2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/56360In these notes Yang-Mills theories in 1+1 dimensions are reviewed. Instantons on a sphere prove to be -in the decompactification limit- the key issue to clarify an old controversy between equal-time and light-front quantization.11 pages, Revtex, amssymb. Talk given by F. Vian at the XVII Autumn School "QCD: Perturbative or Nonperturbative?", Lisbon (Portugal), September 29 - October 4, 1999. To appear in the proceedingsHigh Energy Physics - Theorytext