Impact of gravity on vacuum stability

In a pioneering paper on the role of gravity on false vacuum decay, Coleman and De Luccia showed that a strong gravitational field can stabilize the false vacuum, suppressing the formation of true vacuum bubbles. This result is obtained for the case in which the energy density difference between the two vacua is small, the so-called thin-wall regime, but is considered of more general validity. Here we show that when this condition does not hold, however, the effect of gravity on the bubble nucleation rate amounts to a small correction to the flat space-time result even in a strong gravity regime. This result suggests that the impact of gravity on the stability analysis of the electroweak vacuum could be essentially negligible.