Closed spectral measures in Fréchet spaces.
Boolean algebras of projections and ranges of spectral measures
CONTENTSIntroduction...............................................................................51. Preliminaries.........................................................................72. Relative weak compactness of the range............................133. Closed spectral measures...................................................164. Spectral measures and B.a.'s of projections........................22References..............................................................................45...
Vector-valued multipliers: convolution with operator-valued measures
CONTENTS Preface.........................................................................................................5 1. Introduction...............................................................................................6 1.1. Measurability and vector measures.....................................................6 1.2. Convolution and vector measures.....................................................12 ...
Commutativity of compact selfadjoint operators
The relationship between the joint spectrum γ(A) of an n-tuple of selfadjoint operators and the support of the corresponding Weyl calculus T(A) : f ↦ f(A) is discussed. It is shown that one always has γ(A) ⊂ supp (T(A)). Moreover, when the operators are compact, equality occurs if and only if the operators mutually commute. In the non-commuting case the equality fails badly: While γ(A) is countable, supp(T(A)) has to be an uncountable set. An example is given showing that, for non-compact operators,...
Continuous extensions of spectral measures
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The aim is to investigate certain spectral properties, such as decomposability, the spectral mapping property and the Lyubich-Matsaev property, for linear differential operators with constant coefficients ( and more general Fourier multiplier operators) acting in . The criteria developed for such operators are quite general and p-dependent, i.e. they hold for a range of p in an interval about 2 (which is typically not (1,∞)). The main idea is to construct appropriate functional calculi: this is...
Fréchet-spaces-valued measures and the AL-property.
Associated with every vector measure m taking its values in a Fréchet space X is the space L(m) of all m-integrable functions. It turns out that L(m) is always a Fréchet lattice. We show that possession of the AL-property for the lattice L(m) has some remarkable consequences for both the underlying Fréchet space X and the integration operator f → ∫ f dm.
Integration with respect to the canonical spectral measure in sequence spaces.
Lattice copies of c₀ and in spaces of integrable functions for a vector measure
The spaces L¹(m) of all m-integrable (resp. of all scalarly m-integrable) functions for a vector measure m, taking values in a complex locally convex Hausdorff space X (briefly, lcHs), are themselves lcHs for the mean convergence topology. Additionally, is always a complex vector lattice; this is not necessarily so for L¹(m). To identify precisely when L¹(m) is also a complex vector lattice is one of our central aims. Whenever X is sequentially complete, then this is the case. If, additionally,...
Compactness of the integration operator associated with a vector measure
A characterization is given of those Banach-space-valued vector measures m with finite variation whose associated integration operator Iₘ: f ↦ ∫fdm is compact as a linear map from L¹(m) into the Banach space. Moreover, in every infinite-dimensional Banach space there exist nontrivial vector measures m (with finite variation) such that Iₘ is compact, and other m (still with finite variation) such that Iₘ is not compact. If m has infinite variation, then Iₘ is never compact.
Sequential closedness of Boolean algebras of projections in Banach spaces
Complete and σ-complete Boolean algebras of projections acting in a Banach space were introduced by W. Bade in the 1950's. A basic fact is that every complete Boolean algebra of projections is necessarily a closed set for the strong operator topology. Here we address the analogous question for σ-complete Boolean algebras: are they always a sequentially closed set for the strong operator topology? For the atomic case the answer is shown to be affirmative. For the general case, we develop criteria...
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