-boundedness and -compactness of a class of Fourier integral operators.
La figura espectral del producto tensorial de dos operadores.
Sea H un espacio de Hilbert complejo, separable y de dimensión infinita. Denotaremos por L(H) al álgebra de todos los operadores acotados en H. Carl Pearcy en 1977 introdujo el concepto de figura espectral de un operador T en L(H) [13]. Sin lugar a dudas hay dos resultados que hacen de la figura espectral de un operador un concepto importante. El primero se debe a Brown, Douglas y Fillmore:"Dos operadores esencialmente normales son débilmente equivalentes si y sólo si tienen la misma figura espectral".El...
Le comportement asymptotique des valeurs propres d'un opérateur
Limit points of eigenvalues of truncated unbounded tridiagonal operators
Let T be a self-adjoint tridiagonal operator in a Hilbert space H with the orthonormal basis {e n}n=1∞, σ(T) be the spectrum of T and Λ(T) be the set of all the limit points of eigenvalues of the truncated operator T N. We give sufficient conditions such that the spectrum of T is discrete and σ(T) = Λ(T) and we connect this problem with an old problem in analysis.
Linear maps on Mₙ(ℂ) preserving the local spectral radius
Let x₀ be a nonzero vector in ℂⁿ. We show that a linear map Φ: Mₙ(ℂ) → Mₙ(ℂ) preserves the local spectral radius at x₀ if and only if there is α ∈ ℂ of modulus one and an invertible matrix A ∈ Mₙ(ℂ) such that Ax₀ = x₀ and for all T ∈ Mₙ(ℂ).
Linear maps preserving the generalized spectrum.
Let H be an infinite-dimensional separable complex Hilbert space and B(H) the algebra of all bounded linear operators on H. For an operator T in B(H), let σg(T) denote the generalized spectrum of T. In this paper, we prove that if φ: B(H) → B(H) is a surjective linear map, then φ preserves the generalized spectrum (i.e. σg(φ(T)) = σg(T) for every T ∈ B(H)) if and only if there is A ∈ B(H) invertible such that either φ(T) = ATA-1 for every T ∈ B(H), or φ(T) = ATtrA-1 for every T ∈ B(H). Also, we...
Linear operators as measure preserving transformations
Local behaviour of the polynomial calculus of operators.
Local entropy moduli and eigenvalues of operators in Banach spaces.
In the paper local entropy moduli of operators between Banach spaces are introduced. They constitue a generalization of entropy numbers and moduli, and localize these notions in an appropriate way. Many results regarding entropy numbers and moduli can be carried over to local entropy moduli. We investigate relations between local entropy moduli and s-numbers, spectral properties, eigenvalues, absolutely summing operators. As applications, local entropy moduli of identical and diagonal operators...
Local ergodic theorems.
Local spectral radius formula for operators in Banach spaces
Local spectral theory for operator matrices.
Locally spectrally bounded linear maps
Let be the algebra of all bounded linear operators on a complex Hilbert space . We characterize locally spectrally bounded linear maps from onto itself. As a consequence, we describe linear maps from onto itself that compress the local spectrum.
Lower bounds for eigenvalues of Schatten-von Neumann operators.
Lp-essential Spectral Theory of Ordinary Differential Operators With Almost Constant Coefficients