Projecting onto Helson matrices in Schatten classes
Peer reviewed, Journal article
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Date
2021Metadata
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- Institutt for matematiske fag [2354]
- Publikasjoner fra CRIStin - NTNU [37247]
Abstract
A Helson matrix is an infinite matrix A=(am,n)m,n≥1 such that the entry am,n depends only on the product mn. We demonstrate that the orthogonal projection from the Hilbert–Schmidt class S2 onto the subspace of Hilbert–Schmidt Helson matrices does not extend to a bounded operator on the Schatten class Sq for 1≤q≠2<∞. In fact, we prove a more general result showing that a large class of natural projections onto Helson matrices are unbounded in the Sq-norm for 1≤q≠2<∞. Two additional results are also presented.