New models and Big Bang Nucleosynthesis constraints in $f(Q)$ gravity

Understand

The $f(Q)$ theories of modified gravity arise from the consideration of non-metricity as the basic geometric quantity, and have been proven to be very efficient in describing the late-time Universe.

• We use the Big Bang Nucleosynthesis (BBN) formalism and observations in order to extract constraints on various classes of f(Q) models.
• In particular, we calculate the deviations that f(Q) terms bring on the freeze-out temperature in comparison to that of the standard $\Lambda CDM$ evolution, and then we impose the observational bound on $ |\frac{\delta {T}_f}{{T}_f}|$ to extract constraints on the involved parameters of the considered models.
• Concerning the polynomial model, we show that the exponent parameter should be negative, while for the power-exponential model and the new hyperbolic tangent - power model we find that they pass the BBN constraints trivially.