neutron star binaries.

Mathematical Relativity. There were a wide variety of topics in mathematical relativity. Ulrich Gerlach discussed some recent work on a variety of topics, including paired accelerated frames, diffractive scattering, and achronal spin. Jean Krisch reported on some work on string fluid stress energy. Steve Leonard talked about the appearance of tail effects for various types of fields in curved spacetimes. Ted Quinn reported his investigations into an axiomatic approach to electromagnetic and gravitational radiation reaction. Shyan-Ming Perng talked about his research on conserved quantities at spatial infinity. Ed Glass discussed the calculation of the Bondi mass from Taub numbers, while Jim Chan discussed radiative falloff in non-asymptotically flat spacetimes. Juan Perez-Mercader presented his views on how self-organized criticality may be expressed in the universe. Kevin Chan talked about modifications of the spinning BTZ black hole when the theory contains a dilaton field. Masafumi Seriu gave an overview of his work to characterize the global geometrical structure of a space in terms of the spectra of a suitable operator, including discussion of a measure of closeness of two universes based on the spectra. There were two talks utilizing torsion. Richard Hammond discussed gravitation with torsion derived as the exterior derivative of a second potential, built so that electromagnetism may be generalized such that the source of the torsion gives rise to the magnetic dipole moment of the electron. Harry Ringermacher gave a treatment in which gravity with torsion is present to encode the electromagnetic field and discussed several solutions.

Observational Topics. Mark Beilby gave a talk about methods of predicting test mass thermal noise by measurement of the anelastic aftereffect in the context of the LIGO project. Eric Poisson talked about the dual use of space-based interferometers to measure black hole parameters and as a means of testing general relativity. Andrew de Laix gave a treatment of the gravitational lensing signature of long cosmic strings. Bob Wald gave an overview of some recent work on galactic and smaller scale gravitational lensing, while Daniel Holz followed with further developments and some applications. Philip Hughes discussed some recent high resolution relativistic extra-galactic jet simulations as a possible probe of aspects of super-massive black holes.

Quantum Gravity. The variety of topics which are quantum related was quite wide in scope. Leonard Parker gave a talk about his research on 2D black holes, reporting on his work on the formation and evaporation of 2D black holes in dilatonic quantum gravity. Louis Witten talked about the formation and evaporation of naked singularities in 2D which suggest that the naked singularity will not exist but instead there would be a large outburst of radiation. Ivan Booth reported on the cosmological production of charged and rotating black hole pairs. James Geddes gave a discussion of some recent work on whether there exists a measure on the space of all paths in Schroedinger quantum mechanics such that the time evolution of the system is given by an appropriate path integral. He give an example of a system for which the answer is no. Hong Liu talked about quantum hair, instantons, and black hole thermodynamics. Bob Mann then gave a report on the pair production of topological anti de Sitter black holes. The talks by Michael Pfenning and Matt Visser were of a different orientation. Pfenning discussed quantum inequalities in static curved spacetimes. Visser gave an overview of the violation of energy conditions at order hbar, showing how the polarization of the vacuum by the semi-classical gravitational field causes a shift in the stress-energy which violates all the classical energy conditions. Rhett Herman talked about the use of the DeWitt-Schwinger point-splitting technique to construct the stress-energy of a complex scalar field in curved spacetime.

Alternative Theories of Relativity. Ken Seto discussed a special relativity alternative. Edward Schaefer talked about means of eliminating black holes from relativity theory.

The Sixth Midwest Relativity Conference included a wide variety of talks, giving ample evidence of the breadth of interests of relativists in and around the midwest. The meeting at Bowling Green demonstrated that the midwest meetings have achieved a stable status.

Thanks to all who attended! The next meeting will be at Washington U. in St. Louis with Wa Mo Suen the prime contact. See you all at the next meeting!

Jorge Pullin
Tue Feb 4 22:28:54 EST 1997