Lattice QCD and String Theory

TL;DR

This paper reviews the connection between lattice QCD and string theory, focusing on the properties of confining flux tubes, their spectra, and recent results on string excitations and effective string descriptions.

Contribution

It provides a comprehensive review of the string description of confining flux in lattice QCD, including recent findings on spectra and the role of effective string theories.

Findings

Lattice string spectra align with universal effective string predictions.

Casimir energy and excitation spectra have been analyzed in the Dirichlet string limit.

Higher derivative operators encode flux stiffness and massive modes, posing challenges for lattice studies.

Abstract

Bosonic string formation in gauge theories is reviewed with particular attention to the confining flux in lattice QCD and its string theory description. Recent results on the Casimir energy of the ground state and the string excitation spectrum are analyzed in the Dirichlet string limit of large separation between static sources. The closed string-soliton (torelon) with electric flux winding around a compact dimension and the three-string with a Y-junction created by three static sources are also reviewed. It is shown that string spectra from lattice simulations are consistent with universal predictions of the leading operators from the derivative expansion of a Poincare invariant effective string Lagrangian with reparameterization symmetry. Important characterisitics of the confining flux, like stiffness and the related massive breather modes, are coded in operators with higher derivatives and their determination remains a difficult challenge for lattice gauge theory.