ANOMALOUS FIXED-POINT BEHAVIOR OF 2 KONDO IMPURITIES - A REEXAMINATION

We consider the existence of ''anomalous fixed point behavior'' for the Kondo two-impurity Hamiltonian. This ''anomalous'' behavior is predicted by calculations which use the ''energy-independent coupling constants'' (ECC) approximation. Using well-controlled quantum Monte Carlo methods without the ECC approximation, we find no evidence for ''anomalous'' behavior. We then show that the ECC approximation is, in general, either inconsistent or uninteresting. These results together strongly suggest that the predicted ''anomalous'' behavior of two Kondo impurities is simply the result of an unphysical approximation rather than an intrinsic property of the model itself.