We sharpen ellipticity criteria for random walks in i.i.d. random environments introduced by Campos and Ramírez which ensure ballistic behavior. Furthermore, we construct new examples of random environments for which the walk satisfies the polynomial ballisticity criteria of Berger, Drewitz and Ramírez. As a corollary, we can exhibit a new range of values for the parameters of Dirichlet random environments in dimension $d=2$ under which the corresponding random walk is ballistic.
Élodie Bouchet. Alejandro F. Ramírez. Christophe Sabot. "Sharp ellipticity conditions for ballistic behavior of random walks in random environment." Bernoulli 22 (2) 969 - 994, May 2016. https://doi.org/10.3150/14-BEJ683