Speaker
Eva Silverstein
(Stanford University)
Description
We analyze a tree-level six point scattering process in
which two strings
are separated longitudinally such that they could only
interact directly via a non-local spreading effect such as
that predicted by light cone gauge calculations and the
Gross-Mende saddle point.
One string, the `detector', is produced at a finite time
with energy $E$ by an auxiliary $2\to 2$ sub-process, with
kinematics such that it has sufficient resolution to detect
the longitudinal spreading of an additional incoming string,
the `source'.
We test this hypothesis in a gauge-invariant S-matrix
calculation convolved with an appropriate wavepacket,
discussing several interesting subtleties in the calculation
and interpretation.
The amplitude exhibits support spread over the predicted
large longitudinal separation $\sim\alpha' E$ between the
central trajectories of the strings, simulating a comparable
interaction between time-translated horizon infallers.
This effect results from the inherent UV softness of string
amplitudes, in sharp contrast to tree-level quantum field
theory in a similar kinematic regime.
