Browsing 1  Oberwolfach Preprints (OWP) by Title
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On Unipotent Radicals of PseudoReductive Groups
[OWP201712] (Mathematisches Forschungsinstitut Oberwolfach, 20170427)We establish some results on the structure of the geometric unipotent radicals of pseudoreductive kgroups. In particular, let $k'$ be a purely inseparable field extension of k of degree $p^e$ and let $G$ denote the ... 
On VietorisRips Complexes of Ellipses
[OWP201711] (Mathematisches Forschungsinstitut Oberwolfach, 20170425)For $X$ a metric space and $r > 0$ a scale parameter, the Vietoris–Rips complex $VR_<(X; r)$ (resp. $VR_≤(X; r)$) has $X$ as its vertex set, and a finite subset $\sigma \subseteq X$ as a simplex whenever the diameter of ... 
On Weak Weighted Estimates of Martingale Transform
[OWP201622] (Mathematisches Forschungsinstitut Oberwolfach, 20161112)We consider several weak type estimates for singular operators using the Bellman function approach. We disprove the $A_1$ conjecture, which stayed open after MuckenhouptWheeden's conjecture was disproved by RegueraThiele. 
On Weakly Complete Universal Enveloping Algebras of proLie Algebras
[OWP202010] (Mathematisches Forschungsinstitut Oberwolfach, 20200427) 
An Optimal Bound for the Ratio Between Ordinary and Uniform Exponents of Diophantine Approximation
[OWP201815] (Mathematisches Forschungsinstitut Oberwolfach, 20180709)We provide a lower bound for the ratio between the ordinary and uniform exponents of both simultaneous Diophantine approximation to n real numbers and Diophantine approximation for one linear form in n variables. This ... 
Optimal bounds for the colored Tverberg Problem
[OWP200927] (Mathematisches Forschungsinstitut Oberwolfach, 20090320)We prove a "Tverberg type" multiple intersection theorem. It strengthens the prime case of the original Tverberg theorem from 1966, as well as the topological Tverberg theorem of Bárány et al. (1980), by adding color ... 
Overlap Synchronisation in Multipartite Random Energy Models
[OWP201713] (Mathematisches Forschungsinstitut Oberwolfach, 20170429)In a multipartite random energy model, made of coupled GREMs, we determine the joint law of the overlaps in terms of the ones of the single GREMs. This provides the simplest example of the socalled synchronisation of the ... 
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. 
Plethysms, replicated Schur functions and series, with applications to vertex operators
[OWP201012] (Mathematisches Forschungsinstitut Oberwolfach, 20100314)Specializations of Schur functions are exploited to define and evaluate the Schur functions $s_\lambda [\alpha X]$ and plethysms $s_\lambda [\alpha s_\nu(X))]$ for any $\alpha$integer, real or complex. Plethysms are then ... 
Plethystic Vertex Operators and BosonFermion Correspondences
[OWP201611] (Mathematisches Forschungsinstitut Oberwolfach, 20160617)We study the algebraic properties of plethystic vertex operators, introduced in J. Phys. A: Math. Theor. 43 405202 (2010), underlying the structure of symmetric functions associated with certain generalized universal ... 
Pointwise hyperbolicity implies uniform hyperbolicity
[OWP200906] (Mathematisches Forschungsinstitut Oberwolfach, 20090223)We provide a general mechanism for obtaining uniform information from pointwise data. A sample result is that if a diffeomorphism of a compact Riemannian manifold has pointwise expanding and contracting continuous invariant ... 
Polynomiality, wall crossings and tropical geometry of rational double hurwitz cycles
[OWP201213] (Mathematisches Forschungsinstitut Oberwolfach, 20121204)We study rational double Hurwitz cycles, i.e. loci of marked rational stable curves admitting a map to the projective line with assigned ramification profiles over two fixed branch points. Generalizing the phenomenon ... 
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 ... 
Positive Margins and Primary Decomposition
[OWP201206] (Mathematisches Forschungsinstitut Oberwolfach, 2012)We study random walks on contingency tables with fixed marginals, corresponding to a (loglinear) hierarchical model. If the set of allowed moves is not a Markov basis, then there exist tables with the same marginals that ... 
Positive recurrence of piecewise OrnteinUhlenbeck processes and common quadratic Lyapunov functions
[OWP201126] (Mathematisches Forschungsinstitut Oberwolfach, 2011)We study the positive recurrence of piecewise OrnsteinUhlenbeck (OU) diffusion processes, which arise from manyserver queueing systems with phasetype service requirements. These diffusion processes exhibit different ... 
Positivity of the Tsystem cluster algebra
[OWP200921] (Mathematisches Forschungsinstitut Oberwolfach, 20090314)We give the path model solution for the cluster algebra variables of the $A_r$ Tsystem with generic boundary conditions. The solutions are partition functions of (strongly) nonintersecting paths on weighted graphs. The ... 
A potential reduction algorithm for twoperson zerosum mean payoff stochastic games
[OWP201519] (Mathematisches Forschungsinstitut Oberwolfach, 2015)We suggest a new algorithm for twoperson zerosum undiscounted stochastic games focusing on stationary strategies. Given a positive real $\epsilon$, let us call a stochastic game $\epsilon$ergodic, if its values from any ... 
Preconditioning of Block Tridiagonal Matrices
[OWP200805] (Mathematisches Forschungsinstitut Oberwolfach, 20080309)Preconditioning methods via approximate block factorization for block tridiagonal matrices are studied. Bounds for the resulting condition numbers are given, and two methods for the recursive construction of the approximate ... 
Prediction and Quantification of Individual Athletic Performance
[OWP201511] (Mathematisches Forschungsinstitut Oberwolfach, 20150827)We present a novel, quantitative view on the human athletic performance of individuals. We obtain a predictor for athletic running performances, a parsimonious model, and a training state summary consisting of three numbers, ... 
Products of pairs of Dehn twists and maximal real Lefschetz fibrations
[OWP201132] (Mathematisches Forschungsinstitut Oberwolfach, 2011)We address the problem of existence and uniqueness of a factorization of a given element of the modular group into a product of two Dehn twists. As a geometric application, we conclude that any maximal real elliptic ...