Gauge independence of the bubble nucleation rate in theories with radiative symmetry breaking.

In field theories where a metastable false vacuum state arises as a result of radiative corrections, the calculation of the rate of false vacuum decay by bubble nucleation depends on the effective potential and the other functions that appear in the derivative expansion of the effective action. Beginning with the Nielsen identity, we derive a series of identities that govern the gauge dependence of these functions. Using these, we show, to leading nontrivial order, that even though these functions are individually gauge-dependent, one obtains a gauge-independent result for the bubble nucleation rate. Our formal arguments are complemented by explicit calculations for scalar electrodynamics in a class of Rξ gauges.