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# string\_theory

## Basic idea

Replaces point particles with one-dimensional "strings" whose vibrational modes give particle properties. Requires 10 (superstring) or 11 (M-theory) spacetime dimensions.

## Key formulas

* Nambu-Goto action: $S = -T \int d^2\sigma, \sqrt{-\det h\_{ab}}$
* Polyakov action: $S = -\dfrac{T}{2}\int d^2\sigma,\sqrt{-h},h^{ab}\partial\_a X^\mu \partial\_b X\_\mu$
* String tension: $T = 1/(2\pi\alpha')$