V. Bach, J. Froehlich, A. Pizzo
Infrared-Finite Algorithms in QED II. The Expansion of the Groundstate of An Atom Interacting with the Quantized Radiation Field
(646K, postscript)
ABSTRACT. In this paper, we present an explicit and constructive algorithm enabling us to calculate the groundstate and the groundstate energy of a nonrelativistic atom minimally coupled to the quantized radiation field up to an error of arbitrary finite order in the feinstructure constant. Because of infrared divergences, which invalidate a straightforward Taylor expansion, an iterative construction is employed to remove the infrared cutoff in photon momentum space and to produce a convergent algorithm.