2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/23471Using results on the mass gap in the sine-Gordon model combined with the exact amplitudes in the bosonized representation of the Heisenberg spin-1/2 chain and one-loop renormalization group, we derive a quantitative expression for the gap in a dimerized spin-1/2 chain. This expression is shown to be in good agreement with recent numerical estimates when a marginally irrelevant perturbation is taken into account.5 pages, 2 EPS figures, uses svjour.clsStrongly Correlated ElectronsStatistical Mechanicstext