Research pathwaysCategory TheoryPlanned
Stable ∞-categories
Optional research direction: stable ∞-categories, in which fibre and cofibre sequences coincide, as enhancements of triangulated categories; spectra; and the passage from a stable ∞-category to its triangulated homotopy category.
math.cat.stable-infinity-categories
The lesson for this topic has not been written yet. The outline below is part of the curriculum map and has not been reviewed.
Builds on
Required prerequisites, all the way down: 63
You will learn to
- Define stable ∞-categories and give examples, including derived ∞-categories of rings and the ∞-category of spectra.
- Explain why the homotopy category of a stable ∞-category is triangulated.
- Explain how stable ∞-categories resolve the non-functoriality of cones.
Definition
- An ∞-category is stable if it has a zero object, every morphism has a fibre and a cofibre, and a triangle is a fibre sequence if and only if it is a cofibre sequence.
- Spectra form the stable ∞-category Sp, the stabilisation of the ∞-category of pointed spaces.
Theorem
- The homotopy category of a stable ∞-category is canonically triangulated (Lurie, Higher Algebra).
- In a stable ∞-category, cofibres are functorial.
- The derived category of a ring is the homotopy category of a stable ∞-category.
Common misconceptions
- Thinking stable ∞-categories are triangulated categories under a new name; they carry strictly more information.
Further reading
- Jacob Lurie, Higher Algebra — Book-length manuscript, distributed online by the author.
- Jacob Lurie, Higher Topos Theory (2009)