Quarks, Flux Tubes and String Theory Without Calculus

The theory of strings started as an attempt to describe the forces holding quarks together. Important remnants of that idea survive in the form of the flux tubes of quantum chromodynamics and their description as “strings” in the gauge-string duality. Applications to quark-gluon plasmas have yielded some of the most quantitative comparisons of string theory with experimental data. For example, the friction generated when a string scrapes along a black hole horizon can be used to estimate drag force on quarks in a thermal medium. More recently, related ideas have appeared in a more mathematical context, providing a formulation of classical string dynamics that avoids calculus and does not depend on the continuous structure of spacetime.