【摘要】 本文应用混合作用量作为改进平均场理论的试操作用量，用变分法计算了４维时空中Ｚ（２），Ｕ（ｌ）和ＳＵ（２）纯格点规范场的平均元格内能Ｅ＿ｐ．对于Ｚ（２）格点规范场得出具有范德瓦尔斯型曲线的一级相变的相图。对于Ｕ（ｌ）群，得到很陡的Ｅ＿ｐ－β曲线，显示有解除禁闭的二级相变。对于ＳＵ（２）群，得到光滑的Ｅ＿ｐ－β曲线，显示理论的禁闭性。计算结果与ＭＣ方法所得符合较好。更多还原

【Abstract】 Using mixed action as a trial to the modified mean field theory ,we calculatethe internal energies Ep of Z(2) ,U(l)and SU(2) lattice gauge fields in 4-dimensions。Phase diagram of first order phase transition like Van derwaals curve is obtained for Z(2)group ,which cannot be obtained witn any other trial actions. A very steepcrossover in the E_p-β curve for 4-D U(1) group shows the signal of 2nd order phasetransition。 The E_p-β curve for 4-D SU(2) group is smoothx shawing only a single,con-fining phase, The results are in good agrement with the Monte Carlo results both in thestrong-coupling region and crossver region。更多还原