Speaker
Dimitri Colferai
(FI)
Description
We derive the limiting form of graviton radiation in gravitational scattering at
transplanckian energies ($E \gg M_P$) and small deflection angles. We show that
--- owing to the graviton's spin 2 --- such limiting form unifies the soft- and
Regge- regimes of emission, by covering a broad angular range, from forward
fragmentation to deeply central region. The single-exchange emission amplitudes
have a nice expression in terms of the transformation phases of helicity
amplitudes under rotations. As a result, the multiple-exchange emission
amplitudes can be resummed via an impact parameter $b$-space factorization
theorem that takes into account all coherence effects. We then see the emergence
of an energy spectrum of the emitted radiation which, being tuned on $\hbar/R\sim M_P^2/E \ll M_P$, is reminiscent of Hawking's radiation. Such a spectrum is
much softer than the one naively expected for increasing input energies and
neatly solves a potential energy crisis. Furthermore, by including rescattering
corrections in the (quantum) factorization formula, we are able to recover the
classical limit and to find the corresponding quantum corrections. Perspectives
for the extrapolation of such limiting radiation towards the classical collapse
regime (where $b$ is of the order of the gravitational radius $R$) are also
discussed.
Primary author
Dimitri Colferai
(FI)
Co-authors
Francesco Coradeschi
(INFN)
Prof.
Gabriele Veneziano
(Collège de France and CERN)
Marcello Ciafaloni
(FI)
