D-branes and Fat Black Holes

TL;DR

This paper critically examines D-brane approaches to large black holes, identifies inconsistencies in previous models, and proposes an improved model that aligns with the Hawking entropy formula and earlier theoretical expectations.

Contribution

It provides a corrected analysis of D-brane models for large black holes and introduces an improved model consistent with entropy calculations.

Findings

Previous models were inconsistent with the Hawking entropy.

An improved model reproduces the Bekenstein-Hawking entropy.

The number of string bits scales with the entropy, supporting earlier theories.

Abstract

The application of D-brane methods to large black holes whose Schwarzschild radius is larger than the compactification scale is problematic. Callan and Maldacena have suggested that despite apparent problems of strong interactions when the number of branes becomes large, the open string degrees of freedom may remain very dilute due to the growth of the horizon area which they claim grows more rapidly than the average number of open strings. Such a picture of a dilute weakly coupled string system conflicts with the picture of a dense string-soup that saturates the bound of one string per planck area. A more careful analysis shows that Callan and Maldacena were not fully consistent in their estimates. In the form that their model was studied it can not be used to extrapolate to large mass without being in conflict with the Hawking Bekenstein entropy formula. A somewhat modified model can reproduce the correct entropy formula. In this ``improved model" the number of string bits on the horizon scales like the entropy in agreement with earlier speculations of Susskind.