QCD in Infrared Region and Spontaneous Breaking of the Chiral Symmetry

TL;DR

This paper investigates the spontaneous breaking of chiral symmetry in QCD using the instanton vacuum model, aiming to calculate vacuum properties and low-energy constants and compare them with phenomenological and lattice data.

Contribution

It provides a nonperturbative calculation of QCD vacuum properties and low-energy constants within the instanton vacuum model, linking theory with phenomenology and lattice results.

Findings

Calculated vacuum properties consistent with phenomenology.

Estimated low-energy constants aligning with lattice results.

Supported instanton model as a natural explanation for SBCS.

Abstract

The spontaneous breaking of chiral symmetry (SBCS) is one of the most important phenomena of hadron physics. It defines the properties of all the light mesons and baryons. The Chiral Perturbation Theory (ChPT) encodes QCD hadronic correlators at low-energy region in the terms the low-energy constants (LEC) -- the expansion parameters on light quark current masses $m$ and external momenta $p$. The LEC's can be extracted from the phenomenology or from QCD lattice calculations. On the other hand, QCD instanton vacuum/instanton liquid model provides a very natural nonperturbative explanation of the SBCS. It provides a consistent framework for description of the pions and thus may be used for evaluation of the LEC. Our aim is to calculate the vacuum properties and the LEC's within instanton vacuum model and confront with phenomenology and lattice results.