The Pomeron and Gauge/String Duality

TL;DR

This work presents a unified gauge/string duality framework for high-energy Pomeron exchange in large-$N$ QCD-like theories. By analyzing string scattering on curved backgrounds, it derives a single Pomeron kernel that simultaneously captures both the hard (BFKL) and soft (Regge) regimes as diffusion along holographic coordinates, with an intercept $j_0=2-rac{2}{ ext{√λ}}$ at strong coupling and a model-dependent extension to running couplings. The authors connect Regge trajectories at positive $t$ to the confined hadron spectrum and show how running coupling converts the leading cut into a tower of poles, providing a coherent picture across UV conformal, confining, and running-coupling cases. The framework offers a tractable, all-$t$ description of single-Pomeron exchange and lays groundwork for incorporating confinement, diffusion, and unitarization in a controlled holographic setting with potential QCD phenomenology.

Abstract

The traditional description of high-energy small-angle scattering in QCD has two components -- a soft Pomeron Regge pole for the tensor glueball, and a hard BFKL Pomeron in leading order at weak coupling. On the basis of gauge/string duality, we present a coherent treatment of the Pomeron. In large-N QCD-like theories, we use curved-space string-theory to describe simultaneously both the BFKL regime and the classic Regge regime. The problem reduces to finding the spectrum of a single j-plane Schrodinger operator. For ultraviolet-conformal theories, the spectrum exhibits a set of Regge trajectories at positive t, and a leading j-plane cut for negative t, the cross-over point being model-dependent. For theories with logarithmically-running couplings, one instead finds a discrete spectrum of poles at all t, where the Regge trajectories at positive t continuously become a set of slowly-varying and closely-spaced poles at negative t. Our results agree with expectations for the BFKL Pomeron at negative t, and with the expected glueball spectrum at positive t, but provide a framework in which they are unified. Effects beyond the single Pomeron exchange are briefly discussed.