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Browsing by Author "Lindner, Marko"

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  • thumbnail.journal.alt
    Item type:Article, Access status: Open Access ,
    A note on Hausdorff convergence of pseudospectra
    (Wydawnictwa AGH, 2023) Lindner, Marko; Schmeckpeper, Dennis
    For a bounded linear operator on a Banach space, we study approximation of the spectrum and pseudospectra in the Hausdorff distance. We give sufficient and necessary conditions in terms of pointwise convergence of appropriate spectral quantities.
  • thumbnail.journal.alt
    Item type:Article, Access status: Open Access ,
    Circulant matrices: norm, powers, and positivity
    (Wydawnictwa AGH, 2018) Lindner, Marko
    In their recent paper »The spectral norm of a Horadam circulant matrix«, Merikoski, Haukkanen, Mattila and Tossavainen study under which conditions the spectral norm of a general real circulant matrix ${\bf C}$ equals the modulus of its row/column sum. We improve on their sufficient condition until we have a necessary one. Our results connect the above problem to positivity of sufficiently high powers of the matrix ${\bf C^\top C}$. We then generalize the result to complex circulant matrices.