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The infrared triangle is an equivalence relation which is proposed to govern the longwave energy, or infrared, dynamics of all physical theories involving massless particles. The relation was proposed in a series of lectures on soft theorems in quantum field theory, gravitational memory effects, the Bondi–Metzner–Sachs group, non-abelian gauge theory, and gravity related to black holes by Andrew Strominger in 2016. [1]
The relation identifies a single underlying structure that connects infrared behavior in gravity and quantum field theory. It shows that a physical effect, a spacetime symmetry, and a quantum scattering rule are mathematically equivalent, so that understanding any one of them reveals the content of the others. [2]
The three corners of this triangle are:
- memory effects, which is the lasting displacement left in spacetime after a gravitational wave has passed;
- supertranslation symmetries, which are an infinite set of transformations that empty spacetime satisfies; and
- soft particle theorems, which govern the behavior of particles with nearly zero energy.
This implies there may be a measurable memory signal provides evidence for these symmetries and quantum relations, giving a unified view of infrared dynamics and helping to constrain possible theories of quantum gravity. [2]
