Detecting Stochasticity in Discrete Signals via Nonparametric Excursion Theorem
Pith reviewed 2026-05-21 15:32 UTC · model grok-4.3
The pith
A scaling law for excursion counts in semimartingales distinguishes stochastic diffusions from deterministic signals.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The paper establishes that the number of excursions N_ε of magnitude at least ε in a continuous semimartingale is related to its quadratic variation [X]_T by a universal scaling law that holds for all Ito diffusions with finite quadratic variation. This law fails for deterministic systems, allowing construction of a ratio K(ε) = empirical excursions over theoretical prediction whose log-log slope deviation from the ε^{-2} behavior classifies the dynamics as diffusion-like or not.
What carries the argument
The classical excursion and crossing theorems for continuous semimartingales that provide the theoretical expectation for N_ε based on the quadratic variation [X]_T, which is estimated from the discrete observations to serve as the benchmark.
If this is right
- The method provides a theoretically grounded alternative to entropy-based or recurrence-based tests for stochasticity.
- It applies to general Ito diffusions without requiring knowledge of the drift or diffusion coefficient.
- The test works on a single discrete time series and remains nonparametric.
- Classification is achieved by summarizing the ratio K(ε) via its log-log slope deviation from the expected scaling.
Where Pith is reading between the lines
- Such a test could be applied to financial tick data or physiological signals to detect underlying stochastic components.
- Extensions might include adapting the threshold selection or handling irregularly sampled data.
- Further work could explore the test's power against specific alternatives like fractional Brownian motion or jump processes.
Load-bearing premise
The quadratic variation estimated from the discrete observations accurately reflects the true quadratic variation without the estimation introducing bias that could mimic the stochastic excursion scaling.
What would settle it
Direct computation on a deterministic periodic signal showing that the observed excursion counts do not match the scaling predicted by its estimated quadratic variation, or on a known diffusion where they do match.
Figures
read the original abstract
We develop a practical framework for distinguishing diffusive stochastic processes from deterministic signals using only a single discrete time series. Our approach is based on classical excursion and crossing theorems for continuous semimartingales, which correlates number $N_\varepsilon$ of excursions of magnitude at least $\varepsilon$ with the quadratic variation $[X]_T$ of the process. The scaling law holds universally for all continuous semimartingales with finite quadratic variation, including general Ito diffusions with nonlinear or state-dependent volatility, but fails sharply for deterministic systems -- thereby providing a theoretically-certfied method of distinguishing between these dynamics, as opposed to the subjective entropy or recurrence based state of the art methods. We construct a robust data-driven diffusion test. The method compares the empirical excursion counts against the theoretical expectation. The resulting ratio $K(\varepsilon)=N_{\varepsilon}^{\mathrm{emp}}/N_{\varepsilon}^{\mathrm{theory}}$ is then summarized by a log-log slope deviation measuring the $\varepsilon^{-2}$ law that provides a classification into diffusion-like or not. We demonstrate the method on canonical stochastic systems, some periodic and chaotic maps and systems with additive white noise, as well as the stochastic Duffing system. The approach is nonparametric, model-free, and relies only on the universal small-scale structure of continuous semimartingales.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper develops a nonparametric test to distinguish continuous semimartingales (including general Itô diffusions with state-dependent volatility) from deterministic signals in a single discrete time series. It invokes classical excursion theorems to predict that the number of excursions N_ε of size at least ε scales as ε^{-2} times the quadratic variation [X]_T; the ratio K(ε) = N_ε^emp / N_ε^theory is then summarized by its log-log slope to classify the series as diffusion-like or not. The method is demonstrated on canonical stochastic processes, periodic/chaotic maps, additive-noise systems, and the stochastic Duffing oscillator, and is claimed to be model-free and to rely only on the small-scale structure of continuous semimartingales.
Significance. If the central scaling relation and its robustness to quadratic-variation estimation can be established, the approach supplies a theoretically grounded, nonparametric alternative to entropy- or recurrence-based heuristics for detecting diffusive behavior. The explicit use of excursion theorems for general semimartingales and the provision of a concrete classification statistic constitute a clear strength.
major comments (3)
- [§3] §3 (Method): the theoretical benchmark N_ε^theory is constructed from the realized-volatility estimator ∑(ΔX_i)^2 for [X]_T. For finite sampling grids and state-dependent volatility σ(X), this estimator carries an O(1) relative error that directly rescales N_ε^theory and therefore alters both the level and the log-log slope of K(ε). No error analysis or mesh-refinement study is supplied to show that the classification threshold remains stable under this bias.
- [§4.2] §4.2 (Stochastic Duffing example): the reported separation between the stochastic and deterministic cases relies on the same finite-grid quadratic-variation estimate for both the empirical and theoretical counts. Because the estimation step is performed on the identical series, any systematic bias that mimics the ε^{-2} scaling cannot be ruled out; a controlled experiment with known mesh size or with an independent high-frequency proxy for [X]_T is needed.
- [Abstract / §2] Abstract and §2: the statement that the ε^{-2} law 'holds universally for all continuous semimartingales with finite quadratic variation' is asserted without a self-contained derivation or reference to the precise excursion theorem (e.g., the exact constant relating N_ε to [X]_T). The absence of this formula makes it impossible to verify that the data-driven implementation matches the continuous-theory benchmark.
minor comments (2)
- [Abstract] Abstract: 'theoretically-certfied' is a typographical error.
- [§3] Notation: the symbol K(ε) is introduced without an explicit equation number; subsequent references to its log-log slope would be clearer if the definition were numbered.
Simulated Author's Rebuttal
We thank the referee for the thorough review and constructive feedback. The comments highlight important aspects regarding the finite-sample behavior of the quadratic variation estimator and the need for clearer theoretical grounding. We address each major comment below and indicate the revisions we will make to strengthen the manuscript.
read point-by-point responses
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Referee: [§3] §3 (Method): the theoretical benchmark N_ε^theory is constructed from the realized-volatility estimator ∑(ΔX_i)^2 for [X]_T. For finite sampling grids and state-dependent volatility σ(X), this estimator carries an O(1) relative error that directly rescales N_ε^theory and therefore alters both the level and the log-log slope of K(ε). No error analysis or mesh-refinement study is supplied to show that the classification threshold remains stable under this bias.
Authors: We appreciate this observation. The realized quadratic variation estimator does indeed converge to the true quadratic variation only in the limit of vanishing mesh size, and for finite grids with state-dependent volatility there can be a relative bias. However, our classification relies primarily on the scaling behavior (the log-log slope of K(ε)) rather than the absolute level, which may mitigate the impact of a constant rescaling factor. To rigorously address the concern, we will add an error analysis section and perform mesh-refinement studies in the revised version to confirm that the slope-based threshold remains stable. revision: yes
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Referee: [§4.2] §4.2 (Stochastic Duffing example): the reported separation between the stochastic and deterministic cases relies on the same finite-grid quadratic-variation estimate for both the empirical and theoretical counts. Because the estimation step is performed on the identical series, any systematic bias that mimics the ε^{-2} scaling cannot be ruled out; a controlled experiment with known mesh size or with an independent high-frequency proxy for [X]_T is needed.
Authors: This is a valid point. Using the same series for both empirical counts and the quadratic variation estimate introduces potential circularity in the presence of bias. We will include additional controlled experiments in the revision, such as using a known finer mesh for the quadratic variation proxy or simulating with varying sampling frequencies to demonstrate that the separation persists and is not an artifact of the estimation procedure. revision: yes
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Referee: [Abstract / §2] Abstract and §2: the statement that the ε^{-2} law 'holds universally for all continuous semimartingales with finite quadratic variation' is asserted without a self-contained derivation or reference to the precise excursion theorem (e.g., the exact constant relating N_ε to [X]_T). The absence of this formula makes it impossible to verify that the data-driven implementation matches the continuous-theory benchmark.
Authors: We acknowledge that the manuscript would benefit from a more explicit reference to the underlying excursion theorem. The scaling N_ε ~ [X]_T / ε^2 follows from the occupation time formula and excursion theory for semimartingales. We will add a brief derivation sketch and the precise reference in §2 of the revised manuscript to make the connection transparent and allow verification of the implementation. revision: yes
Circularity Check
No significant circularity: derivation relies on external classical theorem
full rationale
The paper grounds its scaling law in classical excursion theorems for continuous semimartingales, which are independent of the present work. The ratio K(ε) is formed by comparing observed excursion counts to a benchmark computed from the standard realized-volatility estimator of quadratic variation; this estimator is an external input drawn from the data rather than a fitted parameter whose value is forced to reproduce the test statistic. The resulting log-log slope is a falsifiable comparison that can (and does, per the abstract) fail for deterministic signals, so the classification outcome is not equivalent to the inputs by construction. No self-citations, ansatzes, or uniqueness claims appear as load-bearing steps.
Axiom & Free-Parameter Ledger
axioms (1)
- standard math Excursion-count scaling law holds for all continuous semimartingales with finite quadratic variation
Lean theorems connected to this paper
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IndisputableMonolith/Foundation/AlexanderDuality.leanalexander_duality_circle_linking unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
lim ε→0 ε² N_ε(X) = [X]_T / 2 in L¹ (Theorem 2.1, Excursion Law for Continuous Semimartingales)
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IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
N_ε(X) = [X]_T/(2ε²) (1+o(1)) for Ito diffusions with state-dependent σ(X)
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.
Reference graph
Works this paper leans on
-
[1]
Signatures of chaotic and stochastic dynamics uncovered with epsilon-recurrence networks
N. P. Subramaniyam, J. F. Donges, and J. Hyttinen. “Signatures of chaotic and stochastic dynamics uncovered with epsilon-recurrence networks”. In:Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences471.2183 (Nov. 2015), p. 20150349.issn: 1471-2946.doi:10 . 1098/rspa.2015.0349.url:http://dx.doi.org/10.1098/rspa.2015.0349
-
[2]
Detecting dynamical changes in time series by using the Jensen Shannon divergence
D. M. Mateos, L. E. Riveaud, and P. W. Lamberti. “Detecting dynamical changes in time series by using the Jensen Shannon divergence”. In:Chaos: An Interdisciplinary Journal of Nonlinear Science 27.8 (Aug. 2017), p. 083118.issn: 1089-7682.doi:10.1063/1.4999613.url:http://dx.doi.org/ 10.1063/1.4999613
-
[3]
Massimiliano Zanin and Felipe Olivares. “Ordinal patterns-based methodologies for distinguishing chaos from noise in discrete time series”. In:Communications Physics4.1 (Aug. 2021).issn: 2399- 3650.doi:10.1038/s42005- 021- 00696- z.url:http://dx.doi.org/10.1038/s42005- 021- 00696-z
-
[4]
A direct method to detect deterministic and stochastic properties of data
Thiago Lima Prado, Bruno Rafael Reichert Boaretto, Gilberto Corso, Gustavo Zampier dos Santos Lima, J¨ urgen Kurths, and Sergio Roberto Lopes. “A direct method to detect deterministic and stochastic properties of data”. In:New Journal of Physics24.3 (Mar. 2022), p. 033027.issn: 1367- 2630.doi:10.1088/1367-2630/ac5057.url:http://dx.doi.org/10.1088/1367-2630/ac5057
work page doi:10.1088/1367-2630/ac5057.url:http://dx.doi.org/10.1088/1367-2630/ac5057 2022
-
[5]
B. R. R. Boaretto, R. C. Budzinski, K. L. Rossi, T. L. Prado, S. R. Lopes, and C. Masoller. “Discrim- inating chaotic and stochastic time series using permutation entropy and artificial neural networks”. In:Scientific Reports11.1 (Aug. 2021).issn: 2045-2322.doi:10.1038/s41598-021-95231-z.url: http://dx.doi.org/10.1038/s41598-021-95231-z
-
[6]
Can Deep Learning distinguish chaos from noise? Numerical experiments and general considerations
Massimiliano Zanin. “Can Deep Learning distinguish chaos from noise? Numerical experiments and general considerations”. In:Communications in Nonlinear Science and Numerical Simulation114 (Nov. 2022), p. 106708.issn: 1007-5704.doi:10.1016/j.cnsns.2022.106708.url:http://dx. doi.org/10.1016/j.cnsns.2022.106708
work page doi:10.1016/j.cnsns.2022.106708.url:http://dx 2022
-
[7]
L. Zunino, M. C. Soriano, and O. A. Rosso. “Distinguishing chaotic and stochastic dynamics from time series by using a multiscale symbolic approach”. In:Physical Review E86.4 (Oct. 2012).issn: 1550-2376.doi:10.1103/physreve.86.046210.url:http://dx.doi.org/10.1103/PhysRevE.86. 046210
work page doi:10.1103/physreve.86.046210.url:http://dx.doi.org/10.1103/physreve.86 2012
-
[8]
Recurrence plots for characterizing random dynamical systems
Yoshito Hirata. “Recurrence plots for characterizing random dynamical systems”. In:Communica- tions in Nonlinear Science and Numerical Simulation94 (Mar. 2021), p. 105552.issn: 1007-5704. doi:10.1016/j.cnsns.2020.105552.url:http://dx.doi.org/10.1016/j.cnsns.2020.105552
work page doi:10.1016/j.cnsns.2020.105552.url:http://dx.doi.org/10.1016/j.cnsns.2020.105552 2021
-
[9]
Contrasting chaotic with stochastic dynamics via ordinal transition networks
F. Olivares, M. Zanin, L. Zunino, and D. G. P´ erez. “Contrasting chaotic with stochastic dynamics via ordinal transition networks”. In:Chaos: An Interdisciplinary Journal of Nonlinear Science30.6 (June 2020).issn: 1089-7682.doi:10.1063/1.5142500.url:http://dx.doi.org/10.1063/1.5142500. 17
work page doi:10.1063/1.5142500.url:http://dx.doi.org/10.1063/1.5142500 2020
-
[10]
Recurrence networks—a novel paradigm for nonlinear time series analysis
Reik V Donner, Yong Zou, Jonathan F Donges, Norbert Marwan, and Jurgen Kurths. “Recurrence networks—a novel paradigm for nonlinear time series analysis”. In:New Journal of Physics12.3 (Mar. 2010), p. 033025.issn: 1367-2630.doi:10 . 1088 / 1367 - 2630 / 12 / 3 / 033025.url:http : //dx.doi.org/10.1088/1367-2630/12/3/033025
-
[11]
From time series to complex networks: The visibility graph,
Lucas Lacasa, Bartolo Luque, Fernando Ballesteros, Jordi Luque, and Juan Carlos Nu˜ no. “From time series to complex networks: The visibility graph”. In:Proceedings of the National Academy of Sciences105.13 (Apr. 2008), 4972–4975.issn: 1091-6490.doi:10 . 1073 / pnas . 0709247105.url: http://dx.doi.org/10.1073/pnas.0709247105
-
[12]
Distinguish between Stochastic and Chaotic Signals by a Local Structure-Based Entropy
Zelin Zhang, Jun Wu, Yufeng Chen, Ji Wang, and Jinyu Xu. “Distinguish between Stochastic and Chaotic Signals by a Local Structure-Based Entropy”. In:Entropy24.12 (Nov. 2022), p. 1752.issn: 1099-4300.doi:10.3390/e24121752.url:http://dx.doi.org/10.3390/e24121752
work page doi:10.3390/e24121752.url:http://dx.doi.org/10.3390/e24121752 2022
-
[13]
On the persistent homology of almost surelyC 0 stochastic processes
Daniel Perez. “On the persistent homology of almost surelyC 0 stochastic processes”. In:Journal of Applied and Computational Topology7.4 (July 2023), pp. 879–906.issn: 2367-1734.doi:10.1007/ s41468-023-00132-x.url:http://dx.doi.org/10.1007/s41468-023-00132-x. [14]Applications of Random Process Excursion Analysis. Elsevier, 2013.isbn: 9780124095014.doi:10....
-
[14]
Blumenthal.Excursions of Markov Processes
Robert M. Blumenthal.Excursions of Markov Processes. Birkh¨ auser Boston, 1992.isbn: 9781468494129. doi:10.1007/978-1-4684-9412-9.url:http://dx.doi.org/10.1007/978-1-4684-9412-9
work page doi:10.1007/978-1-4684-9412-9.url:http://dx.doi.org/10.1007/978-1-4684-9412-9 1992
-
[15]
Mathematical Analysis of Random Noise
S. O. Rice. “Mathematical Analysis of Random Noise”. In:Bell System Technical Journal23.3 (July 1944), 282–332.issn: 0005-8580.doi:10 . 1002 / j . 1538 - 7305 . 1944 . tb00874 . x.url:http : //dx.doi.org/10.1002/j.1538-7305.1944.tb00874.x
-
[16]
The expected number of zeros of continuous stationary Gaussian processes
Kiyosi Ito. “The expected number of zeros of continuous stationary Gaussian processes”. In:Kyoto Journal of Mathematics3.2 (Jan. 1963).issn: 2156-2261.doi:10 . 1215 / kjm / 1250524817.url: http://dx.doi.org/10.1215/kjm/1250524817
-
[17]
The Expected Number of Zeros of a Stationary Gaussian Process
N. Donald Ylvisaker. “The Expected Number of Zeros of a Stationary Gaussian Process”. In:The Annals of Mathematical Statistics36.3 (June 1965), 1043–1046.issn: 0003-4851.doi:10.1214/aoms/ 1177700077.url:http://dx.doi.org/10.1214/aoms/1177700077
-
[18]
On Homology of Real Algebraic Varieties
M. R. Leadbetter. “On crossings of arbitrary curves by certain Gaussian processes”. In:Proceedings of the American Mathematical Society16.1 (Feb. 1965), 60–68.issn: 1088-6826.doi:10.1090/s0002- 9939-1965-0170382-6.url:http://dx.doi.org/10.1090/S0002-9939-1965-0170382-6
-
[19]
Asymptotically optimal tests for mu ltinomial distributions
M. R. Leadbetter and J. D. Cryer. “On the Mean Number of Curve Crossings by Non-Stationary Normal Processes”. In:The Annals of Mathematical Statistics36.2 (Apr. 1965), 509–516.issn: 0003- 4851.doi:10.1214/aoms/1177700160.url:http://dx.doi.org/10.1214/aoms/1177700160
work page doi:10.1214/aoms/1177700160.url:http://dx.doi.org/10.1214/aoms/1177700160 1965
-
[20]
On the Average Number of Crossings of a Level by the Sample Functions of a Stochastic Process
V. A. Ivanov. “On the Average Number of Crossings of a Level by the Sample Functions of a Stochastic Process”. In:Theory of Probability & Its Applications5.3 (Jan. 1960), 319–323.issn: 1095-7219.doi:10.1137/1105031.url:http://dx.doi.org/10.1137/1105031
work page doi:10.1137/1105031.url:http://dx.doi.org/10.1137/1105031 1960
-
[21]
Nonlinear programming in complex space: Sufficient conditions and duality
Zekai Sen. “Probabilistic modelling of crossing in small samples and application of runs to hydrology”. In:Journal of Hydrology124.3-4 (May 1991), pp. 345–362.issn: 0022-1694.doi:10.1016/0022- 1694(91)90023-b.url:http://dx.doi.org/10.1016/0022-1694(91)90023-B
-
[22]
ESC: Dataset for Environmental Sound Classification,
Karol J. Piczak. “ESC: Dataset for Environmental Sound Classification”. In:Proceedings of the 23rd Annual ACM Conference on Multimedia. Brisbane, Australia: ACM Press, Oct. 13, 2015, pp. 1015– 1018.isbn: 978-1-4503-3459-4.doi:10 . 1145 / 2733373 . 2806390.url:http : / / dl . acm . org / citation.cfm?doid=2733373.2806390. 18 A Benchmark System Definitions ...
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