2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/97936We give a Lieb-Robinson bound for the group velocity of a large class of discrete quantum systems which can be used to prove that a non-vanishing spectral gap implies exponential clustering in the ground state of such systems.v2: corrected proof of Theorem 2. v3: slightly better bound in Theorem 2; updated proofMathematical PhysicsStatistical Mechanics82B10; 82B20text