  For Kraichnan's problem of passive scalar advection by a velocity field
delta-correlated in time, the limit of large space dimensionality $d\gg1$ is
considered. Scaling exponents of the scalar field are analytically found to be
$\zeta_{2n}=n\zeta_2-2(2-\zeta_2)n(n-1)/d$, while those of the dissipation
field are $\mu_{n}=-2(2-\zeta_2)n(n-1)/d$ for orders $n\ll d$. The refined
similarity hypothesis $\zeta_{2n}=n\zeta_2+\mu_{n}$ is thus established by a
straightforward calculation for the case considered.
