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The Cosmological Constant
Recap and synthesis

Basic Idea: Add and contrast different measurements of Lambda, where progress hoped for soon. Summarize combined earlier lectures.

Start with review of evolution of universe again

Effect of Lambda

  • expansion rate of the universe (kinematics)
    age, distance redshift relation, Alcock-Paczynski test
  • structure formation: empty space with cosmological constant doesn't clump so if fix universe at flat there is less matter to clump and structure forms more slowly
    cluster number, bulls eye effect, weak lensing
  • since Omegam + Omegalambda + ... = 1 constraining other cosmological parameters will also constrain lambda
    cosmic microwave background, cluster baryon fraction
  • may have something which is not "constant" but depends on spacetime as universe expands in some intermediate way (still providing acceleration)
  • summarize: which ones are expected to have new information and when
  • strongest/weakest tests
  • complementarity
  • accounting of matter in the universe
  • Major puzzle for particle theorists
    many proposals but as details of string theory, the proposed fundamental theory of gravity, are not yet well enough understood there are no conclusive predictions or mechanisms

Some references

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Comments or Questions? Contact jcohn@astron.berkeley.edu