2 research outputs found
The Accelerated expansion of the Universe as a crossover phenomenon
We show that the accelerated expansion of the Universe can be viewed as a
crossover phenomenon where the Newton constant and the Cosmological constant
are actually scaling operators, dynamically evolving in the attraction basin of
a non-Gaussian infrared fixed point, whose existence has been recently
discussed. By linearization of the renormalized flow it is possible to evaluate
the critical exponents, and it turns out that the approach to the fixed point
is ruled by a marginal and a relevant direction. A smooth transition between
the standard Friedmann--Lemaitre--Robertson--Walker (FLRW) cosmology and the
observed accelerated expansion is then obtained, so that at late times.Comment: 12 pages, latex, use bibtex. In the final version, the presentation
has been improved, and new references have been adde
Noether symmetry approach in pure gravity with variable G and Lambda
We find exact cosmological solutions when the Newton parameter and the
cosmological term are dynamically evolving in a renormalization-group improved
Hamiltonian approach. In our derivation we use the Noether symmetry approach,
leading to an interesting variable transformation which yields exact and
general integration of the cosmological equations. The functional dependence of
Lambda on G is determined by the method itself, therefore generalizing previous
results on symmetry principles in cosmology. We find new functional relations
between Lambda and G, jointly with power-law inflation for pure gravity.Comment: 18 pages, 2 figures. In the final version, physical interpretation
and presentation have been improved in all section