We discuss some properties of the exact four-spinon dynamical correlation function
S4 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 describe its behavior as a function of the neutron momentum transfer
k for fixed values of the neutron energy
ω and compare it to the one corresponding to the exact two-spinon dynamical correlation function
S2. We show that the overall shapes are quite similar, even though the expression of
S4 is much more involved than that of
S2. We finish with concluding remarks.
We derive the exact contribution of two spinons to the dynamical correlation function of the spin-\textonehalf{} Heisenberg model. For this, we use the isotropic limits of the exact form factors that have been recently computed through the quantum affine symmetry of the anisotropic Heisenberg model
XXZ.
Using Monte Carlo integration methods, we describe the behaviour of the exact four-spinon dynamic structure function S 4 in the antiferromagnetic spin Heisenberg quantum spin chain as a function of the neutron energy ω and momentum transfer k . We also determine the four-spinon continuum, the extent of the region in the ( k , ω) plane outside which S 4 is identically zero. In each case, the behaviour of S 4 is shown to be consistent with the four-spinon continuum and compared to that of the exact two-spinon dynamic structure function S 2 . Overall shape similarity is noted.