Atomic physics - Positronic lithium and the many-body problem

If more than two particles or bodies are interacting simultaneously, then no general solution can be found to their equations of motion. This is the many-body problem. A surprising new tool to explore it has been found in atomic physics: it should be possible to attach a positron to a neutral lithium atom. This will allow experiments to be made on the simplest many-body systems — atoms — that avoid a quantum mechanical complication called the exchange force.