Monte Carlo algorithm for simulating the O(N) loop model on the square lattice.

An efficient algorithm is presented to simulate the O(N) loop model on the square lattice for arbitrary values of N>0. The scheme combines the worm algorithm with a new data structure to resolve both the problem of loop crossings and the necessity of counting the number of loops at each Monte Carlo update. With the use of this scheme, the line of critical points (and other properties) of the O(N) model on the square lattice for 0

Stream of asymmetric bubbles in a Hele-Shaw channel.

Exact solutions are reported for a stream of asymmetric bubbles steadily moving in a Hele-Shaw channel. From the periodicity along the streamwise direction, the flow region is reduced to a rectangular unit cell containing one bubble, which is conformally mapped to an annulus in an auxiliary complex plane. Analytic expressions for the bubble shape as well as for the velocity field are obtained in terms of the generalized Schwarz-Christoffel formula for doubly connected domains.