Despite the overwhelming evidence for the existence of an acceleration of
the Universe, the underlying fundamental physics remains unknown. As an
alternative to cosmological constant, the cosmic acceleration can result
from large scale modification of gravity which necessarily include
additional degrees of freedom. If these additional degrees are welcomed at
large scales they should be screened at small scales where General
Relativity is a perfect theory.
During this talk, I will present the 3 screening mechanisms known in the
literature: chameleon, symmetron and Vainshtein mechanisms. I will show the
strengths and weaknesses of these models.