By Kipton Barros

Nucleation in the Clump Model

Run the simulation (Java web start).

This program demonstrates monte-carlo dynamics applied to a collection of particles with a long range repulsive step function interaction. This model is interesting because for long ranges it is well described by a coarse grained field theory, and it exhibits liquid, solid and glassy phases.

Using the default parameters (T=0.14), decay to a solid phase should become apparent in this simulation after approximately 100 to 150 monte-carlo steps in time. In the units that I am using the spinodal temperature is approximately 0.132. As the interaction range is made larger, one must get closer to the spinodal temperature in order to observe nucleation.

Fluid Dynamics using a Lattice Gas Algorithm

Run the simulation (Java web start).

Simulation of turbulent fluid flow. This code uses a cellular automaton lattice model to solve the Navier Stokes equations. Lattice methods are interesting because they are more resilient to singularities than are traditional PDE methods. This simulation runs slowly, but if you are patient enough, a Von Karman vortex street will appear, as shown in the graphic above. This program is written in Java and uses the Open Source Physics library. The source code is presented and described in chapter 14 of Introduction to Computer Simulation Methods (3rd edition), freely available online.

Some people have written asking me about Lattice Boltzmann methods. I don't know much about them, but I will say that there is a lot of interesting work with LBM. The cellular automata which I implemented has the advantage that it is conceptually very simple.

I thank Bruce Boghosian for discussions of many aspects of fluid dynamics simulation.

One-Component Plasma

Run the simulation (Java web start).

Watch electrons repel each other. This simulation uses an electrostatic coloumb potential (force goes as inverse distance squared). It is unusual in that the electrons are constrained to a sphere, and that distance is given by arc-length. This program is written in Java, and uses the Open Source Physics library and the JOGL OpenGL bindings. Email me for the source code.

Based on J.P. Hansen, D. Levesque, J.J. Weis, Phys. Rev. Lett. 14, 43

Statistical and Thermal Physics Applets

A variety of interactive applets are designed to complement an undergraduate course in Statistical Mechanics. These should work in any browser with a recent version of Java.

Words

Words is a more exciting way to learn vocabulary (GRE words are the default.) The game is to select among several options the word which best matches a definition. To spice things up, you can play against your friends in a race to complete 20 correct answers. Incorrect guesses incur a time delay. The game is written in Java.

Words.tgz (includes source code).

Manifold

When considering curved space-time geometries, free particle trajectories (geodesics) can appear to be curved. For example, on the surface of a sphere, a free particle trajectory will be a great circle. If two separated space ships were on a sphere, and they started travelling parallel to each other, their paths would eventually intersect. You can experience this yourself with Manifold (1 or 2 players). The game is written in C++ and OpenGL.

Developed in collaboration with Keiron Stoddart.

Manifold.tgz (OS X application), Manifold-source.tgz (source code).