  Real scalar field models incorporating asymmetric double well potentials will
decay to the state of lowest energy. While the eventual nature of the system
can be discerned, the determination of the dynamics of the bubble wall provides
many difficulties. In the present study we investigate numerically the
evolution of spherically symmetric expanding bubbles coupled to a thermal bath
in 3+1 dimensions. A Markovian Langevin equation is employed to describe the
interaction between bubble and bath. We find the shape and velocity of the wall
to be independent of temperature, yet extremely sensitive to both asymmetry and
viscosity.
