Quintessence hypothesis

The quintessence hypothesis was proposed by J. P. Ostriker and Steinhardt (2001). The authors use the term quintessence ( fifth substance ) to describe a quantum force field which is gravitationally repulsive. It has a certain similarity to an electrical or magnetic field and could lead to an invisible energy field which accelerates cosmic expansion. 

This investigation, involving the most up-to-date instruments such as the Hubble Space Telescope, led to the following conclusion the data disagree strongly with the hypothesis that the Universe is flat and contains no quintessence, thus ruling out one of the most favoured cosmological models. 

In the hypothesis of an exponential potential, the situation is even worse because Jeans instability is always reduced by the presence of quintessence (i.e., o ia is never equal to 1). More detailed calculation give the following value of the matter power spectrum normalization as as a function of Wq in Fig. 8.2. 

The most direct probe of quintessence lies in supernovae data. The reason, as we said, is that supernovae data (in the hypothesis that supernovae are... 

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