Decomposition of smooth functions of two multidimensional variables
Decomposition of unbounded derivations into invariant and approximately inner parts.
Decompositions and asymptotic limit for bicontractions
The asymptotic limit of a bicontraction T (that is, a pair of commuting contractions) on a Hilbert space is used to describe a Nagy-Foiaş-Langer type decomposition of T. This decomposition is refined in the case when the asymptotic limit of T is an orthogonal projection. The case of a bicontraction T consisting of hyponormal (even quasinormal) contractions is also considered, where we have .
Decompositions for real Banach spaces with small spaces of operators
We consider real Banach spaces X for which the quotient algebra (X)/ℐn(X) is finite-dimensional, where ℐn(X) stands for the ideal of inessential operators on X. We show that these spaces admit a decomposition as a finite direct sum of indecomposable subspaces for which is isomorphic as a real algebra to either the real numbers ℝ, the complex numbers ℂ, or the quaternion numbers ℍ. Moreover, the set of subspaces can be divided into subsets in such a way that if and are in different subsets,...
Decompositions of Beurling type for E₀-semigroups
We define tensor product decompositions of E₀-semigroups with a structure analogous to a classical theorem of Beurling. Such decompositions can be characterized by adaptedness and exactness of unitary cocycles. For CCR-flows we show that such cocycles are convergent.
Decompositions of operator-valued functions in Hilbert spaces
Decompositions of tensor products of contractions
Deficiency Indices of Singular Schrödinger Operators.
Definition Theory and Systems of Simultaneous Equations in the Perdual of an Operator Algebra. II.
Definitizing polynomials of unitary and Hermitian operators in Pontrjagin spaces.
Deformation quantization and Borel's theorem in locally convex spaces
It is well known that one can often construct a star-product by expanding the product of two Toeplitz operators asymptotically into a series of other Toeplitz operators multiplied by increasing powers of the Planck constant h. This is the Berezin-Toeplitz quantization. We show that one can obtain in a similar way in fact any star-product which is equivalent to the Berezin-Toeplitz star-product, by using instead of Toeplitz operators other suitable mappings from compactly supported smooth functions...
Degeneracy in the Blasius problem.
Degenerate convergence of semigroups.
Degenerate differential operators with parameters.
Degenerate evolution problems and Beta-type operators
The present paper is concerned with the study of the differential operator Au(x):=α(x)u”(x)+β(x)u’(x) in the space C([0,1)] and of its adjoint Bv(x):=((αv)’(x)-β(x)v(x))’ in the space , where α(x):=x(1-x)/2 (0≤x≤1). A careful analysis of their main properties is carried out in view of some generation results available in [6, 12, 20] and [25]. In addition, we introduce and study two different kinds of Beta-type operators as a generalization of similar operators defined in [18]. Among the corresponding...
Degeneration and complexity of bilinear maps: Some asymptotic spectra.
Degré et théorèmes de point fixe pour les fonctions multivoques ; applications
Degree of convergence of iterative algorithms for boundedly Lipschitzian strong pseudocontractions.
Degree of T-equivariant maps in ℝⁿ
A special case of G-equivariant degree is defined, where G = ℤ₂, and the action is determined by an involution given by T(u,v) = (u,-v). The presented construction is self-contained. It is also shown that two T-equivariant gradient maps are T-homotopic iff they are gradient T-homotopic. This is an equivariant generalization of the result due to Parusiński.
Degree theory for VMO maps on metric spaces
We construct a degree theory for Vanishing Mean Oscillation functions in metric spaces, following some ideas of Brezis & Nirenberg. The underlying sets of our metric spaces are bounded open subsets of and their boundaries. Then, we apply our results in order to analyze the surjectivity properties of the -harmonic extensions of VMO vector-valued functions. The operators we are dealing with are second order linear differential operators sum of squares of vector fields satisfying the hypoellipticity...