Nuclear and hadron physics
Hadron physics aims at understanding how the elementary constituents of matter, the quarks and gluons, are synthesized into strongly interacting particles. Hence, it is interesting to study the structures and properties of hadrons. The most common hadrons, the proton and the neutron, further combine into the atomic nuclei. In nuclear physics, one studies nuclei with a large excess of protons and neutrons to understand the creation of the elements in the universe.
Nonperturbative methods to QCD
The strong interaction between quarks and gluons is described by Quantum Chromodynamics (QCD), which is successfully tested at high energies. At low energies where hadrons are the effective degrees of freedom, the perturbative expansion of QCD can not be done due to the strong running coupling. Therefore, nonperturbative methods for the strongly interacting systems are being developed, e.g. effective models, QCD sum rule, lattice gauge theory, and so on. Prof. Su Houng Lee, in particular, has been doing pioneering works on the applications of QCD sum rules to hot and/or dense nuclear medium.
QCD at high temperature and density
One of the central questions in modern nuclear and hadron physics is how the properties of hadrons are modified in hot and dense matter. This topic is closely related to understanding the early universe, e.g. Quark-Gluon Plasma (QGP) phase, or extreme forms of compressed hadrons, e.g. in the interior of neutron stars. They can be created for a very short time in the laboratory in the collision of ultra-relativistic heavy ions. Major accelerator facilities, e.g. LHC (Geneva), RHIC (Brookhaven), GSI (Darmstadt), are used to study such nuclear matters at high temperatures and densities, mimicking the conditions of the early universe.