Big Bang Nucleosynthesis constraints on higher-order modified gravities

Understand

We use Big Bang Nucleosynthesis (BBN) data in order to impose constraints on higher-order modified gravity, and in particular on: (i) $f(G)$ Gauss-Bonnet gravity, and $f(P)$ cubic gravities, arising respectively through the use of the quadratic-curvature Gauss-Bonnet $G$ term, and the cubic-curvature combination, (ii) string-inspired quadratic Gauss-Bonnet gravity coupled to the dilaton field, (iii) models with string-inspired quartic curvature corrections, and (iv) running vacuum models.

• We perform a detailed investigation of the BBN epoch and we calculate the deviations of the freeze-out temperature $T_f$ in comparison to $\Lambda$CDM paradigm.
• We then use the observational bound on $ \left|\frac{\delta {T}_f}{{T}_f}\right|$ in order to extract constraints on the involved parameters of various models.
• We find that all models can satisfy the BBN constraints and thus they constitute viable cosmological scenarios, since they can additionally account for the dark energy sector and the late-time acceleration, in a quantitative manner, without spoiling the formation of light elements during the BBN epoch.