Hamming distance of repeated-root constacyclic codes of length 2ps over Fpm+uFpm

Let p be an odd prime, and δ be an arbitrary unit of the finite chain ring F p m + u F p m ( u 2 = 0 ) . The Hamming distances of all δ -constacyclic codes of length 2 p s over F p m + u F p m are completely determined. We provide some examples from which some codes have better parameters than the existing ones. As applications, we determine all MDS repeated-root δ -constacyclic codes of length 2 p s over F p m + u F p m .