Functions of self-adjoint operators in ideals of compact operators

For self-adjoint operators $A,B$, a bounded operator $J$, and a function $f:\mathbb{R}\to \mathbb{C}$ we obtain bounds in quasi-normed ideals of compact operators for the difference $f(A)J-Jf(B)$ in terms of the operator $AJ-JB$. The focus is on functions $f$ that are smooth everywhere except for finitely many points. A typical example is the function $f(t)=\mathrm{\mid }t{\mathrm{\mid }}^{\gamma }$ with $\gamma \in (0, 1)$. The obtained results are applied to derive a two-term quasi-classical asymptotic formula for the trace $trf(S)$ with $S$ being a Wiener-Hopf operator with a discontinuous symbol.