Browsing 2019 by Title
Now showing items 18-26 of 26
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On a Cheeger Type Inequality in Cayley Graphs of Finite Groups
[OWP-2019-20] (Mathematisches Forschungsinstitut Oberwolfach, 2019-07-22) - (7 July - 7 October 2017)Let $G$ be a finite group. It was remarked by Breuillard-Green-Guralnick-Tao that if the Cayley graph $C(G,S)$ is an expander graph and is non-bipartite then the spectrum of the adjacency operator $T$ is bounded away from ... -
On a Group Functor Describing Invariants of Algebraic Surfaces
[OWP-2019-08] (Mathematisches Forschungsinstitut Oberwolfach, 2019-03-01)Liedtke (2008) has introduced group functors $K$ and $\tilde K$, which are used in the context of describing certain invariants for complex algebraic surfaces. He proved that these functors are connected to the theory of ... -
On Co-Minimal Pairs in Abelian Groups
[OWP-2019-19] (Mathematisches Forschungsinstitut Oberwolfach, 2019-07-09)A pair of non-empty subsets $(W,W')$ in an abelian group $G$ is a complement pair if $W+W'=G$. $W'$ is said to be minimal to $W$ if $W+(W'\setminus \{w'\}) \neq G, \forall \,w'\in W'$. In general, given an arbitrary subset ... -
On Residuals of Finite Groups
[OWP-2019-17] (Mathematisches Forschungsinstitut Oberwolfach, 2019-05-28)A theorem of Dolfi, Herzog, Kaplan, and Lev [DHKL07, Thm. C] asserts that in a finite group with trivial Fitting subgroup, the size of the soluble residual of the group is bounded from below by a certain power of the group ... -
On the Lie Algebra Structure of $HH^1(A)$ of a Finite-Dimensional Algebra A
[OWP-2019-10] (Mathematisches Forschungsinstitut Oberwolfach, 2019-04-17)Let $A$ be a split finite-dimensional associative unital algebra over a field. The first main result of this note shows that if the Ext-quiver of $A$ is a simple directed graph, then $HH^1(A)$ is a solvable Lie algebra. ... -
A Quantitative Analysis of the “Lion-Man” Game
[OWP-2019-18] (Mathematisches Forschungsinstitut Oberwolfach, 2019-07-08)In this paper we analyze, based on an interplay between ideas and techniques from logic and geometric analysis, a pursuit-evasion game. More precisely, we focus on a discrete lion and man game with an $\varepsilon$-capture ... -
Reflective Prolate-Spheroidal Operators and the KP/KdV Equations
[OWP-2019-24] (Mathematisches Forschungsinstitut Oberwolfach, 2019-11-05)Commuting integral and differential operators connect the topics of Signal Processing, Random Matrix Theory, and Integrable Systems. Previously, the construction of such pairs was based on direct calculation and ... -
Time Discretization Schemes for Hyperbolic Systems on Networks by ε-Expansion
[OWP-2019-03] (Mathematisches Forschungsinstitut Oberwolfach, 2019-02-12)We consider partial differential equations on networks with a small parameter $\epsilon$, which are hyperbolic for $\epsilon>0$ and parabolic for $\epsilon=0$. With a combination of an $\epsilon$-expansion and Runge-Kutta ... -
Weighted Surface Algebras: General Version
[OWP-2019-07] (Mathematisches Forschungsinstitut Oberwolfach, 2019-02-28)We introduce general weighted surface algebras of triangulated surfaces with arbitrarily oriented triangles and describe their basic properties. In particular, we prove that all these algebras, except the singular disc, ...