Cosmology: Inflation-In 1980s, Alan Guth etal. proposed the inflationary scenario, i.e., the Universe experienced a period of  expansion with acceleration  in early times to solve the problems encountered in the standard big bang cosmology. Inflationary models predict  that the geometry of the universe is flat. Inflation models also give good  explanations on primordial density fluctuations which seed the formation of  large scale structure. The observational data by the measurements on the cosmic microwave background anisotropy makes it possible to test  inflationary models more precisely. 

Dark energy-In  1998, the SCP and HZT groups independently discovered the evidence that the  Universe is in a phase of accelerating expansion. The simplest explanation of  this phenomenon is to introduce the cosmological constant. To avoid the  cosmological constant problem, a type of anti-gravity force is usually invoked  to explain an accelerating universe. The models are called dark energy models.

Gravitational Waves-In 2016, LIGO announced the detection of first gravitational wave event GW150914 coming from the coalescence of two black holes in the early Universe. The detection of gravitational waves open a new era of multimessenger astronomy and the test of gravitatonal theory in the strong field regime.