Browsing 1  Oberwolfach Preprints (OWP) by Title
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A Characterization of Semisimple Plane Polynomial Automorphisms
[OWP200808] (Mathematisches Forschungsinstitut Oberwolfach, 20080312)It is wellknown that an element of the linear group $GL_n(\mathbb{C})$ is semisimple if and only if its conjugacy class is Zariski closed. The aim of this paper is to show that the same result holds for the group of complex ... 
Characterization of Tropical Planar Curves up to Genus Six
[OWP202206] (Mathematisches Forschungsinstitut Oberwolfach, 20220316)We provide new forbidden criterion for realizability of smooth tropical plane curves. This in turn provides us a complete classification of smooth tropical plane curves up to genus six. 
A Cheeger Type Inequality in Finite Cayley Sum Graphs
[OWP201921] (Mathematisches Forschungsinstitut Oberwolfach, 20190731)  (5 May  27 July 2019)Let $G$ be a finite group and $S$ be a symmetric generating set of $G$ with $S = d$. We show that if the undirected Cayley sum graph $C_{\Sigma}(G,S)$ is an expander graph and is nonbipartite, then the spectrum of its ... 
Chirality of Real NonSingular Cubic Fourfolds and Their Pure Deformation Classification
[OWP201914] (Mathematisches Forschungsinstitut Oberwolfach, 20190515)In our previous works we have classified real nonsingular cubic hypersurfaces in the 5dimensional projective space up to equivalence that includes both real projective transformations and continuous variations of ... 
Classification of idempotent states on the compact quantum groups Uq(2), SUq(2) and SOq(3)
[OWP200908] (Mathematisches Forschungsinstitut Oberwolfach, 20090302)We give a simple characterisation of those idempotent states on compact quantum groups which arise as Haar states on quantum subgroups, show that all idempotent states on quantum groups $U_q(2)$, $SU_q(2)$, and $SO_q(3) ... 
Classification of totally real elliptic Lefschetz fibrations via necklace diagrams
[OWP201113] (Mathematisches Forschungsinstitut Oberwolfach, 2011)We show that totally real elliptic Lefschetz brations that admit a real section are classified by their "real loci" which is nothing but an $S^1$valued Morse function on the real part of the total space. We assign to ... 
The Cleavage Operad and String Topology of Higher Dimension
[OWP201137] (Mathematisches Forschungsinstitut Oberwolfach, 2011) 
Cluster structures on simple complex lie groups and the BelavinDrinfeld classification
[OWP201110] (Mathematisches Forschungsinstitut Oberwolfach, 20110512)We study natural cluster structures in the rings of regular functions on simple complex Lie groups and PoissonLie structutures compatible with these cluster structures. According to our main conjecture, each class in the ... 
Cocharacterclosure and spherical buildings
[OWP201512] (Mathematisches Forschungsinstitut Oberwolfach, 20150729)Let $k$ be a field, let $G$ be a reductive $k$group and $V$ an affine $k$variety on which $G$ acts. In this note we continue our study of the notion of cocharacterclosed $G(k)$orbits in $V$. In earlier work we used a ... 
CocharacterClosure and the Rational HilbertMumford Theorem
[OWP201416] (Mathematisches Forschungsinstitut Oberwolfach, 20141220)For a field $k$, let $G$ be a reductive $k$group and $V$ an affine $k$variety on which $G$ acts. Using the notion of cocharacterclosed $G(k)$orbits in $V$ , we prove a rational version of the celebrated HilbertMumford ... 
Cocycle Superrigidity and Group Actions on Stably Finite C*Algebras
[OWP201701] (Mathematisches Forschungsinstitut Oberwolfach, 20170117)Let $\Lambda $ be a countably infinite property (T) group, and let $D$ be UHFalgebra 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 KontsevichZagier Series for Double Twist Knots
[OWP201729] (Mathematisches Forschungsinstitut Oberwolfach, 20171020)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 ... 
Combinatorics of Vassiliev invariants
[OWP201122] (Mathematisches Forschungsinstitut Oberwolfach, 20110520)This paper is an introductory survey of the combinatorial aspects of the Vassiliev theory of knot invariants following the lectures delivered at the Advanced School on Knot Theory and its Applications to Physics and Biology ... 
Commuting Differential Operators and Higherdimensional Algebraic Varieties
[OWP201202] (Mathematisches Forschungsinstitut Oberwolfach, 20120320)Several algebrogeometric properties of commutative rings of partial differential operators as well as several geometric constructions are investigated. 
Composition of Irreducible Morphisms in Coils
[OWP201732] (Mathematisches Forschungsinstitut Oberwolfach, 20171030)We study the nonzero composition of n irreducible morphisms between modules lying in coils in relation with the powers of the radical of their module category. 
Composition of Irreducible Morphisms in QuasiTubes
[OWP201503] (Mathematisches Forschungsinstitut Oberwolfach, 20150409)We study the composition of irreducible morphisms between indecomposable modules lying in quasitubes of the AuslanderReiten quivers of artin algebras $A$ in relation with the powers of the radical of their module category ... 
Computer Algebra with GAP
[OWP202303] (Mathematisches Forschungsinstitut Oberwolfach, 20230413)This monograph includes the following topics: a basic introduction to the language, basic arithmetic, permutations, matrices, polynomial rings, finite fields, finite and finitely presented groups, small groups, group ... 
Computing Congruence Quotients of Zariski Dense Subgroups
[OWP201822] (Mathematisches Forschungsinstitut Oberwolfach, 20181026)We obtain a computational realization of the strong approximation theorem. That is, we develop algorithms to compute all congruence quotients modulo rational primes of a finitely generated Zariski dense group $H \leq ... 
Congruences Associated with Families of Nilpotent Subgroups and a Theorem of Hirsch
[OWP201916] (Mathematisches Forschungsinstitut Oberwolfach, 20190527)Our main result associates a family of congruences with each suitable system of nilpotent subgroups of a finite group. Using this result, we complete and correct the proof of a theorem of Hirsch concerning the class number ... 
A construction of hyperbolic Coxeter groups
[OWP201004] (Mathematisches Forschungsinstitut Oberwolfach, 2010)We give a simple construction of Gromov hyperbolic Coxeter groups of arbitrarily large virtual cohomological dimension. Our construction provides new examples of such groups. Using this one can construct e.g. new groups ...