Browsing 2018 by Issue Date
Now showing items 1-20 of 29
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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 ... -
Deformation Classification of Real Non-Singular Cubic Threefolds with a Marked Line
[OWP-2018-02] (Mathematisches Forschungsinstitut Oberwolfach, 2018-02-21)We prove that the space of pairs $(X,l)$ formed by a real non-singular 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
[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 ... -
Exceptional Legendrian Torus Knots
[OWP-2018-04] (Mathematisches Forschungsinstitut Oberwolfach, 2018-03-21)We present classification results for exceptional Legendrian realisations of torus knots. These are the first results of that kind for non-trivial topological knot types. Enumeration results of Ding-Li-Zhang concerning ... -
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 ... -
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 ... -
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 ... -
Categorical Linearly Ordered Structures
[OWP-2018-08] (Mathematisches Forschungsinstitut Oberwolfach, 2018-04-26)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 ... -
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 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 ... -
A Deformed Quon Algebra
[OWP-2018-11] (Mathematisches Forschungsinstitut Oberwolfach, 2018-06-25)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
[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 ... -
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 ... -
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 ... -
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 ... -
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 ... -
Generalized Vector Cross Products and Killing Forms on Negatively Curved Manifolds
[OWP-2018-17] (Mathematisches Forschungsinstitut Oberwolfach, 2018-07-17)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
[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*} ... -
Affine Space Fibrations
[OWP-2018-19] (Mathematisches Forschungsinstitut Oberwolfach, 2018-09-05)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
[OWP-2018-20] (Mathematisches Forschungsinstitut Oberwolfach, 2018-10-08)Demailly's conjecture, which is a consequence of the Green-Griffiths-Lang conjecture on varieties of general type, states that an algebraically hyperbolic complex projective variety is Kobayashi hyperbolic. Our aim is to ...