New Horizons: GR Beyond 4D

The study of general relativity in higher dimensions has been a fruitful area of research, in particular, for producing insights into the structure of superstring and M-theory, as well as for understanding the phenomenology of braneworld scenarios. Black holes and their relatives are of particular interest in this higher dimensional context. Past investigations have produced an impressive catalogue of black hole solutions for various effective theories of Einstein gravity coupled to many different kinds of matter fields. However, one expects that the physics of event horizons in higher-dimensional general relativity is far richer and more complex than in the standard four-dimensional theory. For example, in contrast to the stability proven for four-dimensional black holes, Gregory and Laflamme made the surprising discovery that the extended black branes appearing in higher dimensions are unstable. Ten years later, the question of the endpoint reached with the onset of this instability remains unresolved. However, this question leads to a conjecture that static inhomogeneous black brane solutions may also exist. This recent conjecture produced a surge of activity in this area, including the discovery of a certain class of such in homogeneous solutions. As this work requires examining the Einstein equations in a strong field regime, recent progress here relies on numerical work. Another startling result in this area was the recent construction by Emparan and Reall of an asymptotically flat solution describing a rotating black ring in five dimensions, where the horizon topology was the direct product of a two-sphere with a circle. This is a clear indication that, unlike four dimensions, in higher dimensions black hole solutions will not be completely determined by a few asymptotic charges (such as the mass and angular momentum). Rather, it seems that we currently have only glimpses of a rich landscape of solutions with vast unexplored areas.

Perimeter will be hosting a meeting of researchers interested in the instability of black strings and other question in higher dimensional general relativity. We will bring together a small number of researchers from both analytical and numerical backgrounds in an informal setting. The meeting will be held at the Perimeter Institute in the week of April 12 to 16. The format of the meeting will be such that there will be one day of talks on Monday April 12, and the rest of the week will be left for informal interactions between workshop participants.

Speakers:

Roberto Emparan
Sean Hartnoll
Barak Kol
Don Marolf
Luis Lehner
Frans Pretorius
Toby Wiseman