The High-Energy Behavior of String Scattering Amplitudes

Effects of D instantons

String Lessons for Higher-Spin Interactions

We consider Lorentzian correlators of local operators. In perturbation theory, singularities occur when we can draw a position-space Landau diagram with null lines. In theories with gravity duals, we can also draw Landau diagrams in the bulk. We argue that certain singularities can arise only from bulk diagrams, not from boundary diagrams. As has been previously observed, these singularities are a clear diagnostic of bulk locality. We analyze some properties of these perturbative singularities and discuss their relation to the OPE and the dimensions of double-trace operators. In the exact nonperturbative theory, we expect no singularity at these locations. We prove this statement in 1+1 dimensions by CFT methods.

/pdf/looking-for-a-bulk-point-n50ecwwi2y.pdf

Looking for a bulk point

We extend previous techniques for calculations of transplanckian-energy string-string collisions to the high-energy scattering of massless closed strings from a stack of N Dp-branes in Minkowski spacetime. We show that an effective non-trivial metric emerges from the string scattering amplitudes by comparing them against the semiclassical dynamics of high-energy strings in the extremal p-brane background. By changing the energy, impact parameter and effective open string coupling λ = gN, we are able to explore various interesting regimes and to reproduce classical expectations, including tidal-force excitations, even beyond the leading-eikonal approximation

/pdf/high-energy-string-brane-scattering-leading-eikonal-and-3hewadvtg8.pdf

High-energy string-brane scattering: leading eikonal and beyond

A rigorous derivation is given of the asymptotic properties of the one-loop nonplanar amplitude. Boths- andt-channel asymptotic behaviours are investigated. They are controlled by the expected Regge singularities and possible exponentials are ruled out. Thes-channel fixed-angle behaviour is again an exponential. The coefficient ofs in the exponential is exactly half of that obtained for the Born approximation and the planar loop.

The asymptotic behaviour of the dual pomeron amplitude

The amplitudes for radiative corrections for Ke4 decay (K → ππe∨) are obtained in a general form which is useful for experimental analysis. We give also the correction for the K → 3π and K → πe∨ decays obtained from the general formulae of the Ke4 decay.

B. Morel

Papers

The asymptotic behaviour of the dual pomeron amplitude

Radiative corrections for Ke4 decay