Weyl Invariance and the Origins of Mass

Understand

By a uniform and simple Weyl invariant coupling of scale and matter fields, we construct theories that unify massless, massive, and partially massless excitations.

• Masses are related to tractor Weyl weights, and Breitenlohner-Freedman stability bounds in anti de Sitter amount to reality of these weights.
• The method relies on tractor calculus -- mathematical machinery allowing Weyl invariance to be kept manifest at all stages.
• The equivalence between tractor and higher spin systems with arbitrary spins and masses is also considered.