Excitation operators associated with antisymmetrized geminal-power states

Abstract
Various expressions for antisymmetrized geminal-power (AGP) states are reviewed. With the use of a simple relationship for creation and annihilation operators of BCS (Bardeen, Cooper, and Schrieffer)-type states, such operators are characterized for AGP and GAGP (generalized AGP) schemes. The effect of degeneracy in the first-order reduced density matrix on these operators is displayed.