Primordial Cosmology of an Emergent-like Universe from Modified Gravity: Reconstruction and Phenomenology Optimization with a Genetic Algorithm

Understand

In this work we consider the realization of a variant emergent Universe scenario in the context of $f(R)$ gravity.

• We use well-known reconstruction techniques existing in the literature, and we find the approximate form of the vacuum $f(R)$ that reproduces the specific variant emergent Universe scale factor in the large curvature approximation.
• As we show, in the variant emergent Universe scenario, the Hubble horizon shrinks primordially and the Universe undergoes in an accelerated expansion era.
• In a perturbation theory approach, the scalar and tensor curvature perturbations can be expressed in terms of the phenomenological indices $\epsilon_i , i=1,3,4$, usually used for inflationary phenomenology, and we extract the spectral indices for the scalar and tensor perturbations, along with the tensor-to-scalar ratio expressed in terms of the perturbation indices.