Comment on "Two Fermi points in the exact solution of the Kondo problem"

describesa m agnetic im purity in a m etal,capturing the radialdynam ics of a 3d m odel. The spectrum is linearized around the Ferm ipoint (there is only 1 point since the Ferm isurface in 3d is sim ply connected) and asa resultthe electronsare chiral-rightm oversby our convention -with a spectrum E = p. Thelinearization isvalid forJ sm alland form om enta sm allcom pared to a cuto D ,ofthe orderofthe bandwidth. The cuto is considered large com pared to any physicalquantity and the only scale rem aining in the problem istheK ondotem peratureTK = D exp 2J .The resultsare universaland param eterized by TK D .If the coupling is not sm allthe spectrum cannot be linearized and the universality islost. The m odelis soluble and its solution is given by the setofequations: