Department of Computer Science | Institute of Theoretical Computer Science | CADMO

Theory of Combinatorial Algorithms

Prof. Emo Welzl and Prof. Bernd Gärtner

Mittagsseminar (in cooperation with A. Steger, D. Steurer and B. Sudakov)

Mittagsseminar Talk Information

Date and Time: Tuesday, November 26, 2013, 12:15 pm

Duration: 30 minutes

Location: OAT S15/S16/S17

Speaker: Hafsteinn Einarsson

Controlled Explosions: Restraining Bootstrap Percolation

Bootstrap Percolation is a process which simulates spread of activity in a graph. The process starts with some vertices being active (bootstrap) and follows a rule to determine which vertices will as a result turn active.

This process has been studied on various graph classes, with various rules to determine how a vertex turns active. We build on a result by Janson, Łuczak, Turova and Vallier. They proved that for G(n,p), if a vertices are initially active and if a vertex turns active if it has at least k active neighbors for some constant k, then the process will either activate all vertices or fewer than 2a vertices a.a.s.

This all-or-nothing behavior is prevalent in the study of bootstrap percolation. Inspired by biological neural networks we decided to study if this activity explosion could be controlled. First we extended the process from above by introducing inhibitory vertices and changing the rule such that a vertex turns active if it has k more excitatory than inhibitory neighbors. Second, we further extend the process by introducing a random delay on every edge in the graph.

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