65 citations · 165 across the 14 of their papers we have counts for
18 papers
Stationary phase with Cauchy singularity. A critical point of signature
Christian Klein, Johannes Sjöstrand, Maher Zerzeri
Asymptotic expressions for an integral appearing in the solution of a d-bar problem are presented. The integral is a solid Cauchy transform of a function with a rapidly oscillating…
Discussing semigroup bounds with resolvent estimates
Bernard Helffer, Johannes Sjöstrand, Joe Viola
The purpose of this paper is to revisit the proof of the Gearhart-Prüss-Huang-Greiner theorem for a semigroup , following the general idea of the proofs that we have seen in…
Characterizing boundedness of metaplectic Toeplitz operators
Lewis Coburn, Michael Hitrik, Johannes Sjoestrand
We study Toeplitz operators on the Bargmann space, with Toeplitz symbols given by exponentials of complex quadratic forms. We show that the boundedness of the corresponding Weyl sy…
Complex FIOs and composition of Toeplitz operators
Lewis Coburn, Michael Hitrik, Johannes Sjoestrand
We study Toeplitz operators on the Bargmann space, with Toeplitz symbols that are exponentials of complex quadratic forms, from the point of view of Fourier integral operators in t…
Large behavior of complex geometric optics solutions to d-bar problems
C. Klein, J. Sjöstrand, N. Stoilov
Complex geometric optics solutions to a system of d-bar equations appearing in the context of electrical impedance tomography and the scattering theory of the integrable Davey-Stew…
The second Weyl coefficient for a first order system
Zhirayr Avetisyan, Johannes Sjoestrand, Dmitri Vassiliev
For a scalar elliptic self-adjoint operator on a compact manifold without boundary we have two-term asymptotics for the number of eigenvalues between zero and lambda when lambda te…
Large bi-diagonal matrices and random perturbations
Johannes Sjoestrand, Martin Vogel
This is a first paper by the authors dedicated to the distribution of eigenvalues for random perturbations of large bidiagonal Toeplitz matrices.
Non-real Eigenvalues for PT-Symmetric Double Wells
Amina Benbernou, Naima Boussekkine, Nawal Mecherout +2
We study small, PT-symmetric perturbations of self-adjoint double-well Schrödinger operators in dimension . We prove that the eigenvalues stay real for a very small pertur…
Interior eigenvalue density of Jordan matrices with random perturbations
Johannes Sjoestrand, Martin Vogel
We study the eigenvalue distribution of a large Jordan block subject to a small random Gaussian perturbation. A result by E.B. Davies and M. Hager shows that as the dimension of th…
Spectra for semiclassical operators with periodic bicharacteristics in dimension two
Michael A. Hall, Michael Hitrik, Johannes Sjoestrand
We study the distribution of eigenvalues for selfadjoint --pseudodifferential operators in dimension two, arising as perturbations of selfadjoint operators with a periodic class…
Quadratic PT-symmetric operators with real spectrum and similarity to self-adjoint operators
Emanuela Caliceti, Sandro Graffi, Michael Hitrik +1
It is established that a PT-symmetric elliptic quadratic differential operator with real spectrum is similar to a self-adjoint operator precisely when the associated fundamental ma…
Weyl law for semi-classical resonances with randomly perturbed potentials
Johannes Sjoestrand
In this work we consider semi-classical Schrödinger operators with potentials supported in a bounded strictly convex subset of with smooth boundary. Letting…
Resolvent estimates for elliptic quadratic differential operators
Michael Hitrik, Johannes Sjoestrand, Joe Viola
Sharp resolvent bounds for non-selfadjoint semiclassical elliptic quadratic differential operators are established, in the interior of the range of the associated quadratic symbol.
Tunnel effect and symmetries for Kramers Fokker-Planck type operators
Frederic Herau, Michael Hitrik, Johannes Sjoestrand
We study operators of Kramers-Fokker-Planck type in the semiclassical limit, assuming that the exponent of the associated Maxwellian is a Morse function with a finite number …
Eigenvalue distribution for non-self-adjoint operators with small multiplicative random perturbations
Johannes Sjoestrand
In this work we continue the study of the Weyl asymptotics of the distribution of eigenvalues of non-self-adjoint (pseudo)differential operators with small random perturbations, by…
Non-selfadjoint perturbations of selfadjoint operators in 2 dimensions I
Michael Hitrik, Johannes Sjoestrand
This is the first in a series of works devoted to small non-selfadjoint perturbations of selfadjoint -pseudodifferential operators in dimension 2. In the present work we treat t…
Transport properties in resonant tunneling heterostructures
Carlo Presilla, Johannes Sjöstrand
We use an adiabatic approximation in terms of instantaneous resonances to study the steady-state and time-dependent transport properties of interacting electrons in biased resonant…
On Schroedinger Equations with Concentrated Nonlinearities
Giovanni Jona-Lasinio, Carlo Presilla, Johannes Sjöstrand
Schrödinger equations with nonlinearities concentrated in some regions of space are good models of various physical situations and have interesting mathematical properties. We show…