Perturbations (r τt)t≥0 of the semigroup of shifts (τt)t≥0 on L(R+) are studied under the assumption that r τt−τt belongs to a certain Schatten–von Neumann class Sp with p ≥ 1. It is shown that, for the unitary component in the Wold– Kolmogorov decomposition of the cogenerator of the semigroup (r τt)t≥0, any singular spectral type may be achieved by S1-perturbations. An explicit construction is...

Let H denote a separable, infinite-dimensional complex Hilbert space. A two-sided ideal / of operators on H possesses the generalized Fuglede property (GFP) if, for every normal operator N and every X e L(H), NX XN e I implies N*X XN* e /. Fuglede's Theorem says that / = {0} has the GFP. It is known that the class of compact operators and the class of Hilbert-Schmidt operators have the GFP. We ...

The CUR decomposition is a factorization of low-rank matrix obtained by selecting certain column and row submatrices it. We perform thorough investigation what happens to such decompositions in the presence noise. Since are nonuniquely formed, we investigate several variants give perturbation estimates for each terms magnitude noise broad class norms which includes all Schatten $p$-norms. given...

We conjecture the following so-called norm compression inequality for 2×N partitioned block matrices and the Schatten p-norms: for p ≥ 2,

A Helson matrix is an infinite $A = (a_{m,n})_{m,n\geq1}$ such that the entry $a_{m,n}$ depends only on product $mn$. We demonstrate orthogonal projection from Hilbert--Schmidt class $\mathcal{S}_2$ onto subspace of matrices does not extend to a bounded operator Schatten $\mathcal{S}_q$ for $1 \leq q \neq 2 < \infty$. In fact, we prove more general result showing large natural projections are u...