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SUMMARY:Unravelling Cosmic Acceleration with Gravitational Waves and Large
 -Scale Structure - Lucas Lombriser (Geneva)
DTSTART:20190311T130000Z
DTEND:20190311T140000Z
UID:TALK117820@talks.cam.ac.uk
CONTACT:Tobias Baldauf
DESCRIPTION:Abstract: Identifying the nature of the late-time accelerated 
 expansion of our Universe remains a difficult puzzle to cosmology. Scalar-
 tensor modifications of gravity have long been considered as an alternativ
 e explanation to the cosmological constant. I will first discuss how the d
 irect detection of gravitational waves and the measurement of electromagne
 tic counterparts\, confirming a luminal speed of gravity\, in combination 
 with observations of the large-scale structure brought the anticipated cha
 llenge to the concept of cosmic self-acceleration from scalar-tensor gravi
 ty. I will then provide an outlook of how a more general model space will 
 ultimately only be exhaustively probed by Standard Sirens. In a second par
 t\, I will show how a simple additional variation of the standard Einstein
 -Hilbert action with respect to the Planck mass may solve both the old and
  new cosmological constant problems. The additional variation yields a top
 ological constraint that prevents vacuum energy from gravitating and when 
 accounting for the nonlinear structure formation predicts a current energy
  density parameter of the cosmological constant of Omega_Lambda=0.704\, in
  good agreement with observations.
LOCATION:CMS\, Pav. B\, CTC Common Room (B1.19) [Potter Room]
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