EFFECTIVE SAMPLING OF RANDOM SURFACES BY BABY UNIVERSE SURGERY

We propose a new, very efficient algorithm for sampling of random surf aces in the Monte Carlo simulations, based on so-called baby universe surgery, i.e. cutting and pasting of baby universes. It drastically re duces slowing down as compared to the standard local flip algorithm, t hereby allowing simulations of large random surfaces coupled to matter fields. As an example we investigate the efficiency of the algorithm for 2d simplicial gravity interacting with a one-component free scalar field. The radius of gyration is the slowest mode in the standard loc al flip/shift algorithm. The use of baby universe surgery decreases th e autocorrelation time by three order of magnitude for a random surfac e of 0.5 . 10(5) triangles, where it is found to be tau(int) = 150 +/- 31 sweeps.