Abstract
We study the collision of a highly energetic light closed string off a stack of Dp-branes at (sub)string-scale impact parameters and in a regime justifying a perturbative treatment. Unlike at larger impact parameters - where elastic scattering and/or tidal excitations dominate - here absorption of the closed string by the brane system, with the associated excitation of open strings living on it, becomes important. As a first step, we study this phenomenon at the disk level, in which the energetic closed string turns into a single heavy open string at rest whose particularly simple properties are described.
Highlights
There is a weak-gravity regime in which string-size effects can be neglected and general-relativity expectations are recovered in terms of gravitational deflection and Shapiro time delay
We study the collision of a highly energetic light closed string off a stack of Dp-branes atstring-scale impact parameters and in a regime justifying a perturbative treatment
Unlike at larger impact parameters — where elastic scattering and/or tidal excitations dominate — here absorption of the closed string by the brane system, with the associated excitation of open strings living on it, becomes important. We study this phenomenon at the disk level, in which the energetic closed string turns into a single heavy open string at rest whose simple properties are described
Summary
When a closed string propagates in the presence of a stack of N coincident Dp-branes, the simplest new processes that can occur at leading order in perturbation theory are its scattering (elastic or inelastic) off the Dp-branes and its absorption by the Dp-branes. Elastic and inelastic amplitudes for arbitrary states of the string spectrum become more and more complex as the number of possible contractions between momenta and polarizations increases Their structure drastically simplifies in the Regge limit and, as discussed in [5], it is possible to give a general and explicit formula in terms of the matrix elements of the phase of the eikonal operator [4, 11, 12]. The couplings of the external states to the Reggeon become elementary and all the treelevel scattering amplitudes in the Regge limit can be represented as matrix elements of a very simple operator W (s, q), closely related to the phase δ(s, q) of the eikonal operator These simplifications occur if the null vector required by the DDF construction is chosen proportional to e+. The aim of the three sections will be to find a precise and explicit form for this highly excited open string state
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