THE STUDY OF CHIRAL RESTORATION USING THE QUARK-GLUON MIXED CONDENSATE g〈q̄σμνGμνq〉 IN LATTICE QCD AT FINITE TEMPERATURE∗

The quark-gluon mixed condensate g〈q̄σμνGμνq〉 is studied using SU(3)c lattice QCD with the Kogut-Susskind fermion at the quenched level. Using the lattices as β = 6.0 with 16 × Nt(Nt = 16, 12, 10, 8, 6, 4), β = 6.1 with 20 × Nt(Nt = 20, 12, 10, 8, 6) and β = 6.2 with 24 ×Nt(Nt = 24, 16, 12, 10, 8) in high statistics of 100-1000 gauge configurations, we perform accurate measurement of the thermal effects on g〈q̄σμνGμνq〉 as well as 〈q̄q〉 in the chiral limit. We find that the thermal effects on both the condensates are very weak except for the vicinity of Tc, while both the condensates suddenly vanish around Tc ≃ 280MeV, which indicates strong chiral restoration near Tc. We also find that the ratio m20 ≡ g〈q̄σμνGμνq〉/〈q̄q〉 is almost independent of the temperature even in the very vicinity of Tc, which means that these two different condensates obey the same critical behavior. This nontrivial similarity between them would impose constraints on the chiral structure of the QCD vacuum near Tc.