Stressing the Internal Viscosity Approach

We now may ask whether the Allegra model can reproduce some of the features experimentally found for the other correlators. The incoherent intermediate scattering fimction can be calculated from an adaptation of Eq. 3.16 to Fig. 3.18 to the results of Allegra et al. We note that in the Q-range where experimental data are available, the line shape deduced from the model is significantly less stretched than the experimental one [ 187]. Therefore, the char- 

Finally, it is worthy of remark that, though the comparison between the timescales leads to an almost perfect agreement between the predictions of the Allegra and Ganazzoli model and the collective and self-motion results, it is evident that clear differences appear when comparing the spectral shapes of the respective functions. The model delivers close to exponential decays for both correlators while experimentally one observes significantly stretched relaxation function (j0=O.5). 

---