Brendle–Margalit conjectures on complexes of regions and geometric normal subgroups
Brendle–Margalit conjectures on complexes of regions and geometric normal subgroups
Let be a surface, let be a complex of regions, and let be a normal subgroup of . Brendle–Margalit conjectures for complexes of regions.
- The natural map
is an isomorphism if and only if is connected and admits no exchange automorphisms.
- The natural map
is an isomorphism if and only if contains elements whose supports are disjoint and separated by a pair of pants. The first assertion concerns automorphisms of complexes of regions, while the second characterizes geometric normal subgroups through elements with separated supports. The supplied text presents this as a rephrasing and generalization of a Brendle–Margalit conjecture and does not give a resolution of both assertions.
Sources & referencesView supporting material
Primary source
Alan McLeay, “The mapping class group of the Cantor tree has only geometric normal subgroups”, arXiv:2002.06970 (2020).
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