title: Effective projection theory in a correlated electron system.
abstract: We propose an efficient method for nonperturbative calculation of Green's function in a correlated electron system. The key idea of the method is to project out irrelevant operators having zero norm in the ground state, which we refer to as effective projection theory. We apply the method to a mesoscopic Anderson model and show that for a given wavefunction ansatz, equations of motion can be closed only by relevant operators, allowing easy calculation of the zero-temperature Green's function. It turns out that the resulting Green's functions reproduce exact limits of both weak and strong interactions. The accuracy is also verified for small systems by comparison with exact diagonalization results, revealing that effective projection theory captures the essential correlated features in the entire regime of interactions.
authors.affiliation: Department of Physics, Pusan National University, Busan, Korea.
authors.forename: Juyeon
authors.initials: J
authors.lastname: Yi
authors.forename: Seongjin
authors.initials: S
authors.lastname: Kim
authors.forename: Jaegon
authors.initials: J
authors.lastname: Um
authors.forename: Sun-Yong
authors.initials: SY
authors.lastname: Hwang
authors.forename: Ara
authors.initials: A
authors.lastname: Go
authors.forename: Gun Sang
authors.initials: GS
authors.lastname: Jeon