String Fluctuations, AdS/CFT and the Soft Pomeron Intercept

TL;DR

This paper investigates how quadratic string worldsheet fluctuations affect high energy scattering amplitudes in a confining gauge theory via AdS/CFT, revealing a shift in the Pomeron intercept close to experimental observations.

Contribution

It calculates the correction to the Pomeron intercept from string fluctuations, showing a coupling-independent shift proportional to transverse dimensions, aligning with experimental data.

Findings

Intercept shift of approximately 0.073 for 7 transverse dimensions

Intercept shift of approximately 0.083 for 8 transverse dimensions

Close agreement with the observed soft Pomeron intercept of 0.08

Abstract

We study high energy scattering amplitudes in a strongly coupled (confining) gauge theory using the AdS/CFT correspondence. The scattering described by a Wilson line/loop correlation function was shown earlier to correspond to minimal surfaces of the helicoid type, and gave amplitudes with unit intercept and linear trajectory. In this paper we find the correction to the intercept from quadratic fluctuations of the string worldsheet around the helicoid. The relevant term comes from analytical continuation of a L\"uscher like term. It is coupling-constant independent and proportional to the number of effective transverse flat dimensions. The shift of the intercept, under our assumptions, is $n_\perp /96$, and for $n_\perp=7,8$ gives respectively 0.0729, 0.083. Incidentally we note that this is surprisingly close to the observed value of 0.08.