Physical Society Colloquium

Interview for Faculty Position

Not Anything Goes: Low-Energy Constraints from High-Energy Physics

Allan Adams

Harvard University

The discovery of an apparent landscape of vacua in string theory has led to the widespread belief that essentially any effective theory of particle physics governed by a local lagrangian can be UV completed into a consistent quantum field or string theory. We demonstrate the fallacy of this assumption by identifying explicit obstructions, deriving from familiar analyticity properties of the S-matrix, to the UV completion of generic effective field theories: the signs of a set of leading irrelevant operators are forced to be strictly positive. This constraint is violated, for example, by the Dvali-Gabadadze-Porrati brane-world model modifying gravity in the IR, giving a simple explanation for the difficulty of embedding this model into controlled stringy backgrounds. This result also predicts that the signs of certain anomalous quartic electroweak gauge boson couplings must be positive. Conversely, any experimental support for the DGP model, or measured negative signs for anomalous quartic gauge boson couplings at future accelerators, would indicate an underlying non-locality unlike anything seen in weakly coupled field theory or string theory.