Why is it interesting?

Natural phenomena, when observed with poorer resolution, become simpler. This is simple fact. When we describe the Moon trajectory orbiting around Earth, we can safely approximate both bodies with material points and neglect all the complexity of geography, crystalline structure, chemical composition, and terrestrial biology. This is technically known as the “spherical-cow approximation”, which is a basic tool of effective field theory. The observation that the universe is roughly uniform and isotropic at large scales supports the point of view that simplicity dominates the far IR.

https://arxiv.org/pdf/1710.07663.pdf

Layman

• http://www.preposterousuniverse.com/blog/2013/06/20/how-quantum-field-theory-becomes-effective/

Student

An effective field theory is one where we have factorized information about possibly-but-notnecessarily unknown UV physics from low-energy ‘active’ degrees of freedom. The UV information lives in $C_i$, the Wilson coefficient, which is simply a number—a coupling which generally depends on the scale at which it is probed. The IR information lives in Oi , the effective operator. These are composed of all of the ‘low energy’ excitations that are physically accessible at the scales where the EFT is valid. […] [T]he map sending UV information into $C_i$ is not invertible. [..] The sum over Wilson coefficient should run over all allowed operators, including nonrenormalizable operators. […] [W]e have chosen an energy scale so that physics above that scale goes into the Ci while physics below that scale goes into the Oi. […] By construction, the EFT is only useful (but we’ll see it’s very useful) for answering questions about physics below Λ. […] This scale also serves to balance the dimension of the effective operators Oi so that very non-renormalizable (large dimension) operators are suppressed by large powers of 1/Λ. [..] The UV physics that we factorize into the Wilson coefficients need not be known.

http://www.physics.uci.edu/~tanedo/files/notes/FlavorNotes.pdf

• How to use the Standard Model effective field theory by Brian Henning et. al.

Researcher

Common Question 1

Common Question 2

Examples

Example1

Example2:

History