Negacyclic codes of length 2ps over Fpm+uFpm

For any odd prime p, the structures of all negacyclic codes of length 2ps over the finite commutative chain ring Fpm+uFpm are established in term of their polynomial generators. When pm≡1(mod4), each negacyclic code of length 2ps is represented as a direct sum of a −α-constacyclic code and an α-constacyclic code of length ps. In the case pm≡3(mod4), such negacyclic codes are classified into 4 distinct types of ideals, and the detailed structures of ideals in each type are provided. Among other results, the number of codewords, and the dual of each negacyclic code are obtained.