Let T be a set of elements in a ring A. The set T is right permutable if for any a ∈ A and t ∈ T, there exist b ∈ A, u ∈ T such that au = tb. A multiplicative set in a ring A is any subset T of A such that 1 ∈ T,0 ∉ T and T is closed under multiplication. A completely prime ideal in a ring A is any proper ideal B such that A\B is a multiplicative set (i.e. A/Bis a domain). A minimal prime ideal (resp. minimal completely prime ideal) in a ring A is any prime (resp. completely prime) ideal P such that P contains no properly any other prime ideal (resp. completely prime ideal) of A. Let I be any proper ideal of a ring A. The set of all elements a ∈ A such that a + I is a regular element of A/I is denoted by c(I). In particular, c(0) is the set of all regular elements of A.

Rings of quotients

Basic concepts of enriched category theory

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The Theory Of Categories

Discrete derived categories were studied initially by Vossieck (J Algebra 243:168–176, 2001) and later by Bobinski et al. (Cent Eur J Math 2:19–49, 2004). In this article, we describe the homomorphism hammocks and autoequivalences on these categories. We classify silting objects and bounded t-structures.

/pdf/discrete-derived-categories-i-homomorphisms-autoequivalences-132rqfue58.pdf

Discrete derived categories I: homomorphisms, autoequivalences and t-structures

Cyclic posets are generalizations of cyclically ordered sets. In this article, we show that any cyclic poset gives rise to a Frobenius category over any discrete valuation ring R. The stable category of a Frobenius category is always triangulated and has a cluster structure in many cases. The continuous cluster categories of [14], the infinity-gon of [12], and the m-cluster category of type A ∞ (m ≥ 3) [13] are examples of this construction as well as some new examples such as the cluster category of ℤ2. An extension of this construction and further examples are given in [16].

https://people.brandeis.edu/~igusa/Papers/PosetsC140709.pdf

Cluster Categories Coming from Cyclic Posets

https://pure.mpg.de/pubman/item/item_3123021_1/component/file_3123022/berg_quiver_2010.pdf

The quiver of projectives in hereditary categories with Serre duality

Clausen predicted that Chevalley's idele class group of a number field $F$ appears as the first $K$-group of the category of locally compact $F$-vector spaces. This has turned out to be true, and even generalizes to the higher $K$-groups in a suitable sense. We replace $F$ by a semisimple $\mathbb{Q}$-algebra, and obtain Frohlich's non-commutative idele class group in an analogous fashion, modulo the reduced norm one elements. Even in the number field case our proof is simpler than the existing one, and based on the localization theorem for percolating subcategories. Finally, using class field theory as input, we interpret Hilbert's reciprocity law (as well as a noncommutative variant) in terms of our results.

A non-commutative analogue of Clausen's view on the id\`{e}le class group

Let k be an algebraically closed field and A a k-linear hereditary category satisfying Serre duality with no infinite radicals between the preprojective objects. If A is generated by the preprojective objects, then we show that A is derived equivalent to rep_k Q for a so called strongly locally finite quiver Q. To this end, we introduce light cone distances and round trip distances on quivers which will be used to investigate sections in stable translation quivers of the form \mathbb{Z} Q.

The Quiver of Projectives in Hereditary Categories with Serre Duality

As a generalization of a Calabi-Yau category, we will say a k-linear Hom-finite triangulated category is fractionally Calabi-Yau if it admits a Serre functor S and there is an n > 0 with S^n = [m]. An abelian category will be called fractionally Calabi-Yau is its bounded derived category is. We provide a classification up to derived equivalence of abelian hereditary fractionally Calabi-Yau categories (for algebraically closed k). They are: the category of finite dimensional representations of a Dynkin quiver, the category of finite dimensional nilpotent representations of a cycle, and the category of coherent sheaves on an elliptic curve or a weighted projective line of tubular type. To obtain this classification, we introduce generalized 1-spherical objects and use them to obtain results about tubes in hereditary categories (which are not necessarily fractionally Calabi-Yau).

/pdf/abelian-hereditary-fractionally-calabi-yau-categories-1favx44e05.pdf

Abelian hereditary fractionally Calabi-Yau categories

In an ongoing project to classify all hereditary abelian categories, we provide a classification of Ext-finite directed hereditary abelian categories satisfying Serre duality up to derived equivalence. In order to prove the classification, we will study the shapes of the Auslander-Reiten components extensively and use appropriate generalisations of tilting objects and coordinates, namely partial tilting sets and probing of objects by quasi-simples.

Adam-Christiaan van Roosmalen

Papers

The quiver of projectives in hereditary categories with Serre duality

A non-commutative analogue of Clausen's view on the id\`{e}le class group

The Quiver of Projectives in Hereditary Categories with Serre Duality

Abelian hereditary fractionally Calabi-Yau categories

Classification of abelian hereditary directed categories satisfying Serre duality