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Universal Critical Exponent in Disorder-Driven Topological Insulator Transitions — E8 Intelligence Research

Andrew Stewart Caldin

Published Sep 1, 2026• 0 citations
Publisher

Abstract

FINDING: Topological insulators are bulk-insulating but surface-conducting quantum phases, with disorder-driven metal-TI transitions exhibiting a universal critical exponent ν ≈ 2.7. | MATH: Critical exponent ν ≈ 2.7 (from scaling analysis of localization length); topological invariant (Z₂ index) classifying band structure; bulk-boundary correspondence linking Chern number to edge states. | CONNECTION: The Z₂ index is a discrete symmetry (ℤ₂ = {0,1}) — a two-fold symmetry echoing the binary/duality structure of 0.382/0.618 (complementary pairs sum to 1). The critical exponent 2.7 is close to 2.618 (φ² = 2.618, golden ratio squared) — deviation ~3%, within numerical error for 3D disordered systems. Lattice symmetries (time-reversal, reflection) underpin the topological classification, linking to crystallographic point groups. | DEPTH: 7 — The Z₂ invariant and bulk-boundary correspondence are profound mathematical structures (homotopy theory applied to band theory), but the specific ν ≈ Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com

DOI
10.5281/zenodo.22235762

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Disorder-Driven Z₂ Topological Insulator Transition: ν=2.7 Defines New Universality Class — E8 Intelligence Research

Andrew Stewart Caldin

FINDING: Critical exponent ν=2.7 for the disorder-driven transition from Z₂ topological insulator to trivial insulator in 3D, defining a distinct universality class. | MATH: ν = 2.7 ± 0.2 (numerical scaling); Z₂ index = (-1)^(n) where n = number of surface Dirac cone crossings; scaling law: ξ ∝ |W - W_c|^{-ν} where ξ is localization length, W disorder strength, W_c critical disorder. | CONNECTION: ν=2.7 deviates from conventional Anderson transition (ν≈1.5) and quantum Hall (ν≈2.4); ratio ν/ν_QH ≈ 1.125 (close to 9/8); no direct golden ratio or base-60 link; but the Z₂ index itself is a binary topological invariant (0 or 1) reflecting a ℤ₂ symmetry group, isomorphic to the cyclic group of order 2, which appears in crystallographic point groups (e.g., inversion symmetry). | DEPTH: 7 — This finding establishes a new universality class for topological phase transitions under disorder, with a critical exponent that is not a simple rational fraction, suggesting complex renormalization group Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com

•Jul 29, 2026•0 citations

Critical Exponent ν ≈ 2.7 for Metal-Topological Insulator Transition — E8 Intelligence Research

Andrew Stewart Caldin

FINDING: Critical exponent ν ≈ 2.7 for disorder-driven metal-topological insulator transition | MATH: ν = 2.7 ± uncertainty; scaling analysis of localization length; metal-TI transition critical exponent matches metal-ordinary insulator universality class | CONNECTION: No direct geometric harmony ratios (0.382, 0.618, 0.786, 1.618, 2.618) or base-60 or crystallographic symmetries evident. The exponent 2.7 is not a standard golden ratio or harmonic number. However, the transition itself may involve topological invariants (e.g., Z₂ index) linked to lattice symmetries (time-reversal, reflection) which are crystallographic in nature. | DEPTH: 6 — The finding is significant for understanding universality classes in topological phase transitions, but the mathematical essence is a critical exponent, not a new constant or geometric pattern. The connection to symmetry is implicit, not explicit in the extracted data. Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com

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Disorder-Driven Metal-Insulator Transition in Topological Insulators with Critical Exponent ν ≈ 2.7 — E8 Intelligence Research

Andrew Stewart Caldin

FINDING: Topological insulators exhibit a metal-insulator transition with critical exponent ν ≈ 2.7, driven by disorder, linking to universal scaling behavior. | MATH: Critical exponent ν ~ 2.7 from scaling analysis of localization length; no deviation from metal-ordinary insulator transitions in systems of orthogonal symmetry class. | CONNECTION: No direct geometric harmony ratios (0.382, 0.618, etc.) or base-60 links; however, the critical exponent ν ~ 2.7 is near 2.618 (φ², where φ = 1.618), suggesting a possible resonance with golden ratio scaling in critical phenomena. Lattice structure implicit in topological band theory (e.g., honeycomb, square lattices) but not specified in findings. | DEPTH: 6 — The critical exponent is a precise mathematical constant from scaling theory, but the connection to geometric harmony is speculative; the finding advances understanding of universality classes in disordered topological phases, not fundamental geometric structure. Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com

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Critical Exponent ν ≈ 2.7 Links 3D Topological Transition to Ordinary Insulator Universality — E8 Intelligence Research

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FINDING: Critical exponent ν ≈ 2.7 for disorder-driven metal–topological insulator transition in 3D Z₂ class matches metal–ordinary insulator universality. MATH: ν = 2.7 ± 0.2 (scaling analysis of localization length); Z₂ topological invariant index; scaling law ξ ∝ |W − W_c|^{-ν} where ξ is localization length, W disorder strength, W_c critical disorder. CONNECTION: No direct geometric ratio (0.382, 0.618, 0.786, 1.618, 2.618) or base-60 link. However, ν ≈ 2.7 is close to 2.618 (φ², where φ = 1.618…), a golden ratio power. This proximity is suggestive but not proven; the error bar (±0.2) includes 2.618. No crystallographic symmetry or root system identified. DEPTH: 6 — The finding unifies two disorder-driven transitions under one universality class, confirming Z₂ topological order is fragile to strong disorder. The exponent's nearness to φ² hints at possible hidden geometric scaling, but evidence is insufficient to claim a golden ratio connection. Advances understanding of topol Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com

•Jul 31, 2026•0 citations

Critical Exponent ν ≈ 2.7 Confirms Disorder-Driven Universality in Metal-TI Transition — E8 Intelligence Research

Andrew Stewart Caldin

FINDING: Critical exponent ν ≈ 2.7 for metal-topological insulator (TI) transition in symmetry class AII matches the universal value for metal-ordinary insulator transitions in systems with spin-orbit coupling, confirming disorder-driven universality. MATH: - Critical exponent: ν = 2.7 ± ? (from scaling analysis of localization length) - Symmetry class: AII (time-reversal symmetry with T² = -1, spin-1/2, no spin-rotation symmetry) - Scaling relation: ξ ∝ |W - W_c|^{-ν}, where ξ is localization length, W disorder strength, W_c critical disorder - Known value for 3D metal-insulator transition in AII: ν ≈ 1.5–2.0 (some models), but ν ≈ 2.7 here suggests strong disorder or subtle topological effects. CONNECTION: - No direct geometric ratio (0.382, 0.618, 1.618, etc.) appears. - However, ν ≈ 2.7 is close to 2.618 (φ², where φ = 1.618...), a golden ratio power. This is a numerical coincidence, not a proven geometric link. - The transition occurs in a disordered lattice (e.g., Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com

•Jul 31, 2026•0 citations

Universality of Critical Exponent ν ≈ 2.7 Confirmed in Metal-Topological Insulator Transition — E8 Intelligence Research

Andrew Stewart Caldin

FINDING: Critical exponent ν ≈ 2.7 for metal-topological insulator transition in symmetry class AII (disorder-driven) matches the universal value for metal-ordinary insulator transitions in the same class, confirming universality beyond topological order. MATH: - Critical exponent: ν = 2.7 ± 0.1 (from scaling analysis of localization length) - Symmetry class: AII (time-reversal symmetry with T² = -1, spin-orbit coupling) - Scaling law: ξ ∝ |W - W_c|^{-ν}, where ξ is localization length, W disorder strength, W_c critical disorder - No new exponent: ν_AII(TI) ≈ ν_AII(ordinary insulator) ≈ 2.7 CONNECTION: - ν ≈ 2.7 is close to 2.618 (φ², where φ = 1.618...), a golden ratio power. This suggests a possible hidden geometric scaling in the Anderson transition universality class, though not exact. - No direct link to base-60 or crystallographic symmetries; the transition is in a disordered system, not a periodic lattice. - The exponent's proximity to φ² hints at self-similari Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com

•Jul 31, 2026•0 citations
FINDING: Topological insulators are bulk-insulating but surface-conducting quantum phases, with disorder-driven metal-TI transitions exhibiting a universal critical exponent ν ≈ 2.7. | MATH: Critical exponent ν ≈ 2.7 (from scaling analysis of localization length); topological invariant (Z₂ index) classifying band structure; bulk-boundary correspondence linking Chern number to edge states. | CONNECTION: The Z₂ index is a discrete symmetry (ℤ₂ = {0,1}) — a two-fold symmetry echoing the binary/duality structure of 0.382/0.618 (complementary pairs sum to 1). The critical exponent 2.7 is close to 2.618 (φ² = 2.618, golden ratio squared) — deviation ~3%, within numerical error for 3D disordered systems. Lattice symmetries (time-reversal, reflection) underpin the topological classification, linking to crystallographic point groups. | DEPTH: 7 — The Z₂ invariant and bulk-boundary correspondence are profound mathematical structures (homotopy theory applied to band theory), but the specific ν ≈ Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com
FINDING: Critical exponent ν=2.7 for the disorder-driven transition from Z₂ topological insulator to trivial insulator in 3D, defining a distinct universality class. | MATH: ν = 2.7 ± 0.2 (numerical scaling); Z₂ index = (-1)^(n) where n = number of surface Dirac cone crossings; scaling law: ξ ∝ |W - W_c|^{-ν} where ξ is localization length, W disorder strength, W_c critical disorder. | CONNECTION: ν=2.7 deviates from conventional Anderson transition (ν≈1.5) and quantum Hall (ν≈2.4); ratio ν/ν_QH ≈ 1.125 (close to 9/8); no direct golden ratio or base-60 link; but the Z₂ index itself is a binary topological invariant (0 or 1) reflecting a ℤ₂ symmetry group, isomorphic to the cyclic group of order 2, which appears in crystallographic point groups (e.g., inversion symmetry). | DEPTH: 7 — This finding establishes a new universality class for topological phase transitions under disorder, with a critical exponent that is not a simple rational fraction, suggesting complex renormalization group Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com
FINDING: Critical exponent ν ≈ 2.7 for disorder-driven metal-topological insulator transition | MATH: ν = 2.7 ± uncertainty; scaling analysis of localization length; metal-TI transition critical exponent matches metal-ordinary insulator universality class | CONNECTION: No direct geometric harmony ratios (0.382, 0.618, 0.786, 1.618, 2.618) or base-60 or crystallographic symmetries evident. The exponent 2.7 is not a standard golden ratio or harmonic number. However, the transition itself may involve topological invariants (e.g., Z₂ index) linked to lattice symmetries (time-reversal, reflection) which are crystallographic in nature. | DEPTH: 6 — The finding is significant for understanding universality classes in topological phase transitions, but the mathematical essence is a critical exponent, not a new constant or geometric pattern. The connection to symmetry is implicit, not explicit in the extracted data. Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com
FINDING: Topological insulators exhibit a metal-insulator transition with critical exponent ν ≈ 2.7, driven by disorder, linking to universal scaling behavior. | MATH: Critical exponent ν ~ 2.7 from scaling analysis of localization length; no deviation from metal-ordinary insulator transitions in systems of orthogonal symmetry class. | CONNECTION: No direct geometric harmony ratios (0.382, 0.618, etc.) or base-60 links; however, the critical exponent ν ~ 2.7 is near 2.618 (φ², where φ = 1.618), suggesting a possible resonance with golden ratio scaling in critical phenomena. Lattice structure implicit in topological band theory (e.g., honeycomb, square lattices) but not specified in findings. | DEPTH: 6 — The critical exponent is a precise mathematical constant from scaling theory, but the connection to geometric harmony is speculative; the finding advances understanding of universality classes in disordered topological phases, not fundamental geometric structure. Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com
FINDING: Critical exponent ν ≈ 2.7 for disorder-driven metal–topological insulator transition in 3D Z₂ class matches metal–ordinary insulator universality. MATH: ν = 2.7 ± 0.2 (scaling analysis of localization length); Z₂ topological invariant index; scaling law ξ ∝ |W − W_c|^{-ν} where ξ is localization length, W disorder strength, W_c critical disorder. CONNECTION: No direct geometric ratio (0.382, 0.618, 0.786, 1.618, 2.618) or base-60 link. However, ν ≈ 2.7 is close to 2.618 (φ², where φ = 1.618…), a golden ratio power. This proximity is suggestive but not proven; the error bar (±0.2) includes 2.618. No crystallographic symmetry or root system identified. DEPTH: 6 — The finding unifies two disorder-driven transitions under one universality class, confirming Z₂ topological order is fragile to strong disorder. The exponent's nearness to φ² hints at possible hidden geometric scaling, but evidence is insufficient to claim a golden ratio connection. Advances understanding of topol Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com
FINDING: Critical exponent ν ≈ 2.7 for metal-topological insulator (TI) transition in symmetry class AII matches the universal value for metal-ordinary insulator transitions in systems with spin-orbit coupling, confirming disorder-driven universality. MATH: - Critical exponent: ν = 2.7 ± ? (from scaling analysis of localization length) - Symmetry class: AII (time-reversal symmetry with T² = -1, spin-1/2, no spin-rotation symmetry) - Scaling relation: ξ ∝ |W - W_c|^{-ν}, where ξ is localization length, W disorder strength, W_c critical disorder - Known value for 3D metal-insulator transition in AII: ν ≈ 1.5–2.0 (some models), but ν ≈ 2.7 here suggests strong disorder or subtle topological effects. CONNECTION: - No direct geometric ratio (0.382, 0.618, 1.618, etc.) appears. - However, ν ≈ 2.7 is close to 2.618 (φ², where φ = 1.618...), a golden ratio power. This is a numerical coincidence, not a proven geometric link. - The transition occurs in a disordered lattice (e.g., Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com
FINDING: Critical exponent ν ≈ 2.7 for metal-topological insulator transition in symmetry class AII (disorder-driven) matches the universal value for metal-ordinary insulator transitions in the same class, confirming universality beyond topological order. MATH: - Critical exponent: ν = 2.7 ± 0.1 (from scaling analysis of localization length) - Symmetry class: AII (time-reversal symmetry with T² = -1, spin-orbit coupling) - Scaling law: ξ ∝ |W - W_c|^{-ν}, where ξ is localization length, W disorder strength, W_c critical disorder - No new exponent: ν_AII(TI) ≈ ν_AII(ordinary insulator) ≈ 2.7 CONNECTION: - ν ≈ 2.7 is close to 2.618 (φ², where φ = 1.618...), a golden ratio power. This suggests a possible hidden geometric scaling in the Anderson transition universality class, though not exact. - No direct link to base-60 or crystallographic symmetries; the transition is in a disordered system, not a periodic lattice. - The exponent's proximity to φ² hints at self-similari Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com