2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/29825We derive upper bounds for spin velocity in half-integer-spin Heisenberg antiferromagnetic chains. We relate these upper bounds to the instability of the gapless state, which is observed in frustrated systems.3 pages, RevTeXStrongly Correlated ElectronsStatistical MechanicsOn some upper bounds for spin velocity and instability of gapless state of 1-d Heisenberg chainstext