Fumio Hiroshima and Herbert Spohn
Ground state degeneracy of the Pauli-Fierz Hamiltonian including spin
(38K, Latex)

ABSTRACT.  We consider an electron, spin $\han$, minimally coupled to the 
quantized radiation field in the nonrelativistic approximation, a 
situation defined by the Pauli-Fierz Hamiltonian $H$. 
There is no external potential and $H$ fibers as $\int^\oplus \hp 
dp$ according to 
the total momentum $p$. 
We prove that the ground state subspace of $\hp$ is two-fold 
degenerate provided the charge $e$ and the total momentum $p$ are 
sufficiently small. 
We also establish that the total angular momentum of the ground state 
subspace is $\pm\han$ and study the case of a confining external 
potential.