Lado Samushia

Physics Department, Kansas State University

"Measuring" Quintessence: Constraining Scalar Field Dark Energy with Cosmological Observations

Astro Lunch Seminar, Friday, February 20, 2009
12:00 PM, Wean Hall 8327, CMU

Abstract:

Cosmological observations of the last decade show that about 70% of the universe's energy budget is in dark energy.  Simple LambdaCDM model fits all the available data very well, but at the same time brings up new questions: Why is the energy density of cosmological constant so small?  Why did we happen to live in a (very short) period when energy densities of dark energy and nonrelativistic matter are roughly equal?  If a uniform, slowly varying in time, scalar field is present on cosmological scales it can replace the cosmological constant as a dark energy candidate.  Slowly-rolling scalar field gives accelerated expansion of the universe and at the same time naturally explains the small value of dark energy density.  Next generation of cosmological probes might already be able to discriminate between scalar-field dark energy and cosmological constant.