Halting eternal acceleration with an effective negative cosmological constant

Understand

In order to solve the problem of eternal acceleration, a model has been recently proposed including both a negative cosmological constant $\Lambda$ and a scalar field evolving under the action of an exponential potential.

• We further explore this model by contrasting it against the Hubble diagram of Type Ia supernovae, the gas mass fraction in galaxy clusters and the acoustic peak and shift parameters.
• It turns out that the model is able to fit quite well this large dataset so that we conclude that a negative $\Lambda$ is indeed allowed and could represent a viable mechanism to halt eternal acceleration.
• In order to avoid problems with theoretical motivations for both a negative $\Lambda$ term and the scalar field, we reconstruct the gravity Lagrangian $f(R)$ of a fourth order theory of gravity predicting the same dynamics (scale factor and Hubble parameter) as the starting model.