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While the Chow groups of 0-dimensional cycles on the moduli spaces of Deligne-Mumford stable pointed curves can be very complicated, the span of the 0-dimensional tautological cycles is always of rank 1. The question of whether a given…

Algebraic Geometry · Mathematics 2024-04-17 Rahul Pandharipande , Johannes Schmitt

We study the cohomology with twisted coefficients of the geometric realization of a linking system associated to a saturated fusion system $\mathcal{F}$. More precisely, we extend a result due to Broto, Levi and Oliver to twisted…

Algebraic Topology · Mathematics 2016-09-14 Rémi Molinier

This article records multiple results coming from interplay between de-completed topological periodic cyclic homology, Segal conjecture, and F-smoothness. We establish completeness of motivic filtration on de-completed topological periodic…

K-Theory and Homology · Mathematics 2025-12-22 Zhouhang Mao

After Katok, a homeomorphism $f\colon M\to M$ is said to be cohomologically $C^0$-stable when its space of real $C^0$-coboundaries is closed in $C^0(M)$. In this short note we completely classify cohomologically $C^0$-stable homeomorphisms,…

Dynamical Systems · Mathematics 2012-09-24 Alejandro Kocsard

The positive cohomology groups of a finite group acting on a ring vanish when the ring has a norm-one element. In this note we give explicit homotopies on the level of cochains when the group is cyclic, which allows us to express any…

Group Theory · Mathematics 2010-03-25 Christian Kassel

In this paper, we initiate a study of motivic homotopy theory at infinity. We use the six functor formalism to give an intrinsic definition of the stable motivic homotopy type at infinity of an algebraic variety. Our main computational…

Algebraic Geometry · Mathematics 2021-04-08 Adrien Dubouloz , Frédéric Déglise , Paul Arne Østvær

Based on various strategies and a new general doubling operator, we obtain several simple proofs of the celebrated Sharkovsky's cycle coexistence theorem. A simple non-directed graph proof which is especially suitable for a calculus course…

Dynamical Systems · Mathematics 2015-04-13 Bau-Sen Du

For a symplectic manifold $(M,\om)$ with exact symplectic form we construct a 2-cocycle on the group of symplectomorphisms and indicate cases when this cocycle is not trivial.

Group Theory · Mathematics 2007-07-05 Rais S. Ismagilov , Mark Losik , Peter W. Michor

A group is boundedly acyclic if its bounded cohomology with trivial real coefficients vanishes in all positive degrees. Amenable groups are boundedly acyclic, while the first non-amenable examples were the group of compactly supported…

Group Theory · Mathematics 2022-06-14 Francesco Fournier-Facio , Clara Loeh , Marco Moraschini

For every Hecke C*-algebra of right-angled, hyperbolic type, we construct a smooth subalgebra to which traces associated with arbitrary conjugacy classes in the associated Coxeter group extend. We calculate the pairing with K-theory of the…

Operator Algebras · Mathematics 2026-03-25 Piotr Nowak , Sanaz Pooya , Sven Raum , Adam Skalski

We prove that, for semi-invertible linear cocycles, Oseledets subspaces associated to ergodic measures may be approximated by Oseledets subspaces associated to periodic points.

Dynamical Systems · Mathematics 2019-05-23 Lucas Backes

Using new as well as known results on dimerized quantum spin chains with frustration, we are able to infer some properties on the low-energy spectrum of the O(3) Nonlinear Sigma Model with a topological theta-term. In particular, for…

Statistical Mechanics · Physics 2011-02-16 L. Campos Venuti , C. Degli Esposti Boschi , E. Ercolessi , F. Ortolani , G. Morandi , S. Pasini , M. Roncaglia

In this expository paper we present some ideas of algebraic topology (more precisely, of homology theory) in a language accessible to non-specialists in the area. A $1$-cycle in a graph is a set $C$ of edges such that every vertex is…

History and Overview · Mathematics 2026-01-08 A. Miroshnikov , O. Nikitenko , A. Skopenkov

The rigidity theory for circle homeomophisms with breaks was studied intensively in the last 20 years. It was proved that under mild conditions of the Diophantine type on the rotation number any two $C^{2+\alpha}$ smooth circle…

Dynamical Systems · Mathematics 2021-12-07 Nataliya Goncharuk , Konstantin Khanin , Yury Kudryashov

We show that for a noetherian algebra $A$ whose bounded dg derived category is smooth, the singular Hochschild cohomology (=Tate--Hochschild cohomology) is isomorphic, as a graded algebra, to the Hochschild cohomology of the dg singularity…

Representation Theory · Mathematics 2020-09-10 Bernhard Keller

In the present paper we investigate the noncommutative geometry of a class of algebras, called the Hom-associative algebras, whose associativity is twisted by a homomorphism. We define the Hochschild, cyclic, and periodic cyclic homology…

K-Theory and Homology · Mathematics 2015-12-09 Mohammad Hassanzadeh , Ilya Shapiro , Serkan Sütlü

We consider two different $\text{SU}(2)^2$-invariant cohomogeneity one manifolds, one non-compact $M=\mathbb{R}^4 \times S^3$ and one compact $M=S^4 \times S^3$, and study the existence of coclosed $\text{SU}(2)^2$-invariant…

Differential Geometry · Mathematics 2024-12-06 Izar Alonso

If a non-ergodic, partially hyperbolic diffeomorphism on the 3-torus is homotopic to an Anosov diffeomorphism $A$, it is topologically conjugate to $A$.

Dynamical Systems · Mathematics 2012-08-29 Andy Hammerlindl , Raúl Ures

Any knot in $S^3$ may be reduced to a slice knot by crossing changes. Indeed, this slice knot can be taken to be the unknot. In this paper we study the question of when the same holds for knots in homology spheres. We show that a knot in a…

Geometric Topology · Mathematics 2020-02-19 Christopher W. Davis

The ${\ell}^1$-convolution algebra of a semilattice is known to have trivial cohom ology in degrees 1,2 and 3 whenever the coefficient bimodule is symmetric. We ex tend this result to all cohomology groups of degree $\geq 1$ with symmetric…

Functional Analysis · Mathematics 2008-11-03 Yemon Choi