### Lattice QCD

Quantum Chromodynamics (QCD) is a quantum theory of the strong interaction in nature. At low energy region, the analytical technique does not work and we need non-perturbative tools to understand hadron spectrum and weak matrix elements. The best tool is lattice gauge theory which also preserves the gauge invariance. In addition, the lattice gauge theory allows us to calculate Feynman path integrals numerically using super-computers. This flexibility makes it possible to perform a non-perturbative study on QCD extensively.