Extremal effective field theories

By S. Caron-Huot, Vincent Duong. Journal of High Energy Physics, 2020

168 citations recorded by the source corpus.

Effective field theories (EFT) parameterize the long-distance effects of short-distance dynamics whose details may or may not be known. Previous work showed that EFT coefficients must obey certain positivity constraints if causality and unitarity are satisfied at all scales. We explore those constraints from the perspective of 2 → 2 scattering amplitudes of a light real scalar field, using semi-definite programming to carve out the space of allowed EFT coefficients for a given mass threshold M . We point out that all EFT parameters are bounded both below and above, effectively showing that dimensional analysis scaling is a consequence of causality. This includes the coefficients of s 2 + t 2 + u 2 and stu type interactions. We present simple 2 → 2 extremal amplitudes which realize, or “rule in”, kinks in coefficient space and whose convex hull span a large fraction of the allowed space.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/57b5d572fb5edaa08f7c4321dc6ca3abd340504f

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Citations in the corpus

The EFT-hedron (2020, result): “Bounds involving the combination of positivity away from the forward limit and full permutation invariance was discussed in [9] and [10], which have some overlap with the s-u polytope discussion in subsection 8.”
Sharp boundaries for the swampland (2021, methodology): “The bound can be improved by considering combinations of more functionals, see [10, 36].”