Towards a semiclassical description of QCD vacuum around Tc

We study the vacuum topology of 2 + 1 flavor QCD above the chiral crossover transition, at T ≲ 1.2 Tc, on lattices of size 323 × 8. Since overlap fermions have exact chiral symmetry and an index theorem even on a finite lattice, we use them to detect the topological content of gauge fields generated using domain wall fermion discretization for quarks. We further use different periodicity phases along the temporal direction for the valence overlap quarks, which allows us to probe different topological structures present in the gauge field ensembles, through their zero modes. Through this procedure we provide some first evidences that fermion zero modes can be understood to arise due to different species of instanton-dyons. We resolve the so-called "topological clusters" via multiparameter fits to their density, providing therefore an understanding of the interactions between instanton-dyons. The typical separation between dyons we obtain, is ∼ 0.3 fm . Surprisingly, it emerges out from this study that a semiclassical description of the fermionic zero modes in the QCD vacuum may be possible, just above Tc.