  In the DGP model, the graviton is unstable, which leads to a modification of
gravity at cosmological distances. In particular, this leads to the leakage of
gravitational waves from the brane into an extra dimension at large distances
from the source. However, the calculation of the gravitational wave leakage
intensity is a non-trivial task due to the violation of the Huygens principle
in the five-dimensional bulk of the DGP setup. The odd dimension of the bulk
makes it difficult to extract the radiated part of the field. In this paper, we
consider a simplified problem of scalar radiation from a point charge localized
on a brane in the framework of the scalar field analog of the DGP model. In
this model, the scalar field on the brane can be represented as a continuous
spectrum of Kaluza-Klein massive modes. To extract the emitted part of such a
field, we generalize the Rohrlich-Teitelboim approach to radiation to the case
of a massive four-dimensional field, using its connections to massless fields
in four and five dimensions. In the case of a charge moving along a circular
trajectory, we obtain the dependence of the radiation energy flux through a
2-sphere localized on the brane on the sphere radius, which provides the
intensity of leakage of scalar radiation from the brane. Consistent with the
infrared transparency of the bulk, the leakage intensity is found to be higher
for low frequency signals. We are also analyzing the possibility of detecting
this leak by current and future gravitational-wave observatories.
