Clique conflict graph 2026-10-06
The clique conflict graph has one vertex for each -clique of a fixed graph, and joins two when they share an edge. Its independent sets correspond exactly to edge-disjoint clique packings. The Caro-Wei bound converts clique-count and overlap estimates into a packing lower bound.
Graphs in admit a partition into total classes, of which are designated cliques and are designated independent sets. Cross edges are arbitrary and empty classes are allowed. Balanced cross-edge choices give quadratic labelled speed coefficient . Comparing this count with every -class type shows that the hereditary colouring number of this class is exactly .
Clique number 2026-10-06
The maximum number of vertices in a clique of a graph. If the graph contains and no , its clique number is exactly , since every larger clique contains a -clique.
Choose a fixed sample size for which the normalized Turan theorem bound lies below the given density by a positive margin. The expected edge count in a random -vertex subset then forces a positive proportion of subsets to contain a forbidden-size clique. Each clique belongs to a known number of subsets, so double counting gives a positive constant times cliques.
An edge-disjoint clique packing is a collection of -cliques no two of which share an edge; they may share vertices. Its maximum cardinality changes by at most one when a single edge is toggled. Removing that edge destroys at most one packed clique, which makes this variable suitable for an edge-exposure martingale.
For fixed positive integers and sufficiently large , the unique extremal graph forbidding vertex-disjoint copies of the complete graph is the join of graphs , up to isomorphic graphs. Each forbidden clique would require a distinct vertex of .
For fixed forbidden induced patterns, a regularity and Ramsey refinement uses internal clique/independent types and sparse, almost-complete, or intermediate cross pairs. A clique of intermediate pairs realizes every bounded induced pattern consistent with those internal types, using both edge and nonedge regularity. This is the induced embedding consequence used in hereditary graph enumeration theorem; the exceptional-pair budget can be arbitrarily small.
For the number of -cliques in a binomial random graph , with and ,
Two -sets overlapping in vertices share edges. Overlaps of zero or one vertex give independent indicators; includes the diagonal terms. The identity is useful for the second moment method.