Monday 14th May 2012 – 14:15 to 15:15

Speaker(s): Bruno Schapira (Université Paris-Sud)

The model of Vertex Reinforced Random Walk (VRRW) on Z goes back to Pemantle & Volkov, ’99, who proved a result of localization on5 sites with positive probability. They also conjectured that this was the a.s. behavior of the walk. In 2004, Tarrès managed to prove this conjecture. Then in 2006, inspired by Davis’paper ’90 on the edge reinforced version of the model, Volkov studied VRRW with weight on Z.

He proved that in the strongly reinforced case, i.e. when the weight sequence is reciprocally summable, the walk localizes a.s. on 2 sites, as expected. He also proved that localization is a.s. not possible for weights growing sublinearly, but like a power of n. However, the question of localization remained open for other weights, like n*log n or n/log n, for instance. In the talk I will first review these results and formulate more precisely the open questions. Then I will present some recent results giving partial answers.

This is based on joint (partly still on-going) work with Anne-Laure Basdevant and Arvind Singh.

Part of the Stochastic Analysis Seminar Series