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Marat Akhmet

Publications and source records attributed to Marat Akhmet.

At least 19 recordsLinked to original sources
arXiv2026

Almost Periodicity in Exponential Dichotomous Linear Dynamics with Piecewise Constant Argument

The paper examines an inhomogeneous system of differential equations with generalized piecewise constant arguments. The focus of the research is on the almost periodicity of both the perturbation and the solution. The system demonstrates exponential dichotomy, indicating complex asymptotic behavior among neighboring motions. A notable methodological aspect of the analysis is the use of Green's function to construct a unique almost periodic solution. Additionally, a comparison with previous results has been made. An illustrative example with numerical visualizations is provided to clarify this concept.

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arXiv2025

How one can assess the chaos?

We propose an uncertainty principle for chaos, focusing on two key characteristics: alpha unpredictability and Lorenz sensitivity. This principle outlines a limitation on the relationship between two infinite sequences that underpin these concepts. It is applicable to both deterministic and stochastic dynamics, marking a significant step toward integrating these two fields. Our initial progress in this area was achieved through research on Markov chains utilizing alpha labeling. Additionally, we offer suggestions on how this principle can assess the degree of chaos in specific processes. We also outline open questions regarding the relationships among various types of chaos, including a modification of the recurrence theorem.

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arXiv2023

Unpredictable solutions of Duffing type equations with Markov coefficients

The paper considers a stochastic differential equation of Duffing type with Markov coefficients. The existence of unpredictable solutions is considered. The unpredictability is a property of bounded functions characterized by unbounded sequences of moments of divergence and convergence in Bebutov dynamics. Markov components of the equation coefficients admit the unpredictability property. The components of the equation coefficients are derived from a Markov chain. The existence, uniqueness and exponential stability of an unpredictable solution are proved. The sequences of divergence and convergence of the coefficients and the solution are synchronized. Numerical example that support the theoretical results are provided.

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arXiv2022

A Novel Criterion for Unpredictable Motions

We demonstrate the extension of unpredictable motions in coupled autonomous systems with skew product structure in the case that generalized synchronization takes place. Sufficient conditions for the existence of unpredictable motions in the dynamics of the response system are provided. The theoretical results are exemplified for coupled autonomous systems in which the drive is a hybrid dynamical system and the response is a Lorenz system. The auxiliary system approach and conditional Lyapunov exponents are utilized to detect the presence of generalized synchronization.

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arXiv2021

Strange Non-Chaotic Attractors with Unpredictable Trajectories

Continuous and discrete time systems possessing strange non-chaotic attractors are under investigation. It is demonstrated that unpredictable trajectories exist in the dynamics. A recent numerical technique, the sequential test, is utilized to show the presence of unpredictability.

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arXiv2021

Modulo periodic Poisson stable solutions of quasilinear differential equations

We introduce a new type of recurrence in the space of continuous and bounded functions. The property is easily verifiable, and can be considered for differential equations. This time, the existence and asymptotic stability of modulo periodic Poisson stable solutions for quasilinear systems are proved. The significant novelty of the research is the numerical simulation of the functions, which is stemmed from dynamical traditions of trigonometric functions, and contributes to applications of Poisson stable oscillations.

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arXiv2020

Deterministic chaos for Markov chains

We find that Markov chains with finite state space are Poincare chaotic. Moreover, finite realizations of the chains are arcs of each unpredictable orbit for sure. An illustrating example with a proper numerical simulation is provided.

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arXiv2020

Abstract hyperbolic chaos

The abstract hyperbolic sets are introduced. Continuous and differentiable mappings as well as rate of convergence and transversal manifolds are not under discussion, and the symbolic dynamics paradigm is realized in a new way. Our suggestions are for more neat comprehension of chaos in the domain. The novelties can serve for revisited models as well as motivate new ones.

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arXiv2020

Unpredictable Strings

A novel notion of unpredictable strings is revealed and utilized to define deterministic unpredictable sequences on a finite number of symbols. We prove the first law of large strings for random processes in discrete time, which confirms that there exists the uncountable set of unpredictable realizations. The hypothesis on the second law of large strings is formulated, which is relative to the Bernoulli theorem. Theoretical and numerical backgrounds for the laws are provided.

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arXiv2020

Modular chaos for random processes

In the present paper, an essential generalization of the symbolic dynamics is considered. We apply the notions of abstract self-similar sets and the similarity map for a chaos introduction, which orbits are expanded among infinitely many modules. The dynamics is free of dimensional, metrical and topological assumptions. It unites all the three types of Poincare, Li-Yorke and Devaney chaos in a single model, which can be unbounded. The research demonstrates that the dynamics of Poincare chaos is of exceptional use to analyze discrete and continuous-time random processes. Examples, illustrating the results are provided.

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arXiv2020

A randomly determined unpredictable function

In this paper, we construct a new unpredictable function. Our approach is based on adapting the concept of symbolic dynamics to introduce a map on the space of infinite sequences generated by the discrete distribution. We show that there exists an unpredictable sequence on the space and then use the sequence to construct an unpredictable function.

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arXiv2019

Chaos on the Multi-Dimensional Cube

In this article, we show that a chaotic behavior can be found on a cube with arbitrary finite dimension. That is, the cube is a quasi-minimal set with Poincare chaos. Moreover, the dynamics is shown to be Devaney and Li-Yorke chaotic. It can be characterized as a domain-structured chaos for an associated map. Previously, this was known only for unit section and for Devaney and Li-Yorke chaos.

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arXiv2019

Abstract Fractals

We develop a new definition of fractals which can be considered as an abstraction of the fractals determined through self-similarity. The definition is formulated through imposing conditions which are governed the relation between the subsets of a metric space to build a porous self-similar structure. Examples are provided to confirm that the definition is satisfied by large class of self-similar fractals. The new concepts create new frontiers for fractals and chaos investigations.

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arXiv2019

Abstract Similarity, Fractals and Chaos

To prove presence of chaos for fractals, a new mathematical concept of abstract similarity is introduced. As an example, the space of symbolic strings on a finite number of symbols is proved to possess the property. Moreover, Sierpinski fractals, Koch curve as well as Cantor set satisfy the definition. A similarity map is introduced and the problem of chaos presence for the sets is solved by considering the dynamics of the map. This is true for Poincare, Li-Yorke and Devaney chaos, even in multi-dimensional cases. Original numerical simulations which illustrate the results are delivered.

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arXiv2019

The Sequential Test for Chaos

This paper reveals a novel numerical method, the sequential test, which approves chaos through sequences of numbers observations. The method alights alongside the Lyapunov exponent and bifurcation diagram test. Explicitly elucidation of the method application for both continuous and discrete systemswas given affiliated with the corresponding algorithms. The theoretical results are exemplified on systems satisfying different types of definitions of chaos or numerical methods. The results are supplemented with illustrative graphics.

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arXiv2018

Dynamics Motivated by Sierpinski Fractals

Fatou-Julia iteration (FJI) is an effective instrument to construct fractals. Famous Julia and Mandelbrot sets are strong confirmations of this. In the present study, we use the paradigm of FJI to construct and map Sierpinski fractals. The fractals can be mapped by developing a mapping iteration on the basis of FJI. Because of the close link between mappings, differential equations and dynamical systems, one can introduce dynamics for a fractal through differential equations such that it becomes points of the solution trajectory. Thus, in this paper, we consider two types of dynamics motivated by the Sierpinski fractals. The first one is the dynamics of FJI itself, and the second one is the dynamics of a fractal mapping iteration which can be performed through differential equations. The characterization of fractals as trajectory points of the dynamics can help to enhance and widen the scope of their applications in physics and engineering.

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arXiv2018

Unpredictable Solutions of Linear Differential Equations

In this study, the existence and uniqueness of the unpredictable solution for a non-homogeneous linear system of ordinary differential equations is considered. The hyperbolic case is under discussion. New properties of unpredictable functions are discovered. The presence of the solutions confirms the existence of Poincaré chaos. Simulations illustrating the chaos are provided.

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