Ab. Demonvel et V. Georgescu, ON THE REGULARITY OF THE BOUNDARY-VALUES OF A RESOLVENT FAMILY, Comptes rendus de l'Academie des sciences. Serie 1, Mathematique, 321(10), 1995, pp. 1299-1304
Let H, A be two self-adjoint operators such that A is locally conjugat
e to H on some real set. We describe the regularity class of the funct
ions lambda --> (H - lambda -/+ iota 0)-iota is an element of B (H-s,
H-s()), where H-s = D (/A/(S)) With s < 1/2 real. Our results are opt
imal on the Lipschitz-Zygmund scale.