SISSA Preprints
https://preprints.sissa.it:443/xmlui
The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.2020-02-25T09:53:16ZOn real resonances for three-dimensional Schrödinger operators with point interactions
http://preprints.sissa.it:8180/xmlui/handle/1963/35343
On real resonances for three-dimensional Schrödinger operators with point interactions
Michelangeli, Alessandro; Scandone, Raffaele
We prove the absence of positive real resonances for Schroedinger operators with ﬁnitely many point interactions in R3 and we discuss such a property from the perspective of dispersive and scattering features of the associated Schr¨odinger propagator.
2019-02-20T00:00:00ZKrilov solvability of unbounded inverse linear problems
http://preprints.sissa.it:8180/xmlui/handle/1963/35341
Krilov solvability of unbounded inverse linear problems
Caruso, Noe; Michelangeli, Alessandro
The abstract issue of ‘Krylov solvability’ is extensively discussed for the inverse problem Af = g where A is a (possibly unbounded) linear operator on an inﬁnite-dimensional Hilbert space, and g is a datum in the range of A. The question consists of whether the solution f can be approximated in the Hilbert norm by ﬁnite linear combinations of g, Ag, A2g, . . . , and whether solutions of this sort exist and are unique. After revisiting the known picture when A is bounded, we study the general case of a densely deﬁned and closed A. Intrinsic operator-theoretic mechanisms are identiﬁed that guarantee or prevent Krylov solvability, with new features arising due to the unboundedness. Such mechanisms are checked in the self-adjoint case, where Krylov solvability is also proved by conjugate-gradient-based techniques
21 p.
2020-01-23T00:00:00ZTwo-dimensional Schrödinger operators with point interactions: Threshold expansions, zero modes and Lp-boundedness of wave operators
http://preprints.sissa.it:8180/xmlui/handle/1963/35340
Two-dimensional Schrödinger operators with point interactions: Threshold expansions, zero modes and Lp-boundedness of wave operators
Cornean, Horia D.; Michelangeli, Alessandro; Yajima, Kenji
Mathematics Subject Classiffcation 2010: 35P15, 35J10, 47A40, 81Q10
2019-10-10T00:00:00ZPeriodic solutions of nearly integrable Hamiltonian systems bifurcating from infinite-dimensional tori
http://preprints.sissa.it:8180/xmlui/handle/1963/35339
Periodic solutions of nearly integrable Hamiltonian systems bifurcating from infinite-dimensional tori
Fonda, Alessandro; Klun, Giuliano; Sfecci, Andrea
We prove the existence of periodic solutions of some infinite-dimensional nearly integrable
Hamiltonian systems, bifurcating from infinite-dimensional tori, by the use of a generalization
of the Poincaré–Birkhoff Theorem.
Dedicated to Shair Ahmad, on the occasion of his 85th birthday
2019-09-12T00:00:00Z