Anzeige der Dokumente 1-20 von 28

• #### Right Simple Singularities in Positive Characteristic ﻿

[OWP-2013-28] (Mathematisches Forschungsinstitut Oberwolfach, 2013)
We classify isolated singularities $f \in K[[x_1,...,x_n]]$, which are simple, i.e. have no moduli, w.r.t. right equivalence, where $K$ is an algebraically closed field of characteristic $p>0$. For $K=\mathbb{R}$ or ...
• #### Supertropical Quadratic Forms I ﻿

[OWP-2013-27] (Mathematisches Forschungsinstitut Oberwolfach, 2013)
We initiate the theory of a quadratic form q over a semiring $R$. As customary, one can write $q(x+y)=q(x)+q(y)+b(x,y)$, where b is a companion bilinear form. But in contrast to the ring-theoretic case, the companion ...
• #### Low rank differential equations for hamiltonian matrix nearness problems ﻿

[OWP-2013-01] (Mathematisches Forschungsinstitut Oberwolfach, 2013-02-08)
For a Hamiltonian matrix with purely imaginary eigenvalues, we aim to determine the nearest Hamiltonian matrix such that so me or all eigenvalues leave the imaginary axis. Conversely, for a Hamiltonian matrix with all ...
• #### Even-homogeneous supermanifolds on the complex projective line ﻿

[OWP-2013-02] (Mathematisches Forschungsinstitut Oberwolfach, 2013-03-14)
The classification of even-homogeneous complex supermanifolds of dimension $1|m$, $m<=3$, on $\mathbb{CP}^1$ up to isomorphism is given. An explicit description of such supermanifolds in terms of local charts and coordinates ...
• #### Legendrian rational unknots in lens spaces ﻿

[OWP-2013-06] (Mathematisches Forschungsinstitut Oberwolfach, 2013-03-14)
We classify Legendrian rational unknots with tight complements in the lens spaces $L(p,1)$ up to coarse equivalence. As an example of the general case, this classification is also worked out for $L(5, 2)$. The knots are ...
• #### Multiple Bernoulli series and volumes of moduli spaces of flat bundles over surfaces ﻿

[OWP-2013-04] (Mathematisches Forschungsinstitut Oberwolfach, 2013-03-14)
Using Szenes formula for multiple Bernoulli series, we explain how to compute Witten series associated to classical Lie algebras. Particular instances of these series compute volumes of moduli spaces of flat bundles over ...
• #### Sharp constants in the classical weak form of the John-Nirenberg inequality ﻿

[OWP-2013-07] (Mathematisches Forschungsinstitut Oberwolfach, 2013-03-14)
The sharp constants in the classical John-Nirenberg inequality are found by using Bellman function approach.
• #### The algebraic combinatorial approach for low-rank matrix completion ﻿

[OWP-2013-05] (Mathematisches Forschungsinstitut Oberwolfach, 2013-03-14)
We propose an algebraic combinatorial framework for the problem of completing partially observed low-rank matrices. We show that the intrinsic properties of the problem, including which entries can be reconstructed, and ...
• #### On the geometry of regular maps from a quasi-projective surface to a curve ﻿

[OWP-2013-03] (Mathematisches Forschungsinstitut Oberwolfach, 2013-03-14)
We explore consequences of the triviality of the monodromy group, using the condition of purity of the mixed Hodge structure on the cohomology of the surface X.
• #### Calculating conjugacy classes in Sylow p-subgroups of finite Chevalley groups of rank six and seven ﻿

[OWP-2013-10] (Mathematisches Forschungsinstitut Oberwolfach, 2013-04-10)
Let $G(q)$ be a finite Chevalley group, where $q$ is a power of a good prime $p$, and let $U(q)$ be a Sylow $p$-subgroup of $G(q)$. Then a generalized version of a conjecture of Higman asserts that the number $k(U(q))$ of ...
• #### Noncompact harmonic manifolds ﻿

[OWP-2013-08] (Mathematisches Forschungsinstitut Oberwolfach, 2013-04-10)
The Lichnerowicz conjecture asserts that all harmonic manifolds are either flat or locally symmetric spaces of rank 1. This conjecture has been proved by Z.I. Szab ́o [Sz] for harmonic manifolds with compact universal ...
• #### G-complete reducibility in non-connected groups ﻿

[OWP-2013-09] (Mathematisches Forschungsinstitut Oberwolfach, 2013-04-10)
In this paper we present an algorithm for determining whether a subgroup $H$ of a non-connected reductive group $G$ is $G$-completely reducible. The algorithm consists of a series of reductions; at each step, we perform ...
• #### Solid extensions of the Cesàro operator on the Hardy space H2(D) ﻿

[OWP-2013-11] (Mathematisches Forschungsinstitut Oberwolfach, 2013-04-23)
We introduce and study the largest Banach space of analytic functions on the unit disc which is solid for the coefficient-wise order and to which the classical Ces`aro operator $\mathcal{C}:H^2 \to H^2$ can be continuously ...
• #### Obtaining Error-Minimizing Estimates and Universal Entry-Wise Error Bounds for Low-Rank Matrix Completion ﻿

[OWP-2013-12] (Mathematisches Forschungsinstitut Oberwolfach, 2013-06-10)
We propose a general framework for reconstructing and denoising single entries of incomplete and noisy entries. We describe: effective algorithms for deciding if and entry can be reconstructed and, if so, for reconstructing ...
• #### On Concentrators and Related Approximation Constants ﻿

[OWP-2013-14] (Mathematisches Forschungsinstitut Oberwolfach, 2013-06-10)
Pippenger ([Pip77]) showed the existence of (6m, 4m, 3m, 6)-concentrator for each positive integer m using a probabilistic method. We generalize his approach and prove existence of (6m, 4m, 3m, 5.05)-concentrator (which ...
• #### Linking and Closed Orbits ﻿

[OWP-2013-15] (Mathematisches Forschungsinstitut Oberwolfach, 2013-06-10)
We show that the Lagrangian of classical mechanics on a Riemannian manifold of bounded geometry carries a periodic solution of motion with prescribed energy, provided the potential satis es an asymptotic growth ...
• #### Mesh Ratios for Best-Packing and Limits of Minimal Energy Configurations ﻿

[OWP-2013-13] (Mathematisches Forschungsinstitut Oberwolfach, 2013-06-10)
For $N$-point best-packing configurations $\omega_N$ on a compact metric space $(A, \rho)$, we obtain estimates for the mesh-separation ratio $\gamma(\rho_N , A)$, which is the quotient of the covering radius of $\omega_N$ ...
• #### Grassmannian connection between three- and four-qubit observables, mermin's contextualities and black holes ﻿

[OWP-2013-17] (Mathematisches Forschungsinstitut Oberwolfach, 2013-07-23)
We invoke some ideas from finite geometry to map bijectively 135 heptads of mutually commuting three-qubit observables into 135 symmetric four-qubit ones. After labeling the elements of the former set in terms of a ...
• #### On the autonomous metric on groups of Hamiltonian diffeomorphisms of closed hyperbolic surfaces ﻿

[OWP-2013-18] (Mathematisches Forschungsinstitut Oberwolfach, 2013-07-23)
Let $\Sigma_g$ be a closed hyperbolic surface of genus $g$ and let Ham($\Sigma_ g$) be the group of Hamiltonian diffeomorphisms of $\Sigma_g$. The most natural word metric on this group is the autonomous metric. It has ...
• #### Near critical density irregular sampling in bernstein spaces ﻿

[OWP-2013-16] (Mathematisches Forschungsinstitut Oberwolfach, 2013-07-23)
We obtain sharp estimates for the sampling constants in Bernstein spaces when the density of the sampling set is near the critical value.