Softness and amplitudes’ positivity for spinning particles

By B. Bellazzini. 2016

161 citations recorded by the source corpus.

A bstractWe derive positivity bounds for scattering amplitudes of particles with arbitrary spin using unitarity, analyticity and crossing symmetry. The bounds imply the positivity of certain low-energy coefficients of the effective action that controls the dynamics of the light degrees of freedom. We show that low-energy amplitudes strictly softer than O(p4) do not admit unitary ultraviolet completions unless the theory is free. This enforces a bound on the energy growth of scattering amplitudes in the region of validity of the effective theory. We discuss explicit examples including the Goldstino from spontaneous supersymmetry breaking, and the theory of a spin-1/2 fermion with a shift symmetry.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/75162bae79252cfa04b9409b9fe06988d42800cd

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Nuclear and High Energy Physics

Citations in the corpus

Positive moments for scattering amplitudes (2020, methodology): “We discuss first the forward limit t → 0 in theories where it is finite, and define M(s) ≡ limt→0M(s, t); for concreteness we focus on the spin-0 case, but our results carry over to arbitrary spin and flavour structure [5].”
New positivity bounds from full crossing symmetry (2020, background): “eliminate theories with soft behaviour for scattering amplitudes, i.e. for which the leading few terms in an energy expansion of the low energy amplitude are suppressed relative to naive expectations [15,40{42]. One notable example is the case of theories with weakly broken Galileon symmetries. Gali”
Effective field theory of dark energy: A review (2019, background): “The latter arise from requiring basic principles such as a unitary, causal, local UV completion [216, 217, 218, 219].”
UV complete me: positivity bounds for particles with spin (2017, background): “A discussion of the bounds for spinning particles in the forward scattering limit, which applies to more general polarizations, addressing the nontrivial issues with analyticity and statistics for fermions has been given recently in [9].”