Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Relative Entropy and Modular Geometry in Algebraic Quantum Field Theory

Arşen Kaan

Published May 26, 2026• 0 citations
Publisher

Abstract

This preprint investigates structural relations between relative entropy, modular theory, and information geometry in algebraic quantum field theory (AQFT). In finite‑dimensional quantum systems, the Hessian of Umegaki relative entropy coincides with the Bogoliubov–Kubo–Mori (BKM) metric, and modular automorphisms act by isometries of this geometry; these standard results are reviewed as a mathematically controlled reference model. Motivated by this setting, the work formulates minimal structural conditions under which a perturbative modular information‑geometric programme for Type III1_11 von Neumann algebras could become mathematically meaningful. The analysis focuses on admissible perturbation sectors, Araki relative entropy, modular covariance, and the functional‑analytic obstructions caused by unbounded modular operators. A general consequence of positive semidefiniteness of the perturbative entropy Hessian is recorded: whenever the Hessian defines a well‑defined positive semidefinite bilinear form, its null directions annihilate the full form. In the Rindler wedge model, the corresponding regularity problem for candidate perturbations is formulated in terms of spectral properties and domain issues of the Lorentz boost generator. Throughout, explicit separation is maintained between rigorous results, conditional statements, heuristic motivations, and unresolved analytic problems. A conjecture concerning degenerate modular directions is stated together with a necessary falsifiable condition. This document is exploratory in nature and has not been peer reviewed.

DOI
10.5281/zenodo.20392160

Related papers

Modular Fisher Geometry for Bounded Analytic Perturbations of Type III₁ States

Ahmet Senguel

This work presents an exploratory framework for modular information geometry associated with faithful normal states on Type III₁ von Neumann algebras. The construction is based on the second Gâteaux variation (Hessian) of Araki relative entropy for bounded analytic perturbations and leads to a modular Fisher form defined on an explicitly specified admissible domain. Under stated regularity and covariance assumptions, this form is symmetric and positive semidefinite and exhibits canonical null directions generated by the modular derivation. The physically relevant structure is obtained by quotienting the resulting degeneracy space. In the context of algebraic quantum field theory, and assuming the Bisognano–Wichmann property for wedge algebras, the modular derivation coincides with the Lorentz boost generator, so that modular flow directions correspond to gauge/null directions of the information-geometric structure. This note is exploratory and conjectural in nature. It was developed with the assistance of AI-based tools and has not undergone independent mathematical or peer validation. No claim of new theorems, analytical completeness, full differentiability theory, or spacetime reconstruction is made. All nontrivial results are conditional on explicitly stated assumptions and are intended as structural observations rather than definitive conclusions.

•May 22, 2026•0 citations

Modular Self-Duality, Symmetrized Relative Entropy, and Bogoliubov--Kubo--Mori Susceptibility in Quantum Field Theory

Rupak Chatterjee

We develop an operator-algebraic framework for modular self-duality, symmetrized relative entropy, and Bogoliubov--Kubo--Mori (BKM) susceptibility of local states in quantum field theory. In finite dimensions, modular self-duality singles out fixed points at which a state coincides with its modularly reflected partner. At such points, the natural comparison functional is the symmetrized Umegaki relative entropy. It vanishes at coincidence, and its Hessian is governed by the BKM quantum Fisher information along the reflected tangent direction. We then extend this fixed-point construction to the local type~III von Neumann algebras that arise in quantum field theory. Here, a local state is compared with the modular pullback of its commutant restriction, and the intrinsic comparison functional is the symmetrized Araki relative entropy. For sufficiently regular state deformations, the fixed-localization Hessian at the self-dual point defines a type~III BKM susceptibility. This coefficient is obtained by evaluating the BKM bilinear form on the tangent selected by the modular pairing. Exact coherent-state realizations are obtained for the free scalar field on wedge algebras and for the chiral $U(1)$ current on half-line algebras. In both examples, the comparison functional is exactly quadratic in the deformation parameter, and the susceptibility coefficients admit explicit boost-energy, stress-tensor, or half-line integral representations. We also apply the construction to a ball-shaped boundary region in the vacuum state of a conformal field theory with a semiclassical anti-de Sitter (AdS) gravitational dual. For linear bulk coherent excitations in an exact complementary-recovery model of this sector, bulk--boundary modular intertwining identifies the modular partner with the AdS--Rindler-reflected coherent state, and the symmetrized relative entropy is exactly quadratic.

hep-thCross-listedarXiv:2605.19106•Physical review. D/Physical review. D.•May 20, 2026•0 citations

AQFT Information Geometry Framework: Modular Fisher Form and Conditional Canonical Degeneracy

Ahmet Senguel

This repository contains an exploratory theoretical framework at the intersection of Algebraic Quantum Field Theory (AQFT) and information geometry for faithful normal states on Type III₁ von Neumann algebras. The construction is based on second Gâteaux variations of Araki relative entropy and introduces a modular Fisher quadratic form on admissible state perturbations, formulated on the Tomita algebra of analytic elements. A strict logical Kernel (Protocol v3.1.2) is employed to enforce assumption monotonicity, operator-domain discipline, explicit statement typing, and explicit conditionality of all nontrivial claims. This work is an independent, exploratory research project developed with the assistance of AI-based formalization tools. All definitions, assumptions, and claims were manually validated under the Kernel protocol. The framework has not undergone formal academic peer review and is published to archive the methodology and invite rigorous mathematical validation by the AQFT and mathematical physics community.

•May 21, 2026•0 citations

A Rigorous Modular-Time Coordinate in the Weyl-Coherent Rindler Sector

Arşen Kaan, Arşen Kaan

This manuscript establishes a mathematically controlled one-parameter modular-time coordinate for the vacuum representation of a free neutral scalar field on the right Rindler wedge. By restricting the state space strictly to the finite-entropy Weyl-coherent sector, the vacuum relative entropy is shown to be exactly quadratic based on rigorous external results by Longo and Casini–Grillo–Pontello. Consequently, the entropy Hessian exists without remainder estimates (O(t^3)), is strictly positive, and remains invariant under the modular group. By applying the Bisognano–Wichmann theorem, the modular parameter directly identifies with the Rindler boost rapidity up to orientation and the standard KMS-Unruh normalization (s = -2\pi\tau). The manuscript explicitly addresses the separate status of unbounded Araki perturbations (\phi(f)) and defines the exact boundary between proven theorems (⁠[RIGOROUS]⁠) and open matching hypotheses (⁠[OPEN]⁠), avoiding any completing-the-square assumptions for the modular Hamiltonian.

•Sep 1, 2026•0 citations

Cohomological Aspects of Entanglement Entropy: From Information Theory to Noncommutative Geometry

Radoslav C. Rashkov

We develop a cohomological framework for entanglement entropy that unifies information theory, operator algebras, and noncommutative geometry. Entropy is a 1-cocycle in information cohomology; we generalize this to the quantum setting via Hochschild and cyclic cohomology. For an inclusion of von Neumann algebras N contained in M with a faithful normal state w admitting a cyclic and separating vector, and a conditional expectation E: M -> N (whose existence is equivalent to modular invariance of N by Takesaki's theorem), we construct the entanglement complex as the image of the transgression map tau_w on the relative cyclic complex, where A is a dense *-subalgebra of M and B = A intersect N. Our main result identifies entanglement cohomology with the kernel of the restriction map HC*(A) -> HC*(B), up to the connecting homomorphism d of the long exact sequence of the pair (A,B); when d = 0, the identification is exact. The relative modular cocycle u_t = (Dw : D(w|_N) o E)_t generates explicit entanglement classes when E is not w-invariant, with the Araki relative entropy as its infinitesimal generator. The framework accommodates Type III von Neumann algebras, where no local density matrix exists, and leads to a holographic proposal: a subspace of H^1_ent is conjecturally dual to linearized modular Hamiltonian perturbations of the bulk entanglement wedge. We verify the construction in finite-dimensional, type II_1, and type III_1 examples.

arXiv:2609.17195•Sep 15, 2026•0 citations

Quantum Optimal Transport and the Gravitational Metric: Collected Papers (GFI Programme)

David Gogishvili

This document presents a synthesis of research within the "Geometry from Information" (GFI) programme, specifically focusing on Paper 18 and Paper 27. We establish that the Bogoliubov-Kubo-Mori (BKM) metric is the Hessian of relative entropy within the quantum Wasserstein-2 geometry (W_{2}^{Q}) at the de Sitter point. The work demonstrates that the locality of the BKM metric is a consequence of the W_{2}^{Q} geodesic structure. Additionally, it explores the equivalence between the Island formula extremization and W_{2}^{Q}-optimal partitioning, providing a quantum Type II_{\infty} analogue to the Mondino-Suhr theory.

•Mar 18, 2026•0 citations
This preprint investigates structural relations between relative entropy, modular theory, and information geometry in algebraic quantum field theory (AQFT). In finite‑dimensional quantum systems, the Hessian of Umegaki relative entropy coincides with the Bogoliubov–Kubo–Mori (BKM) metric, and modular automorphisms act by isometries of this geometry; these standard results are reviewed as a mathematically controlled reference model. Motivated by this setting, the work formulates minimal structural conditions under which a perturbative modular information‑geometric programme for Type III1_11 von Neumann algebras could become mathematically meaningful. The analysis focuses on admissible perturbation sectors, Araki relative entropy, modular covariance, and the functional‑analytic obstructions caused by unbounded modular operators. A general consequence of positive semidefiniteness of the perturbative entropy Hessian is recorded: whenever the Hessian defines a well‑defined positive semidefinite bilinear form, its null directions annihilate the full form. In the Rindler wedge model, the corresponding regularity problem for candidate perturbations is formulated in terms of spectral properties and domain issues of the Lorentz boost generator. Throughout, explicit separation is maintained between rigorous results, conditional statements, heuristic motivations, and unresolved analytic problems. A conjecture concerning degenerate modular directions is stated together with a necessary falsifiable condition. This document is exploratory in nature and has not been peer reviewed.
This work presents an exploratory framework for modular information geometry associated with faithful normal states on Type III₁ von Neumann algebras. The construction is based on the second Gâteaux variation (Hessian) of Araki relative entropy for bounded analytic perturbations and leads to a modular Fisher form defined on an explicitly specified admissible domain. Under stated regularity and covariance assumptions, this form is symmetric and positive semidefinite and exhibits canonical null directions generated by the modular derivation. The physically relevant structure is obtained by quotienting the resulting degeneracy space. In the context of algebraic quantum field theory, and assuming the Bisognano–Wichmann property for wedge algebras, the modular derivation coincides with the Lorentz boost generator, so that modular flow directions correspond to gauge/null directions of the information-geometric structure. This note is exploratory and conjectural in nature. It was developed with the assistance of AI-based tools and has not undergone independent mathematical or peer validation. No claim of new theorems, analytical completeness, full differentiability theory, or spacetime reconstruction is made. All nontrivial results are conditional on explicitly stated assumptions and are intended as structural observations rather than definitive conclusions.
We develop an operator-algebraic framework for modular self-duality, symmetrized relative entropy, and Bogoliubov--Kubo--Mori (BKM) susceptibility of local states in quantum field theory. In finite dimensions, modular self-duality singles out fixed points at which a state coincides with its modularly reflected partner. At such points, the natural comparison functional is the symmetrized Umegaki relative entropy. It vanishes at coincidence, and its Hessian is governed by the BKM quantum Fisher information along the reflected tangent direction. We then extend this fixed-point construction to the local type~III von Neumann algebras that arise in quantum field theory. Here, a local state is compared with the modular pullback of its commutant restriction, and the intrinsic comparison functional is the symmetrized Araki relative entropy. For sufficiently regular state deformations, the fixed-localization Hessian at the self-dual point defines a type~III BKM susceptibility. This coefficient is obtained by evaluating the BKM bilinear form on the tangent selected by the modular pairing. Exact coherent-state realizations are obtained for the free scalar field on wedge algebras and for the chiral U(1)U(1)U(1) current on half-line algebras. In both examples, the comparison functional is exactly quadratic in the deformation parameter, and the susceptibility coefficients admit explicit boost-energy, stress-tensor, or half-line integral representations. We also apply the construction to a ball-shaped boundary region in the vacuum state of a conformal field theory with a semiclassical anti-de Sitter (AdS) gravitational dual. For linear bulk coherent excitations in an exact complementary-recovery model of this sector, bulk--boundary modular intertwining identifies the modular partner with the AdS--Rindler-reflected coherent state, and the symmetrized relative entropy is exactly quadratic.
This repository contains an exploratory theoretical framework at the intersection of Algebraic Quantum Field Theory (AQFT) and information geometry for faithful normal states on Type III₁ von Neumann algebras. The construction is based on second Gâteaux variations of Araki relative entropy and introduces a modular Fisher quadratic form on admissible state perturbations, formulated on the Tomita algebra of analytic elements. A strict logical Kernel (Protocol v3.1.2) is employed to enforce assumption monotonicity, operator-domain discipline, explicit statement typing, and explicit conditionality of all nontrivial claims. This work is an independent, exploratory research project developed with the assistance of AI-based formalization tools. All definitions, assumptions, and claims were manually validated under the Kernel protocol. The framework has not undergone formal academic peer review and is published to archive the methodology and invite rigorous mathematical validation by the AQFT and mathematical physics community.
This manuscript establishes a mathematically controlled one-parameter modular-time coordinate for the vacuum representation of a free neutral scalar field on the right Rindler wedge. By restricting the state space strictly to the finite-entropy Weyl-coherent sector, the vacuum relative entropy is shown to be exactly quadratic based on rigorous external results by Longo and Casini–Grillo–Pontello. Consequently, the entropy Hessian exists without remainder estimates (O(t^3)), is strictly positive, and remains invariant under the modular group. By applying the Bisognano–Wichmann theorem, the modular parameter directly identifies with the Rindler boost rapidity up to orientation and the standard KMS-Unruh normalization (s = -2\pi\tau). The manuscript explicitly addresses the separate status of unbounded Araki perturbations (\phi(f)) and defines the exact boundary between proven theorems (⁠[RIGOROUS]⁠) and open matching hypotheses (⁠[OPEN]⁠), avoiding any completing-the-square assumptions for the modular Hamiltonian.
We develop a cohomological framework for entanglement entropy that unifies information theory, operator algebras, and noncommutative geometry. Entropy is a 1-cocycle in information cohomology; we generalize this to the quantum setting via Hochschild and cyclic cohomology. For an inclusion of von Neumann algebras N contained in M with a faithful normal state w admitting a cyclic and separating vector, and a conditional expectation E: M -> N (whose existence is equivalent to modular invariance of N by Takesaki's theorem), we construct the entanglement complex as the image of the transgression map tau_w on the relative cyclic complex, where A is a dense *-subalgebra of M and B = A intersect N. Our main result identifies entanglement cohomology with the kernel of the restriction map HC*(A) -> HC*(B), up to the connecting homomorphism d of the long exact sequence of the pair (A,B); when d = 0, the identification is exact. The relative modular cocycle u_t = (Dw : D(w|_N) o E)_t generates explicit entanglement classes when E is not w-invariant, with the Araki relative entropy as its infinitesimal generator. The framework accommodates Type III von Neumann algebras, where no local density matrix exists, and leads to a holographic proposal: a subspace of H^1_ent is conjecturally dual to linearized modular Hamiltonian perturbations of the bulk entanglement wedge. We verify the construction in finite-dimensional, type II_1, and type III_1 examples.
This document presents a synthesis of research within the "Geometry from Information" (GFI) programme, specifically focusing on Paper 18 and Paper 27. We establish that the Bogoliubov-Kubo-Mori (BKM) metric is the Hessian of relative entropy within the quantum Wasserstein-2 geometry (W_{2}^{Q}) at the de Sitter point. The work demonstrates that the locality of the BKM metric is a consequence of the W_{2}^{Q} geodesic structure. Additionally, it explores the equivalence between the Island formula extremization and W_{2}^{Q}-optimal partitioning, providing a quantum Type II_{\infty} analogue to the Mondino-Suhr theory.