数学所周五学术报告—Bondi-Sachs Spacetimes and Gravitational Radiation
主 题: 数学所周五学术报告—Bondi-Sachs Spacetimes and Gravitational Radiation
报告人: 张晓 教授 (中科院数学所)
时 间: 2017-04-07 15:00-16:00
地 点: 理科1号楼1114
Abstract: Bondi-Sachs spacetimes describe the nonlinear effect of gravitational radiation. In the zero cosmological constant, they were originally introduced by Bondi for axisymmetric spacetimes, and generalized by Sachs to general asymptotically flat spacetimes over 50 years ago. Bondi also defined the Bondi energy-momentum at null infinity, the physical conserved quantity which represents the rest energy of spacetimes after the loss duo to gravitational radiation.
In this talk, we shall discuss the solutions of basic questions arisen in gravitational radiation: Whether the Bondi energy is nonnegative, i.e., whether the gravitational waves can carry away more energy than they initially have? How the Bondi energy-momentum relates to the ADM energy-momentum defined at spatial infinity?
As cosmological observations indicated that our universe has a positive cosmological constant, the Bondi-Sachs spacetimes with positive cosmological constant gain much attention recently. We shall also discuss the relevant issue as well as some unsolved problems in this case.
