Some Constacyclic Codes over Z(4)[u]/< u(2)>, New Gray Maps, and New Quaternary Codes

Abstract

this paper, we study lambda-constacyclic codes over the ring R = Z(4) + uZ(4), where u(2) = 0, for lambda = 1 + 3u and 3 + u. We introduce two new Gray maps from R to Z(4)(4) and show that the Gray images of lambda-constacyclic codes over R are quasi-cyclic over Z(4). Moreover, we present many examples of lambda-constacyclic codes over R whose Z(4)-images have better parameters than the currently best-known linear codes over Z(4).