Blar i Fakultet for informasjonsteknologi og elektroteknikk (IE) på forfatter "Queffelec, Herve"
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Approximation numbers of composition operators on H^p spaces of Dirichlet series
Bayart, Frederic; Queffelec, Herve; Seip, Kristian (Journal article; Peer reviewed, 2016)By a theorem of the first named author, $\varphi $ generates a bounded composition operator on the Hardy space ${\mathscr{H}}^p$of Dirichlet series $(1\le p<\infty )$ only if $\varphi (s)=c_0 s+\psi (s)$, where $c_0$ is a ... -
Decay rates for approximation numbers of composition operators
Queffelec, Herve; Seip, Kristian (Journal article; Peer reviewed, 2015)A general method for estimating the approximation numbers of composition operators on the Hardy space H 2, using finite-dimensional model subspaces, is studied and applied in the case when the symbol of the operator maps ... -
Riesz projection and bounded mean oscillation for Dirichlet series
Konyagin, Sergei; Queffelec, Herve; Saksman, Eero; Seip, Kristian (Peer reviewed; Journal article, 2022)We prove that the norm of the Riesz projection from L∞(Tn) to Lp(Tn) is 1 for all n≥1 only if p≤2, thus solving a problem posed by Marzo and Seip in 2011. This shows that Hp(T∞) does not contain the dual space of H1(T∞) ...