Georgia Institute of Technology College of Sciences

Colloids are mixtures of molecules  well-studied in material science that are not well-understood mathematically.  Physicists model colloids as a system of two types of tiles (type A and type B) embedded on a region of the plane, where no two tiles can overlap.  It is conjectured that at high density, the type A tiles tend to separate out and form large "clusters".   To verify this conjecture, we need methods for counting these configurations directly or efficient algorithms for sampling.  Local sampling algorithms are known to be inefficient. However, we provide the first rigorous analysis of a global "DK Algorithm" introduced by Dress and Krauth.  We also examine the clustering effect directly via a combinatorial argument. We prove for a certain class of colloid models that at high density the configurations are likely to exhibit clustering, whereas at low density the tiles are all well-distributed. Joint work with Sarah Miracle and Dana Randall.

The Bohman-Frieze process is a simple modification of the Erdős-Rényi random graph that adds dependence between the edges biased in favor of joining isolated vertices. We present new results on the phase transition of the Bohman-Frieze process and show that qualitatively it belongs to the same class as the Erdős-Rényi process. The results include the size and structure of small components in the barely sub- and supercritical time periods. We will also mention a class of random graph processes that seems to exhibit markedly different critical behavior.

Georgia Tech School of Mathematics will host the 5th Annual Graduate Student Probability Conference (GSPC) from April 29 - May 1, 2011. The conference is open to all graduate students and post-doctoral fellows interested in probability. We will host two keynote speakers: Professor Nathalie Eisenbaum (Université Pierre et Marie Curie) and Professor Philip Protter (Columbia University). The conference will begin at 9:00 AM Friday, April 29 and end at noon on Sunday May 1.

We will show that a quantum xy-spin chain which is exposed to a randomexterior magnetic field satisfies a zero-velocity Lieb-Robinson bound. Thiscan be interpreted as dynamical localization for the spin chain or asabsence of information transport. We will also discuss a general result,which says that zero velocity LR-bounds in a quantum spin system implyexponential decay of ground state correlations. This is joint work withRobert Sims and Eman Hamza and motivated by recent works of Burrell-Osborneas well as Hastings.