Noninvertible Maps Research Articles

On Darboux theorems for geometric structures induced by closed forms

This work reviews the classical Darboux theorem for symplectic, presymplectic, and cosymplectic manifolds (which are used to describe mechanical systems), as well as certain cases of multisymplectic manifolds, while extends the Darboux theorem in new ways to k-symplectic and k-cosymplectic manifolds (all these structures appear in the geometric formulation of first-order classical field theories). Moreover, we discuss the existence of Darboux theorems for classes of precosymplectic, k-presymplectic, k-precosymplectic, and premultisymplectic manifolds, which are the geometrical structures underlying some kinds of singular field theories, i.e. with locally non-invertible Legendre maps. Approaches to Darboux theorems based on flat connections associated with geometric structures are given, while new results on polarisations for (k-)(pre)(co)symplectic structures arise.

From the XXZ chain to the integrable Rydberg-blockade ladder via non-invertible duality defects

Strongly interacting models often possess “dualities” subtler than a one-to-one mapping of energy levels. The maps can be non-invertible, as apparent in the canonical example of Kramers and Wannier. We analyse an algebraic structure common to the XXZ spin chain and three other models: Rydberg-blockade bosons with one particle per square of a ladder, a three-state antiferromagnet, and two Ising chains coupled in a zigzag fashion. The structure yields non-invertible maps between the four models while also guaranteeing all are integrable. We construct these maps explicitly utilising topological defects coming from fusion categories and the lattice version of the orbifold construction, and use them to give explicit conformal-field-theory partition functions describing their critical regions. The Rydberg and Ising ladders also possess interesting non-invertible symmetries, with the spontaneous breaking of one in the former resulting in an unusual ground-state degeneracy.

Propagation properties of a non-linear mapping based on squaring in odd characteristic

Many modern cryptographic primitives for hashing and (authenticated) encryption make use of constructions that are instantiated with an iterated cryptographic permutation that operates on a fixed-width state consisting of an array of bits. Often, such permutations are the repeated application of a relatively simple round function consisting of a linear layer and a non-linear layer. These constructions do not require that the underlying function is a permutation and they can plausibly be based on a non-invertible transformation. Recently, Grassi proposed the use of non-invertible mappings operating on arrays of digits that are elements of a finite field of odd characteristic for so-called MPC-/FHE-/ZK-friendly symmetric cryptographic primitives. In this work, we consider a mapping that we call γ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\gamma $$\\end{document} that has a simple expression and is based on squaring. We discuss, for the first time, the differential and linear propagation properties of γ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\gamma $$\\end{document} and observe that these follow the same rules up to a relabeling of the digits. This is an intriguing property that, as far as we know, only exists for γ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\gamma $$\\end{document} and the binary mapping χ3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\chi _{_{3}}$$\\end{document} that is used in the cryptographic permutation Xoodoo. Moreover, we study the implications of its non-invertibility on differentials with zero output difference and on biases at the output of the γ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\gamma $$\\end{document} mapping and show that they are as small as they can possibly be.

Dynamic Analysis of a Simple Cournot Duopoly Model Based on a Computed Cost

The paper is organized to study some mathematical properties and dynamics of a simple Cournot duopoly game based on a computed quadratic cost. The time evolution of this game is described by a two-dimensional noninvertible discrete time map using the bounded rationality mechanism. For this map, some dynamic characteristics such as multistability and synchronization are investigated. Its equilibrium points are obtained for the asymmetric case, and their conditions of stability are obtained. Our results investigate that the Nash equilibrium point may be unstable due to flip bifurcation and under certain parameter values, and Neimark–Sacker bifurcation is born after the period-4 cycle. Through some restrictions, the coordinate axes of the map construct an invariant manifold, and therefore, their dynamics can be analyzed by using a one-dimensional map. In the symmetric case, both firms behave identically, and this implies that the diagonal set forms an invariant manifold, and hence the synchronization phenomena take place. Furthermore, the global bifurcation of the map is confirmed through contact between critical curves and the boundaries of infeasible domains.

An evolutive model of a boundedly rational consumer with changing preferences and reference group consumption

In this paper, two dynamic models, recently proposed to describe the adaptive repeated choices of a boundedly rational consumer, are joined together. One considers a consumer adjusting the consumption level of a given good over time according to the observed discrepancy between expected and realized utility gain and modifies the utility function according to past consumption experience, also including saturation effects when past consumption is excessive. The other one considers the same adjustment mechanism with constant preferences but with a behavioral effect that introduces a tendency (or bias) to imitate a reference group of consumers. Merging these two models, a two-dimensional nonlinear dynamical system is obtained which describes consumers that decide their next period consumption of a given good by following two different (sometimes contrasting) criteria: their own utility maximization on the one side and imitation of a reference group of consumers on the other side. This leads to a greater uncertainty with respect to the model without the behavioral bias. Such uncertainty is studied through a numerical exploration of the long-run dynamics, guided by some global dynamical features of the nonlinear model, such as the folding action of the critical curves that characterize the behavior of the iterated noninvertible map and the singularities related to the presence of a vanishing denominator, namely focal points and prefocal curves. So, the aim of the paper is twofold: on the one side, it tries to contribute to the literature on the economic theory of boundedly rational consumers represented by evolutionary and behavioral approaches; On the other side, it tries to contribute to the recent literature about the global analysis of discrete dynamical systems characterized by contact bifurcations leading to the creation of complex topological structures of the attractors and their basins of attraction.

Cournot–Bertrand Duopoly Model: Dynamic Analysis Based on a Computed Cost

In this paper, some mathematical properties and dynamic investigations of a Cournot–Bertrand duopoly game using a computed nonlinear cost are studied. The game is repeated and its evolution is presented by noninvertible map. The fixed points for this map are calculated and their stability conditions are discussed. One of those fixed points is Nash equilibrium, and the discussion shows that it can be unstable through flip and Neimark–Sacker bifurcation. The invariant manifold for the game’s map is analyzed. Furthermore, the case when both competing firms are independent is investigated. Due to unsymmetrical structure of the game’s map, global analysis gives rise to complicated basin of attraction for some attracting sets. The topological structure for these basins of attraction shows that escaping (infeasible) domain for some attracting sets becomes unconnected and the rise of holes is obtained. This confirms the existence of contact bifurcation.

Large deviations and conditioning for chaotic non-invertible deterministic maps: analysis via the forward deterministic dynamics and the backward stochastic dynamics

The large deviation properties of trajectory observables for chaotic non-invertible deterministic maps as studied recently by Smith (2022 Phys. Rev. E 106 L042202) and by Gutierrez et al (2023 arXiv:2304.13754) are revisited in order to analyze in detail the similarities and the differences with the case of stochastic Markov chains. More concretely, we focus on the simplest example displaying the two essential properties of local stretching and global folding, namely the doubling map xt+1=2xt[mod1] on the real-space interval x∈[0,1[ that can also be analyzed via the decomposition x=∑l=1+∞σl2l into binary coefficients σl=0,1 . The large deviation properties of trajectory observables can be studied either via deformations of the forward deterministic dynamics or via deformations of the backward stochastic dynamics. Our main conclusions concerning the construction of the corresponding Doob canonical conditioned processes are: (i) non-trivial conditioned dynamics can be constructed only in the backward stochastic perspective where the reweighting of existing transitions is possible, and not in the forward deterministic perspective; (ii) the corresponding conditioned steady state is not smooth on the real-space interval x∈[0,1[ and can be better characterized in the binary space σl=1,2,..,+∞ . As a consequence, the backward stochastic dynamics in the binary space are also the most appropriate framework to analyze higher levels of large deviations, and we obtain the explicit large deviations at level 2 for the probability of the empirical density of long backward trajectories.

An Efficient Image Encryption Method Based on Enhanced Josephus Problem and a Non-Invertible Economic Map

As an increasing number of digital images are created and transmitted over the internet, there is growing concern over their unauthorized use, which has a big impact on both security and privacy concerns. In this research, we provide a fast and secure image encryption scheme by using an enhanced Josephus problem and two-dimensional non-invertible economic chaotic map (2D-ECM) to safely and covertly protect digital image information throughout public channel transmission. First, the initial values of the 2D-ECM map are generated based on Secure Hash Algorithm (SHA-256) and the input secret key. Then, the Josephus problem is enhanced by substituting the extract operation with location exchange and dynamic start location and step size is employed to scramble the image pixels. In order to integrate the confusion process and diffusion process, the enhanced Josephus problem is utilized indirectly to choose two random columns from the scrambled image and random image to XOR them with the current column. The evaluation results prove that the proposed image cryptosystem is more efficient compared to existing cryptosystems.

On the dimension of planar self-affine sets with non-invertible maps

In this paper, we study the dimension of planar self-affine sets, of which generating iterated function system (IFS) contains non-invertible affine mappings. We show that under a certain separation condition the dimension equals to the affinity dimension for a typical choice of the linear-parts of the non-invertible mappings, furthermore, we show that the dimension is strictly smaller than the affinity dimension for certain choices of parameters.

Revisiting the Computation Analysis against Internal Encodings in White-Box Implementations

White-box implementations aim to prevent the key extraction of the cryptographic algorithm even if the attacker has full access to the execution environment. To obfuscate the round functions, Chow et al. proposed a pivotal principle of white-box implementations to convert the round functions as look-up tables which are encoded by random internal encodings. These encodings consist of a linear mapping and a non-linear nibble permutation. At CHES 2016, Bos et al. introduced differential computation analysis (DCA) to extract the secret key from the runtime information, such as accessed memory and registers. Following this attack, many computation analysis methods were proposed to break the white-box implementations by leveraging some properties of the linear internal encodings, such as Hamming weight and imbalance. Therefore, it becomes an alternative choice to use a non-linear byte encoding to thwart DCA. At CHES 2021, Carlet et al. proposed a structural attack and revealed the weakness of the non-linear byte encodings which are combined with a non-invertible linear mapping. However, such a structural attack requires the details of the implementation, which relies on extra reverse engineering efforts in practice. To the best of our knowledge, it still lacks a thorough investigation of whether the non-linear byte encodings can resist the computation analyses.In this paper, we revisit the proposed computation analyses by investigating their capabilities against internal encodings with different algebraic degrees. Particularly, the algebraic degree of encodings is leveraged to explain the key leakage on the non-linear encodings. Based on this observation, we propose a new algebraic degree computation analysis (ADCA), which targets the mappings from the inputs to each sample of the computation traces. Different from the previous computation analyses, ADCA is a higher-degree attack that can distinguish the correct key by matching the algebraic degrees of the mappings. The experimental results prove that ADCA can break the internal encodings from degree 1 to 6 with the lowest time complexity. nstead of running different computation analyses separately, ADCA can be used as a generic tool to attack the white-box implementations.

Global Dynamics of an Oligopoly Game Model with Nonlinear Costs and Strategic Delegation

A dynamic oligopoly game model with nonlinear cost and strategic delegation is built on the basis of isoelastic demand in this paper. And the dynamic characteristics of this game model are investigated. The local stability of the boundary equilibrium points is analyzed by means of the stability theory and Jacobian matrix, and the stability region of the Nash equilibrium point is obtained by Jury criterion. It is concluded that the system may lose stability through Flip bifurcation and Neimark–Sacker bifurcation. And the effects of speed of adjustment, price elasticity, profit weight coefficient and marginal cost on the system stability are discussed through numerical simulation. After that, the coexistence of attractors is analyzed through the basin of attraction, where multiple stability always means path dependence, implying that the long-term behavior of enterprises is strongly affected by historical contingency. In other words, a small perturbation of the initial conditions will have a significant impact on the system. In addition, the global dynamical behavior of the system is analyzed by using the critical curves, the basin of attraction, absorbing areas and a noninvertible map, revealing that three global bifurcations, the first two of which are caused by the interconversion of simply-connected and multiply-connected regions in the basin of attraction, and the third global bifurcation, that is, the final bifurcation is caused by the contact between attractors and the boundary of the basin of attraction.

Complex dynamics of the simplest neuron model: Singular chaotic Shilnikov attractor as specific oscillatory neuron activity

We study complex dynamics of the Chialvo model that is the simplest neuron-type model in form of a four-parameter family of two-dimensional noninvertible maps (endomorphisms). Main elements of bifurcation diagram in the plane of two parameters have been constructed in which regions corresponding to both quasi-periodic and chaotic oscillations are selected. We also indicate special regions corresponding to singular discrete chaotic Shilnikov attractors that we consider as a new type of the so-called snap-back repellers (over an unstable focus). The study of time series was carried out in which there were classified patterns of specific oscillatory activities in the cases when homoclinic orbits to the unstable focus exists and, when such orbits were not yet formed but a strange attractor already exists. New dynamical characteristics are proposed, with the help of which it is possible to assess the level of distinctness of atypical oscillatory activity.

Chaos in coupled heteroclinic cycles and its piecewise-constant representation

We consider two robust heteroclinic cycles rotating in opposite directions, coupled by diffusive terms. A complete synchronization is impossible in this system. Numerical studies show that chaos is abundant at low levels of coupling. With increasing coupling strength, several symmetry-changing transitions are observed, and finally, a stable periodic regime appears via an inverse period-doubling cascade. To reveal the behavior at extremely small couplings, a piecewise constant model for the dynamics is proposed. Within this model, we numerically construct a Poincaré map for a chaotic state, which appears to be an expanding non-invertible circle map, thus confirming the abundance of chaos in the small coupling limit. We also show that within the piecewise constant description, there is a set of periodic solutions with different phase shifts between subsystems due to dead zones in the coupling.

A global picture for the planar Ricker map: convergence to fixed points and identification of the stable/unstable manifolds

A quadratic Lyapunov function is demonstrated for the non-invertible planar Ricker map which shows that for , and all orbits of the planar Ricker map converge to a fixed point. We establish that for 0<r, s<2, whenever a positive equilibrium exists and is locally asymptotically stable, it is globally asymptotically stable (i.e. attracts all of ). Our approach bypasses and improves on methods that rely on monotonicity, which require . We also use the Lyapunov function to identify the one-dimensional stable and unstable manifolds when the positive fixed point exists and is a hyperbolic saddle.

Border collision bifurcations in a piecewise linear duopoly model

We consider a duopoly model characterized by a two-dimensional non-invertible continuous map T given by piecewise linear functions, with several partitions, defining a duopoly game. The structure of the game is such that it has separate second iterate so that its dynamics can be studied via a one-dimensional composite function, that is piecewise linear with multiple partitions in which the definition of the map changes. The number of partitions may change from 2 to 5, depending on the parameters. The dynamics are characterized by degenerate bifurcations and border collision bifurcations, which are typical in maps having kink points. Here the peculiarity is the multiplicity of the partitions, which leads to bifurcations different from those occurring in maps with only one kink point. We show several bifurcations, coexistence of cycles, attracting and superstable, as well chaotic attractors and chaotic repellors, related to the outcome of particular border collision bifurcations.

A transitive homeomorphism on the Lelek fan

ABSTRACT Let X be a continuum and let be a homeomorphism. To construct a dynamical system with interesting dynamical properties, the continuum X often needs to have some complicated topological structure. In this paper, we are interested in one such dynamical property: transitivity. By now, various examples of continua X have been constructed in such a way that the dynamical system is transitive. Mostly, they are examples of continua that are not path-connected, such as the pseudo-arc or the pseudo-circle, or they are examples of locally connected continua (and every locally connected continuum is path-connected), Sierpiński carpet is such an example. In this paper, we present an example of a dynamical system , where φ is a homeomorphism on the continuum X and X is a path-connected but not locally connected continuum. We construct a transitive homeomorphism on the Lelek fan. As a by-product, a non-invertible transitive map on the Lelek fan is also constructed.

Dynamics and Global Bifurcations in Two Symmetrically Coupled Non-Invertible Maps

The theory of critical curves determines the main characteristics of a discrete dynamical system in two dimensions. One important property that has garnered recent attention is the problem of chaos synchronization, along with the location of its chaotic attractors, basin boundaries, and bifurcation mechanisms. Varying the parameters of the maps reveals the instrumental role that these curves play, where the bifurcation leads to complex topological structures of the basins occurs by contact with the basin boundaries, resulting in the appearance or disappearance of some components of the basin. This study focuses on the properties of a discrete dynamical system consisting of two symmetrically coupled non-invertible maps, specifically those with an invariant one-dimensional submanifold (or one-dimensional maps). These maps exhibit a complex structure of basins with the coexistence of symmetric chaotic attractors, riddled basins, blow-out, on-off intermittency, and, most significantly, the appearance of chaotic synchronization with a correlation between all the characteristics. The numerical method of critical curves can be used to demonstrate a wide range of dynamic scenarios and explain the bifurcations that lead to their occurrence. These curves play a crucial role in a system of two symmetrically coupled maps, and their significance will be discussed.

The twisted baker map

As a model to provide a hands-on, elementary understanding of ‘vortex dynamics’, we introduce a piecewise linear non-invertible map called a twisted baker map. We show that the set of hyperbolic repelling periodic points with complex conjugate eigenvalues and that without complex conjugate eigenvalues are simultaneously dense in the phase space. We also show that these two sets equidistribute with respect to the normalised Lebesgue measure, in spite of a non-uniformity in their Lyapunov exponents.

DIMENSIONS OF MEASURES, DEGREES, AND FOLDING ENTROPY IN DYNAMICS

In this survey, we present some methods in the dynamics and dimension theory for invariant measures of hyperbolic endomorphisms (smooth non-invertible maps), and for conformal iterated function systems with overlaps. For endomorphisms, we recall the notion of asymptotic degree of an equilibrium measure, which is shown to be related to the folding entropy; this degree is then applied to dimension estimates. For finite iterated function systems, we present the notion of overlap number of a measure, which is related to the folding entropy of a lift transformation, and also give some examples when it can be computed or estimated. We apply overlap numbers to prove the exact dimensionality of invariant measures, and to obtain a geometric formula for their dimension. Then, for countable conformal iterated function systems with overlaps, the projections of ergodic measures are shown to be exact dimensional, and we give a dimension formula. Relations with ergodic number theory, continued fractions, and random dynamical systems are also presented.

Codimension-one and -two bifurcation analysis of a two-dimensional coupled logistic map

This paper devotes to a detailed bifurcation analysis of a two-dimensional non-invertible map, obtained using a symmetric coupling between one-dimensional logistic maps. The critical normal form coefficients method is employed to detect bifurcations and to explore further critical conditions without explicit reduction to the center manifold. The results show that the two-dimensional map undergoes codimension-one (codim-1) bifurcations such as transcritical, pitchfork, period-doubling, Neimark–Sacker, and codim-2 bifurcations including transcritical-flip, pitchfork-flip, strong resonances 1:2, 1:3, 1:4. For each bifurcation, the critical normal form coefficients are calculated to check the non-degeneracy conditions and predict the bifurcation scenarios around the bifurcation points. To validate the theoretical results, all bifurcation curves of fixed points are plotted with the aid of the numerical continuation method. Weak resonances are also specified by the isoclines on the bi-parameter plane. The results will help in understanding the occurrence and the structure of bifurcation cascades observed in many coupled discrete systems.