Black holes II and CCGRRA 8

Jack Gegenberg, Univ. of New Brunswick and Gabor Kunstatter, Univ. of Winnipeg

Following a tradition established two years ago, the Black Holes Workshop and the Canadian General Relativity and Relativistic Astrophysics Conference were held consecutively and in nearby locales. Black Holes II: Theory and Mathematical Aspects, took place June 6-9,1999 at the resort town of Val Morin in the Laurentian Mountains north of Montreal, Quebec, followed closely by CCGRRA 8 (June 10-12) at McGill University in Montreal. Both conferences were supported by the Canadian Institute of Theoretical Astrophysics, the Centre de Recherches Mathematiques. Black Holes II also received financial support from the Canadian Institute for Advanced Research. The local organizers for both meetings were Cliff Burgess and Rob Myers. The organizers must be congratulated for putting together two very successful and exciting complementary meetings.

Black Holes II
The talks and discussions in Black Holes II revolved around the nature of and origins of black hole thermodynamics, with discussion often considerably heated by the dialogue between string theorists and relativists. The morning sesssions consisted of three plenary talks and were followed by a sumptious lunch. In the afternoon the contributed talks were presented, and after an excellent dinner, the final plenary session of the day took place. Discussions often continued long into the night in the resort's bar. These discussions sometimes came to definitive and startling conclusions that were rarely remembered by morning.

The first speaker at the workshop was Bob Wald, who set the stage by reviewing the geometric basis of black hole thermodynamics. Abhay Ashtekar continued in this spirit by describing his concept of isolated horizons, and the associated quasi-local definitions of mass and surface gravity. The morning session concluded with Werner Israel's re-appraisal of `t Hooft's brick wall model of black holes.

After interesting contributed talks by Renaud Parentini, Claude Barrabes, Bei-lok Hu and Alessandro Fabbri, Leonard Susskind spoke during the first evening session on how to understand superluminosity in the context of the holographic conjecture.

On the second day, Steve Carlip spoke on his construction of black hole statistical mechanics from states induced on the boundary/event horizon of black holes in spacetimes of arbitrary dimension. Gabor Kunstatter presented a general discussion of 2D black hole thermodynamics followed by a summary of recent calculations of quantum corrections to the thermodynamic properties of charged 2-D black holes. Finally Emil Martinec discussed the interplay of D-branes and black hole thermodynamics in the M-theory context. The afternoon session consisted of contributed talks by Amanda Peet, David Kastor and Daniel Kabat, Jennie Traschen and Simon Ross. The plenary talk in the evening was given by Don Page, who described the thermodynamics of nearly extreme black hole under various assumptions about the degeneracy of the ground state and the density of nearby states.

On the last full day of the workshop, Ted Jacobson forcefully presented his perspective on the question of the `ultravioletness' of the source of Hawking radiation, provoking lots of discussion from the mixed stringy/ relativist participants. Valeri Frolov described his program for understanding the origin of black hole thermodynamics from the statistical mechanics of the constituent matter fields in `induced gravity'. Robert Mann then outlined a proceedure for determining the boundary terms in black hole thermodynamics inspired by the AdS/CFT conjecture. That afternoon, the contributed talks were given by Julian Lee, Ivan Booth, Jack Gegenberg, Roberto Casadio and Martin Rainer. The evening talk by Bill Unruh presented the case for taking seriously the sonic analogue of black holes (`dumbholes'). This too sparked considerable debate between those who believed that black hole thermodynamics contained important microscopic properties that were missing in the dumbhole analogy, and those who felt that all the essential (infrared) features were adequately represented in the model.

On the last (half) day of the workshop the only plenary talk was delivered by Juan Maldecena. This talk entailed a discussion on some issues in the AdS/CFT conjecture, in particular on peculiar effects in the boundary CFT. Th e conference closed with three interesting contributed talks, by Finn Larsen, David Lowe and Steve Gubser.

As the participants boarded boarded the bus for Montreal after the last talk, many felt that the controversy pointed to an overall unsettled state of affairs in fundamental physics and signalled interesting times ahead...

Many of the Black Hole II participants went from Val Morin directly to Montreal for CCGRRA 8, where they were joined by many others from across the spectrum of gravitational physics. CCGRRA 8 participants were able to take advantage of Montreal's many fine restaurants and even had the rare opportunity of watching the Expos win a baseball game!

On the first day, we heard from Peter Saulson about progress in building gravity wave detectors. This was followed by Vicky Kaspi's talk on the state of binary radio pulsar timing as a GR effect and then by Jeff Winnicour's discussion of numerically calculating the dynamics of black hole collisions. After lunch, Sharon Morsink demonstrated that certain instabilites in rotating neutron stars may explain the properties of some recently discovered pulsars.

On the second day, Ted Jacobson discussed open questions about black hole entropy, in particular those arising from a conjectured holographic bound. Abhay Ashtekar continued the discussion he begin at Black Holes II, here using quantum geometry to describe black hole thermodynamics, and comparing the result to the stringy discussion. The morning session concluded with an introductory talk by Leonard Susskind on the holographic principle, emphasizing its origins in black hole quantum theory and string theory. Finally, Gilles Fontaine built the case for white dwarfs as a major component of dark matter.

On the last day, we first heard from Lev Kofman on how to build better inflationary models incorportating preheating. This was followed by Bill Unruh's discussion of second order perturbations in the expansion of the universe. The final talk, by Don Page, was on the possibility of testing the many-worlds viewpoint via quantum cosmology.

The contributed talks in the afternoon parallel sessions were in general excellent. Many of these talks were given by grad students and postdocs, and provided an exciting introduction to the breadth and depth of gravitational physics research today. It was clear to all the participants that this conference once again successfully fulfilled the CCGRRA's mandate to bring together Canadian and international researchers in order to discuss the latest developments in Relativity and Astrophysics.

Jorge Pullin