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We construct a compactification of the moduli space of twisted holomorphic maps with varying complex structure and bounded energy. For a given compact symplectic manifold $X$ with a compatible complex structure and a Hamiltonian action of…

Symplectic Geometry · Mathematics 2007-05-23 Ignasi Mundet i Riera , Gang Tian

A famous theorem of Nakaoka asserts that the cohomology of the symmetric group stabilizes. The first author generalized this theorem to non-trivial coefficient systems, in the form of $\mathrm{FI}$-modules over a field, though one now…

Representation Theory · Mathematics 2018-02-14 Rohit Nagpal , Andrew Snowden

A discrete group is matricially stable if every function from the group to a complex unitary group that is "almost multiplicative" in the point-operator norm topology is "close" to a genuine unitary representation. It follows from a recent…

Group Theory · Mathematics 2024-03-25 Forrest Glebe

We give lower bounds for the rank of the first homology group of the real points of the Deligne-Mumford-Knudsen compactification of stable n-pointed curves of genus 0,which coincides with the Chow quotient (RP^1)^n//PGL(2,R).The study has…

Algebraic Topology · Mathematics 2007-05-23 Gefry Barad

We develop a comprehensive theory of the stable representation categories of several sequences of groups, including the classical and symmetric groups, and their relation to the unstable categories. An important component of this theory is…

Representation Theory · Mathematics 2015-06-17 Steven V Sam , Andrew Snowden

We introduce a notion of Gieseker stability for coherent sheaves on tame Deligne-Mumford stacks with projective moduli scheme and some chosen generating sheaf on the stack in the sense of Olsson and Starr \cite{MR2007396}. We prove that…

Algebraic Geometry · Mathematics 2009-09-22 Fabio Nironi

We introduce the idea of *representation stability* (and several variations) for a sequence of representations V_n of groups G_n. A central application of the new viewpoint we introduce here is the importation of representation theory into…

Representation Theory · Mathematics 2014-02-04 Thomas Church , Benson Farb

We give a description of the cohomology groups of the structure sheaf on smooth compactifications $\overline{X}(w)$ of Deligne--Lusztig varieties $X(w)$ for ${\rm GL}_n$, for all elements $w$ in the Weyl group. As a consequence, we obtain…

Algebraic Geometry · Mathematics 2024-03-18 Yingying Wang

Given an isolated, quasi-homogeneous singularity $X$ we prove that there is a group isomorphism between the group of rank one reflexive sheaves on $X$ and the free abelian group generated by $\mathbb{C}^*$-divisors, modulo linear…

Algebraic Geometry · Mathematics 2023-01-13 Ananyo Dan , Agustín Romano-Velázquez

We prove similar theorems concerning the structure of bundles involving complements of fiber-type hyperplane arrangements and orbit configuration spaces. These results facilitate analysis of the fundamental groups of these spaces, which may…

Geometric Topology · Mathematics 2007-05-23 Daniel C. Cohen

We construct Morse homology groups associated with any regular function on a smooth complex algebraic variety, allowing singular and non-compact critical loci. These groups are generated by critical points of a certain large pertubation of…

Geometric Topology · Mathematics 2025-09-26 Aleksander Doan , Juan Muñoz-Echániz

In this paper, a decomposition theorem for (covariant) unitary group representations on Kaplansky-Hilbert modules over Stone algebras is established, which generalizes the well-known Hilbert space case (where it coincides with the…

Dynamical Systems · Mathematics 2024-02-14 Nikolai Edeko , Markus Haase , Henrik Kreidler

We prove that braid group representations associated to braided fusion categories and mapping class group representations associated to modular fusion categories are always semisimple. The proof relies on the theory of extensions in…

Algebraic Geometry · Mathematics 2025-07-10 Pierre Godfard

For any smooth compact manifold $W$ of dimension at least two we prove that the classifying spaces of its group of diffeomorphisms which fix a set of $k$ points or $k$ embedded disks (up to permutation) satisfy homology stability. The same…

Algebraic Topology · Mathematics 2015-12-16 Ulrike Tillmann

A version of group cohomology for locally compact groups and Polish modules has previously been developed using a bar resolution restricted to measurable cochains. That theory was shown to enjoy analogs of most of the standard algebraic…

Group Theory · Mathematics 2012-11-27 Tim Austin , Calvin C. Moore

We study representation stability in the sense of Church, Ellenberg, and Farb \cite{FI-module} through the lens of symmetric function theory and the different symmetric function bases. We show that a sequence, $(F_n)_n$, where $F_n$ is a…

Combinatorics · Mathematics 2025-05-28 Nikita Borisov

We have recently proved a homological stability theorem for moduli spaces of r-Spin Riemann surfaces, which in particular implies a Madsen--Weiss theorem for these moduli spaces. This allows us to effectively study their stable cohomology,…

Algebraic Topology · Mathematics 2013-01-08 Oscar Randal-Williams

The moduli in a 4D N=1 heterotic compactification on an elliptic CY, as well as in the dual F-theoretic compactification, break into "base" parameters which are even (under the natural involution of the elliptic curves), and "fiber" or…

High Energy Physics - Theory · Physics 2009-10-31 Gottfried Curio , Ron Y. Donagi

An equivariant stable birational invariant of an action of a finite group on a smooth projective variety is the first cohomology group of the Picard module. Bogomolov-Prokhorov and Shinder computed this for actions of cyclic groups on…

Algebraic Geometry · Mathematics 2022-03-04 Andrew Kresch , Yuri Tschinkel

For a Riemannian foliation $F$ on a compact manifold $M$ with a bundle-like metric, the de Rham complex of $M$ is $C^{\infty}$-splitted as the direct sum of the basic complex and its orthogonal complement. Then the basic component…

Differential Geometry · Mathematics 2025-10-14 Jesús A. Álvarez López