CONSTACYCLIC AND QUASI-TWISTED CODES OVER Zq[u]/(u2-1) AND NEW Z4-LINEAR CODES

In this paper, we investigate the algebraic structures and properties of constacyclic and quasi-twisted (QT) codes over the ring R = Zq + uZq with u2 = 1. We show that the image of a constacyclic code over R under a natural Gray map is a QT code of index 2 over Zq. Given the decomposition of a QT code, we find the decomposition of its dual code. We present 116 new linear codes over Z4 from the Gray images of QT codes over this ring with q = 4. Finally, a characterization of linear complementary pair (LCP) constacyclic codes over R is provided.