Multicyclic treelike reflexive graphs

Decomposition of Smith graphs in maximal reflexive cacti

The spectrum of a graph is the family of eigenvalues of its (0, 1) adjacency matrix.A simple graph is reflexive if its second largest eigenvalue 2 does not exceed 2. The graphic property 2 2 is a hereditary one, i.e. every induced subgraph of a reflexive graph preserves this property and that is why reflexive graphs are usually represented through maximal graphs. Cacti, or treelike graphs, are ...

Treelike Comparability Graphs: Characterization, Recognition, and Applications

An undirected graph is a treelike comparability graph if it admits a transitive orientation such that its transitive reduction is a tree. We show that treelike comparability graphs are distance hereditary. Utilizing this property, we give a linear time recognition algorithm. We then characterize permutation graphs that are treelike. Finally, we consider the Partitioning into Bounded Cliques pro...

Treelike Comparability Graphs

A comparability graph is a simple graph which admits a transitive orientation on its edges. Each one of such orientations defines a poset on the vertex set, and also it is said that this graph is the comparability graph of the poset. A treelike poset is a poset whose covering graph is a tree. Comparability graphs of arborescence posets are known as trivially perfect graphs. These have been char...

A Class of Reflexive Cactuses with Four Cycles

A simple graph is reflexive if its second largest eigenvalue λ2 is less than or equal to 2. A graph is a cactus, or a treelike graph, if any pair of its cycles (circuits) has at most one common vertex. For a lot of cactuses the property λ2 ≤ 2 can be tested by identifying and deleting a single cut-vetex (Theorem 1). if this theorem cannot be applied to a connected reflexive cactus and if all it...

Treelike and Chordal Graphs: Algorithms and Generalizations