We produce for arbitrary nonamenable group G and field K a nonpreinjective, surjective linear cellular automaton. This answers positively Open Problem (OP-14) in Ceccherini-Silberstein and Coornaert's monograph "Cellular Automata and Groups''.

We also reprove in a direct manner, for linear cellular automata, the result by Capobianco, Kari and Taati that cellular automata over sofic groups are injective if and only if they are postsurjective.

These results come from considerations related to matrices over group rings: we prove that a matrix's kernel and the image of its adjoint are mutual orthogonals of each other. This gives rise to a notion of "dual cellular automaton'', which is preinjective if and only if the original cellular automaton is surjective, and is injective if and only if the original cellular automaton is postsurjective.

This work is supported by the "@raction'' grant ANR-14-ACHN-0018-01