On decoding the string from interfaces in 2d conformal field theories
Abstract
General solutions of a gravitational junction between two copies of a three-dimensional Einstein manifold ℳ correspond to the solutions of the non-linear Nambu-Goto equation for a string in ℳ. We show that, for the junctions in three-dimensional anti-de Sitter spacetimes constituted by tensile strings, which are dual to interfaces between thermal states in conformal field theories, the solutions of the Nambu-Goto equation describing the junction correspond to state-dependent wave-packets, which are perfectly reflected at the interface to future null infinity without shape distortion when incident from past null infinity. These wavepackets are realized by state-dependent half-sided conformal transformations and affect the expectation value of the displacement operator. We further show that the entanglement entropy of an interval straddling the interface deciphers the stringy modes of the dual junction even in the tensionless limit. We also demonstrate that the strong sub-additivity of entanglement entropy is satisfied and is saturated for symmetric intervals generally.
Related
- "Massive" Conformal Field Theories and application to Nambu-Goto string
- Unitary quantum conformal Bondi-Metzner-Sachs field theories
- Mutual Information of Measurement in Conformal Field Theories
- Work fluctuation speed limit in boundary conformal field theories
- Background Effects on Thermal Free Energy in Conformal Field Theories
BibTeX
@article{banerjee2026decoding,
title = {{On decoding the string from interfaces in 2d conformal field theories}},
author = {Avik Banerjee and Tanay Kibe and Ayan Mukhopadhyay and Giuseppe Policastro},
journal = {Journal of High Energy Physics},
year = {2026},
month = jul,
doi = {10.1007/jhep07(2026)118},
eprint = {2511.19592},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05409684v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - On decoding the string from interfaces in 2d conformal field theories
AU - Avik Banerjee
AU - Tanay Kibe
AU - Ayan Mukhopadhyay
AU - Giuseppe Policastro
PY - 2026
DA - 2026/07/13
JO - Journal of High Energy Physics
DO - 10.1007/jhep07(2026)118
UR - https://hal.science/hal-05409684v1
AB - General solutions of a gravitational junction between two copies of a three-dimensional Einstein manifold ℳ correspond to the solutions of the non-linear Nambu-Goto equation for a string in ℳ. We show that, for the junctions in three-dimensional anti-de Sitter spacetimes constituted by tensile strings, which are dual to interfaces between thermal states in conformal field theories, the solutions of the Nambu-Goto equation describing the junction correspond to state-dependent wave-packets, which are perfectly reflected at the interface to future null infinity without shape distortion when incident from past null infinity. These wavepackets are realized by state-dependent half-sided conformal transformations and affect the expectation value of the displacement operator. We further show that the entanglement entropy of an interval straddling the interface deciphers the stringy modes of the dual junction even in the tensionless limit. We also demonstrate that the strong sub-additivity of entanglement entropy is satisfied and is saturated for symmetric intervals generally.
SN - 1126-6708
SN - 1029-8479
ER -