---
_id: '53533'
author:
- first_name: Alena
  full_name: Ernst, Alena
  id: '46953'
  last_name: Ernst
- first_name: Kai-Uwe
  full_name: Schmidt, Kai-Uwe
  last_name: Schmidt
citation:
  ama: Ernst A, Schmidt K-U. Intersection theorems for finite general linear groups.
    <i>Mathematical Proceedings of the Cambridge Philosophical Society</i>. 2023;175(1):129-160.
    doi:<a href="https://doi.org/10.1017/s0305004123000075">10.1017/s0305004123000075</a>
  apa: Ernst, A., &#38; Schmidt, K.-U. (2023). Intersection theorems for finite general
    linear groups. <i>Mathematical Proceedings of the Cambridge Philosophical Society</i>,
    <i>175</i>(1), 129–160. <a href="https://doi.org/10.1017/s0305004123000075">https://doi.org/10.1017/s0305004123000075</a>
  bibtex: '@article{Ernst_Schmidt_2023, title={Intersection theorems for finite general
    linear groups}, volume={175}, DOI={<a href="https://doi.org/10.1017/s0305004123000075">10.1017/s0305004123000075</a>},
    number={1}, journal={Mathematical Proceedings of the Cambridge Philosophical Society},
    publisher={Cambridge University Press (CUP)}, author={Ernst, Alena and Schmidt,
    Kai-Uwe}, year={2023}, pages={129–160} }'
  chicago: 'Ernst, Alena, and Kai-Uwe Schmidt. “Intersection Theorems for Finite General
    Linear Groups.” <i>Mathematical Proceedings of the Cambridge Philosophical Society</i>
    175, no. 1 (2023): 129–60. <a href="https://doi.org/10.1017/s0305004123000075">https://doi.org/10.1017/s0305004123000075</a>.'
  ieee: 'A. Ernst and K.-U. Schmidt, “Intersection theorems for finite general linear
    groups,” <i>Mathematical Proceedings of the Cambridge Philosophical Society</i>,
    vol. 175, no. 1, pp. 129–160, 2023, doi: <a href="https://doi.org/10.1017/s0305004123000075">10.1017/s0305004123000075</a>.'
  mla: Ernst, Alena, and Kai-Uwe Schmidt. “Intersection Theorems for Finite General
    Linear Groups.” <i>Mathematical Proceedings of the Cambridge Philosophical Society</i>,
    vol. 175, no. 1, Cambridge University Press (CUP), 2023, pp. 129–60, doi:<a href="https://doi.org/10.1017/s0305004123000075">10.1017/s0305004123000075</a>.
  short: A. Ernst, K.-U. Schmidt, Mathematical Proceedings of the Cambridge Philosophical
    Society 175 (2023) 129–160.
date_created: 2024-04-17T12:23:18Z
date_updated: 2024-05-07T08:29:59Z
department:
- _id: '100'
doi: 10.1017/s0305004123000075
intvolume: '       175'
issue: '1'
keyword:
- General Mathematics
language:
- iso: eng
page: 129-160
publication: Mathematical Proceedings of the Cambridge Philosophical Society
publication_identifier:
  issn:
  - 0305-0041
  - 1469-8064
publication_status: published
publisher: Cambridge University Press (CUP)
status: public
title: Intersection theorems for finite general linear groups
type: journal_article
user_id: '46953'
volume: 175
year: '2023'
...
---
_id: '66325'
abstract:
- lang: eng
  text: <jats:title>Abstract</jats:title><jats:p>Let<jats:inline-formula><jats:alternatives><jats:inline-graphic
    xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0305004123000518_inline1.png"/><jats:tex-math>$\mathfrak{A}$</jats:tex-math></jats:alternatives></jats:inline-formula>be
    a finite abelian group. In this paper, we classify harmonic<jats:inline-formula><jats:alternatives><jats:inline-graphic
    xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0305004123000518_inline2.png"/><jats:tex-math>$\mathfrak{A}$</jats:tex-math></jats:alternatives></jats:inline-formula>-covers
    of a tropical curve<jats:inline-formula><jats:alternatives><jats:inline-graphic
    xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0305004123000518_inline3.png"/><jats:tex-math>$\Gamma$</jats:tex-math></jats:alternatives></jats:inline-formula>(which
    allow dilation along edges and at vertices) in terms of the cohomology group of
    a suitably defined sheaf on<jats:inline-formula><jats:alternatives><jats:inline-graphic
    xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0305004123000518_inline4.png"/><jats:tex-math>$\Gamma$</jats:tex-math></jats:alternatives></jats:inline-formula>.
    We give a realisability criterion for harmonic<jats:inline-formula><jats:alternatives><jats:inline-graphic
    xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0305004123000518_inline5.png"/><jats:tex-math>$\mathfrak{A}$</jats:tex-math></jats:alternatives></jats:inline-formula>-covers
    by patching local monodromy data in an extended homology group on<jats:inline-formula><jats:alternatives><jats:inline-graphic
    xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0305004123000518_inline6.png"/><jats:tex-math>$\Gamma$</jats:tex-math></jats:alternatives></jats:inline-formula>.
    As an explicit example, we work out the case<jats:inline-formula><jats:alternatives><jats:inline-graphic
    xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0305004123000518_inline7.png"/><jats:tex-math>$\mathfrak{A}=\mathbb{Z}/p\mathbb{Z}$</jats:tex-math></jats:alternatives></jats:inline-formula>and
    explain how realisability for such covers is related to the nowhere-zero flow
    problem from graph theory.</jats:p>
author:
- first_name: Yoav
  full_name: Len, Yoav
  last_name: Len
- first_name: Martin
  full_name: Ulirsch, Martin
  id: '114697'
  last_name: Ulirsch
- first_name: Dmitry
  full_name: Zakharov, Dmitry
  last_name: Zakharov
citation:
  ama: Len Y, Ulirsch M, Zakharov D. Abelian tropical covers. <i>Mathematical Proceedings
    of the Cambridge Philosophical Society</i>. 2023;176(2):395-416. doi:<a href="https://doi.org/10.1017/S0305004123000518">10.1017/S0305004123000518</a>
  apa: Len, Y., Ulirsch, M., &#38; Zakharov, D. (2023). Abelian tropical covers. <i>Mathematical
    Proceedings of the Cambridge Philosophical Society</i>, <i>176</i>(2), 395–416.
    <a href="https://doi.org/10.1017/S0305004123000518">https://doi.org/10.1017/S0305004123000518</a>
  bibtex: '@article{Len_Ulirsch_Zakharov_2023, title={Abelian tropical covers}, volume={176},
    DOI={<a href="https://doi.org/10.1017/S0305004123000518">10.1017/S0305004123000518</a>},
    number={2}, journal={Mathematical Proceedings of the Cambridge Philosophical Society},
    publisher={Cambridge University Press (CUP)}, author={Len, Yoav and Ulirsch, Martin
    and Zakharov, Dmitry}, year={2023}, pages={395–416} }'
  chicago: 'Len, Yoav, Martin Ulirsch, and Dmitry Zakharov. “Abelian Tropical Covers.”
    <i>Mathematical Proceedings of the Cambridge Philosophical Society</i> 176, no.
    2 (2023): 395–416. <a href="https://doi.org/10.1017/S0305004123000518">https://doi.org/10.1017/S0305004123000518</a>.'
  ieee: 'Y. Len, M. Ulirsch, and D. Zakharov, “Abelian tropical covers,” <i>Mathematical
    Proceedings of the Cambridge Philosophical Society</i>, vol. 176, no. 2, pp. 395–416,
    2023, doi: <a href="https://doi.org/10.1017/S0305004123000518">10.1017/S0305004123000518</a>.'
  mla: Len, Yoav, et al. “Abelian Tropical Covers.” <i>Mathematical Proceedings of
    the Cambridge Philosophical Society</i>, vol. 176, no. 2, Cambridge University
    Press (CUP), 2023, pp. 395–416, doi:<a href="https://doi.org/10.1017/S0305004123000518">10.1017/S0305004123000518</a>.
  short: Y. Len, M. Ulirsch, D. Zakharov, Mathematical Proceedings of the Cambridge
    Philosophical Society 176 (2023) 395–416.
date_created: 2026-07-08T06:50:59Z
date_updated: 2026-07-09T07:11:55Z
doi: 10.1017/S0305004123000518
intvolume: '       176'
issue: '2'
language:
- iso: eng
page: 395-416
publication: Mathematical Proceedings of the Cambridge Philosophical Society
publication_identifier:
  issn:
  - 0305-0041
  - 1469-8064
publication_status: published
publisher: Cambridge University Press (CUP)
status: public
title: Abelian tropical covers
type: journal_article
user_id: '82981'
volume: 176
year: '2023'
...
---
_id: '16633'
abstract:
- lang: eng
  text: <jats:title>Abstract</jats:title><jats:p>We obtain normal forms for infinitesimally
    symplectic matrices (or linear Hamiltonian vector fields) that commute with the
    symplectic action of a compact Lie group of symmetries. In doing so we extend
    Williamson's theorem on normal forms when there is no symmetry present.</jats:p><jats:p>Using
    standard representation-theoretic results the symmetry can be factored out and
    we reduce to finding normal forms over a real division ring. There are three real
    division rings consisting of the real, complex and quaternionic numbers. Of these,
    only the real case is covered in Williamson's original work.</jats:p>
author:
- first_name: Ian
  full_name: Melbourne, Ian
  last_name: Melbourne
- first_name: Michael
  full_name: Dellnitz, Michael
  last_name: Dellnitz
citation:
  ama: Melbourne I, Dellnitz M. Normal forms for linear Hamiltonian vector fields
    commuting with the action of a compact Lie group. <i>Mathematical Proceedings
    of the Cambridge Philosophical Society</i>. 1993:235-268. doi:<a href="https://doi.org/10.1017/s0305004100071577">10.1017/s0305004100071577</a>
  apa: Melbourne, I., &#38; Dellnitz, M. (1993). Normal forms for linear Hamiltonian
    vector fields commuting with the action of a compact Lie group. <i>Mathematical
    Proceedings of the Cambridge Philosophical Society</i>, 235–268. <a href="https://doi.org/10.1017/s0305004100071577">https://doi.org/10.1017/s0305004100071577</a>
  bibtex: '@article{Melbourne_Dellnitz_1993, title={Normal forms for linear Hamiltonian
    vector fields commuting with the action of a compact Lie group}, DOI={<a href="https://doi.org/10.1017/s0305004100071577">10.1017/s0305004100071577</a>},
    journal={Mathematical Proceedings of the Cambridge Philosophical Society}, author={Melbourne,
    Ian and Dellnitz, Michael}, year={1993}, pages={235–268} }'
  chicago: Melbourne, Ian, and Michael Dellnitz. “Normal Forms for Linear Hamiltonian
    Vector Fields Commuting with the Action of a Compact Lie Group.” <i>Mathematical
    Proceedings of the Cambridge Philosophical Society</i>, 1993, 235–68. <a href="https://doi.org/10.1017/s0305004100071577">https://doi.org/10.1017/s0305004100071577</a>.
  ieee: I. Melbourne and M. Dellnitz, “Normal forms for linear Hamiltonian vector
    fields commuting with the action of a compact Lie group,” <i>Mathematical Proceedings
    of the Cambridge Philosophical Society</i>, pp. 235–268, 1993.
  mla: Melbourne, Ian, and Michael Dellnitz. “Normal Forms for Linear Hamiltonian
    Vector Fields Commuting with the Action of a Compact Lie Group.” <i>Mathematical
    Proceedings of the Cambridge Philosophical Society</i>, 1993, pp. 235–68, doi:<a
    href="https://doi.org/10.1017/s0305004100071577">10.1017/s0305004100071577</a>.
  short: I. Melbourne, M. Dellnitz, Mathematical Proceedings of the Cambridge Philosophical
    Society (1993) 235–268.
date_created: 2020-04-16T08:31:40Z
date_updated: 2022-01-06T06:52:53Z
department:
- _id: '101'
doi: 10.1017/s0305004100071577
language:
- iso: eng
page: 235-268
publication: Mathematical Proceedings of the Cambridge Philosophical Society
publication_identifier:
  issn:
  - 0305-0041
  - 1469-8064
publication_status: published
status: public
title: Normal forms for linear Hamiltonian vector fields commuting with the action
  of a compact Lie group
type: journal_article
user_id: '15701'
year: '1993'
...
