Tamar Janelidze
We introduce relative homological and weakly homological categories, where ``relative'' refers to a distinguished class of normal epimorphisms. It is a generalization of homological categories, but also protomodular categories can be regarded as examples. We indicate that the relative versions of various homological lemmas can be proved in a relative homological category.
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We study the notion of fundamental group in the framework of descent-exact homological categories. This setting is sufficiently wide to include several categories of "algebraic" nature such as the almost abelian categories, the semi-abelian categories, and the categories of topological semi-abelian algebras. For many adjunctions in this context, the fundamental groups are described by generalised Brown-Ellis-Hopf formulae for the integral homology of groups.
We introduce the notion of homological systems $Θ$ for triangulated categories. Homological systems generalize, on one hand, the notion of stratifying systems in module categories, and on the other hand, the notion of exceptional sequences in triangulated categories. We prove that, attached to the homological system $Θ,$ there are two standardly stratified algebras $A$ and $B,$ which are derived equivalent. Furthermore, it is proved that the category $\F(Θ),$ of the $Θ$-filtered objects in a triangulated category $\T,$ admits in a very natural way an structure of an exact category, and then th…
We show that each rigid monoidal category A over a field defines a family of universal tensor categories, which together classify all faithful monoidal functors from A to tensor categories. Each of the universal tensor categories classifies monoidal functors of a given 'homological kernel' and can be realised as a sheaf category, not necessarily on A. This yields a theory of 'local abelian envelope' which completes the notion of monoidal abelian envelopes.
Some Properties of Homology and Exactness of Nomura's Homology Sequences in a Grandis Homological Category
本文研究了 Grandis 同调范畴中交换方块的 Lambek 不变量，证明了 Nomura 零序列的存在性及其正合性的充分条件，并确立了左右同调的一致性。
Lambek Invariants of Commutative Squares in a Homological Category
本文在 Grandis 的半正合与同调范畴中研究了 Lambek 不变量，将 Lambek 同构定理推广至该范畴，并补充了相关引理的证明。
Relative ideals in homological categories, with an application to MV-algebras
在同调范畴中引入关于忠实保守右伴随的相对理想概念，证明对象可表示为相对理想，并应用于证明 hoops 范畴半阿贝尔性及 MV-代数范畴原模性。
Homological support of big objects in tensor-triangulated categories
本文借助同调剩余域为张量三角范畴中的大对象引入支撑概念，并建立相应的张量积公式。
Finiteness of homological dimensions in triangulated categories
本文研究三角范畴中的有限维数、大有限维数和全局维数，建立重合范畴中这些维数与外范畴中维数的关系不等式，为扩展已知环的同调维数结果到弱近似三角范畴提供统一框架。
Homological Lemmas in a Non-pointed Context
本文证明经典同调引理的非点态版本在配备适当偏序单余反射子范畴的正则原模范畴中成立，并给出酉环、布尔代数、海廷代数、MV-代数及其拓扑模型和基本拓扑斯对偶范畴等实例。
We define model category structures on the category of chain complexes over a Grothendieck abelian category depending on the choice of a generating family, and we study their behaviour with respect to tensor products and stabilization. This gives convenient tools to construct and understand triangulated categories of motives and we consider here the case of mixed motives over a regular base scheme.
Homological lemmas for (non-abelian) group-like structures by diagram chasing in a self-dual context
本文通过引入'诺特形式'的上下文，展示了如何在非阿贝尔群状结构范畴中，利用自对偶方法处理同调引理。
Extriangulated categories were introduced by Nakaoka and Palu as a simultaneous generalization of exact categories and triangulated categories. In this paper, we introduce and develop an analogous theory of Auslander-Buchweitz approximations for extriangulated categories. We establish the existence of precovers pand preenvelopesq and obtain characterizations of relative homological dimensions, which are based on certain subcategories under finiteness of resolutions. Finally, we give a description of cotorsion pairs on extriangulated categories under some conditions, and provide a characterizat…
Di-Exact Categories and Lattices of Normal Subobjects
本文研究arXiv:2404.15896中的同调代数范畴框架，聚焦同调自对偶性等条件并找到区分反例，通过正规子对象格的格理论性质（如模性）刻画框架性质，还考虑正则范畴中的自对偶性。
Relative quasi-Gorenstein homological dimensions in extriangulated categories
本文在扩张三角范畴中建立拟Gorenstein投射与内射子范畴的迭代稳定性，推广相对Ext消没判据，并构造测试模族以检测模的投射维数上界。
We discuss homological mirror symmetry of Fermat polynomials in terms of derived Morita equivalence between derived categories of coherent sheaves and Fukaya-Seidel categories (a.k.a. perfect derived categories of directed Fukaya categories), and some related aspects such as stability conditions, (kinds of) modular forms, and Hochschild homologies.
We show that direct summands of certain additive functors arising as bifunctors with a fixed argument in an abelian category are again of that form whenever the fixed argument has finite length or, more generally, satisfies the descending chain condition on images of nested endomorphisms. In particular, this provides a positive answer to a conjecture of M. Auslander in the case of categories of finite modules over artin algebras. This implies that the covariant Ext functors are the only injectives in the category of defect-zero finitely presented functors on such categories.
Grandis's non-abelian homological algebra generalizes standard homological algebra in abelian categories to \textit{homological categories}, which are a broader class of categories including for example the category of lattices and Galois connections. Here, we prove that if $\mathsf{C}$ is any category with an ideal of null morphisms with respect to which (co)kernels exist, then the arrow category of $\mathsf{C}$ is a homological category. This broadens the applicability of Grandis's framework substantially. In particular, one can form the homology of chain complexes in $\mathsf{C}$ by taking …
We prove an injective version of Schanuel's lemma from homological algebra in the setting of exact categories.
Homological Aspects of Separable Extensions of Triangulated Categories
研究三角范畴在可分离扩张下的同调行为，证明有限全局维数、格氏性质和正则性等同调不变量在扩张下保持不变，并建立奇异范畴之间的关系，证明可分离扩张的奇异范畴等价于其奇异范畴的可分离扩张。
Representations over diagrams of abelian categories I: Global structure and homological objects
本文系统研究阿贝尔范畴图表上的表示，探讨表示范畴的Grothendieck结构、重要函子与伴随关系，并刻画特殊同调对象，为后续工作奠定基础。
We prove that any faithful Frobenius functor between abelian categories preserves the Gorenstein projective dimension of objects. Consequently, it preserves and reflects Gorenstein projective objects. We give conditions on when a Frobenius functor preserves the stable categories of Gorenstein projective objects, the singularity categories and the Gorenstein defect categories, respectively. In the appendix, we give a direct proof of the following known result: for an abelian category with enough projectives and injectives, its global Gorenstein projective dimension coincides with its global Gor…
Intrinsic homological algebra for triangulated categories
本文提出了一种新的框架，用于研究三角范畴的同调性质，包括正则性、有限维数、戈林斯滕性质等，并推广了回溯理论中的结果。
In the first part of this paper, we prove the existence of torsion free covers in the category of representations of quivers, $(Q,R-Mod)$, for a wide class of quivers included in the class of the so-called source injective representation quivers provided that any direct sum of torsion free and injective $R$-modules is injective. In the second part, we prove the existence of $\mathscr{F}_{cw}$-covers and $\mathscr{F}_{cw}^{\perp}$-envelopes for any quiver $Q$ and any ring $R$ with unity, where $\mathscr{F}_{cw}$ is the class of all "componentwise" flat representations of $Q$.
This survey article on relative homological algebra in bivariant K-thoery is mainly intended for readers with a background knowledge in triangulated categories. We briefly recall the general theory of relative homological algebra in triangulated categories and latter specialize it to the non-equivariant and the equivariant bivariant K-thoery, where the actions on C*-algebras is by a finite cyclic group. We conclude by the explicit computation of the universal abelian invariant for separable C*-algebras with the action of $\mathbb{Z}/4$ by automorphisms.
The aim of the paper is twofold. Firstly, we give an axiomatic presentation of Donaldson-Thomas theory for categories of homological dimension at most one with potential. In particular, we provide rigorous proofs of all standard results concerning the integration map, wall-crossing, PT-DT correspondence, etc. following Kontsevich and Soibelman. We also show the equivalence of their approach and the one given by Joyce and Song. Secondly, we relate Donaldson-Thomas functions for such a category with arbitrary potential to those with zero potential under some mild conditions. As a result of this,…
A Homological View of Categorical Algebra
该研究为范畴代数的同调与同伦方法构建基础，选取从z-正合范畴到阿贝尔范畴等多层公理框架并厘清其关系，开发含基本图引理的范畴计算工具，发现其可用于弱范畴环境。
Homological epimorphisms in functor categories and singularity categories
本文研究了函子范畴中的同调满射，证明在理想满足特定条件时奇点范畴间存在等价关系，推广了 Xiao-Wu Chen 的结论，并应用于单点扩张范畴证明其奇点等价。
We generalize the notion of an exact category and introduce weakly exact categories. A proof of the snake lemma in this general setting is given. Some applications are given to illustrate how one can do homological algebra in a weakly exact category.
The theory of derivators enhances and simplifies the theory of triangulated categories. In this article a notion of fibered (multi-)derivator is developed, which similarly enhances fibrations of (monoidal) triangulated categories. We present a theory of cohomological as well as homological descent in this language. The main motivation is a descent theory for Grothendieck's six operations.
In this work, we develop the theory of $k$-idempotent ideals in the setting of dualizing varieties. Several results given previously in \cite{APG} by M. Auslander, M. I. Platzeck, and G. Todorov are extended to this context. Given an ideal $\mathcal{I}$ (which is the trace of a projective module), we construct a canonical recollement which is the analog to a well-known recollement in categories of modules over artin algebras. Moreover, we study the homological properties of the categories involved in such a recollement. Consequently, we find conditions on the ideal $\mathcal{I}$ to obtain quas…
Let $\mathcal{C}$ be a triangulated category with a proper class $ξ$ of triangles. Asadollahi and Salarian introduced and studied $ξ$-Gorenstein projective and $ξ$-Gorenstein injective objects, and developed Gorenstein homological algebra in $\mathcal{C}$. In this paper, we further study Gorenstein homological properties for a triangulated category. First, we discuss the stability of $ξ$-Gorenstein projective objects, and show that the subcategory $\mathcal{GP}(ξ)$ of all $ξ$-Gorenstein projective objects has a strong stability. That is, an iteration of the procedure used to define the $ξ$-Gor…
Ideals are used to define homological functors for additive categories. In abelian categories the ideals corresponding to the usual universal objects are principal, and the construction reduces, in a choice dependent way, to homology groups. Applications are considered: derived categories and functors.
In the context of regular unital categories we introduce an intrinsic version of the notion of a Schreier split epimorphism, originally considered for monoids. We show that such split epimorphisms satisfy the same homological properties as Schreier split epimorphisms of monoids do. This gives rise to new examples of S-protomodular categories, and allows us to better understand the homological behaviour of monoids from a categorical perspective.
We generalise notions of Gorenstein homological algebra for rings to the context of arbitrary abelian categories. The results are strongest for module categories of rngs with enough idempotents. We also reformulate the notion of Frobenius extensions of noetherian rings into a setting which allows for direct generalisation to arbitrary abelian categories. The abstract theory is then applied to the BGG category O for Lie superalgebras, which can now be seen as a "Frobenius extension" of the corresponding category for the underlying Lie algebra and is therefore "Gorenstein". In particular we obta…
The present paper is an extension of a previous paper written in collaboration with Markus Reineke dealing with quiver representations. The aim of the paper is to generalize the theory and to provide a comprehensive theory of Donaldson-Thomas invariants for abelian categories of homological dimension one (without potential) satisfying some technical conditions. The theory will apply for instance to representations of quivers, coherent sheaves on smooth projective curves, and some coherent sheaves on smooth projective surfaces. We show that the (motivic) Donaldson-Thomas invariants satisfy the …
Transfer of homological objects in exact categories via adjoint triples. Applications to functor categories
本文利用正合范畴间的伴随三元组族，从已知余挠对构造两个典范余挠对，并应用于函子范畴，通过茎函子诱导余挠对，最终给出投射与内射对象的内在刻画。
Let $(\mathcal{C},\mathbb{E},\mathfrak{s})$ be an extriangulated category with a proper class $ξ$ of $\mathbb{E}$-triangles. The authors introduced and studied $ξ$-$\mathcal{G}$projective and $ξ$-$\mathcal{G}$injective in \cite{HZZ}. In this paper, we discuss Gorenstein homological dimensions for extriangulated categories. More precisely, we first give some characterizations of $ξ$-$\mathcal{G}$projective dimension by using derived functors on $\mathcal{C}$. Second, let $\mathcal{P}(ξ)$ (resp. $\mathcal{I}(ξ)$) be a generating (resp. cogenerating) subcategory of $\mathcal{C}$. We show that the…
Exactness of the 2-categories of abelian and triangulated categories
本文引入$2$-同调范畴概念，证明双正合、三角、带点、加性及阿贝尔范畴的$2$-范畴均为$2$-同调，并给出统一商构造准则。
Transport of structure in higher homological algebra
本文填补了高阶同调代数中(n+2)-角化等范畴“结构转移”的空白，证明其骨架典范继承同构结构，并引入了n-外角化函子概念。
We consider a notion of exact sequences in any -not necessarily exact- pointed category relative to a given (E;M)-factorization structure. We apply this notion to introduce and investigate a new notion of exact sequences of semimodules over semirings relative to the canonical image factorization. Several homological results are proved using the new notion of exactness including some restricted versions of the Short Five Lemma and the Snake Lemma opening the door for introducing and investigating homology objects in such categories. Our results apply in particular to the variety of commutative …
Homological residue fields as comodules over coalgebras
本文研究张量三角范畴的同调剩余域，通过跨代数、几何与拓扑的多个例子将其明确刻画为余代数上的余模范畴，并揭示其编码谱点切向数据的自然意义。
We introduce new enhancements for the bounded derived category $D^b(Coh(X))$ of coherent sheaves on a suitable scheme $X$ and for its subcategory $Perf(X)$ of perfect complexes. They are used for translating Fourier-Mukai functors to functors between derived categories of dg algebras, for relating homological smoothness of $Perf(X)$ to geometric smoothness of $X,$ and for proving homological smoothness of $D^b(Coh(X)).$ Moreover, we characterize properness of $Perf(X)$ and $D^b(Coh(X))$ geometrically.
We prove nilpotence theorems in tensor-triangulated categories using suitable Gabriel quotients of the module category, and discuss examples.
Homological surrogates in topological and bornological analysis
本文为具有核的强亏格-精确范畴构造同调替代对象，通过三项复形局部化给出显式核余核公式，并为多种完备空间及生糙模范畴建立导出等价阿贝尔模型与极大精确结构。
This article develops several main results for a general theory of homological algebra in categories such as the category of sheaves of idempotent modules over a topos. In the analogy with the development of homological algebra for abelian categories the present paper should be viewed as the analogue of the development of homological algebra for abelian groups. Our selected prototype, the category Bmod of modules over the Boolean semifield B is the replacement for the category of abelian groups. We show that the semi-additive category Bmod fulfills analogues of the axioms AB1 and AB2 for abeli…
We develop the basic constructions of homological algebra in the (appropriately defined) unbounded derived categories of modules over algebras over coalgebras over noncommutative rings (which we call semialgebras over corings). We define double-sided derived functors SemiTor and SemiExt of the functors of semitensor product and semihomomorphisms, and construct an equivalence between the exotic derived categories of semimodules and semicontramodules. Certain (co)flatness and/or (co)projectivity conditions have to be imposed on the coring and semialgebra to make the module categories abelian (an…
Let $G$ and $A$ be objects of a finitely cocomplete homological category $\mathbb C$. We define a notion of an (internal) action of $G$ of $A$ which is functorially equivalent with a point in $\mathbb C$ over $G$, i.e. a split extension in $\mathbb C$ with kernel $A$ and cokernel $G$. This notion and its study are based on a preliminary investigation of cross-effects of functors in a general categorical context. These also allow us to define higher categorical commutators. We show that any proper subobject of an object $E$ (i.e., a kernel of some map on $E$ in $\mathbb C$) admits a "conjugatio…
For any ring R the category of monomorphisms is a full subcategory of the morphsim category over R, where the latter is equivalent to the module category of the triangular matrix ring with entries the ring R. In this work, we consider the monomorphism category as a full subcategory of the module category over the Morita ring with all entries the ring R and zero bimodule homomorphisms. This approach provides an interesting link between Morita rings and monomorphism categories. The aim of this paper is two-fold. First, we construct Gorenstein-projective modules over Morita rings with zero bimodu…
Persistent homological Quillen-McCord theorem
本文遵循 Barmak 的证明方案，表述并证明了关于交错距离稳定的同调 Quillen-McCord 定理，并引入持久对象、条形码式分解等工具以支撑定理的表述与应用。
Triangulated Categories of Big Motives via Enriched Functors
本文利用丰富函子的Grothendieck范畴同调代数，为Voevodsky的合理对应大动机范畴构造了两个模型。
In Enochs' relative homological dimension theory occur the so called (co)resolvent and (co)proper dimensions which are defined using proper and coproper resolutions constructed by precovers and preenvelopes, respectively. Recently, some authors have been interested in relative homological dimensions defined by just exact sequences. In this paper, we contribute to the investigation of these relative homological dimensions. We first study the relation between these two kinds of relative homological dimensions and establish some "transfer results" under adjoint pairs. Then, relative global dimens…
An important example of a model category is the category of unbounded chain complexes of R-modules, which has as its homotopy category the derived category of the ring R. This example shows that traditional homological algebra is encompassed by Quillen's homotopical algebra. The goal of this paper is to show that more general forms of homological algebra also fit into Quillen's framework. Specifically, any set of objects in a complete and cocomplete abelian category A generates a projective class on A, which is exactly the information needed to do homological algebra in A. The main result is t…
We introduce relative preresolving subcategories and precoresolving subcategories of an abelian category and define homological dimensions and codimensions relative to these subcategories respectively. We study the properties of these homological dimensions and codimensions and unify some important properties possessed by some known homological dimensions. Then we apply the obtained properties to special subcategories and in particular to module categories. Finally we propose some open questions and conjectures, which are closely related to the generalized Nakayama conjecture and the strong Na…
Classical homological algebra takes place in additive categories. In homotopy theory such additive categories arise as homotopy categories of ``additive groupoid enriched categories'', in which a secondary analog of homological algebra can be performed. We introduce secondary chain complexes and secondary resolutions leading to the concept of secondary derived functors. As a main result we show that the E_3-term of the Adams spectral sequence can be expressed as a secondary derived functor. This result can be used to compute the E_3-term explicitly by an algorithm.
Relative $Q$-shaped homological algebra
本文研究了基于精确结构的相对Q形同调代数，定义了精确模型结构和上同调函子，并展示了Q形导出范畴作为Q形同调范畴的Verdier商。
Given a rigid tensor-triangulated category and a vector space valued homological functor for which the Künneth isomorphism holds, we construct a universal graded-Tannakian category through which the given homological functor factors. We use this to (unconditionally) construct graded-Tannakian categories of pure motives associated to a fixed Weil cohomology theory, with a fiber functor realizing the given cohomology theory. For $\ell$-adic cohomology and a ground field which is algebraic over a finite field, this category is Tannakian. In this case, we obtain in particular motivic Galois groups…
A functorial approach to $n$-abelian categories
本文发展了$n$-阿贝尔范畴的函子方法，利用有限表示函子范畴重新表述其公理，并借此推广了阿贝尔范畴公理，扩展了高阶Auslander对应。
Remarks on cotorsion theories
本文以 Abel 范畴的余挠理论语言重述经典同调代数结果，涵盖同调维数、Künneth 与万有系数公式，并讨论完全无圈余挠理论及链复形分解。
A subcategory with remarkable homological properties via actions of tensor categories
本文通过给有限维代数的模范畴配备有限张量范畴的作用引入子范畴$\boldsymbol{\textit{PM}}$，证明其同调性质及$\boldsymbol{\textit{C}}$-等变Auslander(-Solberg)对应，结合实例说明其在特定代数中的结构。
The homological spectrum for monoidal triangulated categories
本文为幺半三角范畴引入同调素谱，通过扩展比较映射选取纤维极大元定义，并证明在分层条件下满足扩展的钢之神经条件，适用于有限群概形及Benson--Witherspoon Hopf代数等情形。
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