# Colloquium by Xuefeng Wu (PMO)

**Testing Einstein’s Equivalence Principle with Cosmic Transients**

**Abstract:**

The Einstein equivalence principle (EEP) is an important foundation of general relativity and many other metric theories of gravity. At the post-Newtonian level, the accuracy of the EEP can be tested through the numerical values of the parametrized post-Newtonian (PPN) parameters, such as the parameter γ. Specifically, the EEP accuracy can be constrained by comparing the γ values for different kinds of particles, or for the same kind of particle with different energies, since all gravity theories satisfying the EEP predict the same γ values for different test particles. There are a few precise tests of the EEP using constraints on the differences of the γ values of different tested particles. Among the most famous are the measurements of the time delay of the photons and neutrinos radiated from supernova 1987A in the Large Magellanic Cloud. In this talk, I will show you that the EEP can also be tested using the time delay of particles such as photons, neutrinos and gravitons with different energies arising in cosmic transients, such as gamma-ray bursts (GRBs), fast radio bursts (FRBs), TeV blazar flares, gravitational wave events. I will also talk about our recent work on the constraints of the photon mass with the same time delays in GRBs and FRBs.

**Time: **May 11, 2016, 2:30 pm

**Venue:**A601, NAOC