Université de Fribourg

On star and biclique edge-colorings

Dantas, Simone ; Groshaus, Marina ; Guedes , André ; C.S. Machado, Raphael ; Ries, Bernard ; Sasaki, Diana

In: International Transactions in Operational Research, 2017, vol. 24, p. 339-346

A biclique of G is a maximal set of vertices that induces a complete bipartite subgraph Kp,q of G with at least one edge, and a star of a graph G is a maximal set of vertices that induces a complete bipartite graph K1,q. A biclique (resp. star) edge-coloring is a coloring of the edges of a graph with no monochromatic bicliques (resp. stars). We prove that the problem of determining whether a...

Université de Fribourg

On the ratio between maximum weight perfect matchings and maximum weight matchings in grids

Fonseca, Guilherme D. da ; Ries, Bernard ; Sasaki, Diana

In: Discrete Applied Mathematics, 2016, vol. 207, p. 45–55

Given a graph G that admits a perfect matching, we investigate the parameter η(G) (originally motivated by computer graphics applications) which is defined as follows. Among all nonnegative edge weight assignments, η(G) is the minimum ratio between (i) the maximum weight of a perfect matching and (ii) the maximum weight of a general matching. In this paper, we determine the exact value of η...