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Proceedings of the 44th Symposium on Ring Theory and ...

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POLYCYCLIC CODES AND SEQUENTIAL CODES<br />

MANABU MATSUOKA<br />

Abstract. In this paper we generalize <str<strong>on</strong>g>the</str<strong>on</strong>g> noti<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> cyclicity <str<strong>on</strong>g>of</str<strong>on</strong>g> codes, that is, polycyclic<br />

codes <strong>and</strong> sequential codes. We study <str<strong>on</strong>g>the</str<strong>on</strong>g> relati<strong>on</strong> between polycyclic codes <strong>and</strong><br />

sequential codes over finite commutative QF rings. Fur<str<strong>on</strong>g>the</str<strong>on</strong>g>rmore, we characterized <str<strong>on</strong>g>the</str<strong>on</strong>g><br />

family <str<strong>on</strong>g>of</str<strong>on</strong>g> some c<strong>on</strong>stacyclic codes.<br />

Key Words:<br />

finite rings, (θ, δ)-codes, skew polynomial rings.<br />

2010 Ma<str<strong>on</strong>g>the</str<strong>on</strong>g>matics Subject Classificati<strong>on</strong>: Primary 94B60; Sec<strong>on</strong>dary 94B15.<br />

1. Introducti<strong>on</strong><br />

Let R be a finite commutative ring. A linear code C <str<strong>on</strong>g>of</str<strong>on</strong>g> length n over R is a submodule<br />

<str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> R-module R n = {(a 0 , · · · , a n−1 )|a i ∈ R}. If C is a free R-module, C is<br />

said to be a free code. A linear code C ⊆ R n is called cyclic if (a 0 , a 1 , · · · , a n−1 ) ∈ C<br />

implies (a n−1 , a 0 , a 1 , · · · , a n−2 ) ∈ C. The noti<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> cyclicity has been extended in various<br />

directi<strong>on</strong>s.<br />

In [6], S. R. López-Permouth, B. R. Parra-Avila <strong>and</strong> S. Szabo studied <str<strong>on</strong>g>the</str<strong>on</strong>g> duality<br />

between polycyclic codes <strong>and</strong> sequential codes. By <str<strong>on</strong>g>the</str<strong>on</strong>g> way, J. A. Wood establish <str<strong>on</strong>g>the</str<strong>on</strong>g> extensi<strong>on</strong><br />

<str<strong>on</strong>g>the</str<strong>on</strong>g>orem <strong>and</strong> MacWilliams identities over finite frobenius rings in [9]. M. Greferath<br />

<strong>and</strong> M. E. O’Sullivan study bounds for block codes <strong>on</strong> finite frobenius rings in [2]. In this<br />

paper, we generalize <str<strong>on</strong>g>the</str<strong>on</strong>g> result <str<strong>on</strong>g>of</str<strong>on</strong>g> [6] to codes with finite commutative QF rings.<br />

In secti<strong>on</strong> 2 we define polycyclic codes over finite commutative rings. And we study<br />

<str<strong>on</strong>g>the</str<strong>on</strong>g> properties <str<strong>on</strong>g>of</str<strong>on</strong>g> polycyclic codes. In secti<strong>on</strong> 3 we define sequential codes <strong>and</strong> c<strong>on</strong>sider<br />

<str<strong>on</strong>g>the</str<strong>on</strong>g> properties <str<strong>on</strong>g>of</str<strong>on</strong>g> sequential codes. In secti<strong>on</strong> 4 we study <str<strong>on</strong>g>the</str<strong>on</strong>g> relati<strong>on</strong> between polycyclic<br />

codes <strong>and</strong> sequential codes over finite commutative QF rings. And we characterized <str<strong>on</strong>g>the</str<strong>on</strong>g><br />

family <str<strong>on</strong>g>of</str<strong>on</strong>g> some c<strong>on</strong>stacyclic codes.<br />

Throughout this paper, R denotes a finite commutative ring with 1 ≠ 0, n denotes a<br />

natural number with n ≥ 2, unless o<str<strong>on</strong>g>the</str<strong>on</strong>g>rwise stated.<br />

2. Polycyclic codes<br />

A linear [n, k]-code over a finite commutative ring R is a submodule C ⊆ R n <str<strong>on</strong>g>of</str<strong>on</strong>g> rank<br />

k. We define polycyclic codes over a finite commutative ring.<br />

Definiti<strong>on</strong> 1. Let C be a linear code <str<strong>on</strong>g>of</str<strong>on</strong>g> length n over R. C is a polycyclic code induced by<br />

c if <str<strong>on</strong>g>the</str<strong>on</strong>g>re exists a vector c = (c 0 , c 1 , · · · , c n−1 ) ∈ R n such that for every (a 0 , a 1 , · · · , a n−1 ) ∈<br />

C, (0, a 0 , a 1 , · · · , a n−2 ) + a n−1 (c 0 , c 1 , · · · , c n−1 ) ∈ C. In this case we call c an associated<br />

vector <str<strong>on</strong>g>of</str<strong>on</strong>g> C.<br />

The detailed versi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> this paper will be submitted for publicati<strong>on</strong> elsewhere.<br />

–106–

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