The third cohomology group classifies double central extensions

• Author(s): Rodelo, Diana ; Linden, Tim Van der
• Date: 2008
• Persistent ID: http://hdl.handle.net/10316/11209
• Origin: Estudo Geral - Universidade de Coimbra
• Subject(s): Cohomology; Categorical Galois theory; Semi-abelian category; Higher central extension; Baer sum
• Document Type: Preprint
• Language: English

Description

We characterise the double central extensions in a semi-abelian category in terms of commutator conditions. We prove that the third cohomology group H3(Z;A) of an object Z with coe cients in an abelian object A classi es the double central extensions of Z by A. FCT/Centro de Matemática da Universidade de Coimbra; Vrije Universiteit Brussel