Browsing 2011 by Title
Now showing items 1231 of 38

Coxeter Arrangements and Solomon's Descent Algebra
[OWP201103] (Mathematisches Forschungsinstitut Oberwolfach, 2011056) 
Crystal energy functions via the charge in types A and C
[OWP201125] (Mathematisches Forschungsinstitut Oberwolfach, 20110523)The RamYip formula for Macdonald polynomials (at $t=0$) provides a statistic which we call charge. In types $A$ and $C$ it can be defined on tensor products of KashiwaraNakashima single column crystals. In this ... 
Definable orthogonality classes in accessible categories are small
[OWP201114] (Mathematisches Forschungsinstitut Oberwolfach, 20110515)We lower substantially the strength of the assumptions needed for the validity of certain results in category theory and homotopy theory which were known to follow from Vopenka's principle. We prove that the necessary ... 
Dominance and Transmissions in Supertropical Valuation Theory
[OWP201107] (Mathematisches Forschungsinstitut Oberwolfach, 2011)This paper is a sequel of [IKR1], where we defined supervaluations on a commutative ring $R$ and studied a dominance relation $\Phi >= v$ between supervaluations $\varphi$ and $\upsilon$ on $R$, aiming at an enrichment of ... 
Extremal configurations of polygonal linkages
[OWP201124] (Mathematisches Forschungsinstitut Oberwolfach, 20110522) 
Formal adjoints of linear DAE operators and their role in optimal control
[OWP201115] (Mathematisches Forschungsinstitut Oberwolfach, 20110516)For regular strangenessfree linear differentialalgebraic equations (DAEs) the definition of an adjoint DAE is straightforward. This definition can be formally extended to general linear DAEs. In this paper, we analyze ... 
Higher Finiteness Properties of Reductive Arithmetic Groups in Positive Characteristic: the Rank Theorem
[OWP201105] (Mathematisches Forschungsinstitut Oberwolfach, 2011058)We show that the finiteness length of an $S$arithmetic subgroup $\Gamma$ in a noncommutative isotropic absolutely almost simple group $\mathcal{G}$ over a global function field is one less than the sum of the local ranks ... 
An Identification Therorem for PSU6(2) and its Automorphism Groups
[OWP201108] (Mathematisches Forschungsinstitut Oberwolfach, 20110510)We identify the groups PSU6(2), PSU6(2):2, PSU6(2):3 and Aut(PSU6(2)) from the structure of the centralizer of an element of order 3. 
An inductive approach to coxeter arrangements and solomon's descent algebra
[OWP201116] (Mathematisches Forschungsinstitut Oberwolfach, 20110517)In our recent paper [3], we claimed that both the group algebra of a finite Coxeter group W as well as the OrlikSolomon algebra of W can be decomposed into a sum of induced onedimensional representations of centralizers, ... 
Infeasibility certificates for linear matrix inequalities
[OWP201128] (Mathematisches Forschungsinstitut Oberwolfach, 20110525)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
[OWP201101] (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
[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, ... 
Monoid valuations and value ordered supervaluations
[OWP201117] (Mathematisches Forschungsinstitut Oberwolfach, 2011)We complement two papers on supertropical valuation theory ([IKR1], [IKR2]) by providing natural examples of mvaluations (= monoid valuations), after that of supervaluations and transmissions between them. The supervaluations ... 
New representations of matroids and generalizations
[OWP201118] (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
[OWP201123] (Mathematisches Forschungsinstitut Oberwolfach, 20110521)Modelling stock prices via jump processes is common in financial markets. In practice, to hedge a contingent claim one typically uses the socalled deltahedging strategy. This strategy stems from the Black–Merton–Scholes ... 
On Canonical Forms for Twoperson Zerosum Limit Average Payoff Stochastic Games
[OWP201135] (Mathematisches Forschungsinstitut Oberwolfach, 20110529)We consider twoperson zerosum 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
[OWP201106] (Mathematisches Forschungsinstitut Oberwolfach, 2011059)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 OrnteinUhlenbeck processes and common quadratic Lyapunov functions
[OWP201126] (Mathematisches Forschungsinstitut Oberwolfach, 2011)We study the positive recurrence of piecewise OrnsteinUhlenbeck (OU) diffusion processes, which arise from manyserver queueing systems with phasetype service requirements. These diffusion processes exhibit different ... 
Products of pairs of Dehn twists and maximal real Lefschetz fibrations
[OWP201132] (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
[OWP201136] (Mathematisches Forschungsinstitut Oberwolfach, 20110530)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 ...