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On Threshold Eigenvalues and Resonances for the Linearized NLS Equation

V. Vougalter (2010)

Mathematical Modelling of Natural Phenomena

We prove the instability of threshold resonances and eigenvalues of the linearized NLS operator. We compute the asymptotic approximations of the eigenvalues appearing from the endpoint singularities in terms of the perturbations applied to the original NLS equation. Our method involves such techniques as the Birman-Schwinger principle and the Feshbach map.

On torsional rigidity and principal frequencies: an invitation to the Kohler−Jobin rearrangement technique

Lorenzo Brasco (2014)

ESAIM: Control, Optimisation and Calculus of Variations

We generalize to the p-Laplacian Δp a spectral inequality proved by M.-T. Kohler−Jobin. As a particular case of such a generalization, we obtain a sharp lower bound on the first Dirichlet eigenvalue of Δp of a set in terms of its p-torsional rigidity. The result is valid in every space dimension, for every 1 < p < ∞ and for every open set with finite measure. Moreover, it holds by replacing the first eigenvalue with more general optimal Poincaré-Sobolev constants. The method of proof...

On totally * -paranormal operators

Eungil Ko, Hae-Won Nam, Young Oh Yang (2006)

Czechoslovak Mathematical Journal

In this paper we study some properties of a totally * -paranormal operator (defined below) on Hilbert space. In particular, we characterize a totally * -paranormal operator. Also we show that Weyl’s theorem and the spectral mapping theorem hold for totally * -paranormal operators through the local spectral theory. Finally, we show that every totally * -paranormal operator satisfies an analogue of the single valued extension property for W 2 ( D , H ) and some of totally * -paranormal operators have scalar extensions....

On truncations of Hankel and Toeplitz operators.

Aline Bonami, Joaquim Bruna (1999)

Publicacions Matemàtiques

We study the boundedness properties of truncation operators acting on bounded Hankel (or Toeplitz) infinite matrices. A relation with the Lacey-Thiele theorem on the bilinear Hilbert transform is established. We also study the behaviour of the truncation operators when restricted to Hankel matrices in the Schatten classes.

On two problems studied by A. Ambrosetti

David Arcoya, José Carmona (2006)

Journal of the European Mathematical Society

We study the Ambrosetti–Prodi and Ambrosetti–Rabinowitz problems.We prove for the first one the existence of a continuum of solutions with shape of a reflected C ( -shape). Next, we show that there is a relationship between these two problems.

On two quantum versions of the detailed balance condition

Franco Fagnola, Veronica Umanità (2010)

Banach Center Publications

Quantum detailed balance conditions are often formulated as relationships between the generator of a quantum Markov semigroup and the generator of a dual semigroup with respect to a certain scalar product defined by an invariant state. In this paper we survey some results describing the structure of norm continuous quantum Markov semigroups on ℬ(h) satisfying a quantum detailed balance condition when the duality is defined by means of pre-scalar products on ℬ(h) of the form x , y s : = t r ( ρ 1 - s x * ρ s y ) (s ∈ [0,1]) in order...

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