Fundamental Interactions
Dark matter and Dark energy
Neutrinos
Physics of Neural Networks
My primary research interests are the fundamental interactions in nature. I focus mainly on physics beyond the Standard Model (see 5 mysteries the SM cannot explain), but I am also interested in QCD and gravity. Recently, I have broadened my work to apply physical principles to understanding artificial neural networks.
Interaction is what governs the motion of things, and understanding the fundamental interactions in Nature is of utmost importance. A new gauge interaction might be crucial in understanding the dark matter sector of the Universe. Since we do not know where this new fundamental force is hidden or what it couples to, a proper investigation requires studying broad areas of particle physics.
The Standard Model can explain only about 5% of the total energy of the Universe, and the bigger parts need something called dark matter and dark energy. In general, it is an interaction that distinguishes one particle from another. (An electron has an electromagnetic interaction; a quark has a strong interaction; a neutrino has a weak interaction). It is quite possible that the dark matter might have its own interaction (dark force), and many of my research has been in this field. In the past decade, the focus of dark matter research has moved to the possibility of significantly lighter candidates (compared to the traditionally popular TeV-scale ones), and I have been involved in this effort. (See the Light Dark World International Forum page.)
The dark energy is the biggest mystery in the Universe. Its nature could be a dark energy field that can evolve during the history of the Universe. It is intriguing to investigate if the dark energy field is under a new gauge symmetry. (See our model, which introduced the gauge symmetry in the dark energy sector. )
The neutrino is the least studied matter in the Standard Model due to its rather weak interaction (mediated by W and Z bosons). As the high-energy collider (such as LHC) experiments pass their peak time, the flagship particle physics experiments are moving (or at least expanding) to the long baseline neutrino oscillation experiments (such as DUNE and T2HK). There are certain kinds of new interactions or mechanisms that can be most sensitive to the neutrino oscillation physics, and this is one of my important research topics.
I am also interested in the formal aspects of the strong interaction (Quantum Chromodynamics) in the Standard Model, which is well-known but still mysterious because of its non-perturbative nature. Because the strong interaction is too strong, the perturbative method (which played an important role in the great success of Quantum Electrodynamics) may not work best. I am trying to apply modern mathematics (developed after the Standard Model was devised) to describe QCD in a more efficient way, providing significantly better calculation power.
I also got interested in the effort to find renormalizable quantum gravity. Quantum gravity is something all physicists have been dreaming of since the birth of modern physics (that is, quantum mechanics and general relativity), yet there has been no true success. The main reason is because the interaction mediated by the graviton (of spin 2) is not calculable in quantum field theory due to the nonrenormalizability of gravity. (See also this article.) The conformal symmetry approach may have a potential to make a breakthrough in this aspect, and I plan to launch a study in this direction. See 'tHooft's recent talk.
I truly believe we are living in a new era of the industrial revolution. Just as people did not fully understand thermodynamics when the steam engine was invented, we do not yet understand the fundamental principles of neural networks. It is the role of physicists to make breakthroughs in this field. I am eager to apply physics to illuminate this exciting period. (See our works 1 and 2.)