A matrix identity and perturbation expressions

Abstract

An identity expressing formally the diagonal and off-diagonal elements of an inverse of a matrix is deduced employing operator techniques. Several well-known perturbation expressions for the self-energy are deduced as special cases. A new approximation and other applications following from the above formalism are briefly indicated through illustrations from a perturbed harmonic oscillator, chemisorption approximations and Kelly's result in the problem of electron correlation.

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Notes on contributors

S.K. Rangarajan

SRC Visiting Professor (January to December 1977), Department of Physical Chemistry, The University of Newcastle upon Tyne, U.K.