  We explore possible manifestations of an odd number of extra dimensions in
gravitational radiation, which are associated with violation of Huygens'
principle in flat odd-dimensional spacetime. Our setup can be regarded as the
limit of an infinite compactification radius in ADD model and is not viable as
realistic cosmology, but it still may be useful as a simple analytically
solvable model catching certain features of more realistic scenarios. The model
consists of two point masses moving inside a flat three-dimensional brane,
embedded in a five-dimensional Minkowski space and interacting only through a
massless scalar field localized on the same brane, while gravitational
radiation is emitted into the bulk. This setup avoids the difficulties
associated with taking into account the gravitational stresses binding the
system, which require the cubic terms in the perturbative gravitational
Lagrangian, and permits to limit ourselves to linearized theory. We calculate
radiation in a linearized five-dimensional gravity generalizing the
Rohrlich-Teitelboim approach to extract the emitted part of the retarded
gravitational field. The source term consists of a local contribution from
point particles and a non-local contribution from scalar field stresses, which
is calculated using the DIRE approach to post-Newtonian expansions. In the
nonrelativistic limit, we find an analog of the quadrupole formula containing
an integral over the history of the particles' motion preceding the retarded
time. We also show that, for an observer on the brane, the radiation contains a
third polarization: the breathing mode.
