  We explore generalized symmetry in the context of nonlinear dynamical
gravity. Our basic strategy is to transcribe known results from Yang-Mills
theory directly to gravity via the tetrad formalism, which recasts general
relativity as a gauge theory of the local Lorentz group. By analogy, we deduce
that gravity exhibits a one-form symmetry implemented by an operator $U_\alpha$
labeled by a center element $\alpha$ of the Lorentz group and associated with a
certain area measured in Planck units. The corresponding charged line operator
$W_\rho$ is the holonomy in a spin representation $\rho$, which is the
gravitational analog of a Wilson loop. The topological linking of $U_\alpha$
and $W_\rho$ has an elegant physical interpretation from classical gravitation:
the former materializes an exotic chiral cosmic string defect whose quantized
conical deficit angle is measured by the latter. We verify this claim
explicitly in an AdS-Schwarzschild black hole background. Notably, our
conclusions imply that the standard model exhibits a new symmetry of nature at
scales below the lightest neutrino mass. More generally, the absence of global
symmetries in quantum gravity suggests that the gravitational one-form symmetry
is either gauged or explicitly broken. The latter mandates the existence of
fermions. Finally, we comment on generalizations to magnetic higher-form or
higher-group gravitational symmetries.
