Tarjan described a procedure for decomposing a graph using clique separators in "Decomposition by clique separators", RE Tarjan - Discrete mathematics, 1985 - Elsevier.

He also proposed different divide-and-conquer algorithms for various graph problems such as maximum clique, minimum coloring and maximum independent set. An atom is a subgraph of a graph that does not contain a separator. If one can solve the problem efficiently in the atoms (local solutions) then Tarjan describes in the same paper how to extend these local solutions to a global solution. Therefore characterization of the atoms is very important. For example an atom of a chordal graph is a clique and the atoms of an edge intersection graphs of paths in a tree are exactly line graphs of a multigraph.

I am wondering the characterization of atoms for other graph classes like for example disk graphs or AT-free graphs.


1 Answer 1


Chvátal and Sbihi (Recognizing Claw-free Perfect Graphs, JCTB 44) described the atoms for the class of claw-free perfect graphs, a.k.a. quasi-line perfect graphs. This description was later refined by Maffray and Reed, and essentially consists of two classes: "peculiar", which are kind of a special case, and "elementary", which are constructed by modifying the line graph of a bipartite multigraph through an operation called augmentation.

  • $\begingroup$ I am sure that I will find some more results by looking the publications of the same authors. Thank you. $\endgroup$
    – Arman
    Jul 8, 2012 at 18:23
  • 2
    $\begingroup$ I should mention that there is another class of graphs, clique-separable graphs, whose atoms are the complete multipartite graphs and cliques joined to bipartite graphs. $\endgroup$ Jul 9, 2012 at 4:53

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