On self-dual constacyclic codes of length ps over Fpm + uFpm

The aim of this paper is to establish all self-dual lambda-constacyclic codes of length p(s) over the finite commutative chain ring R = F-p(m) + uF(p)(m), where p is a prime and u(2) = 0. If lambda = alpha+u beta for nonzero elements alpha, beta of F-p(m), the ideal < u > is the unique self-dual (alpha +u beta)-constacyclic codes. If lambda = gamma for some nonzero element gamma of F-p(m) we consider two cases of gamma. When gamma = gamma(-1), i.e., gamma = 1 or -1, we first obtain the dual of every cyclic code, a formula for the number of those cyclic codes and identify all self-dual cyclic codes. Then we use the ring isomorphism phi to carry over the results about cyclic accordingly to negacyclic codes. When gamma not equal gamma(-1), it is shown that < u > is the unique self-dual gamma-constacyclic code. Among other results, the number of each type of self-dual constacyclic code is obtained. (C) 2017 Elsevier B.V. All rights reserved.