A Quantitative Framework of Nonperturbative QCD from Topological Vacuum with Application to Parton Structures

Abstract

This dissertation develops a quantitative framework that provides a physical picture for non-perturbative QCD based on the topological structure of the QCD vacuum. By integrating out the ultraviolet degrees of freedom, the infrared gluon configurations are modeled as a liquid ensemble of instantons and anti-instantons, which induce effective interactions among quarks. This framework captures the origin of trace and axial anomalies through the infrared distributions of QCD and dynamically breaks chiral symmetry. More specifically, this framework can be formulated in two ways: in one, we construct a statistical ensemble with weights defined by the instanton action and Dirac determinant, while in the other we formulate an effective field theory (EFT) by rewriting the determinant as effective quark interactions. By reformulating the EFT on the light front, we explicitly construct the light-front wave functions and calculate various parton observables in linear factorization. We further embed the framework into transverse momentum dependent factorization and establish a vacuum origin for rapidity evolution by computing the soft functions. We also extend this approach to various form factors in light hadrons, including scalar, pseudoscalar, and energy-momentum tensor (EMT), as well as higher-twist color force and multigluon correlations, with applications to hadron mass and spin decomposition, near-threshold quarkonium production, and strong CP problem, highlighting the importance of the vacuum origin in hadron structures. Overall, this work demonstrates that the QCD vacuum provides a quantitatively crucial description of hadronic structure from low to moderate resolution, bridging nonperturbative vacuum physics with partonic phenomenology.