# String Theory

### Overview

Some of the most fundamental questions in science are at the cutting edge of modern mathematical physics. They address the very structure and origin of the universe, the nature of the constituents of all matter and their interactions and the mathematical structures necessary for a quantitative formulation of the fundamental laws of nature. Two concrete goals of current focus in fundamental physics are to find a quantum theory of gravity that avoids the inconsistencies that arise from trying to reconcile Einstein's general theory of relativity with quantum mechanics and to find a unified theory which encompasses all of the forces of nature and describes all of the particles which are subject to those forces.

Superstring theory is a promising candidate for a physical theory that could simultaneously achieve both of these goals. String theory is a physical model which is postulated to describe fundamental interactions at exceedingly small distances where quantum mechanical fluctuations of the geometry of spacetime would become important. As a physical dynamical system, it is still not completely understood. It is clear that the full power of superstring theory will only be realized once significant progress has been made in understanding its mathematical and dynamical structure. This will involve the development of new mathematics and will be an important frontier area for both mathematics and physics in the foreseeable future.

### PIMS Distinguished Chair

Ashoke Sen (Harish-Chandra Research Institute), will give a series of lectures during July and August 2003 at UBC.

Ashoke Sen's significant contributions to string theory include his early work on string field theory, duality symmetries, and black hole solutions. This led him to the study of strong-weak coupling duality of supersymmetric gauge theories. His proof of the existence of the conjectured bound states required by those dualities is now one of the classic works in the field. This work has had enormous influence and is usually credited as the start of the "second superstring revolution" --- a shift of perspective which the field is still undergoing.

In 1998, Professor Sen initiated the study of non-supersymmetric states in string theory. Once again, this has proven to be a very fruitful study. Most recently, he has returned to the study of string field theory in the context of tachyon condensation on D-branes. This has led to his current work on the cosmological consequences of tachyon condensation.

The CRG will have another Distinguished Chair in 2003 and two more in 2004. These chairs will visit the group for at least one month and give a minicourse of lectures

### Faculty

CRG Leaders:

- Gordon Semenoff (UBC)
- Eric Woolgar (U. Alberta)

U. Alberta:

- B. Campbell
- V. Frolov
- D. Page (Physics)
- T. Gannon
- E. Woolgar (Math)

UBC:

- G. Semenoff
- M. Rozali
- M. Van Raamsdonk
- K. Schleich
- D. Witt
- M. Choptuik
- W. Unruh (Physics and Astronomy)
- J. Bryan
- K. Behrend (Math).

U. Lethbridge:

- M. Walton (Physics)

Perimeter Institute:

- R. Myers
- L. Smolin

SFU:

- K. Viswanathan (Physics)

U. Toronto:

- A. Peet (Physics)

U. Washington:

- A. Karch (Physics)

Asia Pacific Center for Theoretical Physics, Korea:

- Taejin Lee

**PIMS Postdoctoral Fellows**

- Jian-Jun Xu, PIMS PDF at SFU
- Jianying Zhang, PIMS/MITACS PDF at UBC

This CRG will include another PDF in 2003 and two more in 2004.

**Graduate Students**

K. Chu, P. de Boer, M. Laidlaw, J. Gardezi, B. Sussman, B. Ramadanovic, D. Young, K. Furuuchi, R. Fazio.