Repeated-root constacyclic codes of length 2ps

The algebraic structures in term of polynomial generators of all constacyclic codes of length 2ps over the finite field Fpm are established. Among other results, all self-dual negacyclic codes of length 2ps, where (any m), or and m is even, are provided. It is also shown the non-existence of self-dual negacyclic codes of length 2ps, where , m is odd, and self-dual cyclic codes of length 2ps, for any odd prime p.