Thursday, February 15, 2018 - 15:05
1 hour (actually 50 minutes)
College of Staten Island
Place Poi(m) particles at each site of a d-ary tree of height n. The particle at the root does a simple random walk. When it visits a site, it wakes up all the particles there, which start their own random walks, waking up more particles in turn. What is the cover time for this process, i.e., the time to visit every site? We show that when m is large, the cover time is O(n log(n)) with high probability, and when m is small, the cover time is at least exp(c sqrt(n)) with high probability. Both bounds are sharp by previous results of Jonathan Hermon's. This is the first result proving that the cover time is polynomial or proving that it's nonpolymial, for any value of m. Joint work with Christopher Hoffman and Matthew Junge.