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We review and extend some recent results concerning the analysis of spacetimesingularities in four-dimensional higher spin gravity, summarizing how thecoupling of the gravitational field to massless higher spins may provideresolution mechanisms. We elucidate such mechanisms at the level of curvaturesingularities and degenerate metrics in exact as well as linearized solutionsto Vasiliev's equations. As a preamble, we review the underlying higher-spinalgebra and its metaplectic group extensions, after which we detail variousgauge functions encoding the $AdS_4$ vacuum and the non-rotatingBanados--Gomberoff--Martinez (BGM) metric, the four-dimensional lift of thespinless BTZ black hole, in different coordinate patches related by transitionfunctions. We then revisit how, within the unfolded formalism, it is naturalextend the BGM black hole through its causal singularity. Finally, we comparethe metric-like and unfolded descriptions of scalar fluctuations over the(extended) BGM background, showing how the latter description mapssingularities to well-defined metaplectic group elements providing regularvalues for the Weyl zero-form master field, which thus admits continuation overthe full extended BGM spacetime.

Unfolding, higher spins, metaplectic groups and resolution of classical singularities