Quiver Presentations for Descent Algebras of Exceptional Type

The descent algebra of a finite Coxeter group $W$ is a basic algebra, and as such it has a presentation as quiver with relations. In recent work, we have developed a combinatorial framework which allows us to systematically compute such a quiver presentation for a Coxeter group of a given type. In this article, we use that framework to determine quiver presentations for the descent algebras of the Coxeter groups of exceptional or non-crystallographic type, i.e., of type $E_6$, $E_7$, $E_8$, $F_4$, $H_3$, $H_4$ or $I_2(m)$.Comment: 25 pages, 10 figure

Variability and Evolution in Systems of Systems

In this position paper (1) we discuss two particular aspects of Systems of Systems, i.e., variability and evolution. (2) We argue that concepts from Product Line Engineering and Software Evolution are relevant to Systems of Systems Engineering. (3) Conversely, concepts from Systems of Systems Engineering can be helpful in Product Line Engineering and Software Evolution. Hence, we argue that an exchange of concepts between the disciplines would be beneficial.Comment: In Proceedings AiSoS 2013, arXiv:1311.319

Federal Contractor Liability: The Hanford Decision

During World War II, the U.S. Government sought out contractors in the name of “patriotism” to research and develop nuclear materials for this country’s defense. Nearly seventy years later, we are still dealing with the effects of that research. However, the issue of who should bear responsibility for the long-term effects is still being argued. One of the major issues is whether those contractors are allowed to raise the federal contractor defense.\ud \ud The common law federal contractor defense arises out of basic principles of governmental immunity. The defense protects government contractors from liability for any harm arising out the performance of a government contract, specifically in the areas of military and defense work, if the contractor was following the government’s directions and the work performed was in an area of “uniquely federal” concern

Purposeful Explanation and Causal Gaps

In this paper, I argue that a commitment to science and the methodo- logical commitment to causal closure do not require a rejection of the idea that the choices of souls explain the occurrence of certain events in the physical world. Stated slightly differently, I maintain that one can both affirm science and believe that souls causally interfere in the course of events in the physical world. Such an affirmation and belief are compatible. In short, science vis-à-vis the methodological principle of causal closure poses no problem for souls as explanatory agents

On the invertibility of "rectangular" bi-infinite matrices and applications in time--frequency analysis

Finite dimensional matrices having more columns than rows have no left inverses while those having more rows than columns have no right inverses. We give generalizations of these simple facts to bi--infinite matrices and use those to obtain density results for $p$--frames of time--frequency molecules in modulation spaces and identifiability results for operators with bandlimited Kohn--Nirenberg symbols

Reading in perspective : what real cops and pretend burglars look for in a story

Bibliography: leaves 26-27Supported in part by the National Institute of Education under contract no. US-NIE-C-400-76-0116 and by the Advanced Research Projects Agency under contract no. N00123-C-062