The first gulf coast gravity conference (GC)

Richard Price, University of Texas at Brownsville
rprice-at-phys.utb.edu

There is a pronounced drift of relativity into the region from Texas
to Florida, a range of states that does not fit into the reach of the
other regional meetings. For that reason there is now yet another
regional meeting: The Gulf Coast Gravity Conference.
The first such meeting took place Feb. 11 and 12 at the University of Texas at Brownsville, organized by Carlos Lousto, and was attended by relativists from Texas (UT Austin as well as Brownsville), Louisiana (LSU and LIGO), and Florida (Florida Atlantic University). As in other regional meetings, this was a meeting in which everyone got the same short time to talk, and in which students were giving their first talk in front of ``outsiders."

The first day's focus was numerical relativity, and showed that the present state of the field has both convergence of some results and controversy about others. There was agreement about plunge radiation. Results reviewed by UTB's Manuela Campanelli from the Lazarus project (numerical relativity plus perturbation theory) showed about 2.5% of the mass-energy and about 12% of the angular momentum radiated in the late stage of infall. Recent results from LSU, reported by Peter Diener, were in good agreement with the conclusion about radiated energy and reasonable (all things considered) agreement about angular momentum.

There was a useful lack of agreement about initial data, however. Pedro Maronetti of FAU, reporting recent results, showed an efficient way of doing short term evolutionary tests of initial data to see whether the thin-sandwich initial data advertised for circular orbits really does give circular orbits. His recent results, for neutron stars, were in good agreement with circular orbits. Results reported by Peter Diener, from Bowen-York initial data for circular orbits sort of suggested the opposite for black holes. Is it thin-sandwich vs Bowen-York, or something else. It will be interesting to watch how answers to this question develop.

The UTB numerical relativity team, Joseph Zochlower (fourth order codes), Mark Hannam (initial data), and Bernard Kelly (reference frames for Lazarus), gave updates on the many refinements that now characterize the state of the art in numerical relativity. Steve Lau, of UTB, reported on work on radiation boundary conditions indicating that reflections off an outer boundary could be eliminated in principle, and probably greatly reduced in practice.

The second day of the conference contained several talks related to my own recent obsession: an ``intermediate" approximation for black hole inspiral: an approximation appropriate to the later-than-PN, too-soon-for-numerical relativity approximation. I showed the efficiency of a new numerical technique we were using. Chris Beetle has reported on a general mathematical result for how Kepler's law would come out of the intermediate approximation, and Mike McLaughlin showed how some modern applied mathematics could be used to reduce the computational infrastructure that our method might require.

In the afternoon, Rayesh Nayak described the orbital dynamics that are the basis of LISA, and we had talks on data analysis by Alexander Dietz of LSU, and by students Andres Rodriguez (LSU), and Arturo Jimenez, and Charlie Torres (UTB). The widely varying approaches described were a reminder of how difficult this problem will be, and on how open the questions remain.

The prize for the best of an exceptionally good set of student talks
was won by Napoleon Hernandez of UTB for his presentation ``Towards the
computation with Dirac Delta sources for the Teukolsky equation."

Jorge Pullin 2005-03-10