Scientific Colloquium
April 8, 2005

 
SEAN CARROLL
UNIVERSITY OF CHICAGO

"Why is the Universe Accelerating?"

Our universe is accelerating, a phenomenon that cannot be accounted

  for by ordinary matter and conventional gravity.  The simplest

  explanation is to invoke a vacuum energy of 120 orders of magnitude

  less than the expected amount.  Alternatively, there could be a

  smoothly-distributed, slowly-varying dynamical component, or a

  breakdown of general relativity on cosmological scales.  All of the

  possibilities are very exciting, and future observations have promise

  for distinguishing between them. I will give an overview of the

  theoretical proposals for explaining the acceleration of the universe

  and the observational constraints which any model must satisfy.

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