Emilio Cirillo, Enzo Olivieri
METASTABILITY AND NUCLEATION FOR THE BLUME-CAPEL MODEL.  
DIFFERENT MECHANISMS OF TRANSITION.
(284K, Plaintex)

ABSTRACT.  We study metastability and nucleation for the Blume-Capel model: a
ferromagnetic
nearest neighbour two-dimensional lattice system with spin variables taking
values in  $\{-1,0,+1\}$.
We consider large but finite volume, small fixed magnetic field $h$ and
chemical
potential $\lambda$ in the limit of zero temperature;
we analyze the first excursion
from the metastable $-1$ configuration to the stable $+1$ configuration.
We compute the asymptotic
behaviour of the transition time and describe the typical
tube of trajectories during the transition. We show that, unexpectedly,
the mechanism of transition changes abruptly when the line $ h = 2 \lambda$
is
crossed.