Regularity of solutions for degenerate/singular fully nonlinear integro-differential equation

We study a series of regularity results for solutions of a degenerate/singular fully nonlinear integro-differential equation - (₁ (|Du|) + a (x) ₂ (|Du|) ) I_ (u, x) = f (x). In the degenerate case, we establish borderline regularity provided the inverse of degeneracy law is Dini-continuous. In addition, we show Schauder-type higher regularity at local extrema point for a concrete non-local degenerate equation. In the singular case, we prove gradient H\"older regularity of solutions to general non-local equation. It is noteworthy that these results are new even for the case a (x) 0. Finally, as a byproduct of the borderline regularity, we show how to apply our strategies in the study of the corresponding regularity for a class of degenerate non-local normalized p-Laplacian equation.