The equation for the charge vertex γ of the t−J model is derived and
solved in leading order of an 1/N expansion, working directly in terms of
Hubbard operators. Various quantities which depend crucially on γ are
then calculated, such as the life time and the transport life time of electrons
due to a charge coupling to other degrees of freedom and the charge-charge
correlation function. Our results show that the static screening of charges and
the dynamics of charge fluctuations depend only weakly on J and are mainly
determined by the constraint of having no double occupancies of sites.Comment: 10 latex pages, 4 figures as post-script file