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In this survey article, we recall some facts about split Kac-Moody groups as defined by J. Tits, describe their main properties and then propose an analogue of Borel-Tits theory for a non-split version of them. The main result is a Galois…

Group Theory · Mathematics 2007-05-23 Bertrand Remy

A subgroup of a Kac-Moody group is called bounded if it is contained in the intersection of two finite type parabolic subgroups of opposite signs. In this paper, we study the isomorphisms between Kac-Moody groups over arbitrary fields of…

Group Theory · Mathematics 2010-02-08 P. -E. Caprace , B. Muehlherr

In \cite{CM06} Caprace and M\"uhlherr solved the isomorphism problem for Kac-Moody groups of non-spherical type over finite fields of cardinality at least $4$. In this paper we solve the isomorphism problem for RGD-systems (e.g.\ Kac-Moody…

Group Theory · Mathematics 2025-04-07 Sebastian Bischof

We use methods developed by Caprace and M\"uhlherr to solve the isomorphism problem of unitary forms of infinite split Kac-Moody groups over finite fields of square order.

Group Theory · Mathematics 2015-03-27 Ralf Köhl , Andreas Mars

Kac-Moody symmetric spaces have been introduced by Freyn, Hartnick, Horn and the first-named author for centered Kac-Moody groups, that is, Kac-Moody groups that are generated by their root subgroups. In the case of non-invertible…

Group Theory · Mathematics 2025-09-26 Ralf Köhl , Christian Vock

Let $G$ be a representation-theoretic Kac--Moody group associated to a nonsingular symmetrizable generalized Cartan matrix. We first consider Kac-Moody analogs of Borel Eisenstein series (induced from quasicharacters on the Borel), and…

Number Theory · Mathematics 2023-06-02 Lisa Carbone , Howard Garland , Kyu-Hwan Lee , Dongwen Liu , Stephen D. Miller

For a split Kac-Moody group G over an ultrametric field K, S. Gaussent and the author defined an ordered affine hovel on which the group acts; it generalizes the Bruhat-Tits building which corresponds to the case when G is reductive. This…

Group Theory · Mathematics 2015-07-16 Guy Rousseau

The relationship between minimal algebraic Kac-Moody groups and twin buildings is well known as is the relationship between formal completions in one direction and affine buildings. Nevertheless, as the completion of a Kac-Moody group in…

Differential Geometry · Mathematics 2010-04-21 Walter Freyn

In this study, we try to generalize Bruhat-Tits's theory to the case of a Kac-Moody group, that is to define an affine building for a Kac-Moody group over a local field. Actually, we will obtain a geometric space wich lacks some of the…

Group Theory · Mathematics 2010-07-28 Cyril Charignon

We introduce a new class of infinite-dimensional Lie algebras, which we refer to as continuum Kac-Moody algebras. Their construction is closely related to that of usual Kac-Moody algebras, but they feature a continuum root system with no…

Representation Theory · Mathematics 2022-07-19 Andrea Appel , Francesco Sala , Olivier Schiffmann

Kac-Moody groups over finite fields are finitely generated groups. Most of them can naturally be viewed as irreducible lattices in products of two closed automorphism groups of non-positively curved twinned buildings: those are the most…

Group Theory · Mathematics 2012-10-04 Pierre-Emmanuel Caprace , Bertrand Remy

Let $G$ be a minimal split Kac-Moody group over a valued field {\mathcal{K}. Motivated by the representation theory of $G$, we define two topologies of topological group on $G$, which take into account the topology on {\mathcal{K}.

Group Theory · Mathematics 2025-01-16 Auguste Hebert

We determine the fundamental groups of symmetrizable algebraically simply connected split real Kac-Moody groups endowed with the Kac-Peterson topology. In analogy to the finite-dimensional situation, the Iwasawa decomposition $G = KAU_+$…

Group Theory · Mathematics 2021-06-10 Paula Harring , Ralf Köhl

We establish automorphisms with closed formulas on quasi-split $\imath$quantum groups of symmetric Kac-Moody type associated to restricted Weyl groups. The proofs are carried out in the framework of $\imath$Hall algebras and reflection…

Quantum Algebra · Mathematics 2022-11-23 Ming Lu , Weiqiang Wang

We prove an analogue of Kostant's convexity theorem for split real and complex Kac-Moody groups associated to free and cofree root data. The result can be seen as a first step towards describing the multiplication map in a Kac-Moody group…

Representation Theory · Mathematics 2024-01-30 Paul Zellhofer , Ralf Köhl

The paper is devoted to model-theoretic properties of Kac-Moody groups with the focus on elementary equivalence of Kac-Moody groups. We show that elementary equivalence of (untwisted) affine Kac-Moody groups implies coincidence of their…

Group Theory · Mathematics 2023-06-21 Jun Morita , Eugene Plotkin

Let G be a split Kac-Moody group over a non-archimedean local field. We define a completion of the Iwahori-Hecke algebra of G. We determine its center and prove that it is isomorphic to the spherical Hecke algebra of G using the Satake…

Representation Theory · Mathematics 2023-09-15 Ramla Abdellatif , Auguste Hébert

We propose a novel way to define imaginary root subgroups associated with (timelike) imaginary roots of hyperbolic Kac-Moody algebras. Using in an essential way the theory of unitary irreducible representation of covers of the group…

Representation Theory · Mathematics 2024-07-31 Alex J. Feingold , Axel Kleinschmidt , Hermann Nicolai

Let $G$ be a Kac-Moody group over a finite field corresponding to a generalized Cartan matrix $A$, as constructed by Tits. It is known that $G$ admits the structure of a BN-pair, and acts on its corresponding building. We study the complete…

Group Theory · Mathematics 2010-06-07 Lisa Carbone , Mikhail Ershov , Gordon Ritter

In this paper we discuss the isomorphism types of parabolic subgroups in Kac-Moody groups. The results have applications in the study of topology of Kac-Moody groups and their classifying spaces.

Group Theory · Mathematics 2019-11-12 Zhao Xu-an , Ruan Yangyang , Wang Ran
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