String

String theory is a still developing mathematical approach to theoretical physics, whose original building blocks are one-dimensional extended objects called strings. more...

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Unlike the point particles in quantum field theories like the standard model of particle physics, strings interact in a way that is almost uniquely specified by mathematical self-consistency, forming an apparently valid quantum theory of gravity.

Since its birth as the dual resonance model which described the strongly interacting hadrons as strings, the term string theory has changed to include any of a group of related superstring theories and larger frameworks such as M-theory, which unite them. A shared property of all these theories is the holographic principle.

String theorists have not yet completely described these theories, nor have they determined if these theories relate to the physical universe or how. The elegance and flexibility of the approach, however, and a number of qualitative similarities with more traditional physical models, have led many physicists to suspect that such a connection is possible. In particular, string theory may be a way to \"unify\" the known natural forces (gravitational, electromagnetic, weak nuclear and strong nuclear) by describing them with the same set of equations, as described in the theory of everything. On the other hand, the models have been criticized for their inability, thus far, to provide any experimentally testable predictions.

Like any other quantum theory of gravity, it is widely believed that testing the theory experimentally would be prohibitively expensive, requiring heroic feats of engineering on a solar-system scale. Although string theory like any other scientific theory is falsifiable in principle, critics maintain that it is unfalsifiable for the foreseeable future, and so should not be called science.

Work on string theory is made interesting because of the mathematics involved, and because of the large number of forms that the theories can take. String theory strongly suggests that spacetime has eleven dimensions , not the usual three space and one time; but the theory can easily describe universes with four observable spacetime dimensions too.

String theories include higher-dimensional objects than strings, called branes. These are black-holes charged with a differential form vector potential which has more than one index, a different type of electricity and magnetism where the fundamental objects are extended. By studying these p-branes and identifying them with D-branes, endpoints for strings, certain types of string theory are shown to be equivalent to certain types of more traditional gauge theory. Research on this equivalence has led to new insights on quantum chromodynamics, the fundamental theory of the strong nuclear force.

Read more at Wikipedia.org