Vector-valued Littewood-Paley-Stein theory for semigroups II

Inspired by a recent work of Hyt\"onen and Naor, we solve a problem left open in our previous work joint with Mart\'{\i}nez and Torrea on the vector-valued Littlewood-Paley-Stein theory for symmetric diffusion semigroups. We prove a similar result in the discrete case, namely, for any $T$ which is the square of a symmetric Markovian operator on a measure space $(\Omega, \mu)$. Moreover, we show that $T\otimes{\rm Id}_X$ extends to an analytic contraction on $L_p(\Omega; X)$ for any $1<p<\infty$ and any uniformly convex Banach space $X$.