Title: Trivial Constraints on Orbital-free Kinetic Energy Density Functionals,
Abstract: Kinetic energy density functionals (KEDFs) are central to orbital-free
density functional theory. Limitations on the spatial derivative dependencies
of KEDFs have been claimed from differential virial theorems. We point out a
central defect in the argument: the relationships are not true for an arbitrary
density but hold only for the minimizing density and corresponding chemical
potential. Contrary to the claims therefore, the relationships are not
constraints and provide no independent information about the spatial derivative
dependencies of approximate KEDFs. A simple argument also shows that validity
for arbitrary $v$-representable densities is not restored by appeal to the
density-potential bijection.