Life as a Voyage

Photograph taken at Niagara Falls

간략소개
생물학적 정보 : 1984년 출생, 남성
직업(?) : 물리학과 대학원생
연구분야 : QCD (Quantum Chromodynamics)

(Current supervisor : prof. Sangyong Jeon @ McGill Univ.)

직업 외 관심분야 : 컴퓨터 하드웨어, 여행, 항공, 슈팅게임
 

Let me give a brief description of my study.

    Usual materials consist of molecules and each molecule consists of atoms. Again, an atom has a nucleus and electrons surrounding the nucleus and a nucleus has protons and neutrons. If we go more microscopic, then it turns out that a proton or neutron consists of three "quarks" - a qqq bound state. Here, a question arises : How can three quarks with electromagnetic(EM) charges be tied together even though they feel repulsive electromagnetic force? The answer is that the "strong" interaction keeps them from being taken apart. In analogy with the EM force, particles carrying "color" charges feel strong interaction and the strong force is acted by exchanging "gluon".

    Quantum Chromodynamics (QCD) is the quantum theory of strong interaction. In particle physics, every particle is described by a field and every force arises by exchanging virtual particles. In the quantum point of view, a particle is an excitation of the field. Whenever we say "we have a quantum field theory", we have the Lagrangian of the theory which describes the dynamics of the fields. All of predictions, such as scattering cross sections, decay rates, etc., can be made from the Lagrangian.

(QCD is Yang-Mills theory with SU(3) gauge group in the fundamental representation.)

    A peculiar feature of strong interaction is that, unlike gravity and EM, it gets stronger and stronger as a quark gets further and further from another quark (or anti-quark). So the quarks prefer to get together rather than staying alone unless they move with very high energy and this is why a single quark have not ever been observed. This property called "asymptotic freedom" is a sort of complexity that makes QCD difficult to solve.

Above plot shows the change in the strength of the interaction as a function of the (experimental) "momentum scale". We can consider the center-of-mass energy of a collision process as the momentum scale. LambdaQCD is a cutoff such that the coupling blows up for the momentum scale comparable or smaller than LambdaQCD. In other words, the perturbation theory works only for momentum scale higher than LambdaQCD.

    There are many methods to study the strong interaction - perturbative QCD, hydrodynamic description, AdS/CFT correspondence and lattice gauge theory. I am a beginner of research in such field but I currently expect that my study will be based on especially hydrodynamic description, perturbative QCD and finite temperature field theory.