String Theory and the Size of Hadrons

TL;DR

This paper explores the size and structure of hadrons using string theory and AdS/CFT, proposing that hadrons are superpositions of 'fat' strings and analyzing their form factors at high momentum.

Contribution

It introduces a novel perspective that hadrons are superpositions of strings of varying thickness and demonstrates how warped geometries regulate fluctuations, aligning with parton model predictions.

Findings

Hadrons can be modeled as superpositions of 'fat' strings.

Warped geometries suppress infinite zero-point fluctuations.

Large momentum form factors agree with parton model expectations.

Abstract

We begin by outlining the ancient puzzle of off shell currents and infinite size particles in a string theory of hadrons. We then consider the problem from the modern AdS/CFT perspective. We argue that although hadrons should be thought of as ideal thin strings from the 5-dimensional bulk point of view, the 4-dimensional strings are a superposition of "fat" strings of different thickness. We also find that the warped nature of the target geometry provides a mechanism for taming the infinite zero point fluctuations which apparently produce a divergent result for hadronic radii. Finally a calculation of the large momentum behavior of the form factor is given in the limit of strong 't Hooft parameter where the classical gravity limit is appropriate. We find agreement with parton model expectations.