Sunday, 25 September 2022

### Astronomy Colloquium (29.6/2022)：Test the Wave-Particle Duality of Gravitational Wave Using the Spin-Orbital-Hall Effect of Structured Light

Calendar

Date
06.29.2022 2:00 pm - 3:00 pm

### Description

Title: Test the Wave-Particle Duality of Gravitational Wave Using the Spin-Orbital-Hall Effect of Structured Light
Speaker：Feng Longlong（冯珑珑）

Abstract: Probing the polarization of gravitational waves (GWs) would provide an evidence of graviton, indicating the quantization of gravity. Motivated by the next generation of gravitational wave detectors, we make an attempt to study the possible helicity coupling of structured lights to GWs.  With the analogue between gravitational fields and the generic electromagnetic media, we present a 4-vector optical Dirac equation based on the Maxwell theory under the paraxial approximation. It is found that twisted lights propagating in a gravitational field can be viewed as a non-Hermitian system with the $\mathcal{PT}$ symmetry. We further demonstrate that the coupling effect between angular momentums of the GWs and twisted lights may make photons undergoing both dipole and quadrupole transitions between different orbital-angular-momentum(OAM) eigenstates and lead to some measurable optical features. The former is spin-independent while the later is spin dependent phenomena, giving the spin-orbital-Hall effect of structured lights in the GWs and revealing the particle nature of GWs. Besides, our theoretical method offers an unified scheme to tackle the various spin-orbital effects in generic media and can find wide applications in photonics.

Bio: Feng Longlong, professor of physics at Sun Yat-sen university. He received his bachelor's degree in physics from the University of Science and Technology of China (USTC) in 1982, and master's degree from Center for Astrophysics of USTC in 1985. He got his PhD degree from Department of  Astronomy of Nanjing university in 1990.  Since 1990, he had been working in USTC.  During this period,  He visited and worked in many universities and astrophysical research institutions in Europe and the United States. In 2003, he was transferred to the Purple Mountain Observatory as the principal researcher of galactic astronomy & cosmology group. He moved to Sun Yat-sen university in 2014 and has been physical professor in School of physics and astronomy. Prof. Feng’s research interests include relativistic astrophysics, galactic astronomy and cosmology, computational astrophysics, etc.

Time:14:00-15:00PM, 29/June, Wednesday
Meeting ID: 831 4360 9634
Passcode: 436377