Spin network of the type used in loop quantum gravity.
In physics, a spin network is a type of diagram that can be used to represent states and interactions between particles and fields. It was devised by Roger Penrose in 1971. Spin networks were applied in physics to the problem of quantum gravity by Lee Smolin, Fotini Markopoulou-Kalamara, and others to reformulate loop quantum gravity and gauge theory.
From a mathematical perspective, a spin network is a graph whose edges are associated with irreducible representations of a compact Lie group, G and whose vertices are associated with equivalent applications of the representations of adjacent edges.
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