New lower bound for 2-identifying code in the square grid

  • Authors:
  • Ville Junnila

  • Affiliations:
  • -

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2013

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Abstract

An r-identifying code in a graph G=(V,E) is a subset C@?V such that for each u@?V the intersection of C and the ball of radius r centered at u is nonempty and unique. Previously, r-identifying codes have been studied in various grids. In particular, it has been shown that there exists a 2-identifying code in the square grid with density 5/29~0.172 and that there are no 2-identifying codes with density smaller than 3/20=0.15. Recently, the lower bound has been improved to 6/37~0.162 by Martin and Stanton (2010) [11]. In this paper, we further improve the lower bound by showing that there are no 2-identifying codes in the square grid with density smaller than 6/35~0.171.