Big-bang nucleosynthesis as a probe of the geometry of superspace

Abstract We study the effect from a general ultralocal supermetric on primordial nucleosynthesis for Friedmann-Robertson-Walker cosmology. The parameter λ of the supermetric changes the effective number of degrees of freedom, g ∗ , which modifies the Friedmann equation. This modification produces variations in the production of primordial 4He. The observations of the primordial abundances of light elements (4He, D, 3He and 7Li) allow to estimate bounds on the values of λ from these observations: we obtain 0.91 ≤ λ ≤ 1.01. This leeway in λ can be used to explain possible incompatibilities in the standard big-bang nucleosynthesis.