English

Stability conditions on morphisms in a category

Algebraic Geometry 2023-02-22 v7 Algebraic Topology Representation Theory

Abstract

Let hC\mathrm{h}\mathscr{C} be the homotopy category of a stable infinity category C\mathscr{C}. Then the homotopy category hCΔ1\mathrm{h}\mathscr{C}^{\Delta^{1}} of morphisms in the stable infinity category C\mathscr{C} is also triangulated. Hence the space StabhCΔ1\mathsf{Stab}\,{ \mathrm{h}\mathscr{C}^{\Delta^{1}}} of stability conditions on hCΔ1\mathrm{h}\mathscr{C}^{\Delta^{1}} is well-defined though the non-emptiness of StabhCΔ1\mathsf{Stab}\,{ \mathrm{h}\mathscr{C}^{\Delta^{1}}} is not obvious. Our basic motivation is a comparison of the homotopy type of StabhC\mathsf{Stab}{\mathrm{h}\mathscr{C}} and that of StabhCΔ1\mathsf{Stab}{\mathrm{h}\mathscr{C}^{\Delta^{1}}}. Under the motivation we show that functors d0d_{0} and d1 ⁣:CΔ1Cd_{1} \colon \mathscr{C}^{\Delta^{1}} \rightrightarrows \mathscr{C} induce continuous maps from StabhC\mathsf{Stab} {\mathrm{h}\mathscr{C}} to StabhCΔ1\mathsf{Stab}{\mathrm{h}\mathscr{C}^{\Delta^{1}}} contravariantly where d0d_{0} (resp. d1d_{1}) takes a morphism to the target (resp. source) of the morphism. As a consequence, if StabhC\mathsf{Stab}{\mathrm{h}\mathscr{C}} is nonempty then so is StabhCΔ1\mathsf{Stab}{\mathrm{h}\mathscr{C}^{\Delta^{1}}}. Assuming C\mathscr{C} is the derived infinity category of the projective line over a field, we further study basic properties of d0d_{0}^{*} and d1d_{1}^{*}. In addition, we give an example of a derived category which does not have any stability condition.

Keywords

Cite

@article{arxiv.1905.05470,
  title  = {Stability conditions on morphisms in a category},
  author = {Kotaro Kawatani},
  journal= {arXiv preprint arXiv:1905.05470},
  year   = {2023}
}

Comments

26 pages, comments are welcome. For v2, added subsection 2.2 which gives a description of a Serre functor of the category of morphisms in $\mathbf D$. For v3, the proof of Proposition 3.3 has been updated. For v5, Section 6 was added. For v6, modified the proof of Proposition 6.1. For v7, minor revision for Proposition 6.1, final version

R2 v1 2026-06-23T09:05:43.818Z