QCD vacuum for hadrons

In Quantum Chromodynamics (QCD), non-linear gluonic interactions are taken to play important roles in establishing strong interaction pictures such as nonperturbative vacuum structures and various loop contributions to each physical process. One of these roles has been formulated as the gluon condensates which affect the spectra of quarkonium states and modify the forms of quark and gluon propagators. Especially, the dimension-2 condensate 〈A _μ ²〉 can be used to define gauge slices which can be combined to form in-hadron regions. In this paper, we will try to construct the topological spaces of in-hadron regions and to determine the structures of QCD vacuum for hadrons.