On a Boundary-Initial Value Problem for Fractional Differential Equation with Sequential Caputo derivatives
Pith reviewed 2026-05-09 21:34 UTC · model grok-4.3
The pith
The boundary-initial value problem for a fractional differential equation with sequential Caputo derivatives admits an exact solution in terms of the bivariate Mittag-Leffler function.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The authors establish that the solution of the boundary-initial value problem can be expressed exactly using the bivariate Mittag-Leffler function after applying standard operational properties of sequential Caputo derivatives; they further show that this representation holds under the stated initial and boundary data without requiring extra compatibility conditions, and they supply a set of auxiliary identities for the bivariate Mittag-Leffler function that facilitate the derivation.
What carries the argument
The bivariate Mittag-Leffler function, which encodes the combined action of the two sequential Caputo operators and directly supplies the closed-form solution coefficients.
If this is right
- The exact formula supplies a benchmark against which any numerical method for sequential Caputo problems can be tested.
- The listed properties of the bivariate Mittag-Leffler function become reusable tools for constructing solutions to other linear sequential fractional equations.
- The sequential reformulation used for the numerical scheme converts the original problem into a system that existing L1-finite element codes can handle with only minor adjustments.
- Analytic expressions of this type allow direct study of long-time decay rates and stability without discretizing time.
Where Pith is reading between the lines
- The same solution strategy could be tested on equations that mix sequential Caputo derivatives with Riemann-Liouville operators to see whether the bivariate Mittag-Leffler form survives.
- The numerical scheme might be extended to nonlinear problems by treating the nonlinearity explicitly while retaining the linear fractional part in closed form.
- Because the bivariate Mittag-Leffler function reduces to ordinary Mittag-Leffler functions when the two orders coincide, the present result specializes to known single-order cases and thereby recovers earlier literature as a consistency check.
Load-bearing premise
The sequential Caputo operators together with the given boundary-initial conditions permit an immediate representation by the bivariate Mittag-Leffler function without extra regularity or compatibility requirements on the data.
What would settle it
A specific choice of initial data and forcing term for which the explicit Mittag-Leffler series fails to satisfy the differential equation or the boundary conditions after direct substitution and differentiation.
Figures
read the original abstract
In this paper, we investigate a fractional differential equation involving sequential Caputo derivatives, motivated by recent research on fractional models with multiple memory effects. Using techniques inspired by earlier works on sequential fractional operators, we derive the exact analytic solution of the problem in terms of the bivariate Mittag-Leffler function. Additionally, several useful properties of the bivariate Mittag-Leffler function are formulated to support the solution construction. Furthermore, we develop a numerical scheme using a sequential reformulation and the L1-finite element method.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper investigates a boundary-initial value problem for a fractional differential equation involving sequential Caputo derivatives. It derives an exact analytic solution expressed in terms of the bivariate Mittag-Leffler function, formulates several useful properties of this function to support the construction, and develops a numerical scheme based on sequential reformulation combined with the L1-finite element method.
Significance. If the exact solution holds rigorously for the stated problem class, the work would provide a useful closed-form representation for fractional models incorporating multiple memory effects, along with supporting properties of the bivariate Mittag-Leffler function and a practical discretization approach. The numerical component adds applicability, but the overall significance depends on whether the analytic claim is general or restricted by unstated conditions.
major comments (2)
- Derivation of the exact analytic solution: The central claim is that the solution of the sequential Caputo problem ^C D^α (^C D^β u) = f(t) with the given boundary-initial conditions is exactly representable by the bivariate Mittag-Leffler function without remainder integrals or correction series. This representation is obtained via Laplace transform inversion, but the inversion produces precisely that form only when fractional-order compatibility relations hold between the initial data at t=0 and the boundary data at the other endpoint (e.g., the fractional integral of the boundary datum matching the initial datum up to order α). No such conditions are imposed or verified in the problem statement or solution construction, so the claimed direct representation does not hold for arbitrary data.
- Numerical scheme section: The paper develops a numerical scheme via sequential reformulation and the L1-finite element method, yet provides no convergence analysis, stability estimates, or error bounds. Without these, it is impossible to assess whether the scheme reliably approximates the analytic solution or satisfies the boundary conditions to the expected order.
minor comments (1)
- Abstract: The orders α and β of the sequential Caputo derivatives and the precise form of the boundary-initial conditions should be stated explicitly to allow readers to evaluate the scope of the exact-solution claim without consulting the full text.
Simulated Author's Rebuttal
We thank the referee for the thorough review and insightful comments on our manuscript. We address each major comment below and outline the revisions we plan to make.
read point-by-point responses
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Referee: Derivation of the exact analytic solution: The central claim is that the solution of the sequential Caputo problem ^C D^α (^C D^β u) = f(t) with the given boundary-initial conditions is exactly representable by the bivariate Mittag-Leffler function without remainder integrals or correction series. This representation is obtained via Laplace transform inversion, but the inversion produces precisely that form only when fractional-order compatibility relations hold between the initial data at t=0 and the boundary data at the other endpoint (e.g., the fractional integral of the boundary datum matching the initial datum up to order α). No such conditions are imposed or verified in the problem statement or solution construction, so the claimed direct representation does not hold for arbitrary data.
Authors: We appreciate the referee highlighting this subtlety in the solution representation. After reviewing the Laplace inversion procedure in our derivation, we recognize that compatibility conditions between the initial conditions and the boundary data are required to ensure the solution is precisely the bivariate Mittag-Leffler function without additional integral remainder terms. In the revised manuscript, we will incorporate these conditions into the problem statement, provide a verification that they are satisfied for the exact representation, and discuss the general case briefly. This will clarify the scope of the analytic result. revision: yes
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Referee: Numerical scheme section: The paper develops a numerical scheme via sequential reformulation and the L1-finite element method, yet provides no convergence analysis, stability estimates, or error bounds. Without these, it is impossible to assess whether the scheme reliably approximates the analytic solution or satisfies the boundary conditions to the expected order.
Authors: We agree that the absence of a convergence analysis limits the assessment of the numerical scheme. We will revise the manuscript to include a detailed convergence analysis, including stability estimates and error bounds for the L1-finite element discretization. This will demonstrate the expected convergence rates and confirm that the scheme approximates the solution while respecting the boundary conditions. revision: yes
Circularity Check
No circularity: derivation uses standard Laplace/series methods for sequential Caputo operators
full rationale
The paper states it derives the exact solution via techniques for sequential fractional operators and formulates bivariate Mittag-Leffler properties to support construction. No quoted step reduces a prediction to a fitted input, self-definition, or load-bearing self-citation chain. The representation follows directly from applying the Laplace transform to ^C D^α (^C D^β u) = f(t) and inverting under the given boundary-initial conditions, which is independent of the target result itself. External benchmarks (standard ML function identities) remain available and are not redefined within the paper.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Caputo fractional derivatives of order alpha satisfy the usual semigroup property under sequential application
- standard math The bivariate Mittag-Leffler function satisfies the required differential relations for the sequential operator
Reference graph
Works this paper leans on
-
[1]
K. Hattaf, On the stability and numerical scheme of fractional differential equations with application to biology, Computation 10 (2022), 97, DOI: 10.3390/computation10060097
-
[2]
A. Traore and N. Sene, Model of economic growth in the context of fractional derivative, Alexandria Engineering Journal 59 (2020), 4843--4850, DOI: 10.1016/j.aej.2020.08.047
-
[3]
F. Cesarone, M. Caputo and C. Cametti, Memory formalism in the passive diffusion across highly heterogeneous systems, Journal of Membrane Science 250 (2005), 79--84, DOI: 10.1016/j.memsci.2004.10.018
-
[4]
K. S. Miller and B. Ross, An Introduction to the Fractional Calculus and Fractional Differential Equations, Wiley Sons, New York, 1993
work page 1993
-
[5]
B. Ahmad and J. J. Nieto, Sequential fractional differential equations with three-point boundary conditions, Computers Mathematics with Applications 64 (2012), 3046--3052, DOI:10.1016/j.camwa.2012.02.036
-
[6]
B. Ahmad and J. J. Nieto, Boundary value problems for a class of sequential integrodifferential equations of fractional order, Journal of Function Spaces and Applications 2013 (2013), Art. ID 149659, DOI:10.1155/2013/149659
-
[7]
B. Ahmad and S. K. Ntouyas, On higher-order sequential fractional differential inclusions with nonlocal three-point boundary conditions, Abstract and Applied Analysis 2014 (2014), Art. ID 659405, DOI: 10.1155/2014/659405
-
[8]
D. Mozyrska, E. Girejko and M. Wyrwas, Fractional nonlinear systems with sequential operators, Central European Journal of Physics 11 (2013), 1295--1303, DOI: 10.2478/s11534-013-0223-3
-
[9]
S. Song and Y. Cui, Existence of solutions for integral boundary value problems of mixed fractional differential equations under resonance, Boundary Value Problems 2020 (2020), 23, DOI: 10.1186/s13661-020-01332-5
-
[10]
K. M. Furati, Bounds on the solution of a Cauchy-type problem involving a weighted sequential fractional derivative, Fractional Calculus and Applied Analysis 16 (2013), 171--188, DOI:10.2478/s13540-013-0012-0
-
[11]
A. M. Djaouti, K. O. Melha and M. A. Latif, New results on the solvability of abstract sequential Caputo fractional differential equations with a resolvent-operator approach and applications, Mathematics 12 (2024), 1268, DOI: 10.3390/math12081268
-
[12]
Yu. E. Fayziev and Sh. F. Jumaeva, On the Cauchy problem for the Langevin-type fractional equation, Uzbek Mathematical Journal 69 (2025), 109--118
work page 2025
-
[13]
Yu. E. Fayziev, Sh. F. Jumaeva and F. Abdullaeva, Inverse problem for the Langevin-type fractional differential equation, Bulletin of the Institute of Mathematics 8 (2025), 30--35
work page 2025
-
[14]
Yu. Fayziev and Sh. Jumaeva, Forward and Inverse Problems for a Langevin-Type Fractional Equation Involving Non-Local Time Condition, preprint (2025), https://arxiv.org/pdf/2507.07446
-
[15]
O. Boichuk and V. Feruk, Fredholm Boundary-Value Problem for the Two-Term Sequential Fractional Differential Equation, Ukrainian Mathematical Journal 77 (2025), 1--11, DOI: 10.3842/umzh.v77i1.8611
-
[16]
R. Ashurov and R. Saparbayev, Fractional Telegraph Equation with the Caputo Derivative, Fractal and Fractional 7 (2023), 483, DOI: 10.3390/fractalfract7060483
-
[17]
R. Ashurov and R. Saparbayev, Forward and Inverse Problems for Fractional Telegraph Equation, Lobachevskii Journal of Mathematics 45 (2024), 4459--4478, DOI: 10.1134/S199508022460506X
-
[18]
R. Saparbayev, A Time-non-local problem for the fractional-order telegraph equation, Bulletin of the Institute of Mathematics 7 (2024), 63--76
work page 2024
-
[19]
R. Ashurov and R. Saparbayev, Time-dependent identification problem for a fractional Telegraph equation with the Caputo derivative, Fractional Calculus and Applied Analysis 27 (2024), 652--676, DOI: 10.1007/s13540-024-00240-0
-
[20]
R. R. Ashurov and R. A. Saparbayev, Inverse Problem for Determining Time-Dependent Coefficient and Source Functions in a Time-Fractional Telegraph Equation, Lobachevskii Journal of Mathematics, to appear
-
[21]
C. Lizama, Abstract linear fractional evolution equations, in: Handbook of Fractional Calculus with Applications 2, De Gruyter (2019), 465--498, DOI: 10.1515/9783110571660-021
-
[22]
R. Ashurov and M. Shakarova, Inverse problem for subdiffusion equation with the integral over-determination condition, Journal of Mathematical Sciences (2024), DOI: 10.13108/2024-16-1-112
-
[23]
M. M. Djrbashian, Integral Transforms and Representation of Functions in the Complex Domain, Nauka, Moscow, 1966
work page 1966
-
[24]
T. R. Prabhakar, A singular integral equation with a generalized Mittag-Leffler function in the kernel, Yokohama Mathematical Journal 19 (1971), 7--15
work page 1971
-
[25]
A. A. Kilbas, H. M. Srivastava and J. J. Trujillo, The Theory and Applications of Fractional Differential Equations, Elsevier, Amsterdam, 2006
work page 2006
-
[26]
M. Garg, P. Manohar and S. L. Kalla, A Mittag-Leffler-type function of two variables, Integral Transforms and Special Functions 24 (2013), 934--944, DOI:10.1080/10652469.2013.789872
-
[27]
E. T. Karimov and A. Hasanov, On a boundary-value problem in a bounded domain for a time-fractional diffusion equation with the Prabhakar fractional derivative, Bulletin of the Karaganda University Mathematics 111 (2023), 39--46, DOI:10.31489/2023m3/39-46
-
[28]
E. Karimov and M. Toshpulatov, Mixed wave-diffusion-wave equation: solvability of an initial-boundary problem, Gulf Journal of Mathematics 20 (2025), 120--139, DOI:10.56947/gjom.v20i.2863
-
[29]
E. Karimov, N. Tokmagambetov and M. Toshpulatov, On a Mixed Equation Involving Prabhakar Fractional Order Integral-Differential Operators, in: Extended Abstracts 2021/2022, APDEGS, Springer
work page 2021
-
[30]
A. Hasanov and H. Yuldashova, Mittag-Leffler type functions of three variables, Mathematical Methods in the Applied Sciences (2024), DOI:10.1002/mma.10401
-
[31]
A. Fernandez, C. Kürt and M. A. Özarslan, A naturally emerging bivariate Mittag-Leffler function and associated fractional-calculus operators, Computational and Applied Mathematics 39 (2020), 200, DOI:10.1007/s40314-020-01224-5
-
[32]
F. Maes and K. Van Bockstal, Existence and uniqueness of a weak solution to fractional single-phase-lag heat equation, Fractional Calculus and Applied Analysis 26 (2023), 1663--1690, DOI:10.1007/s13540-023-00177-w
-
[33]
F. Mainardi, Fractional Calculus and Waves in Linear Viscoelasticity: An Introduction to Mathematical Models, Imperial College Press, London, 2010
work page 2010
discussion (0)
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