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Quintessence (physics)




In Physics , quintessence is a Hypothetical form of Dark Energy postulated as an explanation of observations of an Accelerating Universe . Quintessence is a Scalar Field which has an Equation Of State (relating its pressure ''p''''q'' and density ho''q'') of ''p''''q'' = ''w'' ho''q'', where ''w'' is less than -1/3. Quintessence is dynamic, and generally has a density and equation of state that varies through time and space. By contrast, a cosmological constant is static, with a fixed energy density and ''w'' = −1.

Many models of quintessence have a tracker behavior, which partly solves the Cosmological Constant problem. In these models, the quintessence field has a density which closely tracks (but is less than) the radiation density until Matter-radiation Equality , which triggers quintessence to start having characteristics similar to Dark Energy , eventually dominating the universe. This naturally sets the low Scale of the Dark Energy .

Some special cases of quintessence are Phantom Energy , in which w < −1 and K-essence (short for kinetic quintessence) which has a non-standard form of Kinetic Energy .


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