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arxiv: 2604.02432 · v1 · submitted 2026-04-02 · 🧮 math-ph · math.MP

Dimensional consistency in fractional differential equations with non singular kernels

Pith reviewed 2026-05-13 21:00 UTC · model grok-4.3

classification 🧮 math-ph math.MP
keywords fractional differential equationsdimensional consistencynon-singular kernelschange of variablesfractional calculusphysical units
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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.

Fractional differential equations replace the ordinary time derivative with a fractional operator, but this step often leaves the equation with inconsistent physical dimensions. The paper shows that for operators built on non-singular kernels, a change of variables that meets particular conditions brings the units back into agreement without altering the kernel itself. The adjustment lets the fractional model keep its intended physical interpretation. An example is worked out to illustrate the steps. Readers care because fractional models appear in physics and engineering applications where mismatched units render equations meaningless.

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

These are editorial extensions of the paper, not claims the author makes directly.

  • 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

Figures reproduced from arXiv: 2604.02432 by Gabriel Gonzalez.

Figure 1
Figure 1. Figure 1: FIG. 1: RC circuit [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2: The figure shows the voltage across the capacitor [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
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.

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

2 major / 1 minor

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)
  1. [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.
  2. [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)
  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

2 responses · 0 unresolved

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
  1. 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

  2. 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

0 steps flagged

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

0 free parameters · 1 axioms · 0 invented entities

The paper relies on standard definitions of fractional derivatives and the principle of dimensional homogeneity; no free parameters, new axioms beyond domain assumptions, or invented entities are indicated in the abstract.

axioms (1)
  • domain assumption Fractional derivative operators of non-integer order possess different physical dimensions from ordinary derivatives.
    This is a standard property of fractional calculus invoked to motivate the consistency problem.

pith-pipeline@v0.9.0 · 5337 in / 1123 out tokens · 32589 ms · 2026-05-13T21:00:46.656837+00:00 · methodology

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Reference graph

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