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arXiv:2511.09714 · Journal of High Energy Physics

Geometry Induced Chiral Transport and Entanglement in $AdS_2$ Background

Kazuki Ikeda, Yaron Oz

hep-thcond-mat.mes-hallhep-phnucl-thquant-phSubmitted Nov 12, 2025• Announced Nov 14, 2025• 2 citations• Revised Nov 23, 2025 (v2)
v1 · Nov 12, 2025v2 · Nov 23, 2025v3 · Feb 17, 2026
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Abstract

We study the real-time chiral dynamics of Dirac fermions in AdS$_2$ and AdS$_2$ black hole backgrounds. The spacetime curvature generates a spin connection term, acting as an effective magnetic field and a position-dependent chiral chemical potential. This leads to strongly asymmetric wave propagation, confined within an inhomogeneous Lieb-Robinson cone. The front velocities decrease with increasing fermion mass and horizon radius. Entanglement growth occurs inside the causal cone, and saturates through a string-breaking mechanism driven by screening excitations. In dipole-dipole scattering, the central bipartite entropy rises when the inward Lieb-Robinson fronts intersect, forming a bright ridge in the local entanglement profile. Charge and current correlators peak at the front arrival, providing a real-time diagnostic of chiral transport. These results establish a causality-respecting framework, linking curvature and horizons to transport and entanglement in (1+1)-dimensional fermionic matter.

Journal reference
J. High Energ. Phys. 2026, 177 (2026)
DOI
10.1007/JHEP04(2026)177
Comments
23 pages, 10 figures

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We study the effect of charged excitations in the AdS spacetime on the first law of entanglement thermodynamics. It is found that `boosted' AdS black holes give rise to a more general form of first law which includes chemical potential and charge density. To obtain this result we have to resort to a second order perturbative calculation of entanglement entropy for small size subsystems. At first order the form of entanglement law remains unchanged even in the presence of charged excitations. But the thermodynamic quantities have to be appropriately `renormalized' at the second order due to the corrections. We work in the perturbative regime where Tthermal≪TET_{thermal}\ll T_ETthermal​≪TE​.
Motivated by the new theoretical paradigm that views space–time geometry as emerging from the entanglement of a pre-geometric theory, we investigate the issue of the signature of the presence of horizons and localized matter on the entanglement entropy (EE) [Formula: see text] for the case of three-dimensional AdS (AdS3) gravity. We use the holographically dual two-dimensional CFT on the torus and the related modular symmetry in order to treat bulk black holes and conical singularities (sourced by pointlike masses not shielded by horizons) on the same footing. In the regime where boundary tori can be approximated by cylinders, we are able to give universal expressions for the EE of black holes and conical singularities. We argue that the presence of horizons/localized matter in the bulk is encoded in the EE in terms of (i) enhancement/reduction of the entanglement of the AdS3 vacuum, (ii) scaling as area/volume of the leading term of the perturbative expansion of [Formula: see text], (iii) exponential/periodic behavior of [Formula: see text] and (iv) presence of unaccessible regions in the noncompact/compact dimension of the boundary cylinder. In particular, we show that the reduction effect of matter on the entanglement of the vacuum found by Verlinde for the de Sitter vacuum extends to the AdS3 vacuum.