Browsing 2018 by Issue Date
Now showing items 120 of 28

Herbrand’s Theorem as Higher Order Recursion
[OWP201801] (Mathematisches Forschungsinstitut Oberwolfach, 20180219)We provide a means to compute Herbrand disjunctions directly from sequent calculus proofs with cuts. Our approach associates to a firstorder classical proof $\pi \vdash \exists v F$, where $F$ is quantifier free, an ... 
Deformation Classification of Real NonSingular Cubic Threefolds with a Marked Line
[OWP201802] (Mathematisches Forschungsinstitut Oberwolfach, 20180221)We prove that the space of pairs $(X,l)$ formed by a real nonsingular cubic hypersurface $X\subset P^4$ with a real line $l\subset X$ has 18 connected components and give for them several quite explicit interpretations. ... 
The Martin Boundary of Relatively Hyperbolic Groups with Virtually Abelian Parabolic Subgroups
[OWP201803] (Mathematisches Forschungsinstitut Oberwolfach, 20180319)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 ... 
Exceptional Legendrian Torus Knots
[OWP201804] (Mathematisches Forschungsinstitut Oberwolfach, 20180321)We present classification results for exceptional Legendrian realisations of torus knots. These are the first results of that kind for nontrivial topological knot types. Enumeration results of DingLiZhang concerning ... 
The Sylow Structure of Scalar Automorphism Groups
[OWP201805] (Mathematisches Forschungsinstitut Oberwolfach, 20180322)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 ... 
Homogenization of a nonlinear monotone problem with nonlinear Signorini boundary conditions in a domain with highly rough boundary
[OWP201806] (Mathematisches Forschungsinstitut Oberwolfach, 20180416)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 ... 
On the Gauss Algebra of Toric Algebras
[OWP201807] (Mathematisches Forschungsinstitut Oberwolfach, 20180425)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 ... 
Categorical Linearly Ordered Structures
[OWP201808] (Mathematisches Forschungsinstitut Oberwolfach, 20180426)We prove that for every computable limit ordinal $\alpha$ there exists a computable linear ordering $\mathcal{A}$ which is $\Delta^0_\alpha$categorical and $\alpha$ is smallest such, but nonetheless for every isomorphic ... 
MaxLinear Models on Infinite Graphs Generated by Bernoulli Bond Percolation
[OWP201809] (Mathematisches Forschungsinstitut Oberwolfach, 20180517)We extend previous work of maxlinear 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 WellPosedness Result for Viscous Compressible Fluids with Only Bounded Density
[OWP201810] (Mathematisches Forschungsinstitut Oberwolfach, 20180528)We are concerned with the existence and uniqueness of solutions with only bounded density for the barotropic compressible NavierStokes equations. Assuming that the initial velocity has slightly subcritical regularity and ... 
A Deformed Quon Algebra
[OWP201811] (Mathematisches Forschungsinstitut Oberwolfach, 20180625)The quon algebra is an approach to particle statistics in order to provide a theory in which the Pauli exclusion principle and Bose statistics are violated by a small amount. The quons are particles whose annihilation and ... 
MOSES: A Streaming Algorithm for Linear Dimensionality Reduction
[OWP201812] (Mathematisches Forschungsinstitut Oberwolfach, 20180626)This paper introduces Memorylimited 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 ... 
The Magic Square of Reflections and Rotations
[OWP201813] (Mathematisches Forschungsinstitut Oberwolfach, 20180701)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 ... 
A McKay Correspondence for Reflection Groups
[OWP201814] (Mathematisches Forschungsinstitut Oberwolfach, 20180702)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 ... 
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 ... 
Metric Connections with Parallel SkewSymmetric Torsion
[OWP201816] (Mathematisches Forschungsinstitut Oberwolfach, 20180716)A geometry with parallel skewsymmetric torsion is a Riemannian manifold carrying a metric connection with parallel skewsymmetric torsion. Besides the trivial case of the LeviCivita connection, geometries with nonvanishing ... 
Generalized Vector Cross Products and Killing Forms on Negatively Curved Manifolds
[OWP201817] (Mathematisches Forschungsinstitut Oberwolfach, 20180717)Motivated by the study of Killing forms on compact Riemannian manifolds of negative sectional curvature, we introduce the notion of generalized vector cross products on $\mathbb{R}^n$ and give their classification. Using ... 
Some Results Related to Schiffer's Problem
[OWP201818] (Mathematisches Forschungsinstitut Oberwolfach, 20180816)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*} ... 
Affine Space Fibrations
[OWP201819] (Mathematisches Forschungsinstitut Oberwolfach, 20180905)We discuss various aspects of affine space fibrations. Our interest will be focused in the singular fibers, the generic fiber and the propagation of properties of a given smooth special fiber to nearby fibers. 
Demailly’s Notion of Algebraic Hyperbolicity: Geometricity, Boundedness, Moduli of Maps
[OWP201820] (Mathematisches Forschungsinstitut Oberwolfach, 20181008)Demailly's conjecture, which is a consequence of the GreenGriffithsLang conjecture on varieties of general type, states that an algebraically hyperbolic complex projective variety is Kobayashi hyperbolic. Our aim is to ...