Gravity as a gapless phase and biform symmetries

TL;DR

The paper develops a framework in which gravity and related gauge theories are understood as gapless phases protected by mixed anomalies of maximal biform symmetries. By systematically gauging higher-biform currents and analyzing their two-point functions via Källén–Lehmann spectral decompositions, the authors show that the nonlocal parts of these correlators are fixed by anomaly structure, guaranteeing massless modes such as the graviton. They instantiate this framework in concrete EFTs, including Galileon superfluids and linearized gravity, where the Einstein action emerges as the universal infrared description, while nonlinear diffeomorphism invariance remains absent in the EFT. The approach provides a symmetry-based organizing principle for low-energy gravity, connects to fracton physics, and suggests avenues for emergent gravity and cosmology, with careful discussion of dimensional peculiarities and potential UV completions.

Abstract

We study effective field theories (EFTs) enjoying (maximal) biform symmetries. These are defined by the presence of a conserved (electric) current that has the symmetries of a Young tableau with two columns of equal length. When these theories also have a topological (magnetic) biform current, its conservation law is anomalous. We go on to show that this mixed anomaly uniquely fixes the two-point function between the electric and magnetic currents. We then perform a Källén-Lehmann spectral decomposition of the current-current correlator, proving that there is a massless mode in the spectrum, whose masslessness is protected by the anomaly. Furthermore, the anomaly gives rise to a universal form of the EFT whose most relevant term, which resembles the linear Einstein action, dominates the infrared physics. As applications of this general formalism, we study the theories of a Galileon superfluid and linearized gravity. Thus, one can view the masslessness of the graviton as being protected by the anomalous biform symmetries. The associated EFT provides an organizing principle for gravity at low energies in terms of physical symmetries, and allows interactions consistent with linearized diffeomorphism invariance. These theories are not ultraviolet-complete, the relevant symmetries can be viewed as emergent, nor do they include the nonlinearities necessary to make them fully diffeomorphism invariant, so there is no contradiction with the expectation that quantum gravity cannot have any global symmetries.

Figures (1)

• Figure 1: The contour deformation used to derive the spectral function. We deform the blue contour centered around $z$ into the green contour that runs along the branch cut with an arc at infinity.