Understanding Cosmic Acceleration with Galaxy Redshift Surveys

LUIGI GUZZO
INAF - OSSERVATORIO DI BRERA, MILAN, ITALY

The discovery that the Universe is accelerating will possibly be seen
in a few years as one of the turning points in the history of
cosmology. After nearly ten years, the origin of such accelerated
expansion is still unknown. One possibility is that the Universe is
permeated by a "dark energy" which gives rise to a gravitational
repulsion. Alternatively, perhaps the very equations of General
Relativity need to be modified or generalized to higher-dimensional
worlds.  In my talk I will first review these general ideas. I will
then discuss some new perspective for understanding the nature of
cosmic acceleration using large surveys of galaxy
redshifts. Specifically, I will show how measurements of linear
redshift-space distortions due to galaxy coherent motions can be used
to trace the evolution of the growth rate of cosmic structures f(z) at
different epochs, presenting a first application to data from the VVDS
survey.  Combined to estimates of the cosmic expansion rate H(z) that
can be obtained from Baryonic Acoustic Oscillations, future larger
redshift surveys, as those foreseen for the space missions EUCLID and
JDEM, will be able to use these techniques to pinpoint the physical
origin of the accelerated expansion, distinguishing true ’ªÒ
’ä›’¨Â’áò’ë­’åî’åò’çù’ªÑ models from modifications of the
gravitation theory.