On some constacyclic codes over Z4[u]/⟨u2−1⟩Z4[u]/⟨u2−1⟩, their Z4Z4 images, and new codes
In this paper, we study λ-constacyclic codes over the ring R = Z4 + uZ4 where u2 = 1, for λ = 3+2u and 2+3u. Two new Gray maps from R to Z3 4 are defined with the goal of obtaining new linear codes over Z4. The Gray images of λ-constacyclic codes over R are determined. We then conducted a computer search and obtained many λ-constacyclic codes over R whose Z4-images have better parameters than currently best-known linear codes over Z4.
Designs, Codes and Cryptography