'Heinz' Harcourt's Collaborations: Over 57 Varieties

Secure collaborations over message boards

We provide a message board model for collaborative systems, and propose an architecture and protocol for securing collaborative applications over message boards. The proposed architecture employs only efficient symmetric cryptographic principles, and low complexity trust modules with each participant. The trust modules are used to protect group secrets and reduce susceptibility to denial of ser...

Heinz Nixdorf Institute Heinz Nixdorf

Musician Map: visualizing music collaborations over time

In this paper we introduce MusicianMap, a web-based interactive tool for visualizing relationships among popular musicians who have released recordings since 1950. MusicianMap accepts search terms from the user, and in turn uses these terms to retrieve data from MusicBrainz.org and AudioScrobbler.net, and visualizes the results. MusicianMap visualizes relationships of various kinds between musi...

Semistable Abelian Varieties over Q

We prove that for N = 6 and N = 10, there do not exist any non-zero semistable abelian varieties over Q with good reduction outside primes dividingN . Our results are contingent on the GRH discriminant bounds of Odlyzko. Combined with recent results of Brumer–Kramer and of Schoof, this result is best possible: if N is squarefree, there exists a non-zero semistable abelian variety over Q with go...

Algebraic Varieties over Small Fields

— We study curves and their Jacobians over F̄p and Q̄, and discuss applications to rational connectivity over these fields. We introduce certain dynamical systems on P, induced by translates by torsion points on elliptic curves, and study fields related to these systems.