Gravitational nucleation of vacuum phase transitions by compact objects.

Abstract

The possibility of gravitationally condensed material objects (such as neutron stars, monopoles, etc.) acting as nucleation sites for the decay of the false vacuum is examined. The Einstein equations are solved to determine the classical motion of thin-wall bubbles of the true vacuum which form in or around spherically symmetric bodies of uniform-density perfect fluid. Certain decays of negative-energy-density false-vacuum states, which were previously considered to be forbidden, are shown to be locally possible in the neighborhood of a star. In these solutions, bubbles of the true vacuum form inside the star and then oscillate between two radii. The Euclidean action for bubbles which form at R=3M around a uniform-density star is calculated and compared to the action for O(4)-symmetric decay and for decay nucleated by a black hole. The action in the presence of a star is found to be significantly smaller than the other cases. It thus appears that gravitationally condensed material objects in the appropriate mass and radius range can act as nucleation centers for bubbles of the true vacuum, greatly hastening the phase transition and making supercooling difficult or even impossible to achieve.