Browsing 1  Oberwolfach Preprints (OWP) by Title
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Lifting Spectral Triples to Noncommutative Principal Bundles
[OWP202102] (Mathematisches Forschungsinstitut Oberwolfach, 20210111)Given a free action of a compact Lie group $G$ on a unital C*algebra $\mathcal{A}$ and a spectral triple on the corresponding fixed point algebra $\mathcal{A}^G$, we present a systematic and indepth construction of ... 
Linear Syzygies, Hyperbolic Coxeter Groups and Regularity
[OWP201715] (Mathematisches Forschungsinstitut Oberwolfach, 20170524)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. ... 
Linking and Closed Orbits
[OWP201315] (Mathematisches Forschungsinstitut Oberwolfach, 20130610)We show that the Lagrangian of classical mechanics on a Riemannian manifold of bounded geometry carries a periodic solution of motion with prescribed energy, provided the potential satis es an asymptotic growth ... 
Local and Global Canonical Forms for DifferentialAlgebraic Equations with Symmetries
[OWP202205] (Mathematisches Forschungsinstitut Oberwolfach, 20220221)Linear timevarying differentialalgebraic equations with symmetries are studied. The structures that we address are selfadjoint and skewadjoint systems. Local and global canonical forms under congruence are presented ... 
Local asymptotics for the area of random walk excursions
[OWP201319] (Mathematisches Forschungsinstitut Oberwolfach, 20130905)We prove a local limit theorem for the area of the positive exursion of random walks with zero mean and finite variance. Our main result complements previous work of Caravenna and Chaumont, Sohier, as well as ... 
Localized Endomorphisms of Graph Algebras
[OWP201104] (Mathematisches Forschungsinstitut Oberwolfach, 2011057)Endomorphisms of graph $C^*$algebras are investigated. A combinatorial approach to analysis of permutative endomorphisms is developed. Then invertibility criteria for localized endomorphisms are given. Furthermore, ... 
Locally Compact Abelian pGroups Revisited
[OWP201706] (Mathematisches Forschungsinstitut Oberwolfach, 20170303)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 uptodate ... 
Locally conformally Kähler manifolds admitting a holomorphic conformal flow
[OWP201013] (Mathematisches Forschungsinstitut Oberwolfach, 20100315)A manifold $M$ is locally conformally Kähler (LCK) if it admits a Kähler covering $\tilde{M}$ with monodromy acting by holomorphic homotheties. Let $M$ be an LCK manifold admitting a holomorphic conformal flow of ... 
Logical Relations for Partial Features and Automatic Differentiation Correctness
[OWP202309] (Mathematisches Forschungsinstitut Oberwolfach, 20230619)We present a simple technique for semantic, open logical relations arguments about languages with recursive types, which, as we show, follows from a principled foundation in categorical semantics. We demonstrate how it can ... 
Looking Back on Inverse Scattering Theory
[OWP201724] (Mathematisches Forschungsinstitut Oberwolfach, 20171005)We present an essay on the mathematical development of inverse scattering theory for timeharmonic waves during the past fifty years together with some personal memories of our participation in these events. 
Low rank differential equations for hamiltonian matrix nearness problems
[OWP201301] (Mathematisches Forschungsinstitut Oberwolfach, 20130208)For a Hamiltonian matrix with purely imaginary eigenvalues, we aim to determine the nearest Hamiltonian matrix such that so me or all eigenvalues leave the imaginary axis. Conversely, for a Hamiltonian matrix with all ... 
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 ... 
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 ... 
Matchings and Squarefree Powers of Edge Ideals
[OWP201925] (Mathematisches Forschungsinstitut Oberwolfach, 20191111)Squarefree powers of edge ideals are intimately related to matchings of the underlying graph. In this paper we give bounds for the regularity of squarefree powers of edge ideals, and we consider the question of when such ... 
Matrix Elements of Irreducible Representations of SU(n+1) x SU(n+1) and Multivariable MatrixValued Orthogonal Polynomials
[OWP201716] (Mathematisches Forschungsinstitut Oberwolfach, 20170614)In Part 1 we study the spherical functions on compact symmetric pairs of arbitrary rank under a suitable multiplicity freeness assumption and additional conditions on the branching rules. The spherical functions are ... 
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 ... 
Maximal CohenMacaulay modules over nonisolated surface singularities and matrix problems
[OWP201506] (Mathematisches Forschungsinstitut Oberwolfach, 20150513)In this article we develop a new method to deal with maximal CohenMacaulay modules over nonisolated surface singularities. In particular, we give a negative answer on an old question of Schreyer about surface singularities ... 
Maximal Quaternion Orders in Quadratic Extensions  in Hurwitz’s Diaries
[OWP202016] (Mathematisches Forschungsinstitut Oberwolfach, 20200803)We present and comment on some unpublished work of Adolf Hurwitz on quaternion arithmetic from his diaries. 
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 ... 
The McKayconjecture for exceptional groups and odd primes
[OWP200707] (Mathematisches Forschungsinstitut Oberwolfach, 2007)Let $\mathbf{G}$ be a simplyconnected simple algebraic group over an algebraically closed field of characteristic p with a Frobenius map $F:\mathbf{G}→\mathbf{G}$ and $\mathbf{G}:=\mathbf{G}^F$, such that the root system ...