  While multifractal spectra are convex, general field theoretic arguments show
that power of field operators $\phi^f$ yield a concave spectrum of exponents as
function of $f$. This is resolved by appropriate choice of operators to
describe multifractal moments. In a Lagrangian field theory of two mutually
interacting species of fields $\phi,\psi$, operators $O_{f'f}=\psi^{f'}\phi^f$
with traceless symmetry give rise to multifractal spectra of harmonic diffusion
near absorbing fractals when evaluated for zero component fields.
