| Abstract: | The amplitude (Higgs) mode is a collective excitation that describes the fluctuations of the order parameter in condensed matter systems with broken continuous symmetry. I will show that the amplitude mode survives as a well defined resonance arbitrarily close to the critical point in two space dimensions. I will present a numerical calculation of the universal scaling function of the dynamical scalar susceptibly and of the optical conductivity by means of a large scale quantum Monte Carlo simulation combined with numerical analytic continuation. The results are relevant for recent experiments in cold atoms in an optical lattice near the superfluid to Mott insulator transition. |
