Can we be tricked into thinking that w is less than -1?

Aug, 2004
20 pages
Published in:
  • Phys.Rev.D 71 (2005) 023525
e-Print:

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Abstract: (arXiv)
Dark energy candidates for which the equation-of-state parameter w is less than -1 violate the dominant energy condition, and are typically unstable. In scalar-tensor theories of gravity, however, the expansion of the universe can mimic the behavior of general relativity with w<-1 dark energy, without violating any energy conditions. We examine whether this possibility is phenomenologically viable by studying Brans-Dicke models and characterizing both the naturalness of the models themselves, and additional observational constraints from limits on the time-dependence of Newton's constant. We find that only highly contrived models would lead observers to measure w<-1.
  • 98.80.Cq
  • dark energy
  • Brans-Dicke model
  • gravitation: scalar
  • gravitation: tensor
  • gravitation: fundamental constant
  • fundamental constant: time dependence
  • acceleration
  • dark energy: density