Exact four-spinon dynamical correlation function

We discuss some properties of the exact four-spinon dynamical correlation function in the antiferromagnetic spin 1/2 XXX-model the expression of which we derived recently. We show that the region in which it is not identically zero is different from and larger than the spin-wave continuum. We discuss its behavior as a function of the neutron momentum transfer $k$ for fixed values of the neutron energy $\omega$ and compare it to the one corresponding to the exact two-spinon dynamical correlation function. We show that the overall shapes are quite similar but there are differences that we discuss. Particular is the fact that the symmetry about the axis $k=\pi$ present in the two-spinon case seems to be lost in the four-spinon one. We finish with concluding remarks.