Color Ferromagnetic Vacuum States in QCD and Two-Loop Energy Densities. Bounds on MIT Bag Constant in Relation to QCD lambda

摘要

Two-loop energy densities of color ferromagnetic states are obtained using the beta -function calculated to two-loop approximation and the exact formula for the energy density of such a state. This is used to derive bounds on the MIT bag constant correcting the previous bound in one-loop approximation. For a constant field color ferromagnetic ansatz state the bound on the QCD scale parameter lambda /sub p/ <= 0.88 GeV is obtained when B/sup 1/4/ = 0.145 GeV. The correction by going from one-loop to two-loop is only of the order of 20%. Correcting for instanton effects yields lambda /sub p/<= 0.40 GeV. The theta sub 3 -vacuum ansatz with two-loop and instanton correction gives lambda /sub p/<= 0.16 GeV. It is stressed that the 'perturbative vacuum', which is identified with the inside bag state, is a somewhat ill-defined concept due to a path-dependence in the integral giving the energy density. (Atomindex citation 11:523580)