Progress of Non-Equilibrium Green's Functions 9 (PNGF9)

Gauge invariant derivation of the matter–only Hamiltonian

27 Aug 2026, 11:00

35m

Auditorium (Paul Scherrer Institut)

Invited Talk

Speaker

Andrea Marini (CNR-ISM)

Description

Enrico Fermi in 1932, used classical Gauss equation to derive the Coloumb density–density interaction from the longitudinal electro–magnetic potential, in a gauge–invariant way. In this work we extend the Fermi procedure to the transverse component of the vector potential. By using a fully quantistic canonical transformation we replace the transverse vector potential with a current– current and current–current–density interactions. The transformed Hamiltonian is, then, projected in the fermionic space providing a matter–only gauge respecting Hamiltonian. We discuss how this Hamiltonian provides the quantistic origin of the longitudinal–transverse splitting observed in phonons and other elemental excitations.