Improved bounds on coloring of graphs

  • Authors:
  • Sokol Ndreca;Aldo Procacci;Benedetto Scoppola

  • Affiliations:
  • Dep. Estatística-ICEx, UFMG, CP 702 Belo Horizonte - MG, 30161-970, Brazil;Dep. Matemática-ICEx, UFMG, CP 702 Belo Horizonte - MG, 30161-970, Brazil;Dipartimento di Matematica - Universita Tor Vergata di Roma, 00133 Roma, Italy

  • Venue:
  • European Journal of Combinatorics
  • Year:
  • 2012

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Abstract

Given a graph G with maximum degree @D=3, we prove that the acyclic edge chromatic number a^'(G) of G is such that a^'(G)@?@?9.62(@D-1)@?. Moreover we prove that: a^'(G)@?@?6.42(@D-1)@? if G has girth g=5; a^'(G)@?@?5.77(@D-1)@? if G has girth g=7; a^'(G)@?@?4.52(@D-1)@? if g=53; a^'(G)@?@D+2 if g=@?25.84@Dlog@D(1+4.1/log@D)@?. We further prove that the acyclic (vertex) chromatic number a(G) of G is such that a(G)@?@?6.59@D^4^/^3+3.3@D@?. We also prove that the star-chromatic number @g"s(G) of G is such that @g"s(G)@?@?4.34@D^3^/^2+1.5@D@?. We finally prove that the @b-frugal chromatic number @g^@b(G) of G is such that @g^@b(G)@?@?max{k"1(@b)@D,k"2(@b)@D^1^+^1^/^@b/(@b!)^1^/^@b}@?, where k"1(@b) and k"2(@b) are decreasing functions of @b such that k"1(@b)@?[4,6] and k"2(@b)@?[2,5]. To obtain these results we use an improved version of the Lovasz Local Lemma due to Bissacot et al. (2011) [6].