Ext(Q,Z) is the additive group of real numbers
James Wiegold · Bulletin of the Australian Mathematical Society · 1969
Standard homological methods and a theorem of Harrison on cotorsion groups are used to prove the result mentioned. In this note Z denotes an infinite cyclic group, Q the additive group of rational numbers, Zp ∞ a p–quasicyclie group, and Ip the group of p–adic integers. Pascual Llorente proves in [3] that Ext(Q,z) is an uncountable group, and gives explicitly a countably infinite subset. Very little extra effort produces the result embodied in the title, as follows.