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We give a self-contained algebraic description of a formal symplectic groupoid over a Poisson manifold M. To each natural star product on M we then associate a canonical formal symplectic groupoid over M. Finally, we construct a unique…

Quantum Algebra · Mathematics 2009-11-10 Alexander V. Karabegov

Fuchsian groups with a modular embedding have the richest arithmetic properties among non-arithmetic Fuchsian groups. But they are very rare, all known examples being related either to triangle groups or to Teichmueller curves. In Part I of…

Number Theory · Mathematics 2019-02-20 Martin Moeller , Don Zagier

We produce first examples of p-local height three TAF homology theories. The corresponding one-dimensional formal groups arise as split summands of the formal groups of certain abelian three-folds, the Shimura variety of which can be…

Algebraic Topology · Mathematics 2017-05-08 Hanno von Bodecker , Sebastian Thyssen

Let $(G,g)$ be a 4-dimensional Riemannian Lie group with a 2-dimensional left-invariant, conformal foliation $\F$ with minimal leaves. Let $J$ be an almost Hermitian structure on $G$ adapted to the foliation $\F$. We classify such…

Differential Geometry · Mathematics 2022-01-12 Emma Andersdotter Svensson , Sigmundur Gudmundsson

In this paper, we make use of the relations between the braid and mapping class groups of a compact, connected, non-orientable surface N without boundary and those of its orientable double covering S to study embeddings of these groups and…

Geometric Topology · Mathematics 2016-10-12 Daciberg Lima Gonçalves , John Guaschi , Miguel Maldonado

It is shown that a locally geometrical structure of arbitrarily curved Riemannian space is defined by a deformed group of its diffeomorphisms

Differential Geometry · Mathematics 2020-06-11 Serhiy E. Samokhvalov

We explicitly describe the derived Picard groups of symmetric representation-finite algebras of type $D$. In particular, we prove that these groups are generated by spherical twists along collections of $0$-spherical objects, the shift and…

Representation Theory · Mathematics 2026-02-17 Anya Nordskova

We study automorphic Lie algebras using a family of evaluation maps parametrised by the representations of the associative algebra of functions. This provides a descending chain of ideals for the automorphic Lie algebra which is used to…

Representation Theory · Mathematics 2024-04-16 Drew Duffield , Vincent Knibbeler , Sara Lombardo

Let M be a surface, perhaps with boundary, and either compact, or with a finite number of points removed from the interior of the surface. We consider the inclusion i: F\_n(M) --\textgreater{} M^n of the nth configuration space F\_n(M) of M…

Geometric Topology · Mathematics 2017-03-01 Daciberg Lima Gonçalves , John Guaschi

We prove that the symplectic group $Sp(2n,\mathbb Z)$ and the mapping class group $Mod_{S}$ of a compact surface $S$ satisfy the $R_{\infty}$ property. We also show that $B_n(S)$, the full braid group on $n$-strings of a surface $S$,…

Group Theory · Mathematics 2007-12-16 Alexander Fel'shtyn , Daciberg L. Gonçalves

These notes grew out of our learning and applying the methods of Fock and Goncharov concerning moduli spaces of real projective structures on surfaces with ideal triangulations. We give a self-contained treatment of Fock and Goncharov's…

Geometric Topology · Mathematics 2018-01-12 Alex Casella , Dominic Tate , Stephan Tillmann

In this paper, we solve the problem of giving a gauge-theoretic description of the natural Dirac structure on a Lie Group which plays a prominent role in the theory of D- branes for the Wess-Zumino-Witten model as well as the theory of…

Symplectic Geometry · Mathematics 2017-09-27 Alejandro Cabrera , Marco Gualtieri , Eckhard Meinrenken

We present a graded-geometric approach to modular classes of Lie algebroids and their generalizations, introducing in this setting an idea of relative modular class of a Dirac structure for a certain type of Courant algebroids, called…

Differential Geometry · Mathematics 2017-01-17 Janusz Grabowski

Given a Hamiltonian action of a proper symplectic groupoid (for instance, a Hamiltonian action of a compact Lie group), we show that the transverse momentum map admits a natural constant rank stratification. To this end, we construct a…

Symplectic Geometry · Mathematics 2021-09-29 Maarten Mol

We define algebras of admissible functions associated to twisted Dirac structures, and we show that they are Poisson algebras. We study the standard cases associated to Dirac structures defined by graphs of non-degenerate 2-forms.

Symplectic Geometry · Mathematics 2012-08-01 Alexander Cardona

After recalling some basic facts about F-wound commutative unipotent algebraic groups over an imperfect field F we study their regular integral models over Dedekind schemes of positive characteristic and compute the group of isomorphisms…

Algebraic Geometry · Mathematics 2021-05-17 Igor Dolgachev

Given a formal symplectic groupoid $G$ over a Poisson manifold $(M, \pi_0)$, we define a new object, an infinitesimal deformation of $G$, which can be thought of as a formal symplectic groupoid over the manifold $M$ equipped with an…

Quantum Algebra · Mathematics 2015-05-19 Alexander Karabegov

To show that certain wild character varieties are multiplicative analogues of quiver varieties, Boalch introduced colored multiplicative quiver varieties. They form a class of (nondegenerate) Poisson varieties attached to colored quivers…

Representation Theory · Mathematics 2025-04-14 Maxime Fairon , David Fernández

Let G be a Lie group and g its Lie algebra. We develop a theory of quasi Poisson structures relative to a not necessarily non-degenerate Ad-invariant symmetric 2-tensor in the tensor square of g and one of general not necessarily…

Differential Geometry · Mathematics 2026-01-22 Johannes Huebschmann

Among plenty of applications, low-dimensional homogeneous spaces appear in cosmological models as both, classical factor spaces of multidimensional geometry and minisuperspaces in canonical quantization. Here a new tool to restrict their…

General Relativity and Quantum Cosmology · Physics 2016-08-31 M. Rainer