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SUMMARY:Zero Active Mass in FRW Cosmologies - Fulvio Melia\, University of
  Arizona
DTSTART:20150611T153000Z
DTEND:20150611T163000Z
UID:TALK59245@talks.cam.ac.uk
CONTACT:Simon Hodgkin
DESCRIPTION:The standard model of cosmology is based on the Friedmann-Robe
 rtson-Walker\n(FRW) metric. Often written in terms of co-moving coordinate
 s\, this elegant and\nhighly practical solution to Einstein's equations is
  based on the Cosmological\nprincipal and Weyl's postulate. But not all of
  the physics behind such symmetries\nhas yet been recognized. We invoke th
 e fact that the co-moving frame also happens\nto be in free fall to demons
 trate that the FRW metric is apparently valid only for\na medium with zero
  active mass. In other words\, the application of FRW appears\nto require 
 an equation-of-state rho+3p = 0\, in terms of the total energy density\nrh
 o and total pressure p. Though the standard model is not framed in these\n
 terms\, the optimization of its parameters brings it ever closer to this c
 onstraint\nas the precision of the observations continues to improve. For 
 example\, the\nlatest high-precision BAO measurements rule out the standar
 d model at better\nthan the 99.95% C.L. if the zero active mass condition 
 is ignored.
LOCATION:Sackler Lecture Theatre\, IoA (tea at 4:00 pm)
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