
arXiv: 1609.04477
We give an $O(n)$ time and space algorithm for constructing a diagonal matrix congruent to A+xI, where A is the adjacency matrix of a cograph and $x\in \mathbb{R}$. Applications include determining the number of eigenvalues of a cograph's adjacency matrix that lie in any interval, obtaining a formula for the inertia of a cograph, and exhibiting infinitely many pairs of equienergetic cographs with integer energy.
adjacency matrix, Graphs and linear algebra (matrices, eigenvalues, etc.), FOS: Mathematics, eigenvalue, Mathematics - Combinatorics, 05C50, 05C85, 15A18, Combinatorics (math.CO), cograph
adjacency matrix, Graphs and linear algebra (matrices, eigenvalues, etc.), FOS: Mathematics, eigenvalue, Mathematics - Combinatorics, 05C50, 05C85, 15A18, Combinatorics (math.CO), cograph
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