ИСТИНА

We consider the classical bremsstrahlung of an ultrarelativistic point-like particle on the wide range of potentials, generated by the free Nambu-Goto objects. Making use of the perturbation theory, we derive the radiation amplitudes of the integer-spin fields (scalar, vector and linearized gravity). The structure of radiation amplitudes is shown to explicitly depend upon the kind of interaction: whether it is gravitational or not. Finally, we compute or estimate the emitted energy during the collision. For the gravitational bremsstrahlung we also consider the special massless-limit case with finite energy. The collision of two point-like masses is of the special interest. The angular and frequency characteristics of the gravitational radiation, emitted in collisions of massless particles, are studied perturbatively in the context of classical General Relativity for small values of the deflection angle. The particles are described with their trajectories, while the contribution of the leading nonlinear terms of the gravitational action is also taken into account. The old quantum results are reproduced in the zero-frequency limit. The validity of classical consideration and is discussed. The results are analyzed in the context of co-dimensionality of the Nambu-Goto object with respect to the total number of spacetime's dimensions.