Below is the ascii version of the abstract for 97-465. The html version should be ready soon.

Pablo A. Ferrari, Servet Martinez
Hamiltonians on random walk trajectories
(271K, ps)

ABSTRACT.  We consider Gibbs measures on the set of paths of nearest neighbors
random walks on $Z_+$. The basic measure is the uniform measure on the set
of paths of the simple random walk on $Z_+$ and the Hamiltonian awards each
visit to site $x\in Z_+$ by an amount $\alpha_x\in R$, $x\in Z_+$. We
give conditions on $(\alpha_x)$ that guarantee the existence of the (infinite
volume) Gibbs measure.  When comparing the measures in $Z_+$ with the
corresponding measures in $Z$, the so called entropic repulsion appears as a
counting effect.