Black Holes and branes
September 4, 2009 6 Comments
A black hole is an object that described by a space time geometry that a solution to the Einstein equation. In string theory large distance scales, solution to the Einstein equation are only modified by very small corrections. But it has been discovered through string duality that spad time geometry is not a fundamental concept in string theory, and there alternate description which is very different.
A special type of black hole that very different in string is is called a BPS black gold having both mass and charge, and both satisfies an equality that lead to unbroken supersymmetry in space time near black hole. This is important because it results in disappearances of messy quantum corrections. String theories contain objects called p branes and D brane. Since a point can be though of as a zero brane, a natural generalization of black hole is p brane. And are also BPS black p branes. But there’s also a relationship between black p branes and D branes. A large values of the charge, space time geometry is good description of a black p branes when charge is small, system could be described by a bunch of weakly interacting D branes, in this weakly coupled D branes. With BPS condition satisfies, it is possible to calculate number of available quantum states. This answer depends upon charges of the D branes in the system. When we go back to the geometrical limit of the equivalen black hole of p brane system with the same charges and masses, we find that the entropy of the D crane system matches the entropy calculated fro black hole horizon area. This was a fantastic result in string theory. But can we now say that p branes provide the fundamental quantum microstates of black hold that underlie black hole thermodynamics?
Usually black holes in universe are far away from being a BPS black hole, having very little or no charge. It is still mammoth task to compute this using D branes.