Let R be a ring, Proj be the class of all the projective right R-modules, K be the full subcategory of the homotopy category K(Proj) whose class of objects consists of all the totally acyclic complexes, and MorK be th...Let R be a ring, Proj be the class of all the projective right R-modules, K be the full subcategory of the homotopy category K(Proj) whose class of objects consists of all the totally acyclic complexes, and MorK be the class of all the morphisms in K(Proj) whose cones belong to K. We prove that if K(Proj) has enough MorK-injective objects, then the Verdier quotient K(Proj)/K has small Hom-sets, and this last condition implies the existence of Gorenstein-projective precovers in Mod-R and of totally acyclic precovers in C(Mod-R).展开更多
Given a triangle functor F : A → B, the authors introduce the half image hIm F,which is an additive category closely related to F. If F is full or faithful, then hIm F admits a natural triangulated structure. However...Given a triangle functor F : A → B, the authors introduce the half image hIm F,which is an additive category closely related to F. If F is full or faithful, then hIm F admits a natural triangulated structure. However, in general, one can not expect that hIm F has a natural triangulated structure. The aim of this paper is to prove that hIm F admits a natural triangulated structure if and only if F satisfies the condition(SM). If this is the case, hIm F is triangle-equivalent to the Verdier quotient A/Ker F.展开更多
An additive functor F:A→B between additive categories is said to be objective,provided any morphism f in A with F(f)=0 factors through an object K with F(K)=0.We concentrate on triangle functors between triangulated ...An additive functor F:A→B between additive categories is said to be objective,provided any morphism f in A with F(f)=0 factors through an object K with F(K)=0.We concentrate on triangle functors between triangulated categories.The first aim of this paper is to characterize objective triangle functors F in several ways.Second,we are interested in the corresponding Verdier quotient functors VF:A→A/Ker F,in particular we want to know under what conditions VF is full.The third question to be considered concerns the possibility to factorize a given triangle functor F=F2F1with F1a full and dense triangle functor and F2a faithful triangle functor.It turns out that the behavior of splitting monomorphisms and splitting epimorphisms plays a decisive role.展开更多
Laszlo and Olsson constructed Grothendieck＇s six operations for constructible complexes on Artin stacks in etale cohomology under an assumption of finite cohomological dimension, with base change established on the l...Laszlo and Olsson constructed Grothendieck＇s six operations for constructible complexes on Artin stacks in etale cohomology under an assumption of finite cohomological dimension, with base change established on the level of sheaves. We give a more direct construction of the six operations for complexes on Deligne- Mumford stacks without the finiteness assumption and establish base change theorems in derived categories. One key tool in our construction is the theory of gluing finitely many pseudofunctors developed by Zheng （2014）. As an application, we prove a Lefschetz-Verdier formula for Deligne-Mumford stacks. We include both torsion and l-adic coefficients.展开更多
基金supported by the Spanish Government (Grant No. PID2020-113206GBI00, funded by MCIN/AEI/10.13039/501100011033)Junta de Andalucia (Grant No. P20-00770)。
文摘Let R be a ring, Proj be the class of all the projective right R-modules, K be the full subcategory of the homotopy category K(Proj) whose class of objects consists of all the totally acyclic complexes, and MorK be the class of all the morphisms in K(Proj) whose cones belong to K. We prove that if K(Proj) has enough MorK-injective objects, then the Verdier quotient K(Proj)/K has small Hom-sets, and this last condition implies the existence of Gorenstein-projective precovers in Mod-R and of totally acyclic precovers in C(Mod-R).
基金supported by the National Natural Science Foundation of China(Nos.11401001,11571329)the Project of Introducing Academic Leader of Anhui University(No.01001770)the Research Project of Anhui Province(No.KJ2015A101)
文摘Given a triangle functor F : A → B, the authors introduce the half image hIm F,which is an additive category closely related to F. If F is full or faithful, then hIm F admits a natural triangulated structure. However, in general, one can not expect that hIm F has a natural triangulated structure. The aim of this paper is to prove that hIm F admits a natural triangulated structure if and only if F satisfies the condition(SM). If this is the case, hIm F is triangle-equivalent to the Verdier quotient A/Ker F.
基金supported by National Natural Science Foundation of China(Grant Nos.11271251 and 11431010)Specialized Research Fund for the Doctoral Program of Higher Education(GrantNo.20120073110058)
文摘An additive functor F:A→B between additive categories is said to be objective,provided any morphism f in A with F(f)=0 factors through an object K with F(K)=0.We concentrate on triangle functors between triangulated categories.The first aim of this paper is to characterize objective triangle functors F in several ways.Second,we are interested in the corresponding Verdier quotient functors VF:A→A/Ker F,in particular we want to know under what conditions VF is full.The third question to be considered concerns the possibility to factorize a given triangle functor F=F2F1with F1a full and dense triangle functor and F2a faithful triangle functor.It turns out that the behavior of splitting monomorphisms and splitting epimorphisms plays a decisive role.
基金supported by China’s Recruitment Program of Global Experts,National Natural Science Foundation of China(Grant No.11321101)Hua Loo-Keng Key Laboratory of Mathematics,Chinese Academy of Sciences,National Center for Mathematics and Interdisciplinary Sciences and Chinese Academy of Sciences
文摘Laszlo and Olsson constructed Grothendieck＇s six operations for constructible complexes on Artin stacks in etale cohomology under an assumption of finite cohomological dimension, with base change established on the level of sheaves. We give a more direct construction of the six operations for complexes on Deligne- Mumford stacks without the finiteness assumption and establish base change theorems in derived categories. One key tool in our construction is the theory of gluing finitely many pseudofunctors developed by Zheng （2014）. As an application, we prove a Lefschetz-Verdier formula for Deligne-Mumford stacks. We include both torsion and l-adic coefficients.
