Français Anglais
Accueil Annuaire Plan du site
Accueil > Evenements > Séminaires
Séminaire d'équipe(s)
Homomorphism and minor of signed bipartite graphs
Reza Naserasr

12 April 2013, 10h30 - 12 April 2013, 11h30
Salle/Bat : 475/PCRI-N
Contact :

Activités de recherche :

Résumé :
A signature on a graph is an assignment of signs (+ or -) to the edges. Resigning at a vertex $x$ is to change the signs of all the edges incident $x$. Let $Sigma$ be the set of negative edges. Two signatures $Sigma_1$ and $Sigma_2$ on a same graph are said to be equivalent if one can be obtained from the other by a sequence of resigning. A signed graph, denoted $(G, Sigma)$ is a graph together with a set of equivalent signatures.

A singed minor of $(G,Sigma)$ is a signed graph obtained from $(G,Sigma)$ by a sequence of (i) deleting edges or vertices, (ii) contracting positive edges and (iii) resigning. A homomorphism of $(G, Sigma)$ to $(H, Sigma_1)$ is homomorphism of $G$ to $H$ which preserves signs of edges with respect to some signatures $Sigma'$ and $Sigma_1'$ equivalent to $Sigma$ and $Sigma_1$ respectively.

In this talk we show that homomorphism of signed bipartite graphs captures the notion of graph homomorphisms. Thus many coloring theories on graphs can be extend to this set of signed graphs. In particular we consider possible extensions of Hadwiger's conjecture. We also show some results on the complexity of homomorphism problem for this set of signed graphs.

Pour en savoir plus : https://www.lri.fr/~reza/
Séminaires
A Two-level Auction for Resource Allocation in Mul
Réseaux sans fil et mobiles
Friday 09 March 2018 - 14h30
Salle : 445 - PCRI-N
Mira Morcos .............................................

Binary pattern of length greater than 14 are abeli
Combinatoire
Friday 09 February 2018 - 14h30
Salle : 445 - PCRI-N
Matthieu Rosenfeld .............................................

Approximate Bayesian Computation and Random Forest
Thursday 08 February 2018 - 00h00
Salle : 455 - PCRI-N
Valentin Thouzeau .............................................

A concurrent lock-free algorithm for computing a f
Combinatoire
Friday 12 January 2018 - 14h30
Salle : 445 - PCRI-N
James Mitchell .............................................

Acyclic Partitioning of Large Directed Acyclic Gra
Calcul à haute performance
Tuesday 09 January 2018 - 10h30
Salle : 465 - PCRI-N
Julien Herrmann .............................................