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...

It is shown that the identity component of the group of all homeo-morphisms of a manifold with boundary is perfect, i.e. equal to its commutator subgroup. Diierences between homeomorphism and diieomorphism groups are exhibited.

Various questions on Lie ideals of C∗-algebras are investigated. They fall roughly under the following topics: relation of Lie ideals to closed two-sided ideals; Lie ideals spanned by special classes of elements such as commutators, nilpotents, and the range of polynomials; characterization of Lie ideals as similarity invariant subspaces.

Not much has been known about these spaces except for some special cases. It was known since 1953 that every operator A ∈ B(H) is the sum of two commutators of bounded linear operators [35], [16] while the commutator spaces of Schatten ideals Lp , p > 0, were the subject of several studies over the last 30 years, notably [49], [66], [3], [68], [67], [4], [38] and [18]. Aside from these efforts,...

We show how an induced invariance of the massless particle action can be used to construct an extension of the Heisenberg canonical commuta-tion relations in a non-commutative space-time.

Let P be the orthogonal projection from L(B, dv) onto the Bergman space La(B, dv) of the unit ball in C . In this paper we characterize the membership of commutators of the form [Mf , P ] in the norm ideal CΦ, where the symmetric gauge function Φ is allowed to be arbitrary.

Using the Freese-McKenzie commutator theory for congruence modular varieties as the starting point, we develop commutator theory for the variety of loops. The fundamental theorem of congruence commutators for loops relates generators of the congruence commutator to generators of the total inner mapping group. We specialize the fundamental theorem into several varieties of loops, and also discus...

In a free group no nontrivial commutator is a square. And in the free group F2 = F (x1, x2) freely generated by x1, x2 the commutator [x1, x2], is never the product of two squares in F2, although it is always the product of three squares. Let F2,3 = 〈x1, x2〉 be a free nilpotent group of rank 2 and class 3 freely generated by x1, x2. We prove that in F2,3 = 〈x1, x2〉, it is possible to write cert...

For countably generated ideals, J , of B(H), geometric stability is necessary for the canonical spectral characterization of sums of (J ; B(H)){commutators to hold. This answers a question raised by Dykema, Figiel, Weiss and Wodzicki. There are some ideals, J , having quasi{nilpotent elements that are not sums of (J ; B(H)){commutators. Also, every trace on every geometrically stable ideal is a...