Quantum field theory, String theory, Mathematical physics
Recent research interests:
- Scattering amplitudes ►
- Spin chain and form factors ►
- Gauge/string duality and minimal surface ►
- Gauge theoris and integrable systems ►
Physics at very small scales is well described by the so-called Standard Model of particle physics, which is based on quantum field theory. It is, however, also well-known that the Standard Model is an incomplete description of the Universe. For example, it has nothing to say about gravity, and it can not explain what the dark matter is.
One major goal of the currently running Large Hadron Collider (LHC) experiments at CERN is to discover possible new physics beyond the Standard Model. If we are to discover any new physics, it is paramount to have a good enough quantitative control of possible 'new' as well as known 'old' physics, namely, the huge Standard Model backgrounds. This has been a formidable technical challenge using the standard textbook methods based on Feynman diagrams, which work in principle but quickly become cumbersome beyond the simplest examples.
This is a main driving force for the developoments of modern amplitudes techniques in the past 30 years, starting roughly from the Parke-Taylor formula for maximally helicity violating (MHV) amplitudes discovered in 1986, and then revived due to Witten's twistor string paper in 2003. In particular, the tremendous progress made in the past 10 years has not only significant phenomenological impacts, but also provides new deep insights to fundamental aspects of quantum field theory and string theory.
As another major challenge to theoretical physics, we have very few tools to study strongly coupled systems. Knowing only fundamental laws does not necessarily mean that we can explain their phenomena. A typical example is the so-called quark confinement, where a microscopic Lagrangian description of the interactions of quarks and gluons has been known for over four decades, but a quantitative understanding is still missing. This is because the interaction of quarks and gluons are so strong at low energy that perturbative methods fail. Tools to tackle strong coupling or non-perturbative phenomenon include gauge/string duality, localization method, and integrability techniques.