Spyros Basilakos, Florian Bauer, Joan Sola
In order to deal with a large cosmological constant a relaxation mechanism
based on modified gravity has been proposed recently. By virtue of this
mechanism the effect of the vacuum energy density of a given quantum
field/string theory (no matter how big is its initial value in the early
universe) can be neutralized dynamically, i.e. without fine tuning, and hence a
Big Bang-like evolution of the cosmos becomes possible. Remarkably, a large
class F^n_m of models of this kind, namely capable of dynamically adjusting the
vacuum energy irrespective of its value and size, has been identified. In this
paper, we carefully put them to the experimental test. By performing a joint
likelihood analysis we confront these models with the most recent observational
data on type Ia supernovae (SNIa), the Cosmic Microwave Background (CMB), the
Baryonic Acoustic Oscillations (BAO) and the high redshift data on the
expansion rate, so as to determine which ones are the most favored by
observations. We compare the optimal relaxation models F^n_m found by this
method with the standard or concordance LambdaCDM model, and find that some of
these models may appear as almost indistinguishable from it. Interestingly
enough, this shows that it is possible to construct viable solutions to the
tough cosmological fine tuning problem with models that display the same basic
phenomenological features as the concordance model.
View original:
http://arxiv.org/abs/1109.4739
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