Jul 5 – 12, 2017
Venice, Italy
Europe/Zurich timezone
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Radiation enhancement and ``temperature'' in the collapse regime of gravitational scattering

Jul 8, 2017, 11:30 AM
Room Welles (Palazzo del Casinò)

Room Welles

Palazzo del Casinò

Parallel Talk Quantum Field and String Theory QFT and string theory


Dimitri Colferai


We generalize the semiclassical treatment of graviton radiation to
gravitational scattering at very large energies $\sqrt{s}\gg m_P$ and finite
scattering angles $\Theta_s$, so as to approach the collapse regime of impact
parameters $b \simeq b_c \sim R\equiv 2G\sqrt{s}$. Our basic tool is the
extension of the recently proposed, unified form of radiation to the string-based ACV
reduced-action model and to its resummed-eikonal exchange. By superimposing
that radiation all-over eikonal scattering, we are able to derive the
corresponding (unitary) coherent-state operator. The resulting graviton
spectrum, tuned on the gravitational radius $R$, fully agrees with previous
calculations for small angles $\Theta_s\ll 1$ but, for sizeable angles
$\Theta_s(b)\leq \Theta_c = O(1)$ acquires an exponential cutoff of the
large $\omega R$ region, due to energy conservation, so as to emit a finite
fraction of the total energy. In the approach-to-collapse regime of
$b\to b_c^+$ we find a radiation enhancement due to large tidal forces, so
that the whole energy is radiated off, with a large multiplicity
$\langle N \rangle \sim Gs \gg 1$ and a well-defined frequency cutoff of order $R^{-1}$.
The latter corresponds to the Hawking temperature for a black hole of mass
notably smaller than $\sqrt{s}$.
I shall also show preliminary results for collisions below the critical impact parameter ($b < b_c$) where a classical collapse is expected, but a quantum-mechanical mechanism can avoid or reduce information loss.

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