Presentation 1 : Invited
Quintessence
Jerome Martin
Recent measurements of the luminosity distance versus redshift
relation for type Ia supernovae seem to suggest that our Universe
is accelerating implying that it is dominated by a fluid whose
equation of state is negative. Since the most natural explanation,
i.e. the presence of a cosmological constant, faces serious theoretical
problems, another hypothesis named "quintessence" has recently been
proposed. It consists in assuming that the acceleration of the Universe
is due to a scalar field whose final evolution is insensitive to the
initial conditions. The main mechanisms which underlie the quintessence
scenario, in particular the notion of "tracking field", will be presented
and the observational consequences will be discussed.