  We compute the dynamical charge susceptibility in the two-dimensional Hubbard
model within the dynamical cluster approximation. In order to understand the
connection between charge susceptibility and pseudogap, we investigate the
momentum, doping, and temperature dependence. We find that as a function of
frequency, the dynamical charge susceptibility is well represented by a single
peak at a characteristic frequency. It shows little momentum or temperature
dependence, while the doping dependence is more evident, and no clear signature
of the pseudogap is observed. Data for the doping evolution of the static
susceptibility and for fluctuation diagnostics are presented. Our
susceptibilities should be directly measurable in future Momentum-resolved
electron energy-loss spectroscopy experiments.
