Distributed Symmetry Breaking in Hypergraphs

Fundamental local symmetry breaking problems such as Maximal Independent Set (MIS) and coloring have been recognized as important by the community, and studied extensively in (standard) graphs. In particular, fast (i.e., logarithmic run time) randomized algorithms are well-established for MIS and $\Delta +1$-coloring in both the LOCAL and CONGEST distributed computing models. On the other hand, comparatively much less is known on the complexity of distributed symmetry breaking in {\em hypergraphs}. In particular, a key question is whether a fast (randomized) algorithm for MIS exists for hypergraphs. In this paper, we study the distributed complexity of symmetry breaking in hypergraphs by presenting distributed randomized algorithms for a variety of fundamental problems under a natural distributed computing model for hypergraphs. We first show that MIS in hypergraphs (of arbitrary dimension) can be solved in $O(\log^2 n)$ rounds ($n$ is the number of nodes of the hypergraph) in the LOCAL model. We then present a key result of this paper --- an $O(\Delta^{\epsilon}\text{polylog}(n))$-round hypergraph MIS algorithm in the CONGEST model where $\Delta$ is the maximum node degree of the hypergraph and $\epsilon > 0$ is any arbitrarily small constant. To demonstrate the usefulness of hypergraph MIS, we present applications of our hypergraph algorithm to solving problems in (standard) graphs. In particular, the hypergraph MIS yields fast distributed algorithms for the {\em balanced minimal dominating set} problem (left open in Harris et al. [ICALP 2013]) and the {\em minimal connected dominating set problem}. We also present distributed algorithms for coloring, maximal matching, and maximal clique in hypergraphs.Comment: Changes from the previous version: More references adde

A review on DISC 2005, the 19th International Symposium on Distributed Computing

DISC is an international symposium on the theory, design, analysis, implementation and application of distributed systems and networks. The well-known International Symposium on Distributed Computing is organized annually in cooperation with the European Association for Theoretical Computer Science (EATCS). This is a review on the 19th International Symposium on Distributed Computing, which took place in Kraków, Poland, on September 26--29, 2005. The proceedings of DISC 2005 are published by Springer, as volume 3724 of the Lecture Notes in Computer Science (LNCS) series. The conference website can be found at www.mimuw.edu.pl/~disc2005.Postprint (published version

Urban Democracy and the Canadian Constitution

Brief: 24pp., Digital file.A brief written for the Special Joint Comittee of the Senate and House of Commons on the Constitution of Canada on Urban Democracy and the Canadian Constitution

Urban democracy and the Canadian Constitution : a brief

22, [2] leave

Getting out of the vicious traffic circle: attemps at restructuring the cultural ambience of the automobile throughout the 20th century

For years, alternative vehicle and propulsion concepts have had a very difficult time catching on, even though technicians and engineers have repeatedly pointed out that the design quality of electric propulsion systems or other novel vehicle concepts is available and feasible. Often enough, this state of affairs allowed free rein for various conspiracy theories, in which extraneous issues were made responsible for the lack of technological breakthrough. This paper agues, however, that innovation research has itself focused too narrowly on the process of the establishment of new products. On the basis of five case examples —the implementation of diesel engine propulsion for street vehicles; the EV1, the first electrically propelled standard car by General Motors; Ford’s prototype electric car study “Pivco”; the NSU Wankel engine; and the “Smart” car manufactured by DaimlerChrysler — an attempt is made to develop a comprehensive understanding of innovation processes which does not stop at the “technical invention” of a device. The thesis is that a new device requires a relevant cultural ambience, which must be more or less invented alongside it in multiple dimensions. Technical-constructive work is thus only one part of a successful innovation process; parallel to this, complementary measures must be taken with regard to the overall sectoral environment, law-making, user perceptions and attributions of meaning, as well as the cultural appropriation of a given device. Without the appropriate “adaptive measures”, even the most interesting technical projects runs the risk of sinking onto oblivion for lack of relevance. -- Alternative Antriebs- und Fahrzeugkonzepte tun sich in der Durchsetzung schon seit Jahren sehr schwer, obwohl immer wieder von Technikern und Ingenieuren darauf verwiesen wird, dass die konstruktive Qualität von elektrischen Antriebssystemen oder anderen neuartigen Fahrzeugkonzepten vorhanden sei. Oft genug konnten daher Verschwörungstheorien Raum greifen, in denen sachfremde Tatbestände für die fehlenden technischen Durchbrüche verantwortlich gemacht wurden. Im vorliegenden Beitrag wird argumentiert, dass die Innovationsforschung selbst einen zu engen Blick auf die Prozesse der Etablierung neuer Produkte eingenommen hat. Anhand von fünf Fallbeispielen, der Durchsetzung des dieselmotorischen Antriebes für Strassenfahrzeuge, des EV1, des ersten elektrisch betriebenen Serienfahrzeuges von General Motors, der Konzeptstudie Pivco, einem Elektroautomobilprojekt des Ford-Konzerns, des NSU-Wankelmotors sowie des neuartigen Fahrzeugkonzeptes Smart wird hingegen versucht, ein umfassendes Verständnis von Innovationsprozessen zu entwickeln, das nicht bei der technischen Erfindung eines Gerätes halt macht. Die These ist, dass neue Geräte zur Durchsetzung am Markt auch einen entsprechenden Funktionsraum benötigen (cultural ambience), der mehrdimensional sozusagen immer gleich miterfunden werden muss. Die technisch-konstruktive Arbeit ist daher nur ein Teilbereich eines erfolgreichen Innovationsprozesses. Parallel müssen weitere Vorkehrungen im Branchenumfeld, bei der Gesetzgebung, bei den Nutzerperzeptionen und Bedeutungszuschreibungen sowie den kulturellen Aneignungsweisen vorgenommen werden. Ohne die entsprechenden Anpassungsmassnahmen droht auch den interessantesten technischen Projekten aus Mangel an Relevanz die Bedeutungslosigkeit.