Constraints on parameters of models with extra dimension from primordial
  nucleosynthesis
  5D models with one 3D brane and one infinite extra dimension are studied.
Matter is confined to the brane, gravity extends to the bulk. Models with
positive and negative tension of the brane are studied. Cosmological solutions
on the brane are obtained by solving the generalized Friedmann equation. As the
input in cosmological solutions we use the present-time observational
cosmological parameters. We find constraints on dimensionless combinations of
scales of 5D models which follow from the requirement that the models reproduce
the data on production of ${}^4 He$ in primordial nucleosynthesis.
