Hidden Conformal Invariance of Scalar Effective Field Theories

Abstract

We argue that conformal invariance is a common thread linking scalar effective field theories appearing in the double copy. For a derivatively coupled scalar with a quartic O(p 4 ) vertex, classical conformal invariance dictates an infinite tower of additional interactions that coincide exactly with Dirac-Born-Infeld theory analytically continued to spacetime dimension D = 0. For the case of a quartic O(p 6 ) vertex, classical conformal invariance constrains the theory to be the special Galileon in D = −2 dimensions. We also verify the conformal invariance of these theories by showing that their amplitudes are uniquely fixed by the conformal Ward identities. In these theories conformal invariance is a much more stringent constraint than scale invariance.

Quantum Corrections to Generic Branes: DBI, NLSM, and More

“…Its amplitudes have exceptional soft-limit behavior [6,7,11,13,14,20] and are one of the distinguished theories which arise in double-copy constructions (see [22] for a review). Interesting perspectives on their symmetry properties can be found in [49][50][51] and some phenomenological features are discussed in [21,52]. The DBI literature is vast and the preceding works represent only a select fraction of the whole.…”