Title: Critical values in Bak-Sneppen type models,
Abstract: In the Bak-Sneppen model, the lowest fitness particle and its two nearest
neighbors are renewed at each temporal step with a uniform (0,1) fitness
distribution. The model presents a critical value that depends on the
interaction criteria (two nearest neighbors) and on the update procedure
(uniform). Here we calculate the critical value for models where one or both
properties are changed. We study models with non-uniform updates, models with
random neighbors and models with binary fitness and obtain exact results for
the average fitness and for $p_c$.