Additive cyclic codes over Galois rings were investigated in previous works. In this paper, we investigate the same problem but over a more general ring family, finite commutative chain rings. When we focus on non-Galois finite commutative chain rings, we observe two different kinds of additivity. One of them is a natural generalization of the previous studies, whereas the other one has some unusual properties especially while constructing dual codes. We interpret the reasons of such properties and illustrate our results giving concrete examples.
@cite_9: Bierbrauer (2012) developed the theory of q-linear cyclic codes over (Fq)m and he obtained a parametric description of such codes by cyclotomic cosets. Recently, (2015) obtained the structure of cyclic additive codes over the Galois ring GR(p,m), where m is a prime integer. Let R be a finite commutative ring and Rn=R[x]xn1. In this paper, we generalize the theory of Fq-linear codes over vector spaces to R-linear codes over free R-algebras (free as R-module). We call these codes, R-additive codes. We introduce a one-to-one correspondence between the classes of cyclic R-additive code and the classes of Rn-linear code. Using the structure of Rn-linear codes, we present the structure of cyclic R-additive codes, where R is a chain ring. Among other results, q-linear cyclic codes over (Fq)m are described by ring-theoretic facts, and the structure of cyclic additive codes over the Galois ring GR(p,m) is given for an arbitrary integer m, not necessarily a prime number.
@cite_4: Let R = GR ( p ? , l ) be a Galois ring of characteristic p ? and cardinality p ? l , where p and l are prime integers. First, we give a canonical form decomposition for additive cyclic codes over R . This decomposition is used to construct additive cyclic codes and count the number of such codes, respectively. Then we give the trace dual code for each additive cyclic code over R from its canonical form decomposition and linear codes of length l over some extension Galois rings of Z p ? .
Notice that the idea in @cite_4 has been generalized recently also in @cite_9 . However, the generalization in @cite_9 is from Galois rings to free @math -algebras, where @math is a finite commutative chain ring. Recall that we consider also non-free algebras (a finite commutative chain ring does not have to be a free module over a subring of it). On the other hand, our paper does not cover @cite_9 since every free @math -algebra does not have to be a chain ring.