• Generalized Vector Cross Products and Killing Forms on Negatively Curved Manifolds 

      [OWP-2018-17] Barberis, María Laura; Moroianu, Andrei; Semmelmann, Uwe (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 ...
    • Global Variants of Hartogs' Theorem 

      [OWP-2018-24] Bochnak, Jacek; Kucharz, Wojciech (Mathematisches Forschungsinstitut Oberwolfach, 2018-11-06)
      Hartogs' theorem asserts that a separately holomorphic function, defined on an open subset of $\mathbb{C}^n$, is holomorphic in all the variables. We prove a global variant of this theorem for functions defined on an open ...
    • Herbrand’s Theorem as Higher Order Recursion 

      [OWP-2018-01] Afshari, Bahareh; Hetzl, Stefan; Leigh, Graham E. (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] Gaudiello, Antonio; Mel'nyk, Taras A. (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] Buchweitz, Ragnar-Olaf; Faber, Eleonore; Ingalls, Colin (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] Dussaule, Matthieu; Gekhtman, Ilya; Gerasimov, Victor; Potyagailo, Leonid (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] Klüppelberg, Claudia; Sönmez, Ercan (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] Buchweitz, Ragnar-Olaf; Faber, Eleonore; Ingalls, Colin (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] Cleyton, Richard; Moroianu, Andrei; Semmelmann, Uwe (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] Eftekhari, Armin; Hauser, Raphael A.; Grammenos, Andreas (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] Herzog, Jürgen; Jafari, Raheleh; Nasrollah Nejad, Abbas (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] Douglass, J. Matthew; Pfeiffer, Götz; Röhrle, Gerhard (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] Marnat, Antoine; Moshchevitin, Nikolay (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] Bochnak, Jacek; Kucharz, Wojciech (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] Kawohl, Bernd; Lucia, Marcello (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] Beckus, Siegfried; Bellissard, Jean; De Nittis, Giuseppe (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] Balazard, Michel; Martin, Bruno (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] Herfort, Wolfgang; Hofmann, Karl Heinrich; Kramer, Linus; Russo, Francesco G. (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] Randriamaro, Hery (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] Danchin, Raphaël; Fanelli, Francesco; Paicu, Marius (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 ...