A study of the Kondo model by means of the Asymptotic Field
Approach (*AFA*) is reported in
Ref. [9]. In particular the following
properties have been computed:

- The single-particle properties (i.e., density of states) [9]
- The response functions (i.e., spin correlations) [9]

The *AFA* results have been compared with the ones
obtained by:

By use of a fully self-consistent calculation for composite operators we have shown how to resolve coherent low-energy features embedded in a broad high-energy background. We have illustrated this with the Kondo model in the limit of large spin symmetry group which has often been shown to retain many crucial aspects of low-energy physics. Our numerical estimate for the Kondo temperature agrees very well with the exact solution. At this temperature the Kondo amplitude has a change in the concavity of its slope when plotted as a function of the temperature. At high temperatures the spectral density shows only a high-energy incoherent background. The well-defined singlet excitation mode present at low temperature no longer exists, even if some residual spin-spin interaction persists being energetically favored by a finite bandwidth.