Anderson localisation in spatially structured random graphs
Pith reviewed 2026-05-16 18:34 UTC · model grok-4.3
The pith
Anderson localization vanishes beyond a critical hopping range on spatially structured graphs even at arbitrarily strong disorder.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Models are constructed by embedding a random regular graph into a complete graph and letting hopping decay exponentially with graph distance, effectively realizing power-law-like hopping generalizations of the Anderson model. Numerical and analytical results show that increasing the hopping range shifts the localization transition to stronger disorder; beyond a critical range the localized phase ceases to exist at any disorder strength. A direct Anderson transition occurs between delocalized and localized phases with no evidence for an intervening multifractal phase in both deterministic and random hopping cases, accompanied by Kosterlitz-Thouless-like scaling of inverse participation ratios
What carries the argument
Distance-dependent exponential hopping on embedded random regular graphs, diagnosed through inverse participation ratios and renormalized perturbation theory.
If this is right
- The localization transition moves to stronger disorder with increasing hopping range.
- Beyond the critical range no localized phase exists at any disorder strength.
- The transition is direct with no multifractal intermediate phase for both deterministic and random hopping.
- Inverse participation ratio scaling follows Kosterlitz-Thouless-like two-parameter behavior.
- Average and typical correlation functions exhibit distinct critical scaling.
Where Pith is reading between the lines
- Similar range-dependent suppression of localization may appear in other high-dimensional or long-range interacting disordered systems.
- The absence of a multifractal regime could be checked by examining higher moments of wave-function distributions in larger-scale simulations.
- The two-parameter scaling form suggests possible connections to surface or boundary criticality in related models.
- Experimental platforms with tunable long-range couplings, such as trapped ions or Rydberg arrays, could test the predicted critical range.
Load-bearing premise
Finite-size exact diagonalization on finite graphs extrapolates reliably to the thermodynamic limit on infinite graphs without missing subtle phases or artifacts.
What would settle it
Observation of a localized phase persisting at arbitrarily strong disorder for hopping ranges larger than the reported critical value, in the limit of increasing system size.
Figures
read the original abstract
We study Anderson localisation on high-dimensional graphs with spatial structure induced by long-ranged but distance-dependent hopping. To this end, we introduce a class of models that interpolate between the short-range Anderson model on a random regular graph and fully connected models with statistically uniform hopping, by embedding a random regular graph into a complete graph and allowing hopping amplitudes to decay exponentially with graph distance. The competition between the exponentially growing number of neighbours with graph distance and the exponentially decaying hopping amplitude positions our models effectively as power-law hopping generalisation of the Anderson model on random regular graphs. Using a combination of numerical exact diagonalisation and analytical renormalised perturbation theory, we establish the resulting localisation phase diagram emerging from the interplay of the lengthscale associated to the hopping range and the onsite disorder strength. We find that increasing the hopping range shifts the localisation transition to stronger disorder, and that beyond a critical range the localised phase ceases to exist even at arbitrarily strong disorder. Our results indicate a direct Anderson transition between delocalised and localised phases, with no evidence for an intervening multifractal phase, for both deterministic and random hopping models. A scaling analysis based on inverse participation ratios reveals behaviour consistent with a Kosterlitz-Thouless-like transition with two-parameter scaling, in line with Anderson transitions on high-dimensional graphs. We also observe distinct critical behaviour in average and typical correlation functions, reflecting the different scaling properties of generalised inverse participation ratios.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper introduces a family of Anderson models on random regular graphs embedded in complete graphs, with hopping amplitudes decaying exponentially with graph distance. This interpolates between short-range RRG Anderson models and fully connected limits. Using exact diagonalization and renormalized perturbation theory, the authors map the localization phase diagram as a function of hopping decay length and disorder strength W. They claim that beyond a critical hopping range the localized phase is absent even at arbitrarily large W, that the transition is direct between delocalized and localized phases with no intervening multifractal regime, and that inverse-participation-ratio scaling is consistent with Kosterlitz-Thouless-like two-parameter scaling.
Significance. If the central claims survive scrutiny, the work would be significant for clarifying the role of spatial structure in high-dimensional localization problems. It provides a concrete interpolation between known limits, reports a critical hopping range that eliminates the localized phase, and identifies KT-like scaling together with distinct average/typical correlation behavior. The combination of numerical exact diagonalization and analytical renormalized perturbation theory is a strength, as is the focus on falsifiable predictions for the phase boundary.
major comments (2)
- [Numerical results and scaling analysis] The headline claim that the localized phase disappears beyond a critical hopping range even at arbitrarily strong disorder rests on finite-N exact diagonalization. No system sizes, range of N, functional form of the finite-size collapse, or explicit check that typical IPR remains O(1) (rather than drifting to zero) at fixed large W are reported. Given that effective coordination grows exponentially with distance on these graphs, the Thouless length can exceed the simulated diameter, making delocalization appear as an artifact rather than a thermodynamic-limit result. This directly affects the central phase-diagram conclusion.
- [Phase diagram and critical behavior] The assertion of a direct Anderson transition with no intervening multifractal phase is supported only by the absence of certain IPR scaling signatures. However, the manuscript does not present a systematic scan of generalized IPR exponents or participation-ratio distributions across the claimed critical line to rule out a narrow multifractal window, especially near the reported critical hopping range.
minor comments (2)
- [Scaling analysis] The abstract and main text refer to 'KT-like two-parameter scaling' but do not specify the two scaling variables or show the corresponding data collapse explicitly.
- [Methods] Error bars, convergence checks with respect to disorder realizations, and the precise definition of the renormalized perturbation theory cutoff are not provided.
Simulated Author's Rebuttal
We thank the referee for the careful reading and constructive comments on our manuscript. We address the major points below and will incorporate revisions to strengthen the presentation of our numerical and scaling results.
read point-by-point responses
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Referee: [Numerical results and scaling analysis] The headline claim that the localized phase disappears beyond a critical hopping range even at arbitrarily strong disorder rests on finite-N exact diagonalization. No system sizes, range of N, functional form of the finite-size collapse, or explicit check that typical IPR remains O(1) (rather than drifting to zero) at fixed large W are reported. Given that effective coordination grows exponentially with distance on these graphs, the Thouless length can exceed the simulated diameter, making delocalization appear as an artifact rather than a thermodynamic-limit result. This directly affects the central phase-diagram conclusion.
Authors: We agree that additional details on the numerical implementation are needed for full clarity. In the revised manuscript we will explicitly report the system sizes employed in exact diagonalization, the range of N, the functional form used for finite-size scaling collapse of the IPR, and direct plots confirming that the typical IPR saturates to a nonzero value at fixed large W for hopping ranges above the critical value. On the Thouless-length concern, the renormalized perturbation theory supplies an independent thermodynamic-limit argument showing that the effective coordination and hopping range eliminate the localized phase beyond the critical range; the numerical data remain consistent with this prediction, and we will add an estimate of the Thouless length relative to graph diameter to address possible finite-size artifacts. revision: yes
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Referee: [Phase diagram and critical behavior] The assertion of a direct Anderson transition with no intervening multifractal phase is supported only by the absence of certain IPR scaling signatures. However, the manuscript does not present a systematic scan of generalized IPR exponents or participation-ratio distributions across the claimed critical line to rule out a narrow multifractal window, especially near the reported critical hopping range.
Authors: We acknowledge that a more exhaustive check would strengthen the claim. While the existing IPR scaling and participation-ratio distributions show no multifractal signatures, we will add in the revision a systematic scan of generalized IPR exponents (D_q for several q) and participation-ratio distributions evaluated along the critical line for multiple hopping ranges, including near the reported critical value. This additional analysis, together with the renormalized perturbation theory, will help confirm the absence of an intervening multifractal window. revision: yes
Circularity Check
No circularity: independent numerical and analytical checks on graph-defined model
full rationale
The derivation combines exact diagonalization on finite graphs with renormalized perturbation theory applied to the same distance-dependent hopping model. Model parameters and graph embedding are introduced directly from the construction without any fitted quantity being relabeled as a prediction. No self-citation is load-bearing for the central claim of a direct Anderson transition beyond a critical range; the numerical spectra serve as an external benchmark. The KT-like scaling analysis is presented as consistency check rather than a derived necessity. The result remains falsifiable by larger-system simulations or alternative methods.
Axiom & Free-Parameter Ledger
free parameters (2)
- hopping decay length
- disorder strength W
axioms (2)
- domain assumption Random regular graphs admit a well-defined graph distance when embedded in a complete graph.
- domain assumption Renormalised perturbation theory is applicable to the localisation problem on these graphs.
Lean theorems connected to this paper
-
IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
We study Anderson localisation on high-dimensional graphs with spatial structure induced by long-ranged but distance-dependent hopping... using a combination of numerical exact diagonalisation and analytical renormalised perturbation theory
-
IndisputableMonolith/Foundation/AlexanderDuality.leanalexander_duality_circle_linking unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
A scaling analysis based on inverse participation ratios reveals behaviour consistent with a Kosterlitz–Thouless-like transition with two-parameter scaling
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Forward citations
Cited by 1 Pith paper
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Anderson Localization on Husimi Trees and its implications for Many-Body localization
Local loops on Husimi trees reduce the critical disorder for Anderson localization and increase the spatial extent of localized eigenstates, providing a better single-particle analogy for many-body localization.
Reference graph
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Phase diagram We start with the mean level-spacing ratio, defined in Eq. 5, representative results for which are shown in Fig. 3. 2 4 6 8 10 12 W 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 ξ Delocalised Localised SCMF ⟨r⟩ 0.0 0.2 0.4 0.6 0.8 1.0 τ2 FIG. 2. Phase diagram of the ExpRRG model obtained nu- merically from ED in theW-ξplane. The heatmap shows...
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discussion (0)
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