# Adrian Becedas: The second cohomology group and group extensions

**Time: **
Mon 2019-05-20 10.00 - 11.00

**Doctoral student: **
Alexander Berglund

**Supervisor: **
Alexander Berglund

Abstract: *In this B.Sc. thesis we will show that for a group G and a G-module A there is a bijection between the second cohomology group H^2(G;A) and the equivalence classes of extensions pi0(Ext(G,A). This will be done by showing that there is an equivalence of categories from the category of 2-cocycles Z2(G;A) to the category of extensions Ext(G,A).*

*We will also, by examples, illustrate and show some computational use of some of the theory developed in the proof.*