Graviton emission from the brane in the bulk in a model with extra
  dimension
  In a model of 3-brane embedded in 5D space-time we calculate the graviton
emission from the brane to the bulk. Matter is confined to the brane, gravitons
produced in reactions of matter on the brane escape to the bulk. The Einstein
equations which are modified by the terms due to graviton production are solved
perturbatively, the leading order being that without the graviton production.
In the period of late cosmology, in which in the generalized Friedmann equation
the term linear in the energy density of matter in dominant, we calculate the
spectrum of gravitons (of the tower of Kaluza-Klein states) and the collision
integral in the Boltzmann equation. We find the energy-momentum tensor of the
emitted gravitons in the bulk, and using it show that corrections due to
graviton production to the leading-order terms in the Einstein equations are
small, and the perturbative approach is justified. We calculate the difference
of abundances of ${}^4 He$ produced in primordial nucleosynthesis in the models
with and without the graviton production, and find that the difference is a
very small number, much smaller than that estimated previously.
