Macroscopic Entropy of N=2N=2 Extremal Black Holes

Extremal BPS-saturated black holes in $N=2$, $d=4$ supergravity can carry electric and magnetic charges $(q^\Lambda_{(m)},q_\Lambda^{(e)})$. It is shown that in smooth cases the moduli fields at the horizon take a fixed "rational" value $X^\Lambda(q_{(m)},q^{(e)})$ which is determined by the charges and is independent of the asymptotic values of the moduli fields. A universal formula for the Bekenstein-Hawking entropy is derived in terms of the charges and the moduli space geometry at $X^\Lambda(q_{(m)},q^{(e)})$. This work extends previous results of Ferrara, Kallosh and the author for the pure magnetic case.Comment: Reference corrected, 8 pages, Late

The Black Branes of M-theory

We present a class of black $p$-brane solutions of M-theory which were hitherto known only in the extremal supersymmetric limit, and calculate their macroscopic entropy and temperature.Comment: Latex, 13 pages, minor corrections and reference adde

Electron transport in TiO2 probed by THz time-domain spectroscopy

Euan Hendry, F. Wang, J. Shan, T. F. Heinz, and Mischa Bonn, Physical Review B, Vol. 69, article 081101 (2004). "Copyright © 2004 by the American Physical Society."Electron transport in crystalline TiO2 (rutile phase) is investigated by frequency-dependent conductivity measurements using THz time-domain spectroscopy. Transport is limited by electron-phonon coupling, resulting in a strongly temperature-dependent electron-optical phonon scattering rate, with significant anisotropy in the scattering process. The experimental findings can be described by Feynman polaron theory within the intermediate coupling regime and allow for a determination of electron mobility