Holographic BCFT spectra from brane mergers

Abstract

We use holography to study the spectra of boundary conformal field theories (BCFTs). To do so, we consider a 2-dimensional Euclidean BCFT with two circular boundaries that correspond to dynamical end-of-the-world branes in 3-dimensional gravity. Interactions between these branes inform the operator content and the energy spectrum of the dual BCFT. As a proof of concept, we first consider two highly separated branes whose only interaction is taken to be mediated by a scalar field. The holographic computation of the scalar-mediated exchange reproduces a light scalar primary and its global descendants in the closed-string channel of the dual BCFT. We then consider a gravity model with point particles. Here, the interaction of two separated branes corresponds to a heavy operator which lies below the black hole threshold. However, we may also consider branes at finite separation that “merge” non-smoothly. Such brane mergers can be used to describe unitary sub-threshold boundary-condition-changing operators in the open-string spectrum of the BCFT. We also find a new class of sub-threshold Euclidean bra-ket wormhole saddles with a factorization puzzle for closed-string amplitudes.

AdS/BCFT from conformal bootstrap: construction of gravity with branes and particles

“…It is worth noting the relation between the setups in [28,31] and ours. In [28,31], the authors proposed a holographic dual of an open string with distinct boundaries by introducing a corner defect on the end-of-the-world brane. One main difference comes JHEP01(2023)108 from this corner defect.…”

“…We will show that our proposal nicely reproduces a boundary primary two-point function. An alternative proposal has been given in [28,31], which relates a boundary primary correlation to a defect on the end-of-the-world brane. There is also another proposal in [66] in terms of a generalization of the Ryu-Takayanagi formula.…”

“…Recently, this novel correspondence between AdS/BCFT and the island model has brought many insights into quantum gravity to us. Efforts towards this direction include analyses of the island model from the higher dimensional gravity dual [8][9][10][11][12][13][14][15][16][17][18][19][20], attempts to directly relate island models to BCFT [21,22] and explorations of generalized setups [23][24][25][26][27][28][29][30][31].…”

“…In the black hole phase, the branes are disconnected and do not interact with each other[2,3]. Note that if the tension is negative, the branes can still interact[31].…”

AdS/BCFT with brane-localized scalar field

“…This problem was treated in a probe limit in [86] recently. There is another interesting approach to AdS/BCFT with different boundary conditions by introducing a defect on the EOW brane as discussed in [116,117].…”