Metrics on triangulated categories (1901.01453v3)

Abstract: In this survey we explain the results of the recent article arXiv:1806.06471. Following a 1973 article by Lawvere one can define metrics on categories, and following Kelly's 1982 book one can complete a category with respect to its metric. We specialize these general constructions to triangulated categories, and restrict our attention to "good metrics". And the remarkable new theorem is that, when we start with a triangulated category $\mathcal S$ with a good metric, its completion $\mathfrak{L}(\mathcal{S})$ contains an interesting subcategory $\mathfrak{S}(\mathcal{S})$ which is always triangulated. As special cases we obtain $\mathcal{H}^0(\mathrm{Perf}(X))$ and $D^b_{\mathrm{coh}}(X)$ from each other. We also give a couple of other examples.