Entropy count for extremal three-dimensional black strings

We compute the entropy of extremal black strings in three dimensions, using Stromingerʹs approach to relate the Anti-de-Sitter near-horizon geometry and the conformal field theory at the asymptotic infinity of this geometry. The result is identical to the geometric Bekenstein–Hawking entropy. We further discuss an embedding of three-dimensional black strings in N=1 D=10 supergravity and demonstrate that the extremal strings preserve 1/4 of supersymmetries.