ANYONS

An elementary introduction is given to the concept of anyons-quantum particles whose 'statistics' interpolate smoothly between those of bosons and fermions. Such particles-or quasi-particle excitations-can occur in two-dimensional systems in which the particles experience strong short-range mutual repulsions. These circumstances effectively mean that one has to apply quantum mechanics to a configuration space in which some points are excluded (i.e. it has 'holes')-namely, those points where two particles would coincide. The Aharonov-Bohm effect provides the simplest physical example of quantum mechanics in such a non-simply connected space, and is also fundamental to a simple model for anyons. A qualitative introduction is given to two currently proposed physical applications of anyons: high temperature superconductivity, and the (fractional) quantum Hall effect.