Browsing 2020 by Title
Now showing items 220 of 20

Generating Finite Coxeter Groups with Elements of the Same Order
[OWP202007] (Mathematisches Forschungsinstitut Oberwolfach, 20200316)Supposing $G$ is a group and $k$ a natural number, $d_k(G)$ is defined to be the minimal number of elements of $G$ of order $k$ which generate $G$ (setting $d_k(G) = 0$ if $G$ has no such generating sets). This paper ... 
Homology and $K$Theory of TorsionFree Ample Groupoids and Smale Spaces
[OWP202020] (Mathematisches Forschungsinstitut Oberwolfach, 20201009)Given an ample groupoid, we construct a spectral sequence with groupoid homology with integer coefficients on the second sheet, converging to the $K$groups of the groupoid C*algebra when the groupoid has torsionfree ... 
Hopf Algebras in Combinatorics, Volume 1
[OWP202014] (Mathematisches Forschungsinstitut Oberwolfach, 20200729) 
Hopf Algebras in Combinatorics, Volume 2
[OWP202015] (Mathematisches Forschungsinstitut Oberwolfach, 20200730) 
How Quantum Information Can Improve Social Welfare
[OWP202013] (Mathematisches Forschungsinstitut Oberwolfach, 20200716)In [2, 18, 5, 19, 4] it has been shown that quantum resources can allow us to achieve a family of equilibria that can have sometimes a better social welfare, while guaranteeing privacy. We use graph games to propose ... 
lTorsion Bounds for the Class Group of Number Fields with an l Group as Galois Group
[OWP202011] (Mathematisches Forschungsinstitut Oberwolfach, 20200504)We describe the relations among the $\ell$torsion conjecture for $\ell$extensions, the discriminant multiplicity conjecture for nilpotent extensions and a conjecture of Malle giving an upper bound for the number of ... 
Maximal Quaternion Orders in Quadratic Extensions  in Hurwitz’s Diaries
[OWP202016] (Mathematisches Forschungsinstitut Oberwolfach, 20200803)We present and comment on some unpublished work of Adolf Hurwitz on quaternion arithmetic from his diaries. 
Multivariate Hybrid Orthogonal Functions
[OWP202004] (Mathematisches Forschungsinstitut Oberwolfach, 20200312)We consider multivariate orthogonal functions satisfying hybrid orthogonality conditions with respect to a moment functional. This kind of orthogonality means that the product of functions of different parity order ... 
Nondegenerate Invariant Symmetric Bilinear Forms on Simple Lie Superalgebras in Characteristic 2
[OWP202002] (Mathematisches Forschungsinstitut Oberwolfach, 20200204)As is wellknown, the dimension of the space of nondegenerate invariant symmetric bilinear forms (NISes) on any simple finitedimensional Lie algebra or Lie superalgebra is equal to at most 1 if the characteristic of the ... 
Nonexistence of Subcritical Solitary Waves
[OWP202006] (Mathematisches Forschungsinstitut Oberwolfach, 20200315)We prove the nonexistence of twodimensional solitary gravity water waves with subcritical wave speeds and an arbitrary distribution of vorticity. This is a longstanding open problem, and even in the irrotational case there ... 
On Weakly Complete Universal Enveloping Algebras of proLie Algebras
[OWP202010] (Mathematisches Forschungsinstitut Oberwolfach, 20200427) 
The PelletierRessayre Hidden Symmetry for LittlewoodRichardson Coefficients
[OWP202018] (Mathematisches Forschungsinstitut Oberwolfach, 20200908)We prove an identity for Littlewood–Richardson coefficients conjectured by Pelletier and Ressayre. The proof relies on a novel birational involution defined over any semifield. 
Positive Line Bundles Over the Irreducible Quantum Flag Manifolds
[OWP202001] (Mathematisches Forschungsinstitut Oberwolfach, 20200203)Noncommutative Kähler structures were recently introduced by the third author as a framework for studying noncommutative Kähler geometry on quantum homogeneous spaces. It was subsequently observed that the notion of a ... 
Rational Functions with Small Value Set
[OWP202005] (Mathematisches Forschungsinstitut Oberwolfach, 20200314)In connection with Galois Theory and Algebraic Curves, this paper investigates rational functions $h(x) = f(x)/g(x) \in \mathbb{F}_q(x)$ for which the value set $V_h = {\{h(α)  α \in \mathbb{F}_q \cup\{\infty\}}\}$ is ... 
Singularities and Bifurcations of Pseudospherical Surfaces
[OWP202008] (Mathematisches Forschungsinstitut Oberwolfach, 20200317)We study singularities and bifurcations of constant negative curvature surfaces in Euclidean 3space via their association with Lorentzian harmonic maps. This preprint presents the basic results on this, the full proofs ... 
SpaceTime Euler Discretization Schemes for the Stochastic 2D NavierStokes Equations
[OWP202012] (Mathematisches Forschungsinstitut Oberwolfach, 20200506)We prove that the implicit time Euler scheme coupled with finite elements space discretization for the 2D NavierStokes equations on the torus subject to a random perturbation converges in $L^2(\Omega)$, and describe the ... 
Splitting Necklaces, with Constraints
[OWP202003] (Mathematisches Forschungsinstitut Oberwolfach, 20200211)We prove several versions of Alon's "necklacesplitting theorem", subject to additional constraints, as illustrated by the following results. (1) The "almost equicardinal necklacesplitting theorem" claims that, without ... 
Theoretical Analysis and Simulation Methods for Hawkes Processes and their Diffusion Approximation
[OWP202009] (Mathematisches Forschungsinstitut Oberwolfach, 20200330)Oscillatory systems of interacting Hawkes processes with Erlang memory kernels were introduced in Ditlevsen and Löcherbach (2017). They are piecewise deterministic Markov processes (PDMP) and can be approximated by a ... 
Unexpected Properties of the Klein Configuration of 60 Points in $\mathbb{P}^3$
[OWP202019] (Mathematisches Forschungsinstitut Oberwolfach, 20201007)Felix Klein in course of his study of the regular and its symmetries encountered a highly symmetric configuration of 60 points in $\mathbb{P}^3$. This configuration has appeared in various guises, perhaps post notably as ...