Implications of cosmological perturbations of $$\sqrt{Q}$$ in STEGR

Abstract In this work, the consequences of adding a $$\sqrt{Q}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>Q</mml:mi> </mml:msqrt> </mml:math> term to the simplest functional form in f ( Q ) gravity have been investigated. At the background level, the model describes the cosmological evolution in such a way that the $$\sqrt{Q}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>Q</mml:mi> </mml:msqrt> </mml:math> term is absent, although it appears at the perturbation level. To study the resultant effect, we constrain the model parameter with Planck 18 results and test the strength of the resulting gravitational interaction for different stages of cosmological evolution. Additionally, we compare our result with the big bang nucleosynthesis (BBN) constraint on the Helium abundance.