Now showing items 21-38 of 38

• #### Infeasibility certificates for linear matrix inequalities ﻿

[OWP-2011-28] (Mathematisches Forschungsinstitut Oberwolfach, 2011-05-25)
Farkas' lemma is a fundamental result from linear programming providing linear certi cates for infeasibility of systems of linear inequalities. In semidefinite programming, such linear certificates only exist for strongly ...
• #### Legendrian Knots in Lens Spaces ﻿

[OWP-2011-01] (Mathematisches Forschungsinstitut Oberwolfach, 2011)
In this note, we first classify all topological torus knots lying on the Heegaard torus in Lens spaces, and then we classify Legendrian representatives of torus knots. We show that all Legendrian torus knots in universally ...
• #### Localized Endomorphisms of Graph Algebras ﻿

[OWP-2011-04] (Mathematisches Forschungsinstitut Oberwolfach, 2011-05-7)
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, ...
• #### Monoid valuations and value ordered supervaluations ﻿

[OWP-2011-17] (Mathematisches Forschungsinstitut Oberwolfach, 2011)
We complement two papers on supertropical valuation theory ([IKR1], [IKR2]) by providing natural examples of m-valuations (= monoid valuations), after that of supervaluations and transmissions between them. The supervaluations ...
• #### New representations of matroids and generalizations ﻿

[OWP-2011-18] (Mathematisches Forschungsinstitut Oberwolfach, 2011)
We extend the notion of matroid representations by matrices over fields by considering new representations of matroids by matrices over finite semirings, more precisely over the boolean and the superboolean semirings. This ...
• #### A note on delta hedging in markets with jumps ﻿

[OWP-2011-23] (Mathematisches Forschungsinstitut Oberwolfach, 2011-05-21)
Modelling stock prices via jump processes is common in financial markets. In practice, to hedge a contingent claim one typically uses the so-called delta-hedging strategy. This strategy stems from the Black–Merton–Scholes ...
• #### On Canonical Forms for Two-person Zero-sum Limit Average Payoff Stochastic Games ﻿

[OWP-2011-35] (Mathematisches Forschungsinstitut Oberwolfach, 2011-05-29)
We consider two-person zero-sum mean payoff undiscounted stochastic games. We give a sufficient condition for the existence of a saddle point in uniformly optimal stationary strategies. Namely, we obtain sufficient ...
• #### On Reflection Subgroups of Finite Coxeter Groups ﻿

[OWP-2011-06] (Mathematisches Forschungsinstitut Oberwolfach, 2011-05-9)
Let $W$ be a finite Coxeter group. We classify the reflection subgroups of $W$ up to conjugacy and give necessary and sufficient conditions for the map that assigns to a reflection subgroup $R$ of $W$ the conjugacy class ...
• #### Positive recurrence of piecewise Orntein-Uhlenbeck processes and common quadratic Lyapunov functions ﻿

[OWP-2011-26] (Mathematisches Forschungsinstitut Oberwolfach, 2011)
We study the positive recurrence of piecewise Ornstein-Uhlenbeck (OU) diffusion processes, which arise from many-server queueing systems with phase-type service requirements. These diffusion processes exhibit different ...
• #### Products of pairs of Dehn twists and maximal real Lefschetz fibrations ﻿

[OWP-2011-32] (Mathematisches Forschungsinstitut Oberwolfach, 2011)
We address the problem of existence and uniqueness of a factorization of a given element of the modular group into a product of two Dehn twists. As a geometric application, we conclude that any maximal real elliptic ...
• #### Quotients of Index Two and General Quotients in a Space of Orderings ﻿

[OWP-2011-36] (Mathematisches Forschungsinstitut Oberwolfach, 2011-05-30)
In this paper we investigate quotient structures and quotient spaces of a space of orderings arising from subgroups of index two. We provide necessary and sufficient conditions for a quotient structure to be a quotient ...
• #### Second Main Theorems and Unicity of Meromorphic Mappings with Moving Hypersurfaces ﻿

[OWP-2011-38] (Mathematisches Forschungsinstitut Oberwolfach, 2011)
In this article, we establish some new second main theorems for meromorphic mappings of $\mathbf{C}^m$ into $\mathbf{P}^n(\mathbf{C})$ and moving hypersurfaces with truncated counting functions. As an application, we prove ...
• #### Self-adjoint differential-algebraic equations ﻿

[OWP-2011-27] (Mathematisches Forschungsinstitut Oberwolfach, 2011-05-24)
Motivated from linear-quadratic optimal control problems for differential-algebraic equations (DAEs), we study the functional analytic properties of the operator associated with the necessary optimality boundary value ...
• #### Some Combinatorial Identities Related to Commuting Varieties and Hilbert Schemes ﻿

[OWP-2011-02] (Mathematisches Forschungsinstitut Oberwolfach, 2011)
In this article we explore some of the combinatorial consequences of recent results relating the isospectral commuting variety and the Hilbert scheme of points in the plane.
• #### Steinberg groups for Jordan pairs ﻿

[OWP-2011-29] (Mathematisches Forschungsinstitut Oberwolfach, 2011-05-26)
We introduce categories of groups with commutator relations with respect to root groups and Weyl elements, permuting the root groups. This allows us to view the classical Steinberg groups, for example the Steinberg group ...
• #### The T-Graph of a Multigraded Hilbert Scheme ﻿

[OWP-2011-34] (Mathematisches Forschungsinstitut Oberwolfach, 2011)
The $T$-graph of a multigraded Hilbert scheme records the zero and one-dimensional orbits of the $T=(K^*)^n$ action on the Hilbert scheme induced from the $T$-action on $\mathbb{A}^n$. It has vertices the $T$-fixed points, ...
• #### Upper bounds for the number of solutions to quartic thue equations ﻿

[OWP-2011-21] (Mathematisches Forschungsinstitut Oberwolfach, 2011)
We will give upper bounds for the number of integral solutions to quartic Thue equations. Our main tool here is a logarithmic curve $\phi(x,y)$ that allows us to use the theory of linear forms in logarithms. This manuscript ...
• #### The Weyl group of the Curtz algebra ﻿

[OWP-2011-31] (Mathematisches Forschungsinstitut Oberwolfach, 2011-05-28)
The Weyl group of the Cuntz algebra $\mathcal{O}_n$ is investigated. This is (isomorphic to) the group of polynomial automorphisms $\lambda_u$ of $\mathcal{O}_n$, namely those induced by unitaries u that can be written ...