  We investigate statistical properties of vorticity fluctuations in fully
developed turbulence, which are known to exhibit a strong intermittent
behavior. Taking as the starting point the Navier-Stokes equations with a
random force term correlated at large scales, we obtain in the high Reynolds
number regime a closed analytical expression for the probability distribution
function of an arbitrary component of the vorticity field. The central idea
underlying the analysis consists in the phase-space restriction to a particular
sector where the rate of strain and the rotation tensors can be locally
regarded as slow and fast degrees of freedom, respectively. This prescription
is implemented along the Martin-Siggia-Rose functional framework, whereby
instantons and perturbations around them are taken into account within a
steepest-descent approach.
