报告题目：A Unique Metric for Cosmolgy

　　报 告 人：Prof. Fulvio Melia（Department of Physics, The University of Arizona）

　　报告摘要：The standard model of cosmology is based on the Friedmann-Robertson-Walker (FRW) metric. Often written in terms of co-moving coordinates, this elegant and highly practical solution to Einstein’s equations is based on the Cosmological principal and Weyl's postulate. But not all of the physics behind such symmetries has yet been recognized. We invoke the fact that the co-moving frame also happens to be in free fall to prove that the FRW metric is valid only for a medium with zero active mass. In other words, the spacetime of a perfect fluid in cosmology can be correctly written as FRW only when its equation-of-state is rho + 3p = 0, in terms of the total energy density rho and total pressure p. There is now ample observational evidence supporting this conclusion.

　　时    间：11月22日（星期五）上午10:00

　　地    点：南大苏富特一楼报告厅

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