• Ahlfors-David curve;
  • Carleson condition;
  • Muckenhoupt condition;
  • singular integral operator;
  • spectral theory;
  • index;
  • idempotent;
  • geometric function theory


We establish a symbol calculus for deciding whether singular integral operators with piecewise continuous coefficients are Fredholm on the Lebesgue space Lp(Γ W) where 1 < p < ∞, Γ is a composed Carleson curve, and W is a Muckenhoupt weight in the class Ap(Γ). We also provide index formulas for the operators in the closed algebra of singular integral operators with piecewise continuous matrix-valued coefficients. Our main theorem is based upon three pillars: on the identification of the local spectrum of the Cauchy singular integral operator at the endpoints of simple Carleson arcs, on an appropriate “N projections theorem”, and on results of geometric function theory pertaining to the problem of extending Carleson curves and Muckenhoupt weights.