Now showing items 12-29 of 29

• #### Herbrand’s Theorem as Higher Order Recursion ﻿

[OWP-2018-01] (Mathematisches Forschungsinstitut Oberwolfach, 2018-02-19)
We provide a means to compute Herbrand disjunctions directly from sequent calculus proofs with cuts. Our approach associates to a first-order classical proof $\pi \vdash \exists v F$, where $F$ is quantifier free, an ...
• #### Homogenization of a nonlinear monotone problem with nonlinear Signorini boundary conditions in a domain with highly rough boundary ﻿

[OWP-2018-06] (Mathematisches Forschungsinstitut Oberwolfach, 2018-04-16)
We consider a domain $\Omega_\varepsilon\subset\mathbb{R}^N$, $N\geq2$, with a very rough boundary depending on~$\varepsilon$. For instance, if $N=3$ the domain $\Omega_\varepsilon$ has the form of a brush with an ...
• #### The Magic Square of Reflections and Rotations ﻿

[OWP-2018-13] (Mathematisches Forschungsinstitut Oberwolfach, 2018-07-01)
We show how Coxeter’s work implies a bijection between complex reflection groups of rank two and real reflection groups in 0(3). We also consider this magic square of reflections and rotations in the framework of Clifford ...
• #### The Martin Boundary of Relatively Hyperbolic Groups with Virtually Abelian Parabolic Subgroups ﻿

[OWP-2018-03] (Mathematisches Forschungsinstitut Oberwolfach, 2018-03-19)
Given a probability measure on a finitely generated group, its Martin boundary is a way to compactify the group using the Green's function of the corresponding random walk. We give a complete topological characterization ...
• #### Max-Linear Models on Infinite Graphs Generated by Bernoulli Bond Percolation ﻿

[OWP-2018-09] (Mathematisches Forschungsinstitut Oberwolfach, 2018-05-17)
We extend previous work of max-linear models on finite directed acyclic graphs to infinite graphs, and investigate their relations to classical percolation theory. We formulate results for the oriented square lattice graph ...
• #### A McKay Correspondence for Reflection Groups ﻿

[OWP-2018-14] (Mathematisches Forschungsinstitut Oberwolfach, 2018-07-02)
We construct a noncommutative desingularization of the discriminant of a finite reflection group $G$ as a quotient of the skew group ring $A=S*G$. If $G$ is generated by order two reflections, then this quotient identifies ...
• #### Metric Connections with Parallel Skew-Symmetric Torsion ﻿

[OWP-2018-16] (Mathematisches Forschungsinstitut Oberwolfach, 2018-07-16)
A geometry with parallel skew-symmetric torsion is a Riemannian manifold carrying a metric connection with parallel skew-symmetric torsion. Besides the trivial case of the Levi-Civita connection, geometries with non-vanishing ...
• #### MOSES: A Streaming Algorithm for Linear Dimensionality Reduction ﻿

[OWP-2018-12] (Mathematisches Forschungsinstitut Oberwolfach, 2018-06-26)
This paper introduces Memory-limited Online Subspace Estimation Scheme (MOSES) for both estimating the principal components of data and reducing its dimension. More specifically, consider a scenario where the data vectors ...
• #### On the Gauss Algebra of Toric Algebras ﻿

[OWP-2018-07] (Mathematisches Forschungsinstitut Oberwolfach, 2018-04-25)
Let $A$ be a $K$-subalgebra of the polynomial ring $S=K[x_1,\ldots,x_d]$ of dimension $d$, generated by finitely many monomials of degree $r$. Then the Gauss algebra $\mathbb{G}(A)$ of $A$ is generated by monomials of ...
• #### On the Invariants of the Cohomology of Complements of Coxeter Arrangements ﻿

[OWP-2018-21] (Mathematisches Forschungsinstitut Oberwolfach, 2018-10-22)
We refine Brieskorn's study of the cohomology of the complement of the reflection arrangement of a finite Coxeter group W. As a result we complete the verification of a conjecture by Felder and Veselov that gives an explicit ...
• #### An Optimal Bound for the Ratio Between Ordinary and Uniform Exponents of Diophantine Approximation ﻿

[OWP-2018-15] (Mathematisches Forschungsinstitut Oberwolfach, 2018-07-09)
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 ...
• #### Real Analyticity is Concentrated in Dimension 2 ﻿

[OWP-2018-23] (Mathematisches Forschungsinstitut Oberwolfach, 2018-11-05)
We prove that a real-valued function on a real analytic manifold is analytic whenever all its restrictions to $2$-dimensional analytic submanifolds are analytic functions. We also obtain analogous results in the framework ...
• #### Some Results Related to Schiffer's Problem ﻿

[OWP-2018-18] (Mathematisches Forschungsinstitut Oberwolfach, 2018-08-16)
We consider the following semilinear overdetermined problem on a two dimensional bounded or unbounded domain $\Omega$ with analytic boundary $\partial\Omega$ having at least one bounded connected component \begin{eqnarray*} ...
• #### Spectral Continuity for Aperiodic Quantum Systems II. Periodic Approximations in 1D ﻿

[OWP-2018-27] (Mathematisches Forschungsinstitut Oberwolfach, 2018-12-17)
The existence and construction of periodic approximations with convergent spectra is crucial in solid state physics for the spectral study of corresponding Schrödinger operators. In a forthcoming work [9] this task was ...
• #### Sur le Minimum de la Fonction de Brjuno ﻿

[OWP-2018-26] (Mathematisches Forschungsinstitut Oberwolfach, 2018-12-11)
The Brjuno function attains a strict global minimum at the golden section.
• #### The Sylow Structure of Scalar Automorphism Groups ﻿

[OWP-2018-05] (Mathematisches Forschungsinstitut Oberwolfach, 2018-03-22)
For any locally compact abelian periodic group A its automorphism group contains as a subgroup those automorphisms that leave invariant every closed subgroup of A, to be denoted by SAut(A). This subgroup is again a locally ...
• #### The Tutte Polynomial of Ideal Arrangements ﻿

[OWP-2018-28] (Mathematisches Forschungsinstitut Oberwolfach, 2018-12-21)
The Tutte polynomial is originally a bivariate polynomial enumerating the colorings of a graph and of its dual graph. But it reveals more of the internal structure of the graph like its number of forests, of spanning ...
• #### A Well-Posedness Result for Viscous Compressible Fluids with Only Bounded Density ﻿

[OWP-2018-10] (Mathematisches Forschungsinstitut Oberwolfach, 2018-05-28)
We are concerned with the existence and uniqueness of solutions with only bounded density for the barotropic compressible Navier-Stokes equations. Assuming that the initial velocity has slightly sub-critical regularity and ...