# Bulk cone singularity In AdS/CFT, when two points are related by a bulk null geodesic but not null related on the boundary, there is a singularity in the correlator. ## Refs - [[2006#Hubeny, Liu, Rangamani]] - [[2023#Dodelson, Iossa, Karlsson, Lupsasca, Zhiboedov]]: on black hole background (photon sphere is important) ## Remarks - for 4-pt functions or higher, there could be a [[0128 Bulk point singularity|bulk point singularity]] ## Resolving the singularity - in 2d CFT [[2015#Maldacena, Simmons-Duffin, Zhiboedov]] - Gross-Gende effect - [[2015#Maldacena, Simmons-Duffin, Zhiboedov]] - [[DodelsonOoguri2019]] - [[2020#Dodelson, Ooguri]]: resolving the singularity in thermal 2-pt function by worldsheet particle production