The Gersten Conjecture for p-adic Étale Tate Twists and the p-adic Cycle Class Map
Core Concepts
This research paper proves the Gersten conjecture for p-adic étale Tate twists in mixed characteristic using the projective bundle formula and revisits the p-adic cycle class map, providing a more conceptual approach applicable to arbitrary finite residue fields.
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The Gersten conjecture for $p$-adic \'etale Tate twists and the $p$-adic cycle class map
LÜDERS, M. (2024). The Gersten conjecture for p-adic ´etale Tate twists and the p-adic cycle class map. arXiv preprint arXiv:2403.11853.
This paper aims to prove the Gersten conjecture for p-adic étale Tate twists in the mixed characteristic case, a question stemming from algebraic K-theory and relevant to the study of algebraic cycles. Additionally, it revisits and provides a more conceptual proof for the p-adic cycle class map previously studied in a more restricted setting.
Deeper Inquiries
Can the techniques used in this paper be extended to prove the Gersten conjecture for p-adic étale Tate twists for more general schemes beyond the smooth case?
Extending the Gersten conjecture for p-adic étale Tate twists to more general schemes beyond the smooth case presents significant challenges. While the paper leverages the projective bundle formula and a geometric presentation lemma to establish the conjecture for smooth schemes, these tools might not be sufficient or directly applicable in more general settings.
Here's a breakdown of the challenges and potential avenues for extending the results:
Challenges:
Lack of Projective Bundle Formula: The projective bundle formula, crucial to the paper's approach, might not hold for singular schemes or schemes with more complicated singularities.
Geometric Presentation Lemma: The geometric presentation lemma used in the paper relies on the smoothness of the schemes involved. Adapting this lemma for non-smooth schemes would require careful consideration of singularities.
A¹-Invariance: The lack of strict A¹-invariance for p-adic étale Tate twists poses a significant hurdle. Techniques developed for A¹-invariant theories might not directly translate to this setting.
Potential Avenues for Extension:
Resolution of Singularities: One possible approach could involve utilizing resolution of singularities techniques. If one can resolve the singularities of a more general scheme and relate its p-adic étale Tate twists to those of its resolution, it might be possible to deduce the Gersten conjecture for the original scheme. However, resolution of singularities in mixed characteristic is a highly non-trivial problem.
Logarithmic Geometry: Since p-adic étale Tate twists are closely related to logarithmic de Rham-Witt sheaves, exploring techniques from logarithmic geometry could provide insights. Logarithmic geometry provides tools to handle singularities in a more controlled manner.
Syntomic Techniques: Given the connection between p-adic étale Tate twists and syntomic cohomology, further developing the theory of syntomic cohomology and its properties for more general schemes could offer a path forward.
Could the reliance on the projective bundle formula instead of strict A¹-invariance inspire investigations into other non-A¹-invariant motivic cohomology theories?
Yes, absolutely! The paper's successful use of the projective bundle formula instead of strict A¹-invariance to prove the Gersten conjecture for p-adic étale Tate twists opens up exciting possibilities for investigating other non-A¹-invariant motivic cohomology theories.
Here's how this approach could inspire further research:
Identifying Candidates: Researchers can start by identifying other motivic cohomology theories that, while not strictly A¹-invariant, satisfy the projective bundle formula or a suitable variant.
Developing New Techniques: The paper's methods could serve as a blueprint for developing new techniques tailored specifically for non-A¹-invariant theories. This might involve adapting existing tools or creating entirely new ones.
Exploring Connections: Investigating the connections between different non-A¹-invariant theories and their relationship to more classical A¹-invariant theories could yield valuable insights.
This shift in perspective from strict A¹-invariance to the projective bundle formula could lead to a deeper understanding of the structure and properties of a broader class of motivic cohomology theories.
How can the insights gained from the p-adic cycle class map be further utilized to explore open problems in higher-dimensional unramified class field theory?
The p-adic cycle class map, connecting thickened zero-cycles to étale cohomology with coefficients in p-adic étale Tate twists, provides a powerful tool for investigating higher-dimensional unramified class field theory.
Here are some potential applications:
Understanding the Structure of Chow Groups: The p-adic cycle class map provides a way to study the structure of Chow groups of zero-cycles on smooth projective varieties over local fields. This is directly relevant to understanding unramified extensions of these fields.
Generalizing Class Field Theory: The isomorphism CHd(Xk)/pr ∼= πab
1 (Xk)/pr, studied in classical unramified class field theory, can potentially be generalized to higher dimensions using the thickened analogue provided by the p-adic cycle class map.
Investigating Reciprocity Laws: Reciprocity laws are central to class field theory. The p-adic cycle class map could be used to formulate and study higher-dimensional analogues of these laws.
Relating Different Cohomology Theories: The p-adic cycle class map provides a bridge between different cohomology theories, such as étale cohomology and Milnor K-theory. This connection can be exploited to transfer information and techniques between these theories, potentially leading to progress in unramified class field theory.
By further developing the properties and applications of the p-adic cycle class map, researchers can gain deeper insights into the arithmetic and geometric structures underlying higher-dimensional unramified class field theory.