Nickel and Dime gravity meeting

Eric Poisson, University of Guelph, Canada
poisson@physics.uoguelph.ca

The second Eastern Gravity Meeting (dubbed Nickel and Dime by the organizers, and the sequel to the 1996 New Voices in Relativity meeting [1]) was held at the University of Syracuse on March 28 and 29, 1998. The meeting was hosted by the Syracuse relativity group (Josh Goldberg, Don Marolf, Peter Saulson, and Rafael Sorkin) and most of the organizing was done by post-doctoral fellow Steve Penn. The format of the meeting was identical to the Midwest and Pacific Coast meetings, with 15 minutes given to every speaker.

The meeting brought together approximately 50 participants, of which approximately half were graduate students. The topics covered ranged widely, including numerical relativity (Pablo Laguna, Roberto Gomez, Pedro Marronetti, Grant Mathews), quantum field theory in curved spacetime (Eanna Flanagan, Larry Ford, Ted Jacobson, Wolfgang Tichy), experimental LIGO physics (Peter Csatorday, Gabriela Gonzalez, Andri Gretarsson, Ryan Lawrence, Steve Penn, Peter Saulson, Bill Startin), gravitational waves (Nils Andersson, Serge Droz, Kostas Kokkotas, Eric Poisson), classical general relativity (Arley Anderson, Simonetta Frittelli, Thomas Kling, Bill Laarakkers), and quantum gravity (Chris Beetle, Ivan Booth, Roumen Borissov, Richard Epp, Sameer Gupta, Eli Hawkins, Jim Javor, Kirill Krasnov, Jorge Pullin, David Rideout, Rob Salgado, Wendy Smith, Rafael Sorkin, Sachin Vaidya, Chun-hsien Wu).

Here are some of the conference's highlights. The following discussion is necessarily biased toward those topics I am most familiar with, and I'm afraid it will not do justice to the many good talks on quantum gravity.

Grant Mathews and Pedro Marronetti (Notre Dame) reported on the current status of their numerical work (carried out with Jim Wilson) on close neutron-star binaries [2]. This work has generated quite a bit of controversy over the last couple of years. (See Ref. [3] for many negative papers, and Ref. [4] for positive contributions.) Mathews, Marronetti, and Wilson predict that the central density of the neutrons stars increases as the stars approach each other, sufficiently so that the stars will undergo gravitational collapse when they are still widely separated. This conclusion goes against physical intuition (and the many rebuttals listed in Ref. [3]) which suggests that the stars' mutual tidal interaction should make them more stable against gravitational collapse. In the last several months, these authors have been testing their code for possible errors and inconsistencies, and have found none. It will be interesting to see how this all gets resolved in the future.

Nils Andersson (Tübingen) reported on his recent discovery of the r-mode instability of rotating neutron stars [5]. This instability results in the rapid spin-down of a young neutron star, and produces a large amount of gravitational waves. Needless to say, this is very exciting, because of the possibility that these waves could be eventually detected by LIGO/VIRGO/GEO/TAMA.

Another interesting presentation was from Ted Jacobson (Maryland), who discussed the relevance of super-Planckian frequencies in the usual derivation of the Hawking effect. He presented recent work carried out with Steven Corley [6], in which a quantum scalar field is put on a one-dimensional lattice in a black-hole spacetime. The lattice provides a natural cutoff in the field's dispersion relation, so that super-Planckian frequencies do not occur. For wavelengths which are long compared with the cutoff, the usual Hawking spectrum is recovered.

Finally, Larry Ford (Tufts) reported on an interesting possibility of amplifying the usual Casimir effect by changing the frequency spectrum of the contributing field modes, which can be done by introducing a dielectric into the problem. As a result of his analysis, Ford finds that a small dielectric sphere in the vicinity of a conducting boundary would undergo a potentially measurable force which oscillates (between attraction and repulsion) as a function of the distance from the boundary.

Overall this was a marvelous meeting, during which students and postdocs met with their peers and talked shop, while their advisors exchanged gossip. Like the Pacific Coast and Midwest meetings, the Eastern Gravity Meeting provides a friendly and informal forum for all workers in gravitational physics. Most importantly, it provides a unique opportunity for graduate students and postdocs to gain experience at giving talks. It serves a very useful purpose, and I wish it a very long life!

References:

[1] L. Smolin, Matters of Gravity 9 (Spring 1997).

[2] P. Marronetti, G.J. Mathews, and J.R. Wilson gr-qc/9803093; gr-qc/9710140; gr-qc/9601017.

[3] T.W. Baumgarte, G.B. Cook, M.A. Scheel, S.L. Shapiro, and S.A. Teukolsky gr-qc/9709026; K.S. Thorne gr-qc/9706057; E.E. Flanagan gr-qc/9706045; A.G. Wiseman gr-qc/9704018 ; P.R. Brady and S.A. Hughes gr-qc/9704019; D. Lai astro-ph/9605095 .

[4] S.L. Shapiro gr-qc/9710094 ; G.B. Cook, S.L. Shapiro, and S.A. Teukolsky gr-qc/9512009.

[5] N. Andersson gr-qc/9706075; J.L. Friedman and S.M. Morsink gr-qc/9706073; L. Lindblom, B.J. Owen, and S.M. Morsink gr-qc/9803053; S.M. Morsink, Matters of Gravity 10 (Fall 1997).

[6] S. Corley and T. Jacobson hep-th/9709166.



Jorge Pullin
Mon Sep 7 17:37:02 EDT 1998