Subnormality of the quotients of Td\mathbb T^d-invariant Hilbert modules

This paper investigates the subnormality of quotients of Td\mathbb T^d-invariant Hilbert modules by homogeneous polynomials, establishing that such quotients are subnormal only if the polynomial is square-free and of degree at most one for standard spaces like the Hardy and Drury-Arveson modules, while also demonstrating that higher-degree examples exist for specific invariant modules like the Dirichlet module.

K. S. Amritha, S. Bera, S. Chavan, S. S. SequeiraTue, 10 Ma🔢 math

Unconditional structure of Banach spaces with few operators

This paper demonstrates that the pp-convexification of Gowers' space G\mathbb{G} yields Banach spaces with unique unconditional bases containing block bases with spreading models distinct from 1\ell_1, 2\ell_2, and c0c_0, thereby resolving a long-standing open problem by Bourgain et al. and disproving the conjecture that such spaces must be isomorphic to their squares.

Fernando Albiac, Jose L. AnsorenaTue, 10 Ma🔢 math

Margin in Abstract Spaces

This paper establishes that sufficiently large margins enable learnability in arbitrary metric spaces based solely on the triangle inequality, reveals a sharp threshold for learnability in linear combinations of distance functions, and demonstrates that not all margin-based learning can be reduced to linear classification in Banach spaces by proving that learnability in such spaces implies polynomial sample complexity scaling with the inverse margin.

Yair Ashlagi, Roi Livni, Shay Moran, Tom WaknineTue, 10 Ma🤖 cs.LG

Operators with small Kreiss constants

This paper investigates matrices and operators satisfying the Kreiss condition with constants arbitrarily close to one, establishing refined lower bounds for power growth and demonstrating that specific variants of the condition guarantee similarity to a contraction when the spectrum touches the unit circle at a single point, utilizing a positivity argument involving the double-layer potential operator.

Nikolaos Chalmoukis, Georgios Tsikalas, Dmitry YakubovichThu, 12 Ma🔢 math