From 79a4450ef9a3186d6fd7716b10fe85c454fecf4f Mon Sep 17 00:00:00 2001 From: Marek Kaluba Date: Wed, 7 Jul 2021 10:32:13 +0200 Subject: [PATCH] create mcg_twists from Aut(F_n) directly --- src/groups/symplectic_twists.jl | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/src/groups/symplectic_twists.jl b/src/groups/symplectic_twists.jl index b2a769b..14a7f97 100644 --- a/src/groups/symplectic_twists.jl +++ b/src/groups/symplectic_twists.jl @@ -76,10 +76,13 @@ function Te(λ::ΡΛ, ϱ::ΡΛ, i, j) end end -function mcg_twists(genus::Integer) +function mcg_twists(G::AutomorphismGroup{<:FreeGroup}) + + @assert iseven(ngens(object(G))) + genus = ngens(object(G)) ÷ 2 + genus < 3 && throw("Not Implemented: genus = $genus < 3") - G = SpecialAutomorphismGroup(FreeGroup(2genus), maxrules = 1000) A = KnuthBendix.alphabet(G) λ = ΡΛ(:λ, A, 2genus)