Gravitation and high energy physics in various dimensions |

Unified theories have proven to be a successful and fruitful approach in order to understand seemingly different phenomena in terms of a single picture. A good example is the case of electric and magnetic forces as being part of a unified electromagnetic field. This purely theoretical result, achieved by Maxwell in the 19th century, not only allowed understanding the very nature of light as an electromagnetic wave, but also contained the seed that gave rise to Einstein’s special relativity.
In our current understanding, there are four fundamental interactions (“forces”) in nature: Electromagnetism, weak and strong nuclear forces, and gravity. Unification has also give rise to predictions successfully verified by experiments. This is the case of electromagnetism and the weak nuclear force, once formulated in terms of the electroweak model of Weinberg and Salam. Thus, pursuing this strategy so as to include the remaining interactions has been a guide to propose new models in theoretical physics.
A particularly interesting proposal, as old as General Relativity, concerns the unification of electromagnetism and gravity, so that electromagnetism appears as “the shadow” of a single gravitational field formulated in a higher-dimensional spacetime. In this model, the extra dimensions are supposed to be extremely curled up in such a way that one cannot perceive them in daily experience, as it is hard to distinguish an extremely thin cylinder (of two-dimensions) from one-dimensional line. Even though this proposal runs into conflict with observation, its aesthetic appeal has recently received serious consideration in different seemingly consistent scenarios.
Currently, there is a growing consensus on the fact that unification theories could be formulated within higher-dimensional frameworks. The proposals are increasingly ambitious, not only providing a unifying scheme for the fundamental interactions that could lead to the elusive quantization of gravity, but also describing matter and interactions as a different features of a single unified field. Among the most studied “theories of everything” possessing these features, are the five possible superstring theories, which would have a common origin from a single M-Theory, where the existence of eleven dimensions is required.
The research recently developed by our group along these lines contains: Local supersymmetry and gravity theories in diverse dimensions, including black holes, membrane-like black objects (p-branes) and wormholes in vacuum. New mechanisms to "curl up" the extra dimensions have also been explored, as well as interesting phenomena of gravitational physics and holography in dimensions lower than four. |