Abstract

Bypassing fields, operators and Lagrangians to target directly physical amplitudes advantageously avoids gauge and field-redefinition redundancies. Unitarity and analyticity allow for the construction of on-shell amplitudes, recursively in leg and loop numbers. After decades of developments focusing mostly on renormalisable theories, the associated on-shell amplitude techniques have recently been more extensively applied to effective field theories, including those which parameterise hypothetical heavy physics appearing beyond the standard model. The enumeration of independent operators can be substituted for that of contact-term amplitudes. In a given scattering, the possible kinematic structures can be fully characterised. Unitarity and analyticity allow for the derivation of positivity constraints, for the extraction of anomalous dimensions and of matching coefficients. This talk will cover some of these developments.