Title: A mechanism for pair formation in strongly correlated systems
Abstract: We start from a Hamiltonian describing non-interacting electrons and add bosons to the model, with a Jaynes-Cummings-like interaction between the bosons and electrons. Because of the specific form of the interaction the model can be solved exactly. In the ground state, part of the electrons form bound pairs with opposite momentum and spin. The model also shows a gap in the kinetic energy of the electrons, but not in the spectrum of the full Hamiltonian. This gap is not of a mean-field nature, but is due to the Pauli exclusion principle.