The 2-distance coloring of the Cartesian product of cycles using optimal Lee codes

  • Authors:
  • Jon-Lark Kim;Seog-Jin Kim

  • Affiliations:
  • Department of Mathematics, University of Louisville, Louisville, KY 40292, USA;Department of Mathematics Education, Konkuk University, Seoul 143-701, Republic of Korea

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2011

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Abstract

Let C"m be the cycle of length m. We denote the Cartesian product of n copies of C"m by G(n,m):=C"m@?C"m@?...@?C"m. The k-distance chromatic number @g"k(G) of a graph G is @g(G^k) where G^k is the kth power of the graph G=(V,E) in which two distinct vertices are adjacent in G^k if and only if their distance in G is at most k. The k-distance chromatic number of G(n,m) is related to optimal codes over the ring of integers modulo m with minimum Lee distance k+1. In this paper, we consider @g"2(G(n,m)) for n=3 and m=3. In particular, we compute exact values of @g"2(G(3,m)) for 3@?m@?8 and m=4k, and upper bounds for m=3k or m=5k, for any positive integer k. We also show that the maximal size of a code in Z"6^3 with minimum Lee distance 3 is 26.