  We propose an ultracold atom analogue of early universe vacuum decay using
all three states of a spin-1 Bose gas. We consider a one-dimensional system
with both radio frequency and optical Raman coupling between internal states.
An advantage of our proposal is the lack of a time-modulated coupling, which
can lead to instabilities. Within the elaborate phase structure of the system
we identify an effective Klein-Gordon field and use Gross-Pitaevskii
simulations within the truncated Wigner approximation to model the decay of its
false vacuum. We examine the dependence of the rate of vacuum decay on particle
density for $^{7}$Li and $^{41}$K and find reasonable agreement with instanton
methods.
