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arxiv: 2604.10663 · v2 · submitted 2026-04-12 · ❄️ cond-mat.stat-mech · math-ph· math.MP

Confined kinetics and heterogeneous diffusion driven by fractional Gaussian noise: A path integral approach

Pith reviewed 2026-05-13 07:18 UTC · model grok-4.3

classification ❄️ cond-mat.stat-mech math-phmath.MP
keywords fractional Gaussian noisemultiplicative diffusionpath integralLamperti transformconfined kineticsheterogeneous diffusionFeynman-Kac formula
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The pith

Multiplicative fractional Gaussian noise and confinement together generate an effective drift that accumulates probability in regions of low noise amplitude.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper develops a path-integral method for diffusion driven by fractional Gaussian noise that couples multiplicatively to the state. A stationary-phase approximation produces a Gaussian propagator written in terms of the Lamperti transform. In the additive limit this recovers the known path-integral form of fractional Brownian motion and shows equivalence with the Langevin construction. Subordination via the Feynman-Kac formula then yields kinetic equations governed by effective local Hamiltonians. The central demonstration is that multiplicative diffusion combined with confinement induces a drift term whose consequence is probability accumulation where the noise strength is smallest.

Core claim

Using a stationary-phase approximation applied to the path integral, the propagator for a process driven by multiplicative fractional Gaussian noise is obtained as a Gaussian integral in the Lamperti-transformed variable. This recovers the known representation of fractional Brownian motion when the noise is additive and establishes equivalence between the Riemann-Liouville and Langevin constructions. Within the Feynman-Kac framework, subordination to a killing rate leads to a general procedure for deriving kinetic equations expressed through effective local Hamiltonians. The analysis reveals that the combination of multiplicative diffusion and confinement induces an effective drift, causing

What carries the argument

The stationary-phase approximated path integral for the propagator, expressed in the Lamperti-transformed coordinate that converts multiplicative noise into additive noise.

Load-bearing premise

The stationary-phase approximation remains valid for deriving the Gaussian propagator when the multiplicative noise takes a general form.

What would settle it

Numerical simulation of many trajectories from the Langevin equation with multiplicative fractional Gaussian noise inside a confining potential, followed by construction of the steady-state histogram, would show no excess probability density in low-noise regions if the induced-drift claim is incorrect.

read the original abstract

Many complex systems are described by Langevin-type equations in which the noise exhibits long-range correlations and couples to the system in a state-dependent, multiplicative manner, leading to heterogeneous non-Markovian diffusion. Here, we investigate the problem of diffusion driven by fractional Gaussian noise with a general multiplicative coefficient from a path-integral perspective. Using a stationary-phase approximation, we derive a Gaussian propagator expressed in terms of the Lamperti transform of the process. In the additive limit, our results recover the path-integral representation of fractional Brownian motion based on its Riemann-Liouville formulation and establish its equivalence with the Langevin construction. We further analyze the effect of subordinating the process to a killing rate within the Feynman-Kac framework, and develop a general procedure to derive kinetic equations in terms of effective local Hamiltonians. We show that the interplay between multiplicative diffusion and confinement induces an effective drift term, leading to probability accumulation in regions of low noise amplitude.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 1 minor

Summary. The manuscript develops a path-integral treatment of diffusion driven by fractional Gaussian noise with a general multiplicative prefactor. A stationary-phase approximation yields a Gaussian propagator expressed via the Lamperti transform of the process. The additive limit recovers the Riemann-Liouville path-integral representation of fractional Brownian motion and establishes equivalence with the Langevin equation. Within the Feynman-Kac framework the authors derive effective local Hamiltonians for confined kinetics and show that the combination of multiplicative diffusion and confinement produces an effective drift, resulting in probability accumulation in regions of low noise amplitude.

Significance. If the central approximation is justified, the work supplies a systematic route to effective kinetic equations for heterogeneous non-Markovian diffusion under confinement, with potential relevance to complex systems. The explicit recovery of the additive fractional-Brownian-motion case and the construction of effective Hamiltonians constitute verifiable strengths.

major comments (1)
  1. [Section deriving the propagator (stationary-phase step)] The stationary-phase approximation used to obtain the Gaussian propagator for arbitrary multiplicative noise (the step that precedes the Lamperti-transform expression and the subsequent Feynman-Kac construction) is presented without an error bound or a stated regime of uniform validity. Because the claimed effective drift and the probability accumulation at low-noise regions rest directly on this propagator, the absence of a quantitative control on the approximation constitutes a load-bearing gap.
minor comments (1)
  1. [Throughout] Notation for the multiplicative coefficient and the killing rate should be introduced once and used consistently; occasional redefinitions obscure the transition from the path-integral to the effective Hamiltonian.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and for the positive overall assessment. We address the single major comment below.

read point-by-point responses
  1. Referee: [Section deriving the propagator (stationary-phase step)] The stationary-phase approximation used to obtain the Gaussian propagator for arbitrary multiplicative noise (the step that precedes the Lamperti-transform expression and the subsequent Feynman-Kac construction) is presented without an error bound or a stated regime of uniform validity. Because the claimed effective drift and the probability accumulation at low-noise regions rest directly on this propagator, the absence of a quantitative control on the approximation constitutes a load-bearing gap.

    Authors: We agree that an explicit error bound or a clearly stated regime of uniform validity is absent and that this is a substantive gap, given the central role of the propagator in the subsequent derivations. The stationary-phase step is used in the standard semiclassical sense for path integrals of processes with long-range correlations; it is expected to be accurate for moderate noise strengths and long times, but we did not quantify the remainder. In the revised manuscript we will add a dedicated paragraph (new subsection 2.3) that (i) recalls the conditions under which the stationary-phase approximation is controlled for Gaussian actions, (ii) states the leading-order character of the result, and (iii) supplies direct numerical comparisons between the analytic propagator and Monte-Carlo trajectories of the underlying multiplicative fractional-Gaussian-noise SDE for representative multiplicative prefactors. These additions will make the domain of applicability explicit and will allow readers to assess the accuracy of the effective drift and accumulation predictions. revision: yes

Circularity Check

0 steps flagged

No significant circularity detected in derivation chain

full rationale

The derivation proceeds from the path-integral representation of multiplicative fGn, applies a stationary-phase approximation to obtain a Gaussian propagator expressed via the Lamperti transform, recovers the known additive fBm case through the external Riemann-Liouville formulation, and then invokes the standard Feynman-Kac formula to introduce a killing rate and extract effective local Hamiltonians. None of these steps reduce by construction to their own inputs, fitted parameters renamed as predictions, or load-bearing self-citations; the effective drift and probability accumulation at low-noise regions emerge as consequences of the derived equations rather than being presupposed. The paper remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The paper relies on standard mathematical tools from stochastic processes and path integrals without introducing new free parameters or entities.

axioms (2)
  • domain assumption The stationary-phase approximation can be applied to the path integral formulation of the diffusion process.
    This is used to obtain the Gaussian propagator.
  • domain assumption The Lamperti transform linearizes the multiplicative noise process.
    Central to expressing the propagator.

pith-pipeline@v0.9.0 · 5479 in / 1187 out tokens · 114648 ms · 2026-05-13T07:18:17.466361+00:00 · methodology

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Reference graph

Works this paper leans on

44 extracted references · 44 canonical work pages

  1. [1]

    Mandelbrot, Self-affinity and fractal dimension, Phys

    B. Mandelbrot, Self-affinity and fractal dimension, Phys. Scr.32, 257 (1985)

  2. [2]

    Gneiting and M

    T. Gneiting and M. Schlather, Stochastic models that separate fractal dimension and the Hurst effect, SIAM Rev.46, 269 (2004)

  3. [3]

    H. E. Hurst, Long-term storage capacity of reservoirs, Trans. Am. Soc. Civil Eng.116, 770 (1951)

  4. [4]

    A. N. Kolmogorov, Wienersche spiralen und einige andere 6 interessante kurven in hilbertscen raum, cr (doklady), Acad. Sci. URSS (NS)26, 115 (1940)

  5. [5]

    L´ evy,Random functions: general theory with special reference to Laplacian random functions, Vol

    P. L´ evy,Random functions: general theory with special reference to Laplacian random functions, Vol. 1 (Univer- sity of California Press. California, USA, 1953)

  6. [6]

    B. B. Mandelbrot and J. W. Van Ness, Fractional Brow- nian motions, fractional noises and applications, SIAM Rev.10, 422 (1968)

  7. [7]

    W. Wang, Q. Wei, A. V. Chechkin, and R. Metzler, Dif- ferent behaviors of diffusing diffusivity dynamics based on three different definitions of fractional brownian mo- tion, Phys. Rev. E112, 014108 (2025)

  8. [8]

    Calvo and R

    I. Calvo and R. Sanchez, The path integral formulation of fractional Brownian motion for the general Hurst ex- ponent, J. Phys. A: Math. Theor.41, 282002 (2008)

  9. [9]

    Sebastian, Path integral representation for fractional brownian motion, Journal of Physics A: Mathematical and General28, 4305 (1995)

    K. Sebastian, Path integral representation for fractional brownian motion, Journal of Physics A: Mathematical and General28, 4305 (1995)

  10. [10]

    Wiener, Differential-space, J

    N. Wiener, Differential-space, J. Math. Phys.2, 131 (1923)

  11. [11]

    Wiener, The average value of a functional, Proc

    N. Wiener, The average value of a functional, Proc. Lon- don Math. Soc.2, 454 (1924)

  12. [12]

    Meerson, O

    B. Meerson, O. B´ enichou, and G. Oshanin, Path integrals for fractional Brownian motion and fractional Gaussian noise, Phys. Rev. E106, L062102 (2022)

  13. [13]

    Lutz, Fractional Langevin equation, Phys

    E. Lutz, Fractional Langevin equation, Phys. Rev. E64, 051106 (2001)

  14. [14]

    Kupferman, Fractional kinetics in kac–zwanzig heat bath models, J

    R. Kupferman, Fractional kinetics in kac–zwanzig heat bath models, J. Stat. Phys.114, 291 (2004)

  15. [15]

    Bonfanti, J

    A. Bonfanti, J. L. Kaplan, G. Charras, and A. Kabla, Fractional viscoelastic models for power-law materials, Soft Matter16, 6002 (2020)

  16. [16]

    Joo and J.-H

    S. Joo and J.-H. Jeon, Viscoelastic active diffusion gov- erned by nonequilibrium fractional Langevin equations: Underdamped dynamics and ergodicity breaking, Chaos, Solitons Fractals177, 114288 (2023)

  17. [17]

    Durang, C

    X. Durang, C. Lim, and J.-H. Jeon, Generalized langevin equation for a tagged monomer in a gaussian semiflexible polymer, J. Chem. Phys.161(2024)

  18. [18]

    Lim and J.-H

    C. Lim and J.-H. Jeon, Anomalous diffusion in coupled viscoelastic media: A fractional langevin equation ap- proach, Physical Review Research7, 043356 (2025)

  19. [19]

    Metzler and J

    R. Metzler and J. Klafter, The restaurant at the end of the random walk: recent developments in the description of anomalous transport by fractional dynamics, J. Phys. A: Math. Gen.37, R161 (2004)

  20. [20]

    A. G. Cherstvy, W. Wang, R. Metzler, and I. M. Sokolov, Inertia triggers nonergodicity of fractional brownian mo- tion, Phys. Rev. E104, 024115 (2021)

  21. [21]

    Quevedo, R

    D. Quevedo, R. Verstraten, and C. Morais Smith, Emer- gent transient time crystal from a fractional Langevin equation with white and colored noise, Phys. Rev. A110, 052208 (2024)

  22. [22]

    J. R. Gomez-Solano and F. J. Sevilla, Active particles with fractional rotational Brownian motion, Jour. Stat. Mech: Theory Exp.2020, 063213 (2020)

  23. [23]

    D. S. Quevedo, M. Conte, M. Dijkstra, and C. M. Smith, Active brownian particles in power-law viscoelastic me- dia, arXiv preprint arXiv:2512.20205 (2025)

  24. [24]

    S. M. J. Khadem, R. Klages, and S. H. Klapp, Stochas- tic thermodynamics of fractional brownian motion, Phys. Rev. Res.4, 043186 (2022)

  25. [25]

    Squarcini, A

    A. Squarcini, A. Solon, P. Viot, and G. Oshanin, Frac- tional brownian gyrator, J. Phys. A: Math. Theor.55, 485001 (2022)

  26. [26]

    Giordano, F

    S. Giordano, F. Cleri, and R. Blossey, Infinite ergodicity in generalized geometric brownian motions with nonlin- ear drift, Phys. Rev. E107, 044111 (2023)

  27. [27]

    Abril-Berm´ udez, C

    F. Abril-Berm´ udez, C. Quimbay, J. Trinidad-Segovia, and M. S´ anchez-Granero, Path integral for multiplicative noise: Generalized Fokker-Planck equation and entropy production rate in stochastic processes with threshold, Phys. Rev. Res.7, 023185 (2025)

  28. [28]

    L. M. Ricciardi, Stochastic population theory: diffu- sion processes, inMathematical Ecology: An Introduction (Springer, 1986) pp. 191–238

  29. [29]

    A. G. Cherstvy, A. V. Chechkin, and R. Metzler, Anoma- lous diffusion and ergodicity breaking in heterogeneous diffusion processes, New J. Phys.15, 083039 (2013)

  30. [30]

    W. Wang, A. G. Cherstvy, X. Liu, and R. Metzler, Anomalous diffusion and nonergodicity for heterogeneous diffusion processes with fractional Gaussian noise, Phys. Rev. E102, 012146 (2020)

  31. [31]

    Lamperti, Semi-stable stochastic processes, Trans

    J. Lamperti, Semi-stable stochastic processes, Trans. Am. Math. Soc.104, 62 (1962)

  32. [32]

    Kac, On distributions of certain wiener functionals, Trans

    M. Kac, On distributions of certain wiener functionals, Trans. Am. Math. Soc.65, 1 (1949)

  33. [33]

    H¨ anggi, Path integral solutions for non-markovian pro- cesses, Z

    P. H¨ anggi, Path integral solutions for non-markovian pro- cesses, Z. Phys. B: Condens. Matter75, 275 (1989)

  34. [34]

    D. O. Kharchenko, Path integral solution of the system with coloured multiplicative noise, Physica A308, 113 (2002)

  35. [35]

    Parisi and N

    G. Parisi and N. Sourlas, Random magnetic fields, su- persymmetry, and negative dimensions, Phys. Rev. Lett. 43, 744 (1979)

  36. [36]

    Balaji, Universal nonlinear filtering using feynman path integrals ii: the continuous-continuous model with additive noise, PMC Phys

    B. Balaji, Universal nonlinear filtering using feynman path integrals ii: the continuous-continuous model with additive noise, PMC Phys. A3, 2 (2009)

  37. [37]

    Onsager and S

    L. Onsager and S. Machlup, Fluctuations and irreversible processes, Phys. Rev.91, 1505 (1953)

  38. [38]

    Machlup and L

    S. Machlup and L. Onsager, Fluctuations and irreversible process. ii. systems with kinetic energy, Phys. Rev.91, 1512 (1953)

  39. [39]

    To our knowledge, such generalized version of the CTRW has not been studied yet in the literature

  40. [40]

    Hilfer and L

    R. Hilfer and L. Anton, Fractional master equations and fractal time random walks, Physical Review E51, R848 (1995)

  41. [41]

    Metzler and J

    R. Metzler and J. Klafter, From a generalized Chapman- Kolmogorov equation to the fractional Klein-Kramers equation, J. Phys. Chem. B104, 3851 (2000)

  42. [42]

    Thiel and I

    F. Thiel and I. M. Sokolov, Scaled brownian motion as a mean-field model for continuous-time random walks, Physical Review E89, 012115 (2014)

  43. [43]

    Q. Wei, W. Wang, H. Zhou, R. Metzler, and A. Chechkin, Time-fractional caputo derivative versus other integrod- ifferential operators in generalized fokker-planck and gen- eralized langevin equations, Physical Review E108, 024125 (2023)

  44. [44]

    Stratonovich, A new representation for stochastic in- tegrals and equations, SIAM J

    R. Stratonovich, A new representation for stochastic in- tegrals and equations, SIAM J. Control Optim.4, 362 (1966). 7 Appendix A: Cumulant generating function of the fractional Gaussian noise Recalling that the differential noise increments of the fBm are given byξHµ+1∆t≡B Hµ+1 −BHµ, the covariance between two increments can be obtained from Eq. (3), CHµ...