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We introduce a notion of I-factorial quantum torsor, which consists of an integrable ergodic action of a locally compact quantum group on a type I-factor such that also the crossed product is a type I-factor. We show that any such…

Operator Algebras · Mathematics 2019-01-29 Kenny De Commer

We show that normalized quantum K-theoretic vertex functions for cotangent bundles of partial flag varieties are the eigenfunctions of quantum trigonometric Ruijsenaars-Schneider (tRS) Hamiltonians. Using recently observed relations between…

Algebraic Geometry · Mathematics 2021-05-17 Peter Koroteev , Anton M. Zeitlin

Given an ample Hausdorff groupoid $G$, a unital commutative ring $R$, and a discrete twist $(\Sigma,i,q)$, we establish a generalised uniqueness theorem for the twisted Steinberg algebra $A_R(G;\Sigma)$. By applying this theorem when $G$ is…

Rings and Algebras · Mathematics 2026-05-13 Rizalyn S. Bongcawel , Lyster Rey B. Cabardo , Lisa O. Clark

We generalize to higher algebraic $K$-theory an identity (originally due to Milnor) that relates the Reidemeister torsion of an infinite cyclic cover to its Lefschetz zeta function. Our identity involves a higher torsion invariant, the…

K-Theory and Homology · Mathematics 2022-06-22 John R. Klein , Cary Malkiewich

Let K be a compact semi-simple Lie group. We classify K-invariant Kaehler structures on the space Kc/(P,P), where Kc is the complexification of K, P is a parabolic subgroup of Kc, and (P,P) the commutator subgroup. For each Kaehler…

dg-ga · Mathematics 2008-02-03 Meng-Kiat Chuah

In the previous paper, the author showed that for a smooth family $X \to \mathbb{X} \to B$ of a homotopy $K3$ surface, the obstruction for the tangent bundle along the fibers $T_B \mathbb{X}$ to have a spin structure is canonically…

Differential Geometry · Mathematics 2026-04-29 Mitsuyoshi Adachi

We define an (equivariant) quaternionic analytic torsion for antiselfdual vector bundles on quaternionic Kaehler manifolds, using ideas by Leung and Yi. We compute this torsion for vector bundles on quaternionic homogeneous spaces with…

Differential Geometry · Mathematics 2007-05-23 Kai Koehler , Gregor Weingart

We construct equivariant $KK$-theory with coefficients in $\mathbb{R}$ and $\mathbb{R}/\mathbb{Z}$ as suitable inductive limits over ${\rm II}_1$-factors. We show that the Kasparov product, together with its usual functorial properties,…

Operator Algebras · Mathematics 2015-04-20 Paolo Antonini , Sara Azzali , Georges Skandalis

The first author's recent unexpected discovery of torsion in the integral cohomology of the T\"ubingen Triangle Tiling has led to a re-evaluation of current descriptions of and calculational methods for the topological invariants associated…

Mathematical Physics · Physics 2012-02-16 Franz Gähler , John Hunton , Johannes Kellendonk

For two unital Kirchberg algebras with finitely generated K-groups, we introduce a property, called reciprocality, which is proved to be closely related to the homotopy theory of Kirchberg algebras. We show the Spanier--Whitehead duality…

Operator Algebras · Mathematics 2022-08-30 Taro Sogabe

We reveal a correspondence between the homological torsion of the Bianchi groups and new geometric invariants, which are effectively computable thanks to their action on hyperbolic space. We use it to explicitly compute their integral group…

K-Theory and Homology · Mathematics 2011-09-09 Alexander D. Rahm

We study equivariant coarse homology theories through an axiomatic framework. To this end we introduce the category of equivariant bornological coarse spaces and construct the universal equivariant coarse homology theory with values in the…

K-Theory and Homology · Mathematics 2021-05-28 Ulrich Bunke , Alexander Engel , Daniel Kasprowski , Christoph Winges

We prove that the Schubert structure constants of the quantum $K$-theory ring of any minuscule flag variety or quadric hypersurface have signs that alternate with codimension. We also prove that the powers of the deformation parameter $q$…

Algebraic Geometry · Mathematics 2026-03-24 Anders S. Buch , Pierre-Emmanuel Chaput , Leonardo C. Mihalcea , Nicolas Perrin

We introduce a general framework to unify several variants of twisted topological $K$-theory. We focus on the role of finite dimensional real simple algebras with a product-preserving involution, showing that Grothendieck-Witt groups…

K-Theory and Homology · Mathematics 2015-09-29 Max Karoubi , Charles Weibel

We study deformation of algebras with coaction symmetry of reduced algebra of discrete groups, where the deformation parameter is given continuous family of group $2$-cocycles. When the group satisfies the Baum-Connes conjecture with…

Operator Algebras · Mathematics 2023-08-07 Makoto Yamashita

Higher rank semigraph algebras are introduced by mixing concepts of ultragraph algebras and higher rank graph algebras. This yields a kind of higher rank generalisation of ultragraph algebras. We prove Cuntz--Krieger uniqueness theorems for…

Operator Algebras · Mathematics 2011-11-18 Bernhard Burgstaller

We show that filtered K-theory is equivalent to a substantially smaller invariant for all real-rank-zero C*-algebras with certain primitive ideal spaces -- including the infinitely many so-called accordion spaces for which filtered K-theory…

Operator Algebras · Mathematics 2013-11-05 Sara Arklint , Rasmus Bentmann , Takeshi Katsura

Let $X$ be a compact K\"{a}hler manifold, and let $L$ be a line bundle on $X.$ Define $I_k(L)$ to be the kernel of the multiplication map $ Sym^k H^0 (L) \to H^0 (L^k).$ For all $h \leq k,$ we define a map $\rho : I_k(L) \to Hom (H^{p,q}…

Algebraic Geometry · Mathematics 2007-05-23 Elisabetta Colombo , Gian Pietro Pirola , Alfonso Tortora

In the first part we use Gromov's K--area to define the K--area homology which stabilizes into singular homology on the category of pairs of compact smooth manifolds. The second part treats the questions of certain curvature gaps. For…

Differential Geometry · Mathematics 2012-02-21 Mario Listing

We describe a variant of K-theory for spaces with involution, built from vector bundles which are sent to their negative under the involution.

K-Theory and Homology · Mathematics 2007-05-23 Michael Atiyah , Michael Hopkins