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SUMMARY:Modified Gravity makes Galaxies Brighter - Jeremy Sakstein (DAMTP)
DTSTART:20110314T130000Z
DTEND:20110314T140000Z
UID:TALK30203@talks.cam.ac.uk
CONTACT:Tasos Avgoustidis
DESCRIPTION:One method of accounting for the observed acceleration of the 
 universe is to modify general relativity to include a new degree of freedo
 m\, which plays the role of dark energy.  General relativity has been test
 ed to incredibly high precision over the last century and so there are tig
 ht constraints preventing any radical modifications. However\, these const
 raints all come from local tests and there is nothing precluding modificat
 ions on large\, extra-galactic scales. There is a class of theories that p
 ossess screening mechanisms where the strength of gravity depends on the l
 ocal density. In these theories\, gravity would be screened in our galaxy 
 satisfying local constraints but would vary on cosmic scales.\nIn this tal
 k I will introduce some of these different screening mechanisms before int
 roducing a new\, model independent test of these theories. In unscreened r
 egions of the universe\, the properties of stars are dramatically altered:
  they are more luminous and ephemeral. We therefore expect unscreened gala
 xies to be more luminous and metal-enriched than their screened counterpar
 ts. These phenomena are an excellent probe of new physics and by searching
  for them we can increase the current bound on such theories by at least a
 n order of magnitude.    
LOCATION:CMS\, Pav.B\, CTC Common Room (B1.19)
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