7 papers
An algorithm to exactly compute minimal upper bounds in the Loewner order
Adam Humeniuk, Gabriel Jarry-Bolduc, Patrick Pascua +1
The Loewner order on Hermitian matrices is a partial order that compares matrices in terms of positive semidefiniteness. The Loewner order plays a key role in many fields such as o…
A C*-cover lattice dichotomy
Adam Humeniuk, Christopher Ramsey, Marcel Scherer
In this paper, we show that the lattice of C*-covers of a non-selfadjoint operator algebra is either one point or uncountable. We prove that there are non-selfadjoint operator alge…
An extension property for noncommutative convex sets and duality for operator systems
Adam Humeniuk, Matthew Kennedy, Nicholas Manor
We characterize inclusions of compact noncommutative convex sets with the property that every continuous affine function on the smaller set can be extended to a continuous affine f…
Couniversality for C*-algebras of residually finite-dimensional operator algebras
Adam Humeniuk, Christopher Ramsey, Ian Thompson
The C*-envelope of a non self-adjoint operator algebra is known to encode many properties of the underlying subalgebra. However, the C*-envelope does not always encode the residual…
Diffraction of the primes and other sets of zero density
Adam Humeniuk, Christopher Ramsey, Nicolae Strungaru
In this paper, we show that the diffraction of the primes is absolutely continuous, showing no bright spots (Bragg peaks). We introduce the notion of counting diffraction, extendin…
Crossed products and C*-covers of semi-Dirichlet operator algebras
Adam Humeniuk, Elias G. Katsoulis, Christopher Ramsey
In this paper, we show that the semi-Dirichlet C*-covers of a semi-Dirichlet operator algebra form a complete lattice, establishing that there is a maximal semi-Dirichlet C*-cover.…