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The Cosmological Constant
Gravitational Lensing

Basic Idea: Change the volume of space back to a given time, changes odds that a foreground object (e.g. galaxy) will get close enough to line of sight of a background object to lens it.

Gravitational lensing

  • What it is
    strong, microlensing and weak lensing
    strong lensing by a point mass
    observed examples
  • Use as measurement of Lambda


  • Method
    advantages: statistics improving, many lenses being discovered
    sources of error: extinction, unwanted dependence on galaxy properties, discovery process
  • Current Results
    Castles survey, CLASS survey
  • proposed projects

Other cosmological tests lensing can be used for

  • matter (not just luminous) profiles
  • Hubble constant
  • clumpy dark matter
  • large scale structure -- to be discussed later

Some References

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