Operator algebras and subproduct systems arising from stochastic matrices

Abstract: We study subproduct systems in the sense of Shalit and Solel arising from stochastic matrices on countable state spaces, and their associated operator algebras. We focus on the non-self-adjoint tensor algebra, and Viselter's generalization of the Cuntz-Pimsner C*-algebra to the context of subproduct systems. Suppose that $X$ and $Y$ are Arveson-Stinespring subproduct systems associated to two stochastic matrices over a countable set $\Omega$, and let $\mathcal{T}+(X)$ and $\mathcal{T}+(Y)$ be their tensor algebras. We show that every algebraic isomorphism from $\mathcal{T}+(X)$ onto $\mathcal{T}+(Y)$ is automatically bounded. Furthermore, $\mathcal{T}+(X)$ and $\mathcal{T}+(Y)$ are isometrically isomorphic if and only if $X$ and $Y$ are unitarily isomorphic up to a *-automorphism of $\ell^\infty(\Omega)$. When $\Omega$ is finite, we prove that $\mathcal{T}+(X)$ and $\mathcal{T}+(Y)$ are algebraically isomorphic if and only if there exists a similarity between $X$ and $Y$ up to a *-automorphism of $\ell^\infty(\Omega)$. Moreover, we provide an explicit description of the Cuntz-Pimsner algebra $\mathcal{O}(X)$ in the case where $\Omega$ is finite and the stochastic matrix is essential.