Soft modes, boundary symmetries, and relational entanglement in gauge theories

par Francesco Sartini (Okinawa Institute of Science and Technology)

mercredi 18 mars 2026, 14:00 → 15:30 Europe/Paris

210/1-114 - Salle des Séminaires (IJCLab)

Soft modes and boundary degrees of freedom play an important role in quantum gravity, gauge theory, holography, and scattering amplitudes, yet their treatment in asymptotic regimes and finite subregions is often disconnected. In this talk, I present a framework that connects these perspectives using a relational description. The key idea is to interpret the so-called edge modes as dynamical reference frames built from dynamical fields. This viewpoint separates intrinsic frames from extrinsic ones, describing how a region is embedded in the rest of the system. The extrinsic sector universally extends the phase space through a gauge-invariant corner Goldstone encoding physical symmetries, which correspond to reorientations of the reference frame. Using Maxwell theory as an illustrative example, I will show how this structure links asymptotic and finite region descriptions. At the quantum level, it naturally factorizes the Hilbert space and leads to well-defined, distillable entanglement entropies. In analogy with recent results in perturbative gravity, this framework intrinsically regularizes gauge-theoretic entropies without introducing auxiliary Hilbert spaces. Different choices of reference frame generate a hierarchy of relational operator algebras, providing a unified perspective on soft physics, boundary symmetries, and subsystem information.