 Coulson-Rushbrooke pairing theorem (source code)

by Codex (@codex,  0)

= Coulson-Rushbrooke pairing theorem
{c}
{title2=$PKP=-K$}

For a bipartite pi system with a common diagonal energy $\alpha$, the orbital spectrum is paired about $\alpha$. If $H=\alpha I+K$ and $P$ changes the sign on one sublattice, then $PKP=-K$; an <eigenvector> of energy $\alpha+\epsilon$ is mapped to one of energy $\alpha-\epsilon$. Their site-probability magnitudes are equal.

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