2014/08/06 by Marino Gran, Gran, Marino, Diana Rodelo +1
Mathematics · #08B10 #08C05 #18B10 #18C05 #18E10 #Category Theory (math.CT) #FOS: Mathematics #math.CT #msc:08B10 #msc:08C05 #msc:18B10 #msc:18C05 #msc:18E10
paper · pdf · doi:10.48550/arxiv.1408.1342
12 pages
arxiv created 2014/08/06 · arxiv updated 2014/08/07
We extend some properties of pullbacks which are known to hold in a Mal'tsev context to the more general context of Gumm categories. The varieties of universal algebras which are Gumm categories are precisely the congruence modular ones. These properties lead to a simple alternative proof of the known property that central extensions and normal extensions coincide for any Galois structure associated with a Birkhoff subcategory of an exact Goursat category.