Feynman path integrals for magnetic Schr\"odinger operators on infinite weighted graphs

We prove a Feynman path integral formula for the unitary group $\exp(-itL_{v,\theta})$, $t\geq 0$, associated with a discrete magnetic Schr\"odinger operator $L_{v,\theta}$ on a large class of weighted infinite graphs. As a consequence, we get a new Kato-Simon estimate $$|\exp(-itL_{v,\theta})(x,y)|\leq \exp(-tL_{-\mathrm{deg},0})(x,y),$$ which controls the unitary group uniformly in the potentials in terms of a Schr\"odinger semigroup, where the potential $\mathrm{deg}$ is the weighted degree function of the graph.