Now showing items 1-10 of 10

• #### 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 ...
• #### Algebraic Matroids with Graph Symmetry ﻿

[OWP-2014-02] (Mathematisches Forschungsinstitut Oberwolfach, 2014)
This paper studies the properties of two kinds of matroids: (a) algebraic matroids and (b) finite and infinite matroids whose ground set have some canonical symmetry, for example row and column symmetry and transposition ...
• #### An Explicit Formula for the Dirac Multiplicities on Lens Spaces ﻿

[OWP-2014-19] (Mathematisches Forschungsinstitut Oberwolfach, 2014)
We present a new description of the spectrum of the (spin-) Dirac operator $D$ on lens spaces. Viewing a spin lens space $L$ as a locally symmetric space $\Gamma \setminus Spin(2m)/Spin(2m-1)$ and exploiting the representation ...
• #### 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 $\omega_N$ ...
• #### 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 ...
• #### 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 ...
• #### 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 ...
• #### Spherical Actions on Flag Varieties ﻿

[OWP-2014-04] (Mathematisches Forschungsinstitut Oberwolfach, 2014-04-25)
For every finite-dimensional vector space $V$ and every $V$ -flag variety $X$ we list all connected reductive subgroups in $GL(V)$ acting spherically on $X$.
• #### 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 ...