In one minute

Ruth Gregory and Raymond Laflamme study small perturbations of black strings and branes, low-energy solutions of string theory. In four dimensions black holes are stable and settle into a state fixed by mass, charge and angular momentum. Quantum mechanically, black holes behave quite differently, like thermal systems whose horizon area acts as entropy. For uncharged black strings they find unstable modes over a range of frequencies and wavelengths in the extra dimensions. Compactifying the extra dimensions below the shortest unstable wavelength removes the instability, so large astrophysical black holes are unaffected. They also discuss what the instability means for Penrose's cosmic censorship hypothesis that singularities stay hidden.

Black strings and p-branes are unstable