We define a Levy process on a $d$-dimensional hierarchical lattice. By construction the Green's function for this process decays as $|x|^{2-d}$. For $d = 4$, we prove that the introduction of a sufficiently weak self-avoidance interaction does not change this decay provided the mass $\equiv$ "killing" rate is chosen in a special way, so that the process is critical.
@article{1176989919,
author = {Brydges, David and Evans, Steven N. and Imbrie, John Z.},
title = {Self-Avoiding Walk on a Hierarchical Lattice in Four Dimensions},
journal = {Ann. Probab.},
volume = {20},
number = {4},
year = {1992},
pages = { 82-124},
language = {en},
url = {http://dml.mathdoc.fr/item/1176989919}
}
Brydges, David; Evans, Steven N.; Imbrie, John Z. Self-Avoiding Walk on a Hierarchical Lattice in Four Dimensions. Ann. Probab., Tome 20 (1992) no. 4, pp. 82-124. http://gdmltest.u-ga.fr/item/1176989919/