Near-horizon modifications in finite $N$ holography

Abstract

If one extends the AdS/CFT extrapolate dictionary to large but finite $N$, we are expected to obtain non-perturbative violations of bulk micro-causality. Previously this was achieved by implementing a late boundary time cut-off, while smearing the boundary operator via the HKLL kernel. By performing explicit bulk reconstructions in the backgrounds of near-horizon modified AdS$_2$ and BTZ black holes, we recover the same non-locality estimates as above. For these black hole mimickers, the near-horizon modification is controlled by a throat parameter which sets the scale of this non-locality. In three bulk dimensions, probe dynamics also exhibits a dip-ramp-plateau structure in their spectral form factor when averaged over the throat parameter. Such structure has also been found recently in the background with a stretched horizon or a brick wall.