The λ-Pure Global Dimension of Grothendieck Categories and Its Applications to Derived and Singularity Categories

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This research paper investigates the concept of λ-pure global dimension in Grothendieck categories, demonstrating its impact on the relationship between ordinary and λ-pure derived categories and its connection to the vanishing of λ-pure singularity categories.

Samenvatting

• Bibliographic Information: Wang, X., Yao, H., & Shen, L. (2024). λ-pure global dimension of Grothendieck categories and some applications. arXiv preprint arXiv:2411.05356v1.

• Research Objective: This paper aims to explore the applications of λ-pure global dimension in Grothendieck categories, focusing on its implications for derived and singularity categories.

• Methodology: The authors utilize concepts and techniques from homological algebra, particularly focusing on λ-pure acyclic complexes, λ-pure derived categories, λ-pure projective dimensions, and λ-pure singularity categories. They prove a series of theorems and propositions to establish relationships between these concepts.

• Key Findings:

  • The paper establishes a connection between the finiteness of λ-pure global dimension and the structure of derived categories. Specifically, it shows that if the λ-pure global dimension of a Grothendieck category A is finite, then the ordinary bounded derived category of A and the bounded λ-pure derived category of A differ only by a homotopy category.
  • The authors demonstrate that the λ-pure singularity category of a Grothendieck category A vanishes if and only if the λ-pure global dimension of A is finite.
  • The paper also investigates the feasibility of a λ-pure version of the Buchweitz-Happel Theorem. It concludes that the general construction of the classic theorem does not directly translate to the λ-pure setting due to the specific properties of λ-pure projective objects.

• Main Conclusions: The concept of λ-pure global dimension provides valuable insights into the structure and properties of Grothendieck categories. Its finiteness has significant implications for the relationship between ordinary and λ-pure derived categories and the vanishing of λ-pure singularity categories. However, establishing a direct λ-pure analog of the Buchweitz-Happel Theorem requires further investigation and potentially different approaches.

• Significance: This research contributes to the field of homological algebra by deepening the understanding of λ-pure global dimension and its applications in characterizing Grothendieck categories and their associated derived and singularity categories.

• Limitations and Future Research: The paper primarily focuses on theoretical aspects of λ-pure global dimension. Further research could explore specific examples and applications of these concepts in other areas of mathematics or related fields. Additionally, investigating alternative approaches to formulate a λ-pure version of the Buchweitz-Happel Theorem remains an open question.

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Lambda-pure global dimension of Grothendieck categories and some applications

by Xi Wang, Hai... om arxiv.org 11-11-2024

https://arxiv.org/pdf/2411.05356.pdf

Diepere vragen

How can the concept of λ-pure global dimension be applied to study other homological invariants or structures in Grothendieck categories beyond derived and singularity categories?

The concept of λ-pure global dimension, measuring the resolvability of objects in a Grothendieck category by λ-pure projective resolutions, can be a powerful tool for investigating various homological aspects beyond derived and singularity categories. Here are some potential avenues:
1. Relative Homological Algebra:

λ-Pure Derived Functors: Just as the paper defines Pλext, one can define and study other λ-pure derived functors, like Tor. These functors can reveal finer homological information compared to their classical counterparts, potentially leading to new invariants.
λ-Pure Model Structures: The existence of enough λ-pure projective objects suggests the possibility of constructing and studying λ-pure model structures on categories of chain complexes. This could provide a framework for studying λ-pure homotopy theory and related invariants.
2. Structure of Subcategories:

λ-Pure Projective Dimension of Complexes: Instead of just objects, one can investigate the λ-pure projective dimension of complexes in Dλ(A). This could lead to a deeper understanding of the structure of Dλ(A) and its subcategories.
Classifying Subcategories: Finite λ-pure global dimension might impose restrictions on the existence of certain subcategories within a Grothendieck category. For instance, are there analogues of "thick subcategories" defined using λ-pure short exact sequences?
3. Connections to Other Purity Notions:

Comparison with Other Purity Concepts: Relating λ-pure global dimension to other notions of purity (e.g., pure-injectivity, n-purity) could provide new perspectives on these concepts and their interplay.
Applications to Specific Categories: Exploring λ-pure global dimension in concrete Grothendieck categories like categories of sheaves or representations of quivers could yield specific results and applications within those fields.

Could there be alternative characterizations of Grothendieck categories with finite λ-pure global dimension that do not rely on the vanishing of the λ-pure singularity category?

Yes, it's plausible to seek alternative characterizations of Grothendieck categories with finite λ-pure global dimension without directly invoking the λ-pure singularity category. Here are some potential approaches:
1. Finiteness Conditions on Resolutions:

Bounded λ-Pure Projective Resolutions: One could explore whether finite λ-pure global dimension is equivalent to the existence of bounded λ-pure projective resolutions for all objects in the category.
Syzygies and Resolutions: Investigate properties of syzygies (kernels of differentials) in λ-pure projective resolutions. Finite λ-pure global dimension might be reflected in finiteness conditions on the lengths of these resolutions or the structure of syzygies.
2. Properties of λ-Pure Derived Functors:

Vanishing of Pλext: Instead of the singularity category, focus on the vanishing of Pλext. Perhaps finite λ-pure global dimension is equivalent to the vanishing of Pλext for sufficiently large degrees.
Finiteness of Pλext: Explore whether finite λ-pure global dimension implies finiteness conditions (e.g., finite generation, finite presentation) on the groups Pλext.
3. Axiomatic Approaches:

λ-Pure Version of Kaplansky Classes: Develop a λ-pure analogue of Kaplansky classes, which are classes of modules characterized by certain homological properties. Finite λ-pure global dimension might correspond to a specific λ-pure Kaplansky class.
Model-Theoretic Characterizations: Explore if there are model-theoretic properties (e.g., properties of the first-order theory of a Grothendieck category) that capture the notion of finite λ-pure global dimension.

What mathematical structures or concepts from other fields could potentially provide insights or tools to develop a modified version of the Buchweitz-Happel Theorem applicable to the λ-pure setting?

The difficulty in adapting the Buchweitz-Happel Theorem to the λ-pure setting stems from the rigidity of λ-pure projective objects, as highlighted by Proposition 4.5. To overcome this, we need structures that capture "approximation" or "asymptotic" behavior. Here are some potential avenues:
1. Homotopy Theory and Model Categories:

Weaker Model Structures: Instead of focusing solely on λ-pure projective objects, explore weaker model structures on chain complexes where the cofibrant objects are "close" to being λ-pure projective in a suitable sense.
Homotopy Limits/Colimits: Investigate if homotopy limits or colimits can be used to construct objects that behave like Gorenstein projective objects in the λ-pure setting.
2. Triangulated Categories and Localization:

Localization at Thick Subcategories: Explore localizations of the λ-pure derived category at thick subcategories other than Kb(PPλ). This might lead to alternative "singularity-like" categories that admit a Buchweitz-Happel type description.
Stable ∞-Categories: Consider the framework of stable ∞-categories, which provide a more flexible setting for homotopy theory and might offer tools to construct a suitable stable category equivalent to a "λ-pure singularity category."
3. Representation Theory and Quivers:

Representations of λ-Presentable Categories: If the Grothendieck category arises as a category of representations, investigate representations of the category of λ-presentable objects. This might provide a different perspective on λ-pure projective objects and their generalizations.
Quivers with Relations: If the category has a representation-theoretic interpretation via quivers, explore if adding appropriate relations to the quiver can help define a suitable notion of "λ-pure Gorenstein projective" objects.
4. Higher Category Theory:

Higher Algebraic Structures: Explore if higher algebraic structures like ∞-categories or derivators can provide a more natural framework for capturing the nuances of λ-purity and developing a modified Buchweitz-Happel Theorem.