162 citations · 394 across the 33 of their papers we have counts for
4 papers · 1 filter
Elementary linear algebra for advanced spectral problems
J. Sjoestrand, M. Zworski
We discuss the general method of Grushin problems, closely related to Shur complements, Feshbach projections and effective Hamiltonians, and describe various appearances in spectra…
Functional calculus for non-commuting operators with real spectra via an iterated Cauchy formula
Mats Andersson, Johannes Sjoestrand
We define a smooth functional calculus for a non-commuting tuple of (unbounded) operators on a Banach space with real spectra and resolvents with temperate growth, by means o…
Perturbations of selfadjoint operators with periodic classical flow
Johannes Sjoestrand
We consider non-selfadjoint perturbations of a self-adjoint -pseudodifferential operator in dimension 2. In the present work we treat the case when the classical flow of the unp…
Pseudospectra of semi-classical (pseudo)differential operators
Nils Dencker, Johannes Sjoestrand, Maciej Zworski
The purpose of this note is to show how some results from the theory of partial differential equations apply to the study of pseudo-spectra of non-self-adjoint operators, which is…