On good morphisms of exact triangles
Algebraic Topology
2023-01-10 v3 Category Theory
Abstract
In a triangulated category, cofibre fill-ins always exist. Neeman showed that there is always at least one "good" fill-in, i.e., one whose mapping cone is exact. Verdier constructed a fill-in of a particular form in his proof of the lemma, which we call "Verdier good". We show that for several classes of morphisms of exact triangles, the notions of good and Verdier good agree. We prove a lifting criterion for commutative squares in terms of (Verdier) good fill-ins. Using our results on good fill-ins, we also prove a pasting lemma for homotopy cartesian squares.
Cite
@article{arxiv.2008.03643,
title = {On good morphisms of exact triangles},
author = {J. Daniel Christensen and Martin Frankland},
journal= {arXiv preprint arXiv:2008.03643},
year = {2023}
}
Comments
v3: Minor changes. Accepted for publication in the Journal of Pure and Applied Algebra