The beginning of string theory: a historical sketch

TL;DR

This paper provides a historical overview of the development of string theory, tracing key ideas from Veneziano's initial guess to the determination of critical parameters like dimension and intercept.

Contribution

It offers a detailed historical account of the foundational ideas and milestones that led to the formulation of string theory.

Findings

Identification of the physical spectrum from factorization properties

Determination of the critical dimension as 26

Establishment of the intercept of the Regge trajectory as 1

Abstract

In this note we follow the historical development of the ideas that led to the formulation of String Theory. We start from the inspired guess of Veneziano and its extension to the scattering of $N$ scalar particles, then we describe how the study of its factorization properties allowed to identify the physical spectrum making the string worldsheet manifest and finally we discuss how the critical values of the intercept of the Regge trajectory and of the critical dimension were fixed to 1 and 26.