WorldCat Identities

Mengel, Stefan

Overview
Works: 15 works in 24 publications in 2 languages and 68 library holdings
Roles: Author, Editor, Contributor
Publication Timeline
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Most widely held works by Stefan Mengel
Conjunctive queries, arithmetic circuits and counting complexity by Stefan Mengel( )

2 editions published in 2013 in English and held by 32 WorldCat member libraries worldwide

This thesis deals with several subjects from counting complexity and arithmetic circuit complexity.The first part explores the complexity of counting solutions to conjunctive queries, which are a basic class of queries from database theory. We introduce a parameter, called the quantified star size of a query phi, which measures how the free variables are spread in phi. As usual in database theory, we associate a hypergraph to a query phi. We show that for classes of queries for which these associated hypergraphs have bounded generalized hypertree width, bounded quantified star size exactly characterizes the subclasses of queries for which counting the number of solutions is tractable. In the case of bounded arity, this allows us to fully characterize the classes of conjunctive queries for which counting the solutions is tractable. Finally, we also analyze the complexity of computing the quantified star size of a conjunctive query.In the second part we characterize different classes from arithmetic circuit complexity by different means, including conjunctive queries and constraint satisfaction problems, graph polynomials on bounded treewidth graphs, and an extension of the classical arithmetic branching program model by stack memory.In particular, this yields new characterizations of the arithmetic circuit class VP, a class that is central to the area but arguably not well understood.Finally, the third part studies the complexity of two questions on polynomials given by arithmetic circuits: testing whether a monomial is present and counting the number of its monomials. We show that these problems are complete for different levels of the counting hierarchy, which had few or no known natural complete problems before. ; eng
<> by Stefan Mengel( Book )

2 editions published in 1995 in German and held by 4 WorldCat member libraries worldwide

Das Magnetfeld für den ZEUS-Innendetektor Analyse und Korrektur der Feldmessung by Stefan Mengel( Book )

1 edition published in 1992 in German and held by 4 WorldCat member libraries worldwide

Erste Bestimmung der e Pi-Trennleistung des ZEUS-Übergangsstrahlungsdetektors by Stefan Mengel( Book )

5 editions published in 1995 in German and Undetermined and held by 3 WorldCat member libraries worldwide

Erste Bestimmung der e-p-Trennleistung [e-Pi-Trennleistung] des ZEUS-Übergangsstrahlungsdetektors by Stefan Mengel( Book )

1 edition published in 1995 in German and held by 2 WorldCat member libraries worldwide

The Arithmetic Complexity of Tensor Contraction by Florent Capelli( )

1 edition published in 2015 in English and held by 2 WorldCat member libraries worldwide

Minimal Distance of Propositional Models by Mike Behrisch( )

1 edition published in 2018 in English and held by 2 WorldCat member libraries worldwide

Statusbericht Design und Innovation : Technologie-Monitoring by Sabine Korte( Book )

1 edition published in 1997 in German and held by 2 WorldCat member libraries worldwide

XMR-Technologien : Technologiefrüherkennung by Stefan Mengel( Book )

1 edition published in 1997 in German and held by 1 WorldCat member library worldwide

Molekulare Magnete by Stefan Mengel( Book )

1 edition published in 1999 in German and held by 1 WorldCat member library worldwide

Technologieanalyse Magnetismus( Book )

1 edition published in 1997 in Undetermined and held by 1 WorldCat member library worldwide

XMR-Technologien by Stefan Mengel( Book )

1 edition published in 1997 in German and held by 1 WorldCat member library worldwide

Design und Innovation : Statusbericht ; Technologie-Monitoring by Sabine Korte( Book )

1 edition published in 1996 in German and held by 1 WorldCat member library worldwide

Technologieanalyse Magnetismus( Book )

in Undetermined and held by 1 WorldCat member library worldwide

 
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Audience level: 0.93 (from 0.86 for <> ... to 0.97 for Thromboemb ...)

Languages
German (17)

English (4)