A complete two loop renormalization group calculation of the multicritical
dynamics at a tetracritical or bicritical point in anisotropic antiferromagnets
in an external magnetic field is performed. Although strong scaling for the two
order parameters (OPs) perpendicular and parallel to the field is restored as
found earlier, in the experimentally accessible region the effective dynamical
exponents for the relaxation of the OPs remain different since their equal
asymptotic values are not reached.Comment: 6 pages, 2 figures; some additions, corrected typo
