Rigidity results in Diffusion Markov Triples

We consider stable solutions of semilinear equations in a very general setting. The equation is set on a Polish topological space endowed with a measure and the linear operator is induced by a carr'e du champs (equivalently, the equation is set in a diffusion Markov triple). Under suitable curvature dimension conditions, we establish that stable solutions with integrable carr'e du champs are necessarily constant (weaker conditions characterize the structure of the carr'e du champs and carr'e du champ it'er'e). The proofs are based on a geometric Poincar'e formula in this setting. From the general theorems established, several previous results are obtained as particular cases and new ones are provided as well.