Title:   Magnetized Stars from Normal to Supermassive Ones

Time: 3:00pm, Sep. 30th (Thursday)

Speaker: YU-QING LOU 楼宇庆

Institution: Tsinghua University, Physics Department, Tsinghua Center for Astrophysics, Astronomy Department, and Tsinghua--National Astronomical Observatories of China joint Research Center for Astrophysics

Abstract:

In the framework of general relativity (GR), we investigate magnetized normal to supermassive stars in quasi spherical equilibrium and radial pulsational GR magnetohydrodynamic (MHD) stability/instability problems. In our stellar model, a random transverse magnetic field is presumed and a key relation for magnetic flux conservation is stipulated. We identify distinct features and pertinent physical effects for magnetized and non-magnetic stars. In particular, GR MHD collapses of magnetized massive stars can give rise to black holes (BHs) in a very broad mass range and can certainly avoid the electron-positron pair instabilities to form BHs in the so-called "forbbiden zone of BH masses". This closely relates to the recent inferences of LIGO/Virgo experiments on binary BH masses. We briefly discuss the dynamic or MHD formation of supermassive BHs and hypermassive BHs.

Seminar talk

Title: New source of fluctuations in CMB

Speaker: Ken Kikuchi (YMSC, Tsinghua university)

Time: 1:30pm, Sep. 30th (Thursday)

Location: Middle Room, 3rd floor

Abstract:

It is well known that electromagnetic radiation (photon) was emitted in the early stage of the universe. We observe the radiation as cosmic microwave background (CMB). The CMB has remarkable isotropy. However, it is also known that there are small anisotropy or fluctuations. We propose a new source of radiation which may explain the fluctuation. This talk is based on Phys. Rev. Res. 2 (2020) 3, 033286 [hep-th/1912.07905] with Mamiya Kawaguchi.

Biography:

Dr. Kikuchi got his Ph.D. from Nagoya university, Japan under the supervisor Tadakatsu Sakai. After the graduation, he worked as a postdoctoral fellow at the Fudan university, Shanghai. He is now a postdoctoral fellow at Yau Mathematical Sciences Center, Tsinghua university, Beijing. He works on quantum field theory (QFT), especially anomaly and conformal field theory (CFT).