Accumulation-point amplitudes in string theory

We point out some common qualitative features of the Coon amplitude - a family of deformations of the Veneziano amplitude with logarithmic Regge trajectories - and the open string scattering amplitude for strings ending on a D-brane in AdS. Both reduce to the Veneziano amplitude at relatively low energies. Both systems have an accumulation point in their spectrum, with an infinite number of states below a certain energy. The approach to this point is very similar. Both have the same high-energy fixed-angle behavior. Nevertheless, we find some differences in the spectrum of states with highest angular momentum. These similarities suggest that there may exist a string background that realizes the Coon amplitude.

Automated summary

This paper compares the Coon amplitude with the open string scattering amplitude for strings ending on a D-brane in AdS, and finds several common features in their spectrum and high-energy behavior. These similarities suggest the existence of a string background that can realize the Coon amplitude.