MAJORANA FERMION REPRESENTATION FOR AN ANTIFERROMAGNETIC SPIN-1 2 CHAIN/

We study the one-dimensional Heisenberg antiferromagnet with s = 1/2 u sing a Majorana representation of the s = 1/2 spins. A simple Hartree- Fock approximation of the resulting model gives a bilinear fermionic d escription of the model. This description is rotationally invariant an d gives power-law correlations in the ''ground state'' in a natural fa shion. The excitations are a two-parameter family of particles, which are spin-1 objects. These are contrasted to the ''spinon'' spectrum, a nd the technical aspects of the representation are discussed, includin g the problem of redundant states.