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Let ${\mathfrak g}$ be a complex semisimple Lie algebra, and $Y_h({\mathfrak g})$, $U_q(L{\mathfrak g})$ the corresponding Yangian and quantum loop algebra, with deformation parameters related by $q=\exp(\pi i h)$. When $h$ is not a…

Quantum Algebra · Mathematics 2017-07-14 Sachin Gautam , Valerio Toledano-Laredo

In the present paper, we introduce two-dimensional categorified Hall algebras of smooth curves and smooth surfaces. A categorified Hall algebra is an associative monoidal structure on the stable $\infty$-category…

Algebraic Geometry · Mathematics 2022-11-22 Mauro Porta , Francesco Sala

A 2-Hilbert space is a category with structures and properties analogous to those of a Hilbert space. More precisely, we define a 2-Hilbert space to be an abelian category enriched over Hilb with a *-structure, conjugate-linear on the…

q-alg · Mathematics 2008-02-03 John C. Baez

We introduce a compactification construction for abstract quasi-local C*-algebras over countable metric spaces equipped with an isometric group action which is functorial with respect to bounded spread isomorphisms. In $1$D, the…

Mathematical Physics · Physics 2026-02-03 Jun Ikeda

Starting from a description of various generalized function algebras based on sequence spaces, we develop the general framework for considering linear problems with singular coefficients or non linear problems. Therefore, we prove…

Functional Analysis · Mathematics 2007-05-23 Antoine Delcroix , Maximilian F. Hasler , Stevan Pilipović , Vincent Valmorin

Let $Y_{1},\dots,Y_{l}$ be smooth irreducible projective curves and let $Y$ be its disjoint union. Given a semisimple reductive algebraic group $G$ and a faithful representation $\rho:G\hookrightarrow \textrm{SL}(V)$ we construct a…

Algebraic Geometry · Mathematics 2020-07-28 Ángel Luis Muñoz Castañeda

For a finite-dimensional simple Lie algebra $\mathfrak{g}$ admitting a non-trivial minuscule representation and a connected marked surface $\Sigma$ with at least two marked points and no punctures, we prove that the cluster algebra…

Representation Theory · Mathematics 2023-08-29 Tsukasa Ishibashi , Hironori Oya , Linhui Shen

Let $G'$ be a closed subgroup of a topological group $G$. A principal $G$-bundle $X$ is reducible to a locally trivial principal $G'$-bundle $X'$ if and only if there exists a local trivialisation of $X$ such that all transition functions…

Quantum Algebra · Mathematics 2021-02-05 Piotr M. Hajac , Jan Rudnik , Bartosz Zielinski

We prove new structural results for the rational homotopy type of the classifying space $B\operatorname{aut}(X)$ of fibrations with fiber a simply connected finite CW-complex $X$. We first study nilpotent covers of $B\operatorname{aut}(X)$…

Algebraic Topology · Mathematics 2025-10-15 Alexander Berglund , Tomáš Zeman

We give a novel and effective criterion for algebraicity of rational normal analytic surfaces constructed from resolving the singularity of an irreducible curve-germ on $CP^2$ and contracting the strict transform of a given line and all but…

Algebraic Geometry · Mathematics 2012-11-20 Pinaki Mondal

Given a C*-dynamical system (A,G,\alpha), we say that A is a weakly proper (X\rtimes G)-algebra if there exists a proper G-space X together with a nondegenerate G-equivariant *-homomorphism \phi:C_0(X)->M(A). Weakly proper G-algebras form a…

Operator Algebras · Mathematics 2014-06-02 Alcides Buss , Siegfried Echterhoff

This study introduces a new unified structural framework for orbifold sigma models that incorporates twisted sectors, singularities, and smooth regions into a single algebraic object. Traditional approaches to orbifold theories often treat…

Mathematical Physics · Physics 2025-11-20 Francesco D'Agostino

Standard results from non-abelian cohomology theory specialize to a theory of torsors and stacks for cosimplicial groupoids. The space of global sections of the stack completion of a cosimplicial groupoid $G$ is weakly equivalent to the…

Algebraic Topology · Mathematics 2019-06-17 J. F. Jardine

We generalize Abel's classical theorem on linear equivalence of divisors on a Riemann surface. For every closed submanifold $M^d \subset X^n$ in a compact oriented Riemannian $n$--manifold, or more generally for any $d$--cycle $Z$ relative…

Differential Geometry · Mathematics 2008-12-02 Johan L. Dupont , Franz W. Kamber

Dwyer-Kan localization at pairs of quasi-isomorphisms of the category of dg Lie-Rinehart pairs $(A,M)$, where $A$ is a semi-free cdga over a field $k$ of characteristic zero and $M$ a cell complex in $A$-modules, is shown to be equivalent…

Algebraic Topology · Mathematics 2026-01-07 Damjan Pištalo

Let $R$ be a Lie conformal algebra. The purpose of this paper is to investigate the conformal derivation algebra $CDer(R)$, the conformal quasiderivation algebra $QDer(R)$ and the generalized conformal derivation algebra $GDer(R)$. The…

Quantum Algebra · Mathematics 2016-02-04 Guangzhe Fan , Yanyong Hong , Yucai Su

We introduce a structure termed ``connected cyclic diagonal'' on a chain complex, which induces stable power operations in its cohomology with the property that negative power operations consistently vanish. This chain level structure is…

Algebraic Topology · Mathematics 2024-02-02 Federico Cantero-Morán , Aníbal Medina-Mardones

We provide examples of inductive fibrant replacements in fibrantly generated model categories constructed as Postnikov towers. These provide new types of arguments to compute homotopy limits in model categories. We provide examples for…

Algebraic Topology · Mathematics 2024-04-09 Maximilien Péroux

A conformal metric $g$ with constant curvature one and finite conical singularities on a compact Riemann surface $\Sigma$ can be thought of as the pullback of the standard metric on the 2-sphere by a multi-valued locally univalent…

Differential Geometry · Mathematics 2016-01-20 Qing Chen , Wei Wang , Yingyi Wu , Bin Xu

For a countable group $G$ we construct a small, idempotent complete, symmetric monoidal, stable $\infty$-category $\mathrm{KK}^{G}_{\mathrm{sep}}$ whose homotopy category recovers the triangulated equivariant Kasparov category of separable…

Operator Algebras · Mathematics 2025-12-03 Ulrich Bunke , Alexander Engel , Markus Land