D. Testerman

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20052023

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math.RT2022

Almost cyclic regular elements in irreducible representations of simple algebraic groups

Donna M. Testerman, Alexandre Zalesski

Let $G$ be a simple linear algebraic group defined over an algebraically closed field of characteristic $p \geq 0$ and let $ϕ$ be a $p$ -restricted irreducible representation of $G$ .…

math.RT2021

Spectra of non-regular elements in irreducible representations of simple algebraic groups

Donna M Testerman, Alexandre Zalesski

We study the spectra of non-regular semisimple elements in irreducible representations of simple algebraic groups. More precisely, we prove that if G is a simply connected simple l…

math.RT2021

Multiplicity-free representations of algebraic groups

Martin W. Liebeck, Gary M. Seitz, Donna M. Testerman

Let $K$ be an algebraically closed field of characteristic zero, and let $G$ be a connected reductive algebraic group over $K$ . We address the problem of classifying triples $(G,H,…

math.RT2017

A new family of irreducible subgroups of the orthogonal algebraic groups

Mikaël Cavallin, Donna M. Testerman

Let $n \geq 3,$ and let $Y$ be a simply connected, simple algebraic group of type $D_{n + 1}$ over an algebraically closed field $K .$ Also let $X$ be the subgroup of type $B_{n}$ of $Y,…

math.RT2008

Nilpotent centralizers and Springer isomorphisms

George McNinch, Donna Testerman

Let G be a semisimple algebraic group over a field K whose characteristic is very good for G, and let sigma be any G-equivariant isomorphism from the nilpotent variety to the unipo…

math.RT2005

Completely reducible SL(2)-homomorphisms

George J. McNinch, Donna M. Testerman

Let K be any field, and let G be a semisimple group over K. Suppose the characteristic of K is positive and is very good for G. We describe all group scheme homomorphisms phi:SL(2)…