Fumio Hiroshima, Herbert Spohn
Enhanced binding through coupling to a quantum field
(134K, .dvi)

ABSTRACT.  We consider an electron coupled to the quantized 
radiation field in the dipole approximation. 
Even if the Hamiltonian has no ground state at zero coupling, 
$\alpha=0$, the interaction with the quantized radiation field may induce 
binding. Under suitable assumptions on the external potential, 
we prove that 
there exists a critical constant 
$\alpha_c\geq0$ such that the Hamiltonian 
has a unique ground state for {\it arbitrary} $|\alpha|>\alpha_c$.