An improved lower bound for (1,≤2)-identifying codes in the king grid
: Foucaud F, Laihonen T, Parreau A
Publisher: AMER INST MATHEMATICAL SCIENCES
: 2014
: Advances in Mathematics of Communications
: ADVANCES IN MATHEMATICS OF COMMUNICATIONS
: ADV MATH COMMUN
: 8
: 1
: 35
: 52
: 18
: 1930-5346
DOI: https://doi.org/10.3934/amc.2014.8.35
We call a subset C of vertices of a graph G a (1, <= l)-identifying code if for all subset X of vertices with size at most l, the sets {c is an element of C vertical bar there exists u is an element of X, d(u, c) <= 1} are distinct. The concept of identifying codes was in in 1998 by Karpovsky, Chakrabarty and Levitin. Identifying codes have been studied in various grids. In particular, it has been shown that, there exists a (1, <= 2)-identifying code in the king grid with density (3)(7) and that there are no such identifying codes with density smaller than 5/12. Using a suitable frame and a discharging procedure, we improve the lower bound by showing that any (1, <= 2)-identifying code of the king grid has density at least 47/111. This reduces the gap between the best known lower and upper bounds on this problem by more than 56%.