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arXiv:2604.10583

The Junction Law for Multipartite Entanglement in Confining Holographic Backgrounds

Norihiro Iizuka, Akihiro Miyata

hep-thgr-qcquant-phSubmitted Apr 12, 2026• Announced Apr 14, 2026
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Abstract

We investigate how the junction law for multipartite entanglement is realized in confining holographic backgrounds, using genuine multi-entropy (GM) as our main diagnostic. We first study an AdS$_3$ hard-wall toy model as an analytic benchmark, where multi-way cuts and junction geometries can be analyzed explicitly. In this setup, we classify the relevant saddles, determine the dominant phases, and show that the genuinely multipartite contribution diagnosed by GM is localized near the junction. We also examine how this structure depends on subsystem sizes, asymmetry, and the confinement scale, including phase transitions between competing saddles. We then move beyond the hard-wall benchmark to smooth confining geometries, focusing on the D4-soliton and D3-soliton backgrounds and formulating the corresponding framework also for the Klebanov--Strassler background. In the smooth-cap examples, we find that the junction picture persists, while the detailed phase structure differs from the hard-wall case: in particular, the hard-wall plateau does not survive, and GM instead decreases monotonically and vanishes at a finite critical scale. We also find that the short-distance behavior is background-dependent, with $\mathrm{GM}^{(3)}\sim L^{-4}$ in the D4-soliton background, $\mathrm{GM}^{(3)}\sim L^{-2}$ in the D3-soliton background, and $\mathrm{GM}^{(3)}\sim L^{-2}\cdot (\log L)^{2}$ in the Klebanov--Strassler background. These results clarify which features of the junction-law picture are robust in confining holography and which features of the phase structure and short-distance scaling are background-dependent.

Comments
61 pages, 24 figures

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Multipartite entanglement measures probe how quantum correlations are organized beyond what can be inferred from pairwise entropies. We study how this structure is reshaped by a physical boundary in a holographic BCFT. The end-of-the-world brane opens new relative-homology channels for multipartite entanglement, allowing connected bulk webs to reorganize and factorize at scales that need not coincide with any ordinary Ryu--Takayanagi transition. In static AdS3_33​/BCFT2_22​, this produces a characteristic hierarchy of multipartite phases and a nontrivial dependence of genuine multi-entropy on the boundary. In the thermofield-double state, genuinely connected webs can instead be supported through the Einstein--Rosen bridge, leading to growth, reconnection and saturation scales distinct from the usual Hartman--Maldacena transitions. These results show that multipartite entanglement is sensitive not only to extremal-surface areas but also to how bulk entanglement structures are allowed to join, split and terminate in the presence of a boundary.
Topological states of matter are characterized by nonlocal structures that are naturally encoded in the quantum entanglement of many-body wavefunctions. Topological semimetals are short-range entangled states at weak coupling and their entanglement structure at strong coupling remains largely unexplored. In this work, we investigate the multipartite entanglement structure of strongly coupled holographic nodal line semimetals. Building on previous studies of entanglement entropy and the holographic c-function, we focus on multipartite entanglement measures, including the conditional mutual information, multi-entropy, and the Markov gap which is based on the entanglement wedge cross section. Our results demonstrate that while these multipartite measures vanish in the long-distance limit l→∞l \to \inftyl→∞, which confirms that the holographic nodal line semimetal remains a short-range entangled state, their large lll scaling behavior remains highly sensitive to the underlying topology. The large lll power-law decay and scaling exponents serve as robust, non-local order parameters that exhibit sharp changes at the quantum critical point. This work establishes multi-partite entanglement as a powerful probe of quantum topological phase transitions in strongly coupled topological systems.
Gapless quantum systems support correlations over arbitrarily long distances, giving rise to power-law long-range entanglement. We investigate long-range entanglement at strong coupling for three-dimensional gapless systems using holography, asking whether multipartite entanglement can exhibit scale-growing behavior and become enhanced at large distances. We show that a broad class of multipartite entanglement quantities share the same leading large-distance scaling exponent determined by the IR geometry. To realize different scaling regimes, we consider hyperscaling-violating IR geometries. Depending on the parameters, long-distance multipartite entanglement can decay, become logarithmic, grow subextensively, or reach a volume law. We also analyze an anisotropic IR geometry AdS3×R2\mathrm{AdS}_{3}\times\mathbb{R}^{2}AdS3​×R2, where long-range multipartite entanglement survives along one direction but becomes short-ranged in the transverse gapped directions. These results show that holographic gapless phases can support rich and enhanced long-range multipartite entanglement, providing a nonlocal characterization of the underlying IR physics.
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