• Alternative iterative methods for nonexpansive mappings, rates of convergence and applications 

      [OWP-2009-19] Colao, Vittorio; Leuştean, Laurenţiu; López, Genaro; Martín Márquez, Victoria (Mathematisches Forschungsinstitut Oberwolfach, 2009)
      Alternative iterative methods for a nonexpansive mapping in a Banach space are proposed and proved to be convergent to a common solution to a fixed point problem and a variational inequality. We give rates of asymptotic ...
    • Boundary Representations of Operator Spaces, and Compact Rectangular Matrix Convex Sets 

      [OWP-2016-24] Fuller, Adam H.; Hartz, Michael; Lupini, Martino (Mathematisches Forschungsinstitut Oberwolfach, 2016-12-13)
      We initiate the study of matrix convexity for operator spaces. We define the notion of compact rectangular matrix convex set, and prove the natural analogs of the Krein-Milman and the bipolar theorems in this context. We ...
    • Convolution in Dual Cesàro Sequence Spaces 

      [OWP-2022-20] Curbera, Guillermo P.; Ricker, Werner J. (Mathematisches Forschungsinstitut Oberwolfach, 2022-12-16)
      We investigate convolution operators in the sequence spaces $d_p$, for 1 $\leqslant p<\infty$. These spaces, for $p$ > 1, arise as dual spaces of the Cesàro sequence spaces $ces_p$ thoroughly investigated by G. Bennett. A ...
    • Epsilon-hypercyclic operators 

      [OWP-2008-19] Badea, Catalin; Grivaux, Sophie; Müller, Valdimir (Mathematisches Forschungsinstitut Oberwolfach, 2008-03-19)
      For each fixed number $\varepsilon$ in $(0, 1)$ we construct a bounded linear operator on the Banach space $\ell_1$ having a certain orbit which intersects every cone of aperture $\varepsilon$, but with every orbit avoiding ...
    • Geometry of Free Loci and Factorization of Noncommutative Polynomials 

      [OWP-2017-23] Helton, J. William; Klep, Igor; Volčič, Jurij; Helton, J. William (Mathematisches Forschungsinstitut Oberwolfach, 2017-10-02)
      The free singularity locus of a noncommutative polynomial f is defined to be the sequence $Z_n(f)=\{X\in M_n^g : \det f(X)=0\}$ of hypersurfaces. The main theorem of this article shows that f is irreducible if and only if ...
    • Nonlinear Multi-Parameter Eigenvalue Problems for Systems of Nonlinear Ordinary Differential Equations Arising in Electromagnetics 

      [OWP-2014-15] Angermann, Lutz; Shestopalov, Yury V.; Smirnov, Yury G.; Yatsyk, Vasyl V. (Mathematisches Forschungsinstitut Oberwolfach, 2014-12-20)
      We investigate a generalization of one-parameter eigenvalue problems arising in the theory of nonlinear waveguides to a more general nonlinear multiparameter eigenvalue problem for a nonlinear operator. Using an integral ...
    • On Weak Weighted Estimates of Martingale Transform 

      [OWP-2016-22] Nazarov, Fedor; Reznikov, Alexander; Vasyunin, Vasily; Volberg, Alexander (Mathematisches Forschungsinstitut Oberwolfach, 2016-11-12)
      We consider several weak type estimates for singular operators using the Bellman function approach. We disprove the $A_1$ conjecture, which stayed open after Muckenhoupt-Wheeden's conjecture was disproved by Reguera-Thiele.
    • Reducing sub-modules of the Bergman module $\mathbb A^{(\lambda)}(\mathbb D^n)$ under the action of the symmetric group 

      [OWP-2017-19] Biswas, Shibananda; Ghosh, Gargi; Misra, Gadadhar; Roy, Subrata Shyam (Mathematisches Forschungsinstitut Oberwolfach, 2017-07-20)
      The weighted Bergman spaces on the polydisc, $\mathbb A^{(\lambda)}(\mathbb D^n)$, $\lambda>0,$ splits into orthogonal direct sum of subspaces $\mathbb P_{\boldsymbol p}\big(\mathbb A^{(\lambda)}(\mathbb D^n)\big)$ indexed ...
    • Reflection Positivity and Hankel Operators- the Multiplicity Free Case 

      [OWP-2021-10] Adamo, Maria Stella; Neeb, Karl-Hermann; Schober, Jonas (Mathematisches Forschungsinstitut Oberwolfach, 2021-12-15)
      We analyze reflection positive representations in terms of positive Hankel operators. This is motivated by the fact that positive Hankel operators are described in terms of their Carleson measures, whereas the compatibility ...
    • Solid extensions of the Cesàro operator on the Hardy space H2(D) 

      [OWP-2013-11] Curbera, Guillermo P.; Ricker, Werner J. (Mathematisches Forschungsinstitut Oberwolfach, 2013-04-23)
      We introduce and study the largest Banach space of analytic functions on the unit disc which is solid for the coefficient-wise order and to which the classical Ces`aro operator $\mathcal{C}:H^2 \to H^2$ can be continuously ...
    • Spatial-Skin Effect for a Spectral Problem with "Slightly Heavy" Concentrated Masses in a Thick Cascade Junction 

      [OWP-2012-10] Čečkin, Grigorij A.; Mel'nyk, Taras A. (Mathematisches Forschungsinstitut Oberwolfach, 2012-07-03)
      The asymptotic behavior (as $\varepsilon \to 0$) of eigenvalues and eigenfunctions of a boundary- value problem for the Laplace operator in a thick cascade junction with concentrated masses is studied. This cascade junction ...
    • Spectral Continuity for Aperiodic Quantum Systems II. Periodic Approximations in 1D 

      [OWP-2018-27] Beckus, Siegfried; Bellissard, Jean; De Nittis, Giuseppe (Mathematisches Forschungsinstitut Oberwolfach, 2018-12-17)
      The existence and construction of periodic approximations with convergent spectra is crucial in solid state physics for the spectral study of corresponding Schrödinger operators. In a forthcoming work [9] this task was ...
    • Unconditional Convergence of Spectral Decompositions of 1D Dirac Operators with Regular Boundary Conditions 

      [OWP-2010-21] Djakov, Plamen; Mitjagin, Boris S. (Mathematisches Forschungsinstitut Oberwolfach, 2010-03-19)
    • Varieties of Invariant Subspaces Given by Littlewood-Richardson Tableaux 

      [OWP-2014-01] Kosakowska, Justyna; Schmidmeier, Markus (Mathematisches Forschungsinstitut Oberwolfach, 2014-04-25)
      Given partitions $\alpha, \beta, \gamma$, the short exact sequences $0 \rightarrow N_\alpha \rightarrow N_\beta \rightarrow N_\gamma \rightarrow 0$ of nilpotent linear operators of Jordan types $\alpha, \beta, \gamma$, ...
    • Weyl-Titchmarsh Functions of Vector-Valued Sturm-Liouville Operators on the Unit Interval 

      [OWP-2008-13] Chelkak, Dmitry; Korotyaev, Evgeny (Mathematisches Forschungsinstitut Oberwolfach, 2008)
      The matrix-valued Weyl-Titchmarsh functions $M(\lambda)$ of vector-valued Sturm-Liouville operators on the unit interval with the Dirichlet boundary conditions are considered. The collection of the eigenvalues (i.e., poles ...