A priori estimates for nonvariational operators modeled on Hörmander's vector fields with drift

Abstract

For a nonvariational operator structured on H o rmander's vector fields with drift, where the matrix of coffiecients is real, symmetric and uniformly positive, we prove local a priori estimates on the second order derivatives with respect to the vector fields, in H o lder spaces if the coecients are Holder continuous, in Lp spaces if the coefficients are bounded, measurable and locally VMO.