### Reconciling quantum mechanics and general relavity

Our research is situated within the field of

*theoretical elementary particle physics*. For the novice: it might be a nice idea to first take a tour in the magnificent

Particle Adventure. One of the great successes of twentieth century physics was that all the forces in nature, however diverse they might appear, were reduced to only four fundamental interactions. Three of those, the electro-magnetic, the weak and the strong forces, are very well understood. So it should come as quite a surprise that the force which is most familiar to us, the gravitational force, is also the least understood one! Thanks to Einstein, we do have a very good classical description of gravity: the theory of general relativity. While it works very well at larger distances, we do expect that quantum mechanical effects come into play when studying gravity at very small scales. However, general relativity and quantum mechanics appear to be mutually incompatible!

Till now we have only one candidate quantum theory of gravity: *string theory*. In fact, string theory is right now the most promising candidate for a theory giving a unifying description of all elementary particles and all fundamental interactions in nature.

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Back to top Some good introductions

- A very good non-technical introduction is Beyond String Theory by Jan Troost.
- For Dutch speaking readers, there is an interview with one of us in Knack, a leading Belgian weakly: © Knack Dirk Draulants: Page 1, Page 2, Page 3, Page 4.
- In addition we wrote a text (which appeared in the proceedings of the 2002 Rencontres de Moriond) Strings, Gravity and Particle Physics explaining the main principles and highlighting the major results of string theory. It is somewhat more technical than the previous links and aims at physicists in general. A postscript version can be found here.

For other non-technical introductions to the subject see our links page.

The research of our group focuses on string theory and related topics. Over the past few years the solitonic excitations of string theory, called D-branes, became increasingly important. We are currently investigating various properties of D- and M-branes. A fascinating aspect of D-branes is their close relation to gauge theories. The effective low energy dynamics of D-branes is described by a Born-Infeld theory. While the Born-Infeld action is known to all orders in the abelian case (describing a single D-brane) it is not known yet in the non-abelian case (describing two or more coinciding D-branes).

Our present research efforts are directed towards acquiring a better understanding of systems consisting of multiple coinciding D-branes. Besides this we investigate various geometric properties of D-branes. More recently we have developed an active interest in string inspired cosmology. One of the central questions being investigated is how to resolve cosmological singularities in the context of string theory. Finally, we also have a long running interest in supersymmetric field theories with 4 or more supercharges, their off-shell formulation, their relation to complex geometry and the restrictions supersymmetry imposes on the effective quantum theory.

We are currently also developing a phenomenological activity focusing on Beyond the Standard Model Physics connecting our group to the experimental group at the VUB. More information here.