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Let $G$ be a finite group. Let $U_1,U_2,\dots$ be a sequence of orthogonal representations in which any irreducible representation of $\oplus_{n \geq 1} U_n$ has infinite multiplicity. Let $V_n=\oplus_{i=1}^n U_n$ and $S(V_n)$ denote the…

Algebraic Topology · Mathematics 2019-06-13 Assaf Libman

J.H.C. Whitehead's second free-group algorithm determines whether or not two given elements of a free group lie in the same orbit of the automorphism group of the free group. The algorithm involves certain connected graphs, and Whitehead…

Group Theory · Mathematics 2017-06-30 Warren Dicks

Given a family of groups admitting a braided monoidal structure (satisfying mild assumptions) we construct a family of spaces on which the groups act and whose connectivity yields, via a classical argument of Quillen, homological stability…

Algebraic Topology · Mathematics 2021-04-29 Nathalie Wahl , Oscar Randal-Williams

In this paper we prove a stability theorem for block diffeomorphisms of 2d-dimensional manifolds that are connected sums of S^d x S^d. Combining this with a recent theorem of S. Galatius and O. Randal-Williams and Morlet's lemma of…

Algebraic Topology · Mathematics 2012-09-05 Alexander Berglund , Ib Madsen

Working over an algebraically closed field $k$ of characteristic $0$, we show that the motivic stable homotopy groups of the sphere spectrum can be determined entirely from the motivic homotopy groups of the $p$-completed sphere spectra and…

Algebraic Topology · Mathematics 2026-03-10 Sebastian Gant , Ben Williams

A general overview of the phenomenon of automatic continuity of homomorphisms between Polish groups is given. In particular, we study variants and improvements of the closed graph theorem, applying these to the problem of continuity of…

Group Theory · Mathematics 2025-09-16 Christian Rosendal , Luis Carlos Suarez

A group $G$ is called automatically continuous if any homomorphism from a completely metrizable or locally compact Hausdorff group to $G$ has open kernel. In this paper, we study preservation of automatic continuity under group-theoretic…

Group Theory · Mathematics 2020-10-07 Samuel M. Corson , Ilya Kazachkov

This paper considers the links between the geometry of the various flag manifolds of loop groups and bundles over families of rational curves. Aa an application, a stability result for the moduli on a rational ruled surface of G-bundles…

Algebraic Geometry · Mathematics 2008-12-22 Jacques C. Hurtubise , Michael K. Murray

Let $f$ be an endomorphism of the projective line. There is a natural conjugation action on the space of such morphisms by elements of the projective linear group. The group of automorphisms, or stabilizer group, of a given $f$ for this…

Dynamical Systems · Mathematics 2021-06-14 Brandon Gontmacher , Benjamin Hutz , Grayson Jorgenson , Srinjoy Srimani , Simon Xu

We establish a decomposition of stable homology of automorphism groups of free groups with polynomial contravariant coefficients in term of functor homology. This allows several explicit computations, intersecting results obtained by…

Algebraic Topology · Mathematics 2019-08-15 Aurélien Djament

The holomorph of a free group $F_n$ is the semidirect product $F_n \rtimes Aut(F_n)$. Using the methods of Hatcher and Vogtmann, we derive stability results and calculate the mod-$p$ homology of these holomorphs for odd primes $p$ in…

Group Theory · Mathematics 2007-05-23 Craig A. Jensen

We study the homotopy of the connected sum of a manifold with a projective space, viewed as a typical way to stabilize manifolds. In particular, we show a loop homotopy decomposition of a manifold after stabilization by a projective space,…

Algebraic Topology · Mathematics 2023-08-03 Ruizhi Huang , Stephen Theriault

Wahl recently proved that the homology of the non-orientable mapping class group stabilizes as the genus increases. In this short note we analyse the situation where the underlying non-orientable surfaces have marked points.

Algebraic Topology · Mathematics 2008-06-09 Elizabeth Hanbury

We prove a representation stability result for the second homology groups of Torelli subgroups of mapping class groups and automorphism groups of free groups. This strengthens the results of Boldsen-Hauge Dollerup and Day-Putman. We also…

Algebraic Topology · Mathematics 2020-09-28 Jeremy Miller , Peter Patzt , Jennifer C. H. Wilson

In this paper, we give presentations of the mapping class groups of marked surfaces stabilizing boundaries for any genus. Note that in the existing works, the mapping class groups of marked surfaces were the isotopy classes of…

Geometric Topology · Mathematics 2023-07-31 Jinlei Dong , Fang Li

A group, $\fl{H}$, of automorphisms of a totally disconnected locally compact group, $G$, is flat if there is a compact open $U\leq G$ such that the index $[\alpha(U):U\cap \alpha(U)]$ is mininimized for every $\alpha\in\fl{H}$. The…

Group Theory · Mathematics 2025-12-12 George A. Willis

This paper consists of two related parts. In the first part we give a self-contained proof of homological stability for the spaces C_n(M;X) of configurations of n unordered points in a connected open manifold M with labels in a…

Algebraic Topology · Mathematics 2013-04-12 Oscar Randal-Williams

We will study homological stability of the diffeomorphism groups of the manifolds $W_{g,1}:=D^{2n} \# (S^n \times S^n)^{\#g }$ using $E_k$-algebras. This will lead to new improvements in the stability results, especially when working with…

Algebraic Topology · Mathematics 2023-04-10 Ismael Sierra

We initiate the study of analogues of symmetric spaces for the family of finite dihedral groups. In particular, we investigate the structure of the automorphism group, characterize the involutions of the automorphism group, and determine…

We prove a homological stability theorem for moduli spaces of simply-connected manifolds of dimension $2n > 4$, with respect to forming connected sum with $S^n \times S^n$. This is analogous to Harer's stability theorem for the homology of…

Algebraic Topology · Mathematics 2019-08-07 Soren Galatius , Oscar Randal-Williams