@Article{Juršėnas2020,
author = "Juršėnas, Rytis",
title = "On some extensions of the A-model",
journal = "Opuscula Math.",
year = "2020",
volume = "40",
number = "5",
pages = "569--597",
doi = "https://doi.org/10.7494/OpMath.2020.40.5.569",
url = "https://doi.org/10.7494/OpMath.2020.40.5.569",
abstract = "The A-model for finite rank singular perturbations of class \(\mathfrak{H}_{-m-2}\setminus\mathfrak{H}_{-m-1}\), \(m \in \mathbb{N}\), is considered from the perspective of boundary relations. Assuming further that the Hilbert spaces \((\mathfrak{H}_n)_{n\in\mathbb{Z}}\) admit an orthogonal decomposition \(\mathfrak{H}^-_n \oplus \mathfrak{H}^+_n\), with the corresponding projections satisfying \(P^{\pm}_{n+1}\subseteq P^{\pm}_n\), nontrivial extensions in the A-model are constructed for the symmetric restrictions in the subspaces.",
keywords = "finite rank higher order singular perturbation, cascade (A) model, peak model, Hilbert space, scale of Hilbert spaces, Pontryagin space, ordinary boundary triple, Krein \(Q\)-function, Weyl function, gamma field, symmetric operator, proper extension, resolvent",
issn = "1232-9274"
}