Axio-Chameleons: A Novel String-Friendly Multi-field Screening Mechanism

Understand

Scalar-tensor theories with the shift symmetries required by light scalars are well-explored modifications to GR.

• For these, two-derivative scalar self-interactions usually dominate at low energies and interestingly compete with the two-derivative metric interactions of GR itself.
• Although much effort has been invested in single scalars (on grounds of simplicity) these happen to have no two-derivative interactions, requiring such models to explore higher-derivative interactions (that usually would be less important at low-energies).
• This suggests multiple-scalar sigma models as well-motivated candidates for finding new phenomena in tests of gravity.