Fernández Bretón, David José
(Universidad Michoacana de San Nicolás de Hidalgo. Universidad Nacional Autónoma de México, 2010-08)
The first chapter of the thesis is intended to whitehead problem, which consists in characterizing the abelian groups G such that Ext (G, ?) = 0 (such groups are known as W-groups, or Whitehead groups). The first sections ...