Absorption of Fixed scalars and the D-brane Approach to Black Holes

TL;DR

This paper compares semi-classical and D-brane calculations of fixed scalar absorption by near-extremal five-dimensional black holes, revealing insights into the effective string tension and supporting the D-brane model of black hole microstates.

Contribution

It provides a detailed comparison of absorption rates for fixed scalars using semi-classical and D-brane methods, highlighting the suppression mechanism and extracting the effective string tension.

Findings

Agreement between semi-classical and D-brane calculations.

Fixed scalar absorption cross-section is smaller and depends on properties beyond horizon area.

Effective string tension matches the value needed for near-extremal 5-brane entropy.

Abstract

We calculate the emission and absorption rates of fixed scalars by the near-extremal five-dimensional black holes that have recently been modeled using intersecting D-branes. We find agreement between the semi-classical and D-brane computations. At low energies the fixed scalar absorption cross-section is smaller than for ordinary scalars and depends on other properties of the black hole than just the horizon area. In the D-brane description, fixed scalar absorption is suppressed because these scalars must split into at least four, rather than two, open strings running along the D-brane. Consequently, this comparison provides a more sensitive test of the effective string picture of the D-brane bound state than does the cross-section for ordinary scalars. In particular, it allows us to read off the value of the effective string tension. That value is precisely what is needed to reproduce the near-extremal 5-brane entropy.