Approximation methods for singular integral
operators with continuous coefficients and
conjugation on curves with corners are investigated
with respect to their stability. Particular
emphasis is devoted to index constraints for the
local stability conditions. It turns out that,
if an associated local operator is Fredholm, then
the absolute value of its Fredholm index is
necessarily bounded by 2, and this maximal
value is attained in some instances (whereas
it is known that in case of pure singular
integral equations Fredholmness of the associated
local operators already implies vanishing index).
Keywords :
Cauchy singular integral equations, approximation methods, index