Title:
Wild ramification and the characteristic cycle
of an l-adic sheaf


Abstract: The wild ramification of an l-adic sheaf
is measured by using blowing-ups at the ramification
divisor in the diagonal of the self-product. Using this
construction, one defines the characteristic cycles
as a cycle in the log cotangent bundle, under some assumption.
We discuss also on the analogy between the wild ramification
and irregular singularities.