ARE ALL STATIC BLACK-HOLE SOLUTIONS SPHERICALLY SYMMETRICAL

The static black hole solutions to the Einstein-Maxwell equations are all spherically symmetric, as are many of the recently discovered blac k hole solutions in theories of gravity coupled to other forms of matt er. However, counterexamples demonstrating that static black holes nee d not be spherically symmetric exist in theories, such as the standard electroweak model, with electrically charged massive vector fields. I n such theories, a magnetically charged Reissner-Nordstrom solution wi th sufficiently small horizon radius is unstable against the developme nt of a nonzero vector field outside the horizon. General arguments sh ow that, for generic values of the magnetic charge, this field cannot be spherically symmetric. Explicit construction of the solution shows that it in fact has no rotational symmetry at all.