Gravitational scattering and radiation in the eikonal approach - Emerging Hawking-like radiation in gravitational scattering beyond the Planck scale

We generalize the semiclassical treatment of graviton radiation to
gravitational scattering at very large energies
$E >> m_P$ and finite scattering angles $\Theta_s$, so as to approach the
collapse regime. Our basic tool is the
extension of the recently proposed, unified form of radiation to the
Amati-Ciafaloni-Veneziano reduced-action model.
By resumming eikonal scattering diagrams, we
are able to derive the corresponding (unitary) coherent-state operator.
The resulting graviton spectrum turns out to be tuned on the gravitational
radius $R$ for small angles $\Theta_s << 1$ but, for sizeable
angles $\Theta_s \sim 1$ acquires an exponential cutoff of the large frequency
region ($\omega > 1/R$), due to energy conservation, so as to emit a
finite fraction of the total energy. In the approach-to-collapse regime we
find a radiation enhancement due to large tidal forces, so that
the whole energy is radiated off, with a large multiplicity
$<N> \sim Gs >> 1$ and a well-defined frequency cutoff of order $1/R$. The latter
corresponds to the Hawking temperature for a black hole of mass
somewhat smaller than $E$.