3 papers
math.OA2026
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…
math.OA2025
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…
math.FA2024
On numerical diameters and linear maps
Niel de Beaudrap, Christopher Ramsey
This paper studies the diameter of the numerical range of bounded operators on Hilbert space and the induced seminorm, called the numerical diameter, on bounded linear maps between…