Improved BBN constraints on the variation of the gravitational constant

Abstract

Big Bang Nucleosynthesis (BBN) is very sensitive to the cosmological expansion rate. If the gravitational constant G took a different value during the nucleosynthesis epoch than today, the primordial abundances of light elements would be affected. In this work, we improve the bounds on this variation using recent determinations of the primordial element abundances, updated nuclear and weak reaction rates and observations of the Cosmic Microwave Background (CMB). When combining the measured abundances and the baryon density from CMB observations by Planck, we find GBBN/G0 = 1.02 +0.03 −0.03 at 2σ confidence level. If the variation of G is linear in time, we finḋ G/G0 = −1.4 +2.2 −2.3 × 10 −12 yr −1 , again at 2σ. These bounds are significantly stronger than those from previous primordial nucleosynthesis studies, and are comparable and complementary to CMB, stellar, solar system, lunar laser ranging, pulsar timing and gravitational wave constraints.

The First Three Seconds: a Review of Possible Expansion Histories of the Early Universe

“…However, modified gravity theories can also modify the expansion history of the early Universe. In this context, BBN has been used to constrain, for example, large extra dimensions [727,728], the value of Newton's constant during nucleosynthesis [729,730,731], and scalar-tensor theories of gravity [732,733,734].…”

Constraints on Newton’s constant from cosmological observations

“…In the laboratory, cold atom interferometry is also used to detect Newton's constant [1]. In cosmology, the cosmic microwave background (CMB) [2][3][4][5][6][7], big bang nucleosynthesis (BBN) [8][9][10], type Ia supernovae (SNIa) [11][12][13][14][15] and gravitational waves [14,16] can provide different measurements of Newton's constant at corresponding epochs of our universe. Obviously, there is a problem whether Newton's constant is always a constant really or not.…”

Dark energy, extra dimensions, and the Swampland

“…Since then, the observational limits on secular variation have improved to G BBN G = 0.98 ± 0.06 (4.9) at the 95% confidence level [29], and the observational limits on instantaneous variation of G today have been reduced by roughly two orders of magnitude due to improvements in the ephemeris of Mars together with improved data and modeling of the effects of the asteroid belt [30] where H 0 = 100h and h ≈ 0.7 according to current measurements [14]. The curves labeled ± √ F correspond to the NEC violating boundaries; that is, ζ-trajectories that cross these curves must violate the null energy conditions in addition to having time-varying G and timevarying extra-dimensions.…”