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Aziz El Ghazouani

Publications and source records attributed to Aziz El Ghazouani.

4 recordsLinked to original sources

Relative Chaos for $C_0$-Semigroups Beyond Topological Notions

We investigate instability phenomena for linear evolution equations within the framework of $C_0$--semigroups on infinite--dimensional spaces. We show that Devaney chaos, being formulated in purely topological terms, may depend on the choice of topology and therefore fail to capture intrinsic dynamical behavior. To address this issue, we introduce a trajectory--based notion of relative chaos, defined with respect to a reference solution and measured in a fixed, physically meaningful norm. This criterion is independent of topological refinements and is shown to be strictly weaker than classical Devaney chaos. Its relevance is illustrated on boundary--driven reaction--diffusion--transport semigroups.

math.DS

Chaotic Dynamics of Conformable Semigroups via Classical Theory

Conformable derivatives involve a fractional parameter while preserving locality: on smooth functions they reduce to a classical derivative multiplied by an explicit weight. Exploiting this structural feature, we show that conformable time evolution does not give rise to a genuinely new semigroup theory. Rather, it can be fully interpreted as a classical $C_0$--semigroup observed through a nonlinear change of time. For $δ\in(0,1]$, we introduce the conformable clock \[ Ψ(t)=\frac{t^δ}δ, \] and prove that every $C_0$--$δ$--semigroup $\mathcal S_δ$ admits the representation \[ \mathcal S_δ(t)=\mathcal T(Ψ(t)), \] where $\mathcal T$ is a uniquely determined classical $C_0$--semigroup on the same state space. This correspondence is exact at the infinitesimal level: the $δ$--generator of $\mathcal S_δ$ coincides with the generator of $\mathcal T$ on a common domain, and conformable mild solutions are in one-to-one correspondence with classical mild solutions under the reparametrization $s=Ψ(t)$. In particular, orbit sets are unchanged by the conformable clock, so orbit-based linear dynamical properties are invariant; $δ$--hypercyclicity and $δ$--chaos coincide with their classical counterparts. As an application, we derive a conformable version of the Desch--Schappacher--Webb chaos criterion by transporting the classical result. The analysis is carried out in conformable Lebesgue spaces $L^{p,δ}$, which are shown to be isometrically equivalent to standard $L^p$ spaces, allowing a direct transfer of estimates and spectral arguments. Altogether, the results clarify which dynamical features of conformable models are intrinsic and which arise solely from a nonlinear change of time.

math.DS

Time Reparametrization and Chaotic Dynamics in Conformable $C_0$-Semigroups

Conformable derivatives provide a fractional-looking calculus that remains local and admits a simple representation through classical derivatives with explicit weights. In this paper we develop a systematic operator-theoretic perspective showing that conformable time evolution is, in essence, a classical $C_0$-semigroup observed through a nonlinear clock. We introduce the conformable time map $ψ(t)=t^α/α$ and prove that every $C_0$--$α$-semigroup $\{T_α(t)\}_{t\ge0}$ can be written as $T_α(t)=T(ψ(t))$ for a uniquely determined classical $C_0$-semigroup $\{T(s)\}_{s\ge0}$, with generators agreeing on a common domain. This correspondence yields a one-to-one transfer of mild solutions and shows that orbit-based linear dynamics are invariant under conformable reparametrization. In particular, $α$-hypercyclicity and $α$--chaos coincide with the usual notions for the associated classical semigroup. As a consequence, we obtain a conformable version of the Desch--Schappacher--Webb spectral criterion for chaos. We also place the analysis in the natural functional setting provided by conformable Lebesgue spaces $L^{p,α}$ and their explicit isometric identification with standard $L^p$ spaces, which allows one to transport estimates and spectral arguments without loss. The results clarify which dynamical phenomena in conformable models are genuinely new and which are inherited from classical semigroup dynamics via a nonlinear change of time.

math.AP

Time Reparametrization, Not Fractional Calculus: A Reassessment of the Conformable Derivative

The conformable derivative has been promoted in numerous publications as a new fractional derivative operator. This article provides a critical reassessment of this claim. We demonstrate that the conformable derivative is not a fractional operator but a useful computational tool for systems with power-law time scaling, equivalent to classical differentiation under a nonlinear time reparametrization. Several results presented in the literature as novel fractional contributions can be reinterpreted within a classical framework. We show that problems formulated using the conformable derivative can be transformed into classical formulations via a change of variable. The solution is derived classically and then transformed back, this reformulation highlights the absence of genuinely nonlocal fractional effects. We provide a theoretical analysis, numerical simulations comparing conformable, classical, and truly fractional (Caputo) models, and discuss the reasons why this misconception persists. Our results suggest that classical derivatives, as well as established fractional derivatives, offer a more faithful framework for modeling memory-dependent phenomena.

math.AP