In this paper we give new asymptotically almost sure lower and upper bounds
on the bisection width of random 3βregular graphs. The main contribution is a
new lower bound on the bisection width of 0.103295n, based on a first moment
method together with a structural decomposition of the graph, thereby improving
a 27 year old result of Kostochka and Melnikov. We also give a complementary
upper bound of 0.139822n, combining known spectral ideas with original
combinatorial insights. Developping further this approach, with the help of
Monte Carlo simulations, we obtain a non-rigorous upper bound of 0.131366n.Comment: 48 pages, 20 figure