The Dubins Spider
This talk considers the so called Brownian spider, also known as Walsh Brownian motion, as first introduced in the epilogue of Walsh (1978). In an attempt to understand the unboundedness of the variation of the Wiener process, Lester Dubins asked the following question: for a Brownian spider with n rays how does one design a stopping time to maximize the "coverage" of Brownian motion on the spider for a given expected time? In this formulation, the coverage of the spider is measured as the sum of the lengths of its arms. This talk discusses some advances on the Dubins spider problem that have been made by Ernst (2016) and Ernst (2025). We shall also touch on a solution to a more "friendly" variant of the Dubins spider problem given by Bednarz, Ernst, and Osekowski (2024).