Finite-dimensional Dirac representation for the quotient seminorm L_q
Determine whether, for a finite-dimensional C*-algebra A and a unital C*-subalgebra B ⊆ A, there exists a Dirac-type operator D acting on a finite-dimensional Hilbert space representation π of A such that the quotient seminorm L_q(a) = inf_{b∈B} ||a − b|| satisfies L_q(a) = ||[D, π(a)]|| for all a ∈ A; if not, establish general obstructions to such finite-dimensional realizations.
References
It is an interesting question as to whether $L_q$ can be determined by a Dirac-type operator on a finite-dimensional Hilbert space. I suspect it can not in most cases, but I have no proof of this.
— Quantum Hamming Metrics
(2507.23046 - Rieffel, 30 Jul 2025) in Section 11 (Dirac operators for quantum Hamming seminorms)