### September 25, 2017

**Anaël Grandjean**(LACL)

We are interested in 2-dimensional cellular automata and more precisely in the recognition of langages in small time. The time complexity we consider is called real-time and is rather classic for the study of cellular automata. It consists of the smallest amount of time needed to read the whole imput. It has been shown that this set of langages depend on the neighborhood of the automaton. For example the two most used neighborhoods (Moore and von Neumann ones) are different with respect to this complexity. Our study deals with more generic sets of neighborhoods, round and diamond neighborhoods. We prove that all diamond neighborhoods can recognize the same langages in real time and that the round neighborhoods can recognize stricly less than the diamond ones.