Ergodicity for regime-switching neutral stochastic functional differential equations with infinite delay
Pith reviewed 2026-05-10 15:40 UTC · model grok-4.3
The pith
Regime-switching neutral stochastic functional differential equations with infinite delay exhibit exponential ergodicity in Wasserstein distance for both finite and infinite state spaces.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Under dissipativity conditions that guarantee well-posedness of the non-switching NSFDEs via Skorohod representation, the authors obtain exponential ergodicity in Wasserstein distance for the regime-switching versions. For finite state spaces they apply moment estimates of exponential functionals of the switching component together with the coupling method; for countably infinite state spaces they employ the finite partition method along with Lyapunov functions and M-matrix theory to derive the identical exponential convergence.
What carries the argument
Moment estimates of exponential functionals of the switching component, the coupling method for finite states, and the finite partition method combined with Lyapunov functions and M-matrix theory for infinite states, which together produce contraction in the Wasserstein distance.
If this is right
- Solutions converge exponentially to a unique invariant measure in Wasserstein distance.
- The underlying non-switching neutral equations are well-posed under the stated dissipativity conditions.
- The ergodicity result extends from finite to countably infinite regime spaces without loss of the exponential rate.
- Lyapunov and M-matrix conditions suffice to control stability across the finite partitions of the state space.
Where Pith is reading between the lines
- The finite partition technique may be adapted to establish ergodicity for other classes of stochastic functional equations with infinite memory.
- Numerical path simulations could be used to check the predicted exponential decay of Wasserstein distances to an approximate stationary distribution.
- The Skorohod-representation approach to well-posedness could apply to related neutral delay models even without switching.
Load-bearing premise
The dissipativity conditions that guarantee well-posedness of the non-switching NSFDEs via Skorohod representation, together with the moment bounds on the switching process and the matrix and Lyapunov conditions that enable the infinite-state argument.
What would settle it
A concrete counter-example in which the moment estimates fail or the M-matrix condition is violated, resulting in either multiple invariant measures or convergence slower than exponential in Wasserstein distance.
read the original abstract
This work focuses on a class of regime-switching neutral stochastic functional differential equations (RNSFDEs) with infinite delay, in which the switching component can possess finite or countably infinite many states. To ensure the well-posedness of the underlying process, we first investigate the well-posedness for NSFDEs without Markovian switching under dissipativity conditions, and obtain the desired result by Skorohod's representation. By utilizing the moment estimate of exponential functionals of the switching component, we derive the exponential ergodicity in Wasserstein distance for RNSFDEs with a finite state space using the coupling method. To address the difficulty posed by the infinite state space, we obtain the same exponential ergodicity by applying the finite partition method along with Lyapunov functions and M-matrix theory.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript establishes well-posedness for neutral stochastic functional differential equations (NSFDEs) with infinite delay under dissipativity conditions via Skorohod representation. It then proves exponential ergodicity in Wasserstein distance for the regime-switching versions (RNSFDEs) with finite state space by combining moment estimates on exponential functionals of the Markov chain with a coupling argument. For countably infinite state spaces, the same ergodicity is obtained by a finite-partition reduction together with Lyapunov functions and M-matrix conditions.
Significance. If the stated dissipativity, moment, and M-matrix hypotheses hold, the results extend existing ergodicity theory to neutral infinite-delay equations with regime switching, a setting relevant to applications with memory and abrupt parameter changes. The Wasserstein metric yields quantitative convergence of distributions, and the finite-partition technique for infinite states is a standard and plausible device once the Lyapunov/M-matrix conditions are granted. The proof strategy relies on classical tools (coupling, Skorohod representation, M-matrices) whose applicability appears consistent with the outlined steps.
major comments (2)
- The dissipativity conditions used for well-posedness of the non-switching NSFDE (via Skorohod representation) must be verified to be compatible with the neutral term and infinite delay; if they only control the drift and diffusion without uniform control on the neutral operator, the representation argument may fail to produce a unique strong solution.
- In the infinite-state extension, the finite-partition method combined with the M-matrix condition must be shown to produce a uniform exponential rate independent of the partition; otherwise the ergodicity claim for the original process does not follow directly from the finite-state approximations.
minor comments (2)
- Notation for the switching process and the Wasserstein distance should be introduced consistently in the preliminaries to avoid ambiguity when passing between finite and infinite state spaces.
- The moment estimates on the exponential functionals of the switching component (used in the finite-state coupling) would benefit from an explicit statement of the constants appearing in the bounds.
Simulated Author's Rebuttal
We thank the referee for the careful reading and constructive comments on our manuscript. We address each major comment below, indicating the revisions we will make to clarify the arguments.
read point-by-point responses
-
Referee: The dissipativity conditions used for well-posedness of the non-switching NSFDE (via Skorohod representation) must be verified to be compatible with the neutral term and infinite delay; if they only control the drift and diffusion without uniform control on the neutral operator, the representation argument may fail to produce a unique strong solution.
Authors: We appreciate this observation. Our dissipativity condition (H1) is formulated to control the neutral operator directly through a uniform Lipschitz-type bound on the difference of the neutral functionals, which is compatible with the infinite-delay fading memory space. This ensures the Skorohod representation produces a unique strong solution. We will add a short remark after the statement of (H1) explicitly verifying this compatibility with the neutral term. revision: yes
-
Referee: In the infinite-state extension, the finite-partition method combined with the M-matrix condition must be shown to produce a uniform exponential rate independent of the partition; otherwise the ergodicity claim for the original process does not follow directly from the finite-state approximations.
Authors: This is a valid point. The M-matrix condition is imposed uniformly over the countable state space and is independent of any finite partition; the resulting Lyapunov estimates yield an exponential rate that depends only on the M-matrix spectral gap and the uniform moment bounds, not on the partition. We will insert a new lemma establishing that the Wasserstein contraction rate is uniform across partitions, allowing the limit argument to pass to the infinite-state process. revision: yes
Circularity Check
No significant circularity in the derivation chain
full rationale
This is a pure existence-and-convergence proof paper in stochastic analysis. The derivation proceeds by establishing well-posedness of the non-switching NSFDE under dissipativity conditions via Skorohod representation, then proving Wasserstein exponential ergodicity for finite-state switching via coupling and moment bounds on the switching process, and finally extending to countably infinite states via finite partitioning, Lyapunov functions, and M-matrix theory. None of these steps reduce by construction to fitted parameters, self-referential predictions, or load-bearing self-citations; each applies standard tools to independent hypotheses. No self-definitional loops, renamed empirical patterns, or ansatz smuggling are present.
Axiom & Free-Parameter Ledger
axioms (3)
- domain assumption Dissipativity conditions sufficient for well-posedness of NSFDEs without switching
- domain assumption Existence of moment estimates for exponential functionals of the switching component
- domain assumption Lyapunov functions and M-matrix conditions that guarantee the infinite-state ergodicity
Reference graph
Works this paper leans on
-
[1]
Jianhai Bao, Jinghai Shao, and Chenggui Yuan. Invariant probability measures for path-dependent random diffusions.Nonlinear Analysis, 228:113201, 2023
work page 2023
-
[2]
Jianhai Bao, Feng-Yu Wang, and Chenggui Yuan. Derivative formula and Harnack inequality for degenerate functional SDEs.Stochastics and Dynamics, 13(01):1250013, 2013
work page 2013
-
[3]
Jianhai Bao, Feng-Yu Wang, and Chenggui Yuan. Asymptotic log-Harnack inequality and applications for stochastic systems of infinite memory.Stochastic Processes and their Applications, 129(11):4576–4596, 2019
work page 2019
-
[4]
Jianhai Bao, Feng-Yu Wang, and Chenggui Yuan. Ergodicity for neutral type SDEs with infinite length of memory.Mathematische Nachrichten, 293(9):1675–1690, 2020
work page 2020
-
[5]
Springer Briefs in Mathematics
Jianhai Bao, George Yin, and Chenggui Yuan.Asymptotic analysis for functional stochastic differential equa- tions. Springer Briefs in Mathematics. Springer, Cham, 2016. 30
work page 2016
- [6]
-
[7]
Abraham Berman and Robert J Plemmons.Nonnegative matrices in the mathematical sciences. SIAM, 1994
work page 1994
-
[8]
Brahim Boufoussi and Salah Hajji. Neutral stochastic functional differential equations driven by a fractional brownian motion in a Hilbert space.Statistics&probability letters, 82(8):1549–1558, 2012
work page 2012
-
[9]
Oleg Butkovsky. Subgeometric rates of convergence of Markov processes in the Wasserstein metric.The Annals of Applied Probability, 24(2):526–552, 2014
work page 2014
-
[10]
Oleg Butkovsky, Alexei Kulik, and Michael Scheutzow. Generalized couplings and ergodic rates for SPDEs and other Markov models.The Annals of Applied Probability, 30(1):1–39, 2020
work page 2020
-
[11]
Invariant measures for stochastic functional differential equations
Oleg Butkovsky and Michael Scheutzow. Invariant measures for stochastic functional differential equations. Electronic Journal of Probability, 22(98):1–23, 2017
work page 2017
-
[12]
World Scientific Publishing Co., Inc., River Edge, NJ, second edition, 2004
Mu-Fa Chen.From Markov chains to non-equilibrium particle systems. World Scientific Publishing Co., Inc., River Edge, NJ, second edition, 2004
work page 2004
-
[13]
Springer Science & Business Media, 2006
Mu-Fa Chen.Eigenvalues, inequalities, and ergodic theory. Springer Science & Business Media, 2006
work page 2006
-
[14]
Martin Hairer, Jonathan C Mattingly, and Michael Scheutzow. Asymptotic coupling and a general form of Harris’ theorem with applications to stochastic delay equations.Probability theory and related fields, 149:223–259, 2011
work page 2011
-
[15]
Jun Li and Fubao Xi. Convergence, boundedness, and ergodicity of regime-switching diffusion processes with infinite memory.Frontiers of Mathematics in China, 16:499–523, 2021
work page 2021
-
[16]
NI Mahmudov. Existence and uniqueness results for neutral SDEs in Hilbert spaces.Stochastic Analysis and Applications, 24(1):79–95, 2006
work page 2006
-
[17]
Xuerong Mao.Stochastic Differential Equations and Applications. Elsevier, 2007
work page 2007
-
[18]
Imperial col- lege press, 2006
Xuerong Mao and Chenggui Yuan.Stochastic differential equations with Markovian switching. Imperial col- lege press, 2006
work page 2006
-
[19]
Dang Hai Nguyen and George Yin. Modeling and analysis of switching diffusion systems: past-dependent switching with a countable state space.SIAM Journal on Control and Optimization, 54(5):2450–2477, 2016
work page 2016
-
[20]
Springer Science & Business Media, 2013
Bernt Oksendal.Stochastic differential equations: an introduction with applications. Springer Science & Business Media, 2013
work page 2013
-
[21]
Springer Science & Business Media, 2013
Daniel Revuz and Marc Yor.Continuous martingales and Brownian motion, volume 293. Springer Science & Business Media, 2013
work page 2013
-
[22]
Jinghai Shao. Ergodicity of regime-switching diffusions in Wasserstein distances.Stochastic Processes and their Applications, 125(2):739–758, 2015
work page 2015
-
[23]
Banban Shi, Ya Wang, and Fuke Wu. Ergodicity of regime-switching functional diffusions with infinite delay and application to a numerical algorithm for stochastic optimization.SIAM Journal on Control and Optimiza- tion, 60(5):2658–2683, 2022
work page 2022
-
[24]
Grundlehren der mathematischen Wissenschaften
C ´edric Villani.Optimal transport : old and new. Grundlehren der mathematischen Wissenschaften. Springer- Verlag Berlin Heidelberg, 2009
work page 2009
-
[25]
Feng-Yu Wang and Chenggui Yuan. Harnack inequalities for functional SDEs with multiplicative noise and applications.Stochastic processes and their applications, 121(11):2692–2710, 2011
work page 2011
-
[26]
Ya Wang, Fuke Wu, George Yin, and Chao Zhu. Stochastic functional differential equations with infinite delay under non-lipschitz coefficients: existence and uniqueness, Markov property, ergodicity, and asymptotic log- Harnack inequality.Stochastic Processes and their Applications, 149:1–38, 2022
work page 2022
-
[27]
Fuke Wu and Xuerong Mao. Numerical solutions of neutral stochastic functional differential equations.SIAM Journal on Numerical Analysis, 46(4):1821–1841, 2008
work page 2008
-
[28]
George Yin and Chao Zhu.Hybrid Switching Diffusions: Properties and Applications, volume 63. Springer, New York, 2010
work page 2010
-
[29]
Yafei Zhai and Fubao Xi. Exponential ergodicity for stochastic functional differential equations with Mar- kovian switching.Journal of Mathematical Analysis and Applications, 534(1):128030, 2024
work page 2024
-
[30]
Zuozheng Zhang and Fubao Xi. Existence, uniqueness and stability analysis for neutral stochastic functional differential equations with jumps and infinite delay.Journal of Theoretical Probability, 38(28), 2025
work page 2025
-
[31]
Zuozheng Zhang and Fubao Xi. Exponential ergodicity under wasserstein distance for regime-switching sto- chastic functional differential equations with infinite delay.Journal of Mathematical Analysis and Applica- tions, 552(1):129724, 2025
work page 2025
-
[32]
Min Zhu and Mingtian Tang. Approximation of random periodic solutions for neutral type SDEs with non- uniform dissipativity.Frontiers of Mathematics, pages 1–54, 2025
work page 2025
-
[33]
Xiaofeng Zong and Fuke Wu. Exponential stability of the exact and numerical solutions for neutral stochastic delay differential equations.Applied Mathematical Modelling, 40(1):19–30, 2016. 31
work page 2016
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.