文摘
In this chapter we deal with polymer models on different oriented graphs and compare them with the lattice case. As revealed by Derrida and Spohn in, many interesting questions can be answered on the regular tree. Later on, refined tree-like structures including Derrida’s m-tree has been introduced, yielding further comparisons. There, correlations are simpler compared to the lattice case, since the medium along two paths becomes independent as soon as they visit different sites. In the sense of simplifying the correlation structure, these models play the role of mean-field models.