String theory

A framework in which fundamental particles are modeled as tiny one-dimensional strings whose vibrational states correspond to different particles. It seeks a quantum description that includes gravity.

Worldsheet: The two-dimensional surface traced by a string as it moves through spacetime. String dynamics are described by a theory living on this surface.
Quantum field theory: A framework describing particles and forces as quantized fields in spacetime. String theory extends the particle-based language of quantum fields with vibrating strings.
Dual resonance model: A mathematical model of hadron scattering that became an early form of string theory. String theory originated in this model before its role in particle physics was recognized.
Loop quantum gravity: A research program that quantizes spacetime geometry without starting from strings. It pursues quantum gravity through a different route and does not require string theory’s extra dimensions.
String tension: The energy per unit length of a string, setting the scale of its excitations. It determines the energy scale at which string vibrations become physically significant.
General relativity: Einstein’s theory describing gravity as the curvature of spacetime caused by matter and energy. String theory aims to reproduce general relativity at suitable scales.
Gabriele Veneziano: Theoretical physicist whose 1968 scattering amplitude helped launch the dual resonance model. His amplitude supplied the model’s influential starting point.
Asymptotic safety: A proposed ultraviolet completion of gravity based on a nontrivial renormalization-group fixed point. It seeks a consistent quantum theory of gravity using quantum fields rather than fundamental strings.
Extra dimensions: Spatial dimensions beyond the three familiar large dimensions of everyday experience. Many consistent string models require additional spatial dimensions.
Quantum gravity: The research program seeking a quantum theory that includes gravitational phenomena. String theory is one proposed framework for quantum gravity.

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