Classical and Quantum Aspects of BPS Black Holes in N=2, D=4 Heterotic String Compactifications

We study classical and quantum aspects of D=4, N=2 BPS black holes for T_2 compactification of D=6, N=1 heterotic string vacua. We extend dynamical relaxation phenomena of moduli fields to background consisting of a BPS soliton or a black hole and provide a simpler but more general derivation of the Ferrara-Kallosh's extremized black hole mass and entropy. We study quantum effects to the BPS black hole mass spectra and to their dynamical relaxation. We show that, despite non-renormalizability of string effective supergravity, quantum effect modifies BPS mass spectra only through coupling constant and moduli field renormalizations. Based on target-space duality, we establish a perturbative non-renormalization theorem and obatin exact BPS black hole mass and entropy in terms of renormalized string loop-counting parameter and renormalized moduli fields. We show that similar conclusion holds, in the large T_2 limit, for leading non- perturbative correction. We finally discuss implications to type-I and type-IIA Calabi -Yau black holes.