Problèmes d'identification dans les graphes

Abstract : In this thesis, we study problems on vertices identification of graphs. To identify the vertices of a graph consists in giving to each vertex of the graph an object that makes it unique. We are specially interested in the problem of identifying codes : dominating sets of vertices for which the closed neighborhood of each vertex has a unique intersection with the set. The vertices of the identifying code can be seen as sensors and each vertex of the graph as the location of a potential fault. We first classify all finite graphs for which all but one of the vertices are needed in any identifying code. Finding an optimal identifying code, i.e, an identifying code of minimum size, is a $NP$-hard problem. Therefore, we study this problem in some restricted classes of graphes. Depending on the class considered, we are able to solve this problem (for Sierpi`nski graphs), to give better bounds on the size of an identifying code than the general one (for interval graphs, line graphs and the king grid) or to prove that the problem remains NP-hard even in the restricted class (for line graphs). Then, we consider some variations of identifing codes that give flexibility to the sensors. For example, we study codes sensors able to detect faults within a radius around a fixed value. We give constructions of such codes and bounds on their size for general and asymptotic values of the radius and the tolerance on it. Finally, we introduce identifying colourings of graphs; verex-colouring of graph such that each vertex is identified by the set of colours in its closed neighbourhood. We compare this colouring of graphs with proper vertex-coloring and give bounds on the number of colours required to identify a graph, for several class of graphs.
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Aline Parreau. Problèmes d'identification dans les graphes. Mathématiques générales [math.GM]. Université de Grenoble, 2012. Français. ⟨NNT : 2012GRENM028⟩. ⟨tel-00745054⟩

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