Homological Invariants of Deformations of Groups and Algebras

Projektinformationen

HIDRA

ID Finanzhilfevereinbarung: 101063362

DOI

10.3030/101063362

Projekt abgeschlossen

EK-Unterschriftsdatum 28 September 2022

Startdatum 1 September 2023

Enddatum 31 August 2025

Finanziert unter

• Marie Skłodowska-Curie Actions (MSCA)

Gesamtkosten

Keine Daten

EU-Beitrag

€ 221 669,04

Koordiniert durch

UNIVERSITETET I OSLO
Norway

Periodic Reporting for period 1 - HIDRA (Homological Invariants of Deformations of Groups and Algebras)

Berichtszeitraum: 2023-09-01 bis 2025-08-31

Zusammenfassung vom Kontext und den Gesamtzielen des Projekts

Symmetry is a powerful concept in both nature and mathematics. Traditionally, mathematicians study symmetry using objects called groups. This project explores new and broader ways to understand symmetry, using more flexible mathematical structures called groupoids. These help us study complex systems, such as certain types of chaotic behavior known as hyperbolic dynamical systems.

Another path we're exploring involves quantum groups—mathematical structures that behave like groups but are designed to work in noncommutative spaces (spaces where the usual rules of arithmetic don’t always apply). These are part of a modern mathematical field called noncommutative geometry.

Our focus is on identifying and studying invariants - mathematical properties that stay the same even when the system changes. By developing new ways to compute and compare these invariants, we hope to better understand the underlying structure of these complex systems.

Goals of the Project:

Investigate how different mathematical tools (like homology and K-theory) help us understand chaotic systems.

Study specific phenomena like torsion and explore advanced mathematical ideas, such as the Baum-Connes conjecture, in the context of quantum groups.

Although highly theoretical, this kind of research provides the foundation for many advanced technologies. By deepening our understanding of symmetry and structure, we may uncover insights relevant to physics, computer science, and beyond.

Arbeit, die ab Beginn des Projekts bis zum Ende des durch den Bericht erfassten Berichtszeitraums geleistet wurde, und die wichtigsten bis dahin erzielten Ergebnisse

During my time as a postdoctoral researcher funded through the project, I focused primarily on advancing the core research objectives outlined in the proposal. My work centered on developing and exploring new mathematical ideas within the project's framework- this involved extensive reading of the existing literature, formulating conjectures, and working through complex proofs. A significant part of my time was dedicated to understanding and computing homological invariants in the context of groupoids and quantum groups, and exploring their connections to noncommutative geometry.

I collaborated closely with the host/mentor M. Yamashita, regularly participating in meetings to discuss progress, exchange feedback, and refine our approach. Over the course of the project, I prepared several research manuscripts, some of which have been submitted for publication. To be precise, six academic papers have been written during the project, five of which are now published (the last one is submitted, under review).

This work has produced several foundational results across group theory, dynamical systems, and quantum algebra. New structural theorems on groupoid homology (a type of algebraic invariant for symmetry-capturing structures) were established, including a "Chern character" connecting it to K-theory (another wel-known algebraic invariant) via a rational isomorphism. These tools were applied to dynamical systems, leading to the identification of their homological invariants and resolving conjectures in hyperbolic dynamics. A general framework for the Baum-Connes conjecture (a problem which hypothesizes a deep connection between geomety and analysis) in the groupoid setting was also developed, using triangulated categories and localization to analyze the K-theory of groupoid C*-algebras. In a separate direction, representation theory of quantum groups was applied to condensed matter physics, yielding new spectral formulas for certain Hamiltonians.

Fortschritte, die über den aktuellen Stand der Technik hinausgehen und voraussichtliche potenzielle Auswirkungen (einschließlich der bis dato erzielten sozioökonomischen Auswirkungen und weiter gefassten gesellschaftlichen Auswirkungen des Projekts)

The principal accomplishments of this research program can be grouped into four broad thematic areas:

(i) Structural results on groupoid homology and its connection to K-theory:
We have developed a series of foundational theorems concerning the homology of groupoids, especially ample groupoids. These results explore the behavior of groupoid homology under categorical constructions such as products and dualities. A particularly significant contribution is the construction of a Chern character-type map that establishes a direct, rational isomorphism between the K-theory and the homology of ample groupoids. This provides a conceptual and computational bridge between two important invariants in noncommutative geometry and enhances our understanding of their interplay.

(ii) Homological invariants of Smale spaces and applications to hyperbolic dynamics:
Our work has successfully identified the homology groups associated with Smale spaces – canonical examples of hyperbolic dynamical systems – with those of certain associated groupoids. By importing tools from algebraic topology and adapting them to the setting of dynamical systems, we have been able to define and compute new homological invariants for Smale spaces. This framework has proven powerful, leading to the resolution of several open conjectures concerning the structure and classification of hyperbolic dynamical systems.

(iii) The Baum-Connes conjecture for groupoids and its K-theoretic implications:
We have formulated a comprehensive theoretical framework for studying the Baum-Connes conjecture in the context of groupoids. This approach leverages modern techniques involving triangulated categories, localization, and descent in noncommutative geometry. The framework not only unifies various earlier instances of the conjecture but also facilitates new applications to the computation of the K-theory of reduced C*-algebras associated with groupoids. This contributes to a deeper understanding of the links between topological groupoid theory and operator algebras.

(iv) Quantum groups and their applications in mathematical physics:
In the realm of quantum algebra, we have explored the representation theory of certain elementary quantum groups and applied it to problems arising in condensed matter physics. Specifically, we derived novel formulas that parametrize the spectrum of Hamiltonians linked to quantum integrable systems. These results highlight the utility of quantum group techniques beyond pure mathematics, offering insights into the algebraic structure underlying physical models.