  Recently it has been shown in 0901.0931 [hep-th] that the approach to
extremality for the non-extremal Reissner-Nordstrom black hole is not
continuous. The non-extremal RN black hole splits into two spacetimes at the
extremality: an extremal black hole and a disconnected $AdS_2\times S^2$ space
which has been called the "compactification solution". As a possible resolution
for understanding the entropy of extremal RN black hole, it has been speculated
that the entropy of the non-extremal black hole may be carried by the latter
solution. By uplifting the four dimensional "compactification solution" with
electric charge $Q_e$ to a five dimensional solution, we show that this
solution is dual to a CFT with central charge $c=6Q_e^3$. The Cardy formula
then shows that the microscopic entropy of the CFT is the same as the
macroscopic entropy of the "compactification solution".

High Energy Physics - Theory