Online seminar · 2022–2023

Real Reductive Groups/Atlas of Lie Groups and Representations Seminar

A working/learning seminar on Zoom, on Thursdays, 10:30 AM – noon (EST), beginning January 6, 2022.

The seminar has concluded. Thank you for your attendance! Recordings, slides and notes of the talks are listed below.

About the seminar

This was a working/learning seminar on (infinite-dimensional) representations of real reductive groups, aimed at grad students and researchers having some familiarity with representations of compact Lie groups. It used the atlas software; participants installed it on their laptops following the directions on the software page.

The aim was for each seminar to last approximately one hour; the extra half hour in the schedule was meant to encourage lots of interaction with the audience. The idea of the seminar is that learning how the software does mathematical computations is an excellent way to understand the mathematics, as well as a great source of examples.

First goal is to learn how the software represents real reductive groups (precisely, the group of real points of any complex connected reductive algebraic group) and their representations; making sense of the software will lead to an understanding of the underlying mathematics. Second goal is to use the software to investigate experimentally questions about reductive groups.

A good general introduction to what the seminar is about can be found at www.liegroups.org/workshop2017/workshop/videos_and_computer from a 2017 workshop. The mathematical subject matter is described in the slides www.liegroups.org/workshop2017/workshop/presentations/voganHO.pdf from Vogan’s lecture. The main ideas about how to realize this mathematics on a computer are described in Adams’s lecture www.liegroups.org/workshop2017/workshop/presentations/adams1HO.pdf. A quick introduction to the syntax for the software is in van Leeuwen’s presentation www.liegroups.org/workshop2017/workshop/computer_transcripts/vanLeeuwen1.out.

The home page for the seminar is on the Research Seminars web site: Research Seminars/Atlas. There you’ll find an introduction to the seminar, suggested background reading and a schedule of talks.

When the seminar concluded, it was to continue, based on demand, as an Atlas Help Session, answering questions about the software and the mathematics behind it. There is a Slack workspace for questions and discussions about all aspects of the atlas software: join the workspace.

Recordings and slides

Talks are listed in reverse chronological order. The recordings are on MIT Zoom. The links to the slides for individual talks may require you to be logged in to a Microsoft account; if that’s an issue, use the notebook of all the slides and open the slides for individual talks from there.

2023

DateSpeakerTitleRecording and slides
February 2, 2023Jeffrey AdamsSome examples
January 26, 2023David VoganComputing Unitary Duals III: unitary_dual@RealForm
January 19, 2023David VoganComputing Unitary Duals II: non-unitary certificates
January 12, 2023David VoganComputing Unitary Duals I: cohomological induction

2022

DateSpeakerTitleRecording and slides
December 15, 2022Adams/VoganInteresting examples of Arthur packets, computed by Annegret's script
December 8, 2022David VoganMore on honest Arthur packets/Annegret Paul's magic scripts
December 1, 2022David VoganMore on honest Arthur packets/Annegret Paul's magic scripts
November 17, 2022Jeffrey Adams/David VoganArthur Packets for G2 /Induction for Arthur packets
November 10, 2022Jeffrey AdamsArthur Packets for G2
November 3, 2022Jeffrey AdamsExamples of Duality/Miscellaneous 2
October 27, 2022Jeffrey AdamsExamples of Duality/Miscellaneous
October 20, 2022David VoganDuality, associated varieties, and nilpotent orbits 3
October 13, 2022David VoganDuality, associated varieties, and nilpotent orbits 2
September 29, 2022David VoganDuality, associated varieties, and nilpotent orbits
September 22, 2022Jeffrey AdamsCohomological Arthur packets 3
September 15, 2022Jeffrey AdamsCohomological Arthur packets 2
September 8, 2022Jeffrey AdamsCohomological Arthur packets
September 1, 2022David VoganMore about discrete series restriction
August 25, 2022David VoganCohomological induction and restricting discrete series to K
August 18, 2022Jeffrey AdamsHermitian forms on finite dimensional representations
August 11, 2022David VoganMore on duality for singular and non-integral infinitesimal character
August 4, 2022David VoganDuality for singular and non-integral infinitesimal character
July 28, 2022Jeffrey AdamsVogan duality and Arthur Packets
July 21, 2022Jeffrey AdamsVogan duality
July 7, 2022David VoganAffine Weyl group, facets, and the unitary dual
June 30, 2022David VoganClassifying the unitary dual (part 1 of infinitely many…)
June 23, 2022David VoganDirac Operator in Atlas
June 9, 2022Jeffrey AdamsLoose ends, Jantzen filtration, Questions from the audience
June 2, 2022Jeffrey AdamsLoose ends: More on translation, some answers to questions
May 26, 2022Jeffrey AdamsLoose ends: Hermitian representations, translation, the Jantzen filtration
May 19, 2022David VoganUnitary Dual of F4_B4 in atlas
May 12, 2022David VoganUnitary Dual of SO(2n,1) in atlas
May 5, 2022Jeffrey AdamsTheta-stable parabolic subgroups and cohomological induction in atlas
April 28, 2022David VoganReal parabolic subgroups and induction in atlas
April 21, 2022Jeffrey AdamsUnipotent Representations, Nilpotent Orbits and the Weyl group II
April 14, 2022Jeffrey AdamsUnipotent Representations, Nilpotent Orbits and the Weyl group I
April 7, 2022David VoganNilpotent orbits and atlas
March 31, 2022David VoganGelfand-Kirillov dimension and atlas
March 24, 2022Jeffrey AdamsWeyl group representations in Atlas II
March 17, 2022Jeffrey AdamsWeyl group representations in Atlas I
March 10, 2022David VoganHow atlas does what it says its doing
March 3, 2022Jeffrey AdamsSignature character formulas and unitary representations 2SL2 refcard from the talk File unavailable
February 24, 2022Jeffrey AdamsSignature character formulas and unitary representations(or why we needed this software in the first place)
February 17, 2022David VoganCharacter formulas and Kazhdan-Lusztig polynomials(or why we needed this software in the first place)
February 10, 2022Jeffrey AdamsThe Atlas Way (More on KGB)
February 3, 2022David VoganUnderstanding K: How Atlas understands compact subgroups
January 27, 2022Jeffrey AdamsBranching to K
January 20, 2022David VoganParameters for Representations
January 13, 2022Jeffrey AdamsRoot Data/Complex and Real reductive groups
January 6, 2022David VoganWhat Groups/Representations/Software?