• Abstract Bivariant Cuntz Semigroups 

      [OWP-2017-04] Antoine, Ramon; Perera, Francesc; Thiel, Hannes (Mathematisches Forschungsinstitut Oberwolfach, 2017-02-13)
      We show that abstract Cuntz semigroups form a closed symmetric monoidal category. Thus, given Cuntz semigroups $S$ and $T$, there is another Cuntz semigroup $((S,T))$ playing the role of morphisms from $S$ to $T$. Applied ...
    • Analysis and Simulation of a New Multi-Component Two-Phase Flow Model with Phase Transitions and Chemical Reactions 

      [OWP-2017-08] Hantke, Maren; Müller, Siegfried (Mathematisches Forschungsinstitut Oberwolfach, 2017-03-15)
      A class-II model for multi-component mixtures recently introduced in D. Bothe, W. Dreyer, Continuum thermodynamics of chemically reacting fluid mixtures, Acta Mech., 226 (2015), 1757–1805 is investigated for simple mixtures. ...
    • Bredon Cohomology and Robot Motion Planning 

      [OWP-2017-34] Farber, Michael; Grant, Mark; Lupton, Gregory; Oprea, John (Mathematisches Forschungsinstitut Oberwolfach, 2017-11-29)
      In this paper we study the topological invariant ${\sf {TC}}(X)$ reflecting the complexity of algorithms for autonomous robot motion. Here, $X$ stands for the configuration space of a system and ${\sf {TC}}(X)$ is, roughly, ...
    • Cocycle Superrigidity and Group Actions on Stably Finite C*-Algebras 

      [OWP-2017-01] Gardella, Eusebio; Lupini, Martino (Mathematisches Forschungsinstitut Oberwolfach, 2017-01-17)
      Let $\Lambda $ be a countably infinite property (T) group, and let $D$ be UHF-algebra of infinite type. We prove that there exists a continuum of pairwise non (weakly) cocycle conjugate, strongly outer actions of $\Lambda ...
    • The Colored Jones Polynomial and Kontsevich-Zagier Series for Double Twist Knots 

      [OWP-2017-29] Lovejoy, Jeremy; Osburn, Robert (Mathematisches Forschungsinstitut Oberwolfach, 2017-10-20)
      Using a result of Takata, we prove a formula for the colored Jones polynomial of the double twist knots $K_{(-m,-p)}$ and $K_{(-m,p)}$ where $m$ and $p$ are positive integers. In the $(-m,-p)$ case, this leads to new ...
    • Composition of Irreducible Morphisms in Coils 

      [OWP-2017-32] Chaio, Claudia; Malicki, Piotr (Mathematisches Forschungsinstitut Oberwolfach, 2017-10-30)
      We study the non-zero composition of n irreducible morphisms between modules lying in coils in relation with the powers of the radical of their module category.
    • Counting Curves on Toric Surfaces Tropical Geometry & the Fock Space 

      [OWP-2017-18] Cavalieri, Renzo; Johnson, Paul; Markwig, Hannah; Ranganathan, Dhruv (Mathematisches Forschungsinstitut Oberwolfach, 2017-07-17)
      We study the stationary descendant Gromov–Witten theory of toric surfaces by combining and extending a range of techniques – tropical curves, floor diagrams, and Fock spaces. A correspondence theorem is established between ...
    • Detecting Ineffective Features for Pattern Recognition 

      [OWP-2017-26] Györfi, László; Walk, Harro (Mathematisches Forschungsinstitut Oberwolfach, 2017-10-17)
      For a binary classification problem, the hypothesis testing is studied, that a component of the observation vector is not effective, i.e., that component carries no information for the classification. We introduce nearest ...
    • Exact Rate of Convergence of k-Nearest-Neighbor Classification Rule 

      [OWP-2017-25] Györfi, László; Döring, Maik; Walk, Harro (Mathematisches Forschungsinstitut Oberwolfach, 2017-10-16)
      A binary classification problem is considered. The excess error probability of the k-nearest neighbor classification rule according to the error probability of the Bayes decision is revisited by a decomposition of the ...
    • Experimenting with Zariski Dense Subgroups 

      [OWP-2017-31] Detinko, Alla; Flannery, Dane; Hulpke, Alexander (Mathematisches Forschungsinstitut Oberwolfach, 2017-10-28)
      We give a method to describe all congruence images of a finitely generated Zariski dense group $H\leq SL(n, \mathbb{R})$. The method is applied to obtain efficient algorithms for solving this problem in odd prime degree ...
    • An Extension Problem and Trace Hardy Inequality for the Sublaplacian on H-Type Groups 

      [OWP-2017-20] Roncal, Luz; Thangavelu, Sundaram (Mathematisches Forschungsinstitut Oberwolfach, 2017-07-24)
      In this paper we study the extension problem for the sublaplacian on a H-type group and use the solutions to prove trace Hardy and Hardy inequalities for fractional powers of the sublaplacian.
    • Freeness of Multi-Reflection Arrangements via Primitive Vector Fields 

      [OWP-2017-10] Hoge, Torsten; Mano, Toshiyuki; Röhrle, Gerhard; Stump, Christian (Mathematisches Forschungsinstitut Oberwolfach, 2017-04-20)
      In 2002, Terao showed that every reflection multi-arrangement of a real reflection group with constant multiplicity is free by providing a basis of the module of derivations. We first generalize Terao's result to ...
    • GAP Functionality for Zariski Dense Groups 

      [OWP-2017-22] Detinko, Alla; Flannery, Dane; Hulpke, Alexander (Mathematisches Forschungsinstitut Oberwolfach, 2017-09-14)
      In this document we describe the functionality of GAP [4] routines for Zariski dense or arithmetic groups that are developed in [1, 2, 3]. The research underlying the software was supported through the programme "Research ...
    • Geometry of Free Loci and Factorization of Noncommutative Polynomials 

      [OWP-2017-23] Helton, J. William; Klep, Igor; Volčič, Jurij; Helton, J. William (Mathematisches Forschungsinstitut Oberwolfach, 2017-10-02)
      The free singularity locus of a noncommutative polynomial f is defined to be the sequence $Z_n(f)=\{X\in M_n^g : \det f(X)=0\}$ of hypersurfaces. The main theorem of this article shows that f is irreducible if and only if ...
    • Gradient Canyons, Concentration of Curvature, and Lipschitz Invariants 

      [OWP-2017-35] Paunescu, Laurentiu; Tibăr, Mihai-Marius (Mathematisches Forschungsinstitut Oberwolfach, 2017-12-13)
      We find new bi-Lipschitz invariants of holomorphic functions of two variables by using the gradient canyons and by combining analytic and geometric viewpoints on the concentration of curvature.
    • Holonomy Groups of $G_2^*$-Manifolds 

      [OWP-2017-07] Fino, Anna; Kath, Ines (Mathematisches Forschungsinstitut Oberwolfach, 2017-03-07)
      We classify the holonomy algebras of manifolds admitting an indecomposable torsion free $G_2^*$-structure, i.e. for which the holonomy representation does not leave invariant any proper non-degenerate subspace. We realize ...
    • The Index of Singular Zeros of Harmonic Mappings of Anti-Analytic Degree One 

      [OWP-2017-03] Luce, Robet; Sète, Olivier (Mathematisches Forschungsinstitut Oberwolfach, 2017-02-02)
      We study harmonic mappings of the form $f(z) = h(z) - \overline{z}$, where $h$ is an analytic function. In particular we are interested in the index (a generalized multiplicity) of the zeros of such functions. Outside the ...
    • Inductive Freeness of Ziegler’s Canonical Multiderivations for Reflection Arrangements 

      [OWP-2017-14] Hoge, Torsten; Röhrle, Gerhard (Mathematisches Forschungsinstitut Oberwolfach, 2017-04-30)
      Let $A$ be a free hyperplane arrangement. In 1989, Ziegler showed that the restriction $A''$ of $A$ to any hyperplane endowed with the natural multiplicity is then a free multiarrangement. We initiate a study of the stronger ...
    • Linear Syzygies, Hyperbolic Coxeter Groups and Regularity 

      [OWP-2017-15] Constantinescu, Alexandru; Kahle, Thomas; Varbaro, Matteo (Mathematisches Forschungsinstitut Oberwolfach, 2017-05-24)
      We build a new bridge between geometric group theory and commutative algebra by showing that the virtual cohomological dimension of a Coxeter group is essentially the regularity of the Stanley–Reisner ring of its nerve. ...
    • Locally Compact Abelian p-Groups Revisited 

      [OWP-2017-06] Herfort, Wolfgang; Hofmann, Karl Heinrich; Kramer, Linus (Mathematisches Forschungsinstitut Oberwolfach, 2017-03-03)
      Even though the structure of locally compact abelian groups is generally considered to be rather thoroughly known through a wealth of publications, one keeps encountering corners that are not elucidated in up-to-date ...