PIRSA:20020061

Entropy Variations and Light Ray Operators from Replica Defects

Chandrasekaran, V. (2020). Entropy Variations and Light Ray Operators from Replica Defects. Perimeter Institute. https://pirsa.org/20020061

Chandrasekaran, Venkatesa. Entropy Variations and Light Ray Operators from Replica Defects. Perimeter Institute, Feb. 18, 2020, https://pirsa.org/20020061 

          @misc{ pirsa_PIRSA:20020061,
            doi = {10.48660/20020061},
            url = {https://pirsa.org/20020061},
            author = {Chandrasekaran, Venkatesa},
            keywords = {Quantum Fields and Strings},
            language = {en},
            title = {Entropy Variations and Light Ray Operators from Replica Defects},
            publisher = {Perimeter Institute},
            year = {2020},
            month = {feb},
            note = {PIRSA:20020061 see, \url{https://pirsa.org}}
          }

Venkatesa Chandrasekaran

University of California, Berkeley

Talk number
PIRSA:20020061
Collection
Talk Type
Subject
Abstract

We study the defect operator product expansion (OPE) of displacement operators in free and interacting conformal field theories using replica methods. We show that as n approaches 1 a contact term can emerge when the OPE contains defect operators of twist d−2. For interacting theories and general states we give evidence that the only possibility is from the defect operator that becomes the stress tensor in the n→1 limit. This implies that the quantum null energy condition (QNEC) is always saturated for CFTs with a twist gap. As a check, we show independently that in a large class of near vacuum states, the second variation of the entanglement entropy is given by a simple correlation function of averaged null energy operators as studied by Hofman and Maldacena. This suggests that sub-leading terms in the the defect OPE are controlled by a defect version of the spin-3 non-local light ray operator and we speculate about the possible origin of such a defect operator. For free theories this contribution condenses to a contact term that leads to violations of QNEC saturation.