Ekpyrotic: Encyclopedia II - Ekpyrotic - Outstanding problems

Ekpyrotic - Outstanding problems

There are major outstanding problems with the ekpyrotic scenario. Foremost among them is that colliding branes are not understood by string theorists, and nobody knows if the scale invariant spectrum will be destroyed by the big crunch, or even what happens when two branes collide. Moreover, like cosmic inflation, while the general character of the forces (in the ekpyrotic scenario, a force between branes) required to create the vacuum fluctuations is known, there is no candidate from particle physics. Moreover, the scenario uses some essential ideas from string theory, principally extra dimensions, branes and orbifolds. String theory itself is a controversial idea in the physics community.

Detractors of the original ekpyrotic scenario point out that it requires fine-tuned, nearly supersymmetric initial conditions, and thus replaces the problems solved by cosmic inflation with a new set of problems. The original scenario has been supplanted by a new more flexible and successful set of ideas, embodied in the cyclic model.

Adapted from the Wikipedia article "Outstanding problems", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki