Analyticity of the self-energy in total momentum of an atom coupled to the quantized radiation field

We study a neutral atom with a non-vanishing electric dipole moment coupled to the quantized electromagnetic field. For a sufficiently small dipole moment and small momentum, p→, the one-particle (self-)energy of an atom is proven to be a real-analytic function of its momentum. The main ingredient of our proof is a suitable form of the Feshbach–Schur spectral renormalization group.