16 citations · 60 across the 17 of their papers we have counts for
4 papers · 1 filter
Exponential frames and Riesz sequences at the critical density
Ulrik Enstad, Jordy Timo van Velthoven
We characterize exponential systems on sets of finite measure that form a frame or a Riesz sequence at the critical density. Namely, they are precisely those systems for which the…
Bessel duality of Gabor systems: A von Neumann algebraic perspective
Ulrik Enstad, Franz Luef
Bessel duality of regular Gabor systems states that a Gabor system over a lattice is a Bessel sequence if and only if the corresponding Gabor system over the adjoint lattice is a B…
A Duflo-Moore theorem for ergodic group actions on semifinite von Neumann algebras
Ulrik Enstad, Hannes Wendt
We prove a generalization of the orthogonality relations of Duflo and Moore for ergodic, trace-preserving group actions on von Neumann algebras that are integrable in a suitable se…
Z-stability of twisted group C*-algebras of nilpotent groups
Ulrik Enstad, Eduard Vilalta
We prove that the twisted group C*-algebra of a finitely generated nilpotent group is -stable if and only if it is nowhere scattered, a condition that we characterize…