  I emphasize analogy between Dp-branes in string theories and solitons in
gauge theories comparing their common properties and showing differences. We
will show that for certain excitations of the string/D3-brane system Neumann
boundary conditions emerge from the Born-Infeld dynamics. The excitations which
are coming down the string with a polarization along a direction parallel to
the brane are almost completely reflected. For the wavelengths much larger than
the string scale only a small fraction of the energy escapes in the form of
dipole radiation. The physical interpretation is that a string attached to the
3-brane manifests itself as an electric charge, and waves on the string cause
the end point of the string to freely oscillate and produce electromagnetic
dipole radiation in the asymptotic outer region. The magnitude of emitted power
is in fact exactly equal to the one given by Thompson formula in ordinary
electrodynamics.
