HEISENBERG S=1 2 RING CONSISTING OF A PRIME-NUMBER OF ATOMS/

In this work it will be shown that the dimensionality of the eigenvalu e problem of a Heisenberg s = 1/2 ring with a prime number N of atoms can be reduced by a factor of N. This makes small systems such as N = 5 and 7 particularly easy to solve analytically for the case of neares t-neighbor interactions, without the use of Bethe's ansatz, as well as for the general case of couplings beyond nearest neighbors. Exact exp ressions are given for both the magnon dispersion relations and the ei genvectors.