The Fermi-Pasta-Ulam (FPU) problem is named after the numerical experiments first performed by Enrico Fermi, John Pasta, and Stanislaw Ulam in the summer of 1953 on the Los Alamos MANIAC computer, one of the first electronic computers. They wanted to understand how a one-dimensional crystal evolves toward thermal equilibrium by simulating a chain of particles coupled by spring-like forces that included quadratic and cubic interactions. It was assumed that these nonlinear terms would cause the system to "thermalize" by redistributing energy from an initial mode into many other modes. In other words, an initial mode of vibration would quickly become more or less random.

The Fermi-Pasta_Ulam model was created using the Easy Java Simulations (Ejs) modeling tool.  It is distributed as a ready-to-run (compiled) Java archive.  Double clicking the ejs_sto_FPU.jar file will run the program if Java is installed.  Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models.  Additional Ejs models for statistical and thermal physics are available.  They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Please note that this resource requires at least version 1.5 of Java.