Let T be a singular nonintegral operator; that is, it does not have an integral representation by a kernel with size estimates, even rough. In this paper, we consider the boundedness of commutators with T and Lipschitz functions. Applications include spectral multipliers of self-adjoint, positive operators, Riesz transforms of second-order divergence form operators, and fractional power of elli...

We prove a families version of the index theorem for operators generalizing those studied by C. Callias and later by N. Anghel, which are operators on a manifold with boundary having the form D + iΦ, where D is elliptic pseudodifferential with self-adjoint symbols, and Φ is a self-adjoint bundle endomorphism which is invertible at the boundary and commutes with the symbol of D there. The index ...

Given two self-adjoint, positive, compact operators A,B on a separable Hilbert space, we show that there exists a self-adjoint, positive, compact operator C commuting with B such that limt→∞ ||(e Bt 2 ee Bt 2 ) 1 t − e || = 0. 1

Two different self-adjoint Pauli extensions describing a spin-1/2 two-dimensional quantum system with singular magnetic field are studied. An Aharonov-Casher type formula is proved for the maximal Pauli extension and the possibility of approximation of the two different self-adjoint extensions by operators with regular magnetic fields is investigated.

In this work, we introduce sufficient and necessary conditions for a pair of fuzzy conjunctor and implication considered in a multi-adjoint frame under which the usual combinations of multi-adjoint sufficiency, possibility and necessity operators form either antitone or isotone Galois connections.

We discuss the problem of perturbation of spectral subspaces for linear self-adjoint operators on a separable Hilbert space. Let A and V be bounded self-adjoint operators. Assume that the spectrum of A consists of two disjoint parts σ and Σ such that d = dist(σ,Σ) > 0. We show that the norm of the difference of the spectral projections EA(σ) and EA+V ( {λ | dist(λ, σ) < d/2} ) for A and A+ V is...

The paper deals with semigroups of operators associated with delay diierential equation: _ x(t) = Ax(t) + L 1 x(t ? h) + L 2 xt; where A is the innnitesimal generator of an analytic semigroup on a Hilbert space X and L 1 , L 2 are densely deened closed operators in X and L 2 (?h; 0;X) respectively. The adjoint semigroupof the solution semigroupof the delay diierentialequation is characterized. ...