The Kondo screening cloud: what can we learn from perturbation theory?

We analyse the role which the distance scale $\xi_K = v_F/T_K$ plays in the single-impurity Kondo problem using renormalization group improved perturbation theory. We derive the scaling functions for the local spin susceptibility in various limiting cases. In particular, we demonstrate exactly that the non-oscillating part of it should be short-range, i.e., vanish for distances $r \gg 1/k_F$ and propose a scaling form with factorized $r$ and $T$ dependence.