For the many-anyon system in an external magnetic field, we derive the energy spectrum as an exact solution of the quantum eigenvalue problem with particular topological constraints. Our results agree with the numerical spectra recently obtained for the three- and the four-anyon systems.
The mean field equations for anyons in an external homogeneous magnetic field are studied and two classes of mean field solutions are explicitly constructed. The first class of solutions, corresponding to one filled Landau level in the combined external and smeared out statistical magnetic fields, is compared to the corresponding exact groundstate solutions. The energies are found to agree well at low densities and when the statistical field is not too strong compared to the background field. At high densities the fermi pressure increases the mean field energy indefinitely. The mean field solutions also miss the lower part of the energy spectrum. To the second class of mean field solutions no corresponding anyon state is known. These solutions represent the anyonic continuation of the fermi state with two filled Landau levels.
We study the properties of particles with fractional statistics (anyons) in a uniform magnetic field, to investigate the interplay between the statistical and physical flux. By exact solution of the two-body case, both free and with a harmonic attraction, we find a very clear example of the way in which an external field can offset the frustration caused by the statistics. These solutions also give the second virial coefficient, and hence a thermodynamic signature of the same effect. Finally, the same approach is used to study the problem of many anyons in a magnetic field, in particular the ground state and excitation spectrum.