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Cosmology of a brane radiating gravitons into the extra dimension

David Langlois·Lorenzo Sorbo·Maria Rodriguez-Martinez
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Abstract

We study in a self-consistent way the impact of the emission of bulk gravitons on the (homogeneous) cosmology of a three-brane embedded in a five-dimensional spacetime. In the low energy regime, we recover the well known result that the bulk affects the Friedmann equation only via a radiation-like term $\C/a^4$, called dark or Weyl radiation. By contrast, in the high energy regime, we find that the Weyl parameter $\C$ is no longer constant but instead grows very rapidly as $\C\propto a^4$. As a consequence, the value of $\C$ today is not a free parameter as usually considered but is a fixed number, which, generically, depends only on the number of relativistic degrees of freedom at the high/low energy transition. Our estimated amount of Weyl radiation satisfies the present nucleosynthesis bounds.

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David Langlois, Lorenzo Sorbo, Maria Rodriguez-Martinez. 2002-06-17. Cosmology of a brane radiating gravitons into the extra dimension. https://doi.org/10.1103/physrevlett.89.171301

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