Sign-problem free quantum Monte-Carlo simulations on itinerant ferromagnetism in multi-orbital band systems

In a recent paper by Li, Lieb and Wu, it has been proved recently that certain multiorbital Hubbard models exhibit ferromagnetic ground states in strong coupling limit at zero temperature and any generic fillings. In a suitably defined basis, it can be proved that the sign problem of quantum Monte-Carlo simulations is absent. Quantum Monte Carlo simulations are performed to investigate the nature of itinerant ferromagnetism in such systems.