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Geometry of the tip of the global nilpotent cone

Geometry of the tip of the global nilpotent cone

Tamas Hausel (ORCID: 0000-0002-9582-2634)
  • Grant DOI 10.55776/P35847
  • Funding program Principal Investigator Projects
  • Status ended
  • Start October 1, 2022
  • End September 30, 2025
  • Funding amount € 378,158
  • Project website

Disciplines

Mathematics (85%); Physics, Astronomy (15%)

Keywords

    Integrable System, Higgs bundle, Stratification, Multiplicity, Grassmannian, Hecke transform

Abstract Final report

In this proposal we study the motion of Higgs bundles to develop new theories in diverse areas of theoretical physics and mathematics. Higgs bundles are two-dimensional relatives of the famous Higgs boson an elementary particle living in four-dimensional space-time responsible for endowing other particles with mass and recently found in the Large Hadron Collider in CERN, Geneva. The movements of Higgs bundles can be fully described as their mechanical system is completely solvable. The quantities which solve the motion of Higgs bundles were discovered by Hitchin in 1987 and form a so-called integrable system. This Hitchin integrable system is a prototype of all integrable systems in mathematical physics, which are important model systems to solve complicated dynamics in various contexts. Inside our configuration space of Higgs bundles there is a core a so-called global nilpotent cone which is like an iceberg. We study the Hitchin integrable system around the tip of this iceberg. The metaphorical iceberg has horizontal layers too, which can be scanned from the top. They are multisections of the Hitchin system. We look at the Hitchin system like an x-ray, descending from the top of the nilpotent cone. The main novelty in the proposal is the introduction of explicit algebraic structures so-called multiplicity algebras which give an algebraic measurement of the intersection of the horizontal layer with the iceberg. This multiplicity algebra is located at the single intersection point of the horizontal layer and the iceberg, and it has a surprisingly complex structure. We can compute it in certain cases and surprisingly find that it is the intersection ring of some Grassmannian space. The intersection ring is an algebraic topological quantity of a shape, which measures the intersection structure of high dimensional holes on our surface. The Grassmannian surface is the space of linear subspaces in a high dimensional linear space with an intriguing and well understood shape. Thus, we discover that the intersection between the horizontal layers of the x-ray and the iceberg are understandable in terms of the intersection of holes in certain high dimensional Grassmannian spaces. In turn, this gives explicit formulas for the Hitchin integrable system on these horizontal layers - solving the movement of Higgs bundles with explicit formulas. We find unexpected properties of these multiplicity algebras, which link together questions from representation theory of continuous group of symmetries, geometry of integrable mechanical systems, mirror symmetry in string theory and Langlands duality in number theory. Developing this circle of ideas will lead to new theories related to all the fields in theoretical physics and mathematics mentioned above.

In this proposal we study the motion of Higgs bundles to develop new theories in diverse areas of theoretical physics and mathematics. Higgs bundles are two-dimensional relatives of the famous Higgs boson an elementary particle living in four-dimensional space-time responsible for endowing other particles with mass and recently found in the Large Hadron Collider in CERN, Geneva. The movements of Higgs bundles can be fully described as their mechanical system is completely solvable. The quantities which solve the motion of Higgs bundles were discovered by Hitchin in 1987 and form a so-called integrable system. This Hitchin integrable system is a prototype of all integrable systems in mathematical physics, which are important model systems to solve complicated dynamics in various contexts. Inside our configuration space of Higgs bundles there is a core a so-called global nilpotent cone which is like an iceberg. We study the Hitchin integrable system around the tip of this iceberg. The metaphorical iceberg has horizontal layers too, which can be scanned from the top. They are multisections of the Hitchin system. We look at the Hitchin system like an x-ray, descending from the top of the nilpotent cone. The main novelty in the proposal is the introduction of explicit algebraic structures so-called multiplicity algebras which give an algebraic measurement of the intersection of the horizontal layer with the iceberg. This multiplicity algebra is located at the single intersection point of the horizontal layer and the iceberg, and it has a surprisingly complex structure. We can compute it in certain cases and surprisingly find that it is the intersection ring of some Grassmannian space. The intersection ring is an algebraic topological quantity of a shape, which measures the intersection structure of high dimensional holes on our surface. The Grassmannian surface is the space of linear subspaces in a high dimensional linear space with an intriguing and well understood shape. Thus, we discover that the intersection between the horizontal layers of the x-ray and the iceberg are understandable in terms of the intersection of holes in certain high dimensional Grassmannian spaces. In turn, this gives explicit formulas for the Hitchin integrable system on these horizontal layers - solving the movement of Higgs bundles with explicit formulas. We find unexpected properties of these multiplicity algebras, which link together questions from representation theory of continuous group of symmetries, geometry of integrable mechanical systems, mirror symmetry in string theory and Langlands duality in number theory. Developing this circle of ideas will lead to new theories related to all the fields in theoretical physics and mathematics mentioned above.

Research institution(s)
  • Institute of Science and Technology Austria - ISTA - 100%
International project participants
  • Nigel Hitchin, The University of Oxford

Research Output

  • 8 Citations
  • 13 Publications
  • 1 Artistic Creations
  • 1 Disseminations
  • 3 Scientific Awards
  • 2 Fundings
Publications
  • 2025
    Title Center of Kostant algebra
    DOI 10.48550/arxiv.2509.20159
    Type Preprint
    Author Hausel T
    Link Publication
  • 2025
    Title Spectrum of equivariant cohomology as a fixed point scheme
    DOI 10.46298/epiga.2025.12591
    Type Journal Article
    Author Hausel T
    Journal Épijournal de Géométrie Algébrique
  • 2025
    Title Big algebra in type $A$ for the coordinate ring of the matrix space
    DOI 10.48550/arxiv.2501.04605
    Type Preprint
    Author Ngo N
    Link Publication
  • 2025
    Title Indecomposable characters of inductive limits of symmetric groups
    DOI 10.1090/ert/689
    Type Journal Article
    Author Nessonov N
    Journal Representation Theory
    Pages 256-288
    Link Publication
  • 2024
    Title Locally free representations of quivers over commutative Frobenius algebras
    DOI 10.1007/s00029-023-00914-2
    Type Journal Article
    Author Hausel T
    Journal Selecta Mathematica
  • 2024
    Title On involutions of minuscule Kirillov algebras induced by real structures
    DOI 10.48550/arxiv.2411.16270
    Type Preprint
    Author Elkner M
    Link Publication
  • 2024
    Title Equivariant $K$-theory, affine Grassmannian and perfection
    DOI 10.48550/arxiv.2409.18925
    Type Preprint
    Author Löwit J
    Link Publication
  • 2023
    Title Arithmetic and metric aspects of open de Rham spaces
    DOI 10.1112/plms.12555
    Type Journal Article
    Author Hausel T
    Journal Proceedings of the London Mathematical Society
    Pages 958-1027
    Link Publication
  • 2023
    Title Hitchin map on even very stable upward flows
    DOI 10.48550/arxiv.2303.01404
    Type Preprint
    Author González M
    Link Publication
  • 2024
    Title Commutative avatars of representations of semisimple Lie groups
    DOI 10.1073/pnas.2319341121
    Type Journal Article
    Author Hausel T
    Journal Proceedings of the National Academy of Sciences
    Link Publication
  • 2024
    Title Hitchin map on even very stable upward flows
    DOI 10.1142/s0129167x2441009x
    Type Journal Article
    Author González M
    Journal International Journal of Mathematics
    Pages 2441009
  • 2022
    Title $P=W$ via $\mathcal{H}_2$
    DOI 10.48550/arxiv.2209.05429
    Type Preprint
    Author Hausel T
    Link Publication
  • 2022
    Title Spectrum of equivariant cohomology as a fixed point scheme
    DOI 10.48550/arxiv.2212.11836
    Type Preprint
    Author Hausel T
    Link Publication
Artistic Creations
  • 2024 Link
    Title Anatomy of big algebras: Zoo of big skeletons, crystals and nerves
    Type Artefact (including digital)
    Link Link
Disseminations
  • 2024 Link
    Title Article in Der Standard
    Type A press release, press conference or response to a media enquiry/interview
    Link Link
Scientific Awards
  • 2025
    Title Scientific Advisory Board of Max Planck Institute, Bonn
    Type Prestigious/honorary/advisory position to an external body
    Level of Recognition Continental/International
  • 2024
    Title "What is life?" lecture at Trinity College Dublin (formerly "Annual Schrödinger lecture")
    Type Personally asked as a key note speaker to a conference
    Level of Recognition Continental/International
  • 2023
    Title Editor for Journal of European Mathematical Society
    Type Appointed as the editor/advisor to a journal or book series
    Level of Recognition Continental/International
Fundings
  • 2025
    Title DOC Fellowship
    Type Fellowship
    Start of Funding 2025
  • 2026
    Title Representation theory, equivariant topology and Langlands duality via fixed point schemes
    Type Research grant (including intramural programme)
    DOI 10.3030/101199663
    Start of Funding 2026

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