Zobrazeno 1 - 10
of 45
pro vyhledávání: '"Winklmeier, Monika"'
The aim of this paper is to study the existence of eigenvalues in the gap of the essential spectrum of the one-dimensional Dirac operator in the presence of a bounded potential. We employ a generalized variational principle to prove existence of such
Externí odkaz:
http://arxiv.org/abs/2408.12697
The limit point and limit circle classification of real Sturm-Liouville problems by H. Weyl more than 100 years ago was extended by A.R. Sims around 60 years ago to the case when the coefficients are complex. Here, the main result is a collection of
Externí odkaz:
http://arxiv.org/abs/2310.16128
Autor:
Moreno, Javier, Winklmeier, Monika
We consider a normal operator $T$ on a Hilbert space $H$. Under various assumptions on the spectrum of $T$, we give bounds for the spectrum of $T+A$ where $A$ is $T$-bounded with relative bound less than 1 but we do not assume that $A$ is symmetric o
Externí odkaz:
http://arxiv.org/abs/2309.12550
We consider the explicit relation between two resolvent matrices related to the truncated Hausdorff matrix moment problem (THMM) in the case of an even and odd number of moments. This relation is described with the help of four families of orthogonal
Externí odkaz:
http://arxiv.org/abs/2210.00374
Publikováno v:
Integr. Equ. Oper. Theory (2016) 86: 121
We study the spectrum of a self-adjoint Dirac-Krein operator with potential on a compact star graph $\mathcal G$ with a finite number $n$ of edges. This operator is defined by a Dirac-Krein differential expression with summable matrix potentials on e
Externí odkaz:
http://arxiv.org/abs/1608.05865
Autor:
Strauss, Vladimir, Winklmeier, Monika
In this paper we investigate the one-dimensional harmonic oscillator with a singular perturbation concentrated in one point. We describe all possible selfadjoint realizations and we show that for certain conditions on the perturbation exactly one neg
Externí odkaz:
http://arxiv.org/abs/1506.06264
Autor:
Boulton, Lyonell, Winklmeier, Monika
A certified strategy for determining sharp intervals of enclosure for the eigenvalues of matrix differential operators with singular coefficients is examined. The strategy relies on computing the second order spectrum relative to subspaces of continu
Externí odkaz:
http://arxiv.org/abs/1410.5357
Autor:
Winklmeier, Monika, Wyss, Christian
Publikováno v:
Integral Equations and Operator Theory. 82(1):119-150 (2015)
For an unbounded operator $S$ on a Banach space the existence of invariant subspaces corresponding to its spectrum in the left and right half-plane is proved. The general assumption on $S$ is the uniform boundedness of the resolvent along the imagina
Externí odkaz:
http://arxiv.org/abs/1410.2305
Autor:
Segovia, Carlos, Winklmeier, Monika
Publikováno v:
The Electronic Journal of Combinatorics, Volume 22, Issue 3 (2015)
The sequence $(x_n)_{n\in\mathbb N} = (2,5,15,51,187,\dots)$ given by the rule $x_n=(2^n+1)(2^{n-1}+1)/3$ appears in several seemingly unrelated areas of mathematics. For example, $x_n$ is the density of a language of words of length $n$ with four di
Externí odkaz:
http://arxiv.org/abs/1409.2067
Autor:
Segovia, Carlos, Winklmeier, Monika
The main result of this paper is the construction of a bijection of the set of words in so-called standard order of length $n$ formed by four different letters and the set $\mathbb{N}^n$ of all subspaces of a fixed $n$-dimensional maximal isotropic s
Externí odkaz:
http://arxiv.org/abs/1312.4315