Ferromagnetism from undressing

We have recently proposed that superconductivity may be understood as drive n by the undressing of quasiparticles as the superconducting state develops . Similarly we propose here that ferromagnetism in metals may be understood as driven by the undressing of quasiparticles as the ferromagnetic state d evelops. In ferromagnets, the undressing is proposed to occur due to the re duction in bond charge caused by spin polarization, in contrast to supercon ductors where the undressing is proposed to occur due to the reduction in s ite charge caused by (hole) pairing. The undressing process manifests itsel f in the one and two-particle Green's functions as a transfer of spectral w eight from high to low frequencies. Hence it should have universal observab le consequences in one- and two-particle spectroscopies such as photoemissi on and optical absorption.