Dimensional consistency in fractional differential equations with non singular kernels
Pith reviewed 2026-05-13 21:00 UTC · model grok-4.3
The pith
A simple change of variables restores dimensional consistency to fractional differential equations with non-singular kernels.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
By performing a simple change of variables that fulfills certain conditions, dimensional consistency is ensured in fractional differential equations that employ non-singular kernels.
What carries the argument
The change of variables applied to the time variable in the fractional differential equation to compensate for the dimensions carried by the non-singular kernel operator.
If this is right
- Fractional models using non-singular kernels can be rewritten so that every term shares the same physical units.
- The transformation leaves the original kernel and its memory properties unchanged.
- The method extends directly to concrete examples without requiring new kernel definitions.
Where Pith is reading between the lines
- The same style of transformation could be tested on singular kernels once analogous conditions are identified.
- Comparing results before and after the change of variables might clarify how different kernels affect physical predictions.
- Applying the method to measured data from systems known to obey fractional dynamics would check whether the adjusted equations match observations.
Load-bearing premise
The change of variables must fulfill certain conditions that align the dimensions for the chosen non-singular kernel.
What would settle it
A counterexample of a non-singular kernel for which no change of variables restores dimensional consistency across the equation.
Figures
read the original abstract
The purpose of this article is to address the issues of dimensional consistency that arise in the process of replacing the ordinary time derivative operator by a fractional derivative operator in order to write a fractional differential equation. We show that by performing a simple change of variables fulfilling certain conditions ensures the consistency in physical dimensions for fractional differential equations with non singular kernels. An example of the proposed method is given.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript claims that dimensional inconsistency arising when replacing ordinary derivatives with fractional operators in differential equations can be resolved for non-singular kernels (such as Caputo-Fabrizio or Atangana-Baleanu) by a change of variables that satisfies certain conditions, and it illustrates the approach with a single example.
Significance. If the proposed transformation can be shown to work generally while preserving the fractional order, the non-singular kernel form, and well-posedness, the result would offer a practical route to dimensionally homogeneous fractional models without ad-hoc rescaling of parameters, which is relevant for physical applications of fractional calculus.
major comments (2)
- [Abstract and main text] Abstract and main derivation: the central assertion that a change of variables 'fulfilling certain conditions' restores dimensional consistency is stated without explicit derivation of those conditions, without error analysis, and without verification that the transformed equation retains the original non-singular kernel and fractional order for kernels beyond the single example provided.
- [Main text (example section)] The manuscript does not supply the explicit functional form of the change of variables (e.g., t → τ^α or similar) nor the kernel-independent conditions that must be satisfied, leaving open whether the method is general or requires kernel-specific adjustments that could introduce new singularities or alter the equation's properties.
minor comments (1)
- [Abstract] The abstract would benefit from a brief statement of the concrete change of variables and the example equation used, rather than referring only to 'certain conditions'.
Simulated Author's Rebuttal
We thank the referee for the constructive comments on our manuscript. The points raised highlight areas where additional explicit detail will strengthen the presentation. We have revised the manuscript to provide the requested derivations, explicit functional form, error discussion, and further verification while preserving the original scope and results.
read point-by-point responses
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Referee: [Abstract and main text] Abstract and main derivation: the central assertion that a change of variables 'fulfilling certain conditions' restores dimensional consistency is stated without explicit derivation of those conditions, without error analysis, and without verification that the transformed equation retains the original non-singular kernel and fractional order for kernels beyond the single example provided.
Authors: We agree that the derivation of the conditions should be presented explicitly. The revised manuscript now contains a dedicated subsection deriving the conditions from first principles of dimensional homogeneity. We have added a short error analysis quantifying the effect of the transformation on solution accuracy for the class of equations considered. To address verification beyond the original example, we include a second illustration using the Atangana-Baleanu kernel, confirming that the non-singular character and fractional order remain unchanged under the transformation. revision: yes
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Referee: [Main text (example section)] The manuscript does not supply the explicit functional form of the change of variables (e.g., t → τ^α or similar) nor the kernel-independent conditions that must be satisfied, leaving open whether the method is general or requires kernel-specific adjustments that could introduce new singularities or alter the equation's properties.
Authors: The revised text now states the explicit change of variables t = τ^α (with α the fractional order) together with the kernel-independent conditions: the map must be strictly increasing, bijective, and C^1 so that the chain-rule factors compensate the dimensional mismatch while leaving the kernel non-singular. We demonstrate that these conditions are satisfied uniformly for the family of non-singular kernels (Caputo-Fabrizio and Atangana-Baleanu) without introducing singularities or changing the well-posedness of the original initial-value problem. revision: yes
Circularity Check
No circularity: derivation applies standard dimensional analysis via change of variables
full rationale
The paper's central step is introducing a change of variables (subject to unspecified but kernel-dependent conditions) to restore dimensional homogeneity when replacing ordinary derivatives with non-singular fractional operators. This is presented as a direct application of dimensional analysis rather than a redefinition of quantities in terms of the target result. No equations reduce by construction to fitted inputs, self-citations, or ansatzes imported from prior author work; the single example serves only as illustration. The derivation remains self-contained against external benchmarks of dimensional consistency and does not invoke uniqueness theorems or load-bearing self-references.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption Fractional derivative operators of non-integer order possess different physical dimensions from ordinary derivatives.
Lean theorems connected to this paper
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IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel (J uniquely calibrated reciprocal cost) unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
replace the ordinary time derivative operator by the following one d/dt → dτ/dt d/dτ → 1/ϕ(t(τ),α) CF D^α_t (Eq. 9); ϕ(t,α) has dimension of time
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IndisputableMonolith/Foundation/DimensionForcing.leanalexander_duality_circle_linking (D=3 forced) unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
τ(t,α)=∫dt/ϕ(t,α) (Eq. 8) with condition (10) recovering d/dt at α=1
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
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discussion (0)
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