engleski

Constraining spacetime noncommutativity with primordial nucleosynthesis

We discuss a constraint on the scale LambdaNC of noncommutative (NC) gauge field theory arising from consideration of the big bang nucleosynthesis of light elements. The propagation of neutrinos in the NC background described by an antisymmetric tensor theta&#181; nu does result in a tree-level vectorlike coupling to photons in a generation-independent manner, raising thus a possibility to have an appreciable contribution of three light right-handed (RH) fields to the energy density of the Universe at nucleosynthesis time. Considering elastic scattering processes of the RH neutrinos off charged plasma constituents at a given cosmological epoch, we obtain for a conservative limit on an effective number of additional doublet neutrinos DeltaNnu=1, a bound LambdaNC>~3 TeV. With a more stringent requirement, DeltaNnu<~0.2, the bound is considerably improved, LambdaNC>~103 TeV. For our bounds the theta expansion of the NC action stays always meaningful, since the decoupling temperature of the RH species is perseveringly much less than the inferred bound for the scale of noncommutativit

spacetime noncommutativity; nucleosynthesis

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