On the relation between interior critical points and parameters for a class of nonlinear problems with Neumann–Robin boundary conditions

We consider boundary value problem

where   0, λ > 0 are parameters and f  C²[0, ∞) such that f(0) < 0. In this paper we study for the cases p  (0, β) and p  (β, θ) (p is the value of the solution at x = 0 and β, θ are such that f(β) = 0, , the relation between λ and the number of interior critical points of the positive solutions of the above system.     

On a class of fractal functions with graph Hausdorff dimension 2

We prove that the graph of the continuous function

has Hausdorff dimension 2, where λ > 1, β >  > 1, (x) = 2x, 0  x  1/2, (−x) = (x) and (x + 1) = (x).     

Chaos control on autonomous and non-autonomous systems with various types of genetic algorithm-optimized weak perturbations

Recently, we proposed a chaos control strategy with weak Fourier signals optimized by using a genetic algorithm (GA) and demonstrated its merits in controlling Lorenz and Rössler systems (Physical Review E, 2004). In this continuation work, performance of various types of signals, namely periodic continuous, periodic discrete, and constant bias (non-periodic), applied to an autonomous (Rössler) system and a non-autonomous (Murali–Lakshmanan–Chua, MLC) system are investigated. An index of relative robustness is proposed for measuring the noise-resisting ability of the control signals. The results reveal that the constant signal has the strongest noise-resisting ability, the periodic pulse signal has the weakest, and the Fourier signal falls in between. Phase modulation generally shortens the transient time period and is additionally beneficial to non-autonomous systems in minimizing significantly the signal power. By searching with the present GA-optimization, it is demonstrated that the minimum-power signal for controlling the non-autonomous (MLC) system is the signal with a frequency exactly the same as that of the system forcing but with phase modulation. The effectiveness of the GA-optimized signals of extremely low power employed in alternatively switching control of non-autonomous systems is also demonstrated.     

Stability properties of non-negative solutions to a non-autonomous p-Laplacian equation

We study the stability of non-negative stationary solutions of

where Δ_p denotes the p-Laplacian operator defined by Δ_pz = div(z^p−2z); p > 2, Ω is a bounded domain in R^N(N  1) with smooth boundary where [0,1],h:∂Ω→R⁺ with h = 1 when  = 1, λ > 0, and g:Ω×[0,∞)→R is a continuous function. If g(x, u)/u^p−1 be strictly increasing (decreasing), we provide a simple proof to establish that every non-trivial non-negative solution is unstable (stable).     

Scheduling starting times for an active redundant system with non-identical lifetimes

Here we examine an active redundant system with scheduled starting times of the units. We assume availability of n non-identical, non-repairable units for replacement or support. The original unit starts its operation at time s₁ = 0 and each one of the (n − 1) standbys starts its operation at scheduled time s_i (i = 2, …, n) and works in parallel with those already introduced and not failed before s_i. The system is up at times s_i (i = 2, …, n), if and only if, there is at least one unit in operation. Thus, the system has the possibility to work with up to n units, in parallel structure. Unit-lifetimes T_i (i = 1, …, n) are independent with cdf F_i, respectively. The system has to operate without inspection for a fixed period of time c and it stops functioning when all available units fail before c. The probability that the system is functioning for the required period of time c depends on the distribution of the unit-lifetimes and on the scheduling of the starting times s_i. The reliability of the system is evaluated via a recursive relation as a function of the starting times s_i (i = 2, …, n). Maximizing with respect to the starting times we get the optimal ones. Analytical results are presented for some special distributions and moderate values of n.     

A TAGE iterative method for the solution of non-linear singular two point boundary value problems using a sixth order discretization

We report two parameter alternating group explicit (TAGE) iteration method to solve the tri-diagonal linear system derived from a new finite difference discretization of sixth order accuracy of the two point singular boundary value problem , 0 < r < 1,  = 1 and 2 subject to boundary conditions u(0) = A, u(1) = B, where A and B are finite constants. We also discuss Newton-TAGE iteration method for the sixth order numerical solution of two point non-linear boundary value problem. The proof for the convergence of the TAGE iteration method when the coefficient matrix is real and unsymmetric is discussed. Numerical results are presented to illustrate the proposed iterative methods.     

Periodic solutions of the restricted three-body problem for a small mass ratio

A plane circular restricted three body problem is considered for small values of the ratio of the masses μ of the main bodies. All the limit problems as μ → 0: the two-body problem, Hill's problem, the intermediate Hénon problem and the basic limit problem, are found using a Power Geometry. In each of them, solutions are isolated which are the limits of the periodic solutions of the restricted problem as μ → 0 and the limits of the families of periodic solutions (which are called generating families). Using the generating families in the case of small μ > 0, the families are studied which are started as the reverse (family h) and forward (family i) circular orbits of infinitesimal radius around the body of greater mass. It is shown that, as μ increases, there is a small change in the structure of family h but family i undergoes infinitely many self-bifurcations with the formation of an infinite number of closed subfamilies, each of which only exists in a certain range of values of μ. A theory of the formation of horseshoe-shaped orbits and orbits in the form of “tadpoles” is given, and the structure of the basic families containing periodic solution with these orbits is indicated.     

Analytical and numerical investigation of two families of Lorenz-like dynamical systems

We investigate two families of Lorenz-like three-dimensional nonlinear dynamical systems (i) the generalized Lorenz system and (ii) the Burke–Shaw system. Analytical investigation of the former system is possible under the assumption (I) which in fact concerns four different systems corresponding to  = ±1, m = 0, 1.

(I)

The fixed points and stability characteristics of the Lorenz system under the assumption (I) are also classified. Parametric and temporal (t → ∞) asymptotes are also studied in connection to the memory of both the systems. We calculate the Lyapunov exponents and Lyapunov dimension for the chaotic attractors in order to study the influence of the parameters of the Lorenz system on the attractors obtained not only when the assumption (I) is satisfied but also for other values of the parameters σ, r, b, ω and m.     

Highly symmetric generalized circulant permutation matrices

In this paper we investigate generalized circulant permutation matrices of composite order. We give a complete characterization of the order and the structure of symmetric generalized k-circulant permutation matrices in terms of circulant and retrocirculant block (0, 1)-matrices in which each block contains exactly one or two entries 1. In particular, we prove that a generalized k-circulant matrix A of composite order n = km is symmetric if and only if either k = m − 1 or k ≡ 0 or k ≡ 1 mod m, and we obtain three basic symmetric generalized k-circulant permutation matrices, from which all others are obtained via permutations of the blocks or by direct sums. Furthermore, we extend the characterization of these matrices to centrosymmetric matrices.     

A shortcut to asymptotics for orthogonal polynomials

We consider the asymptotic behavior of the ratios q_n+1(z)/q_n(z) of polynomials orthonormal with respect to some positive measure μ. Let the recurrence coefficients _n and β_n converge to 0 and , respectively. Then, q_n+1(z)/q_n(z) Φ(z),for n→∞ locally uniformly for , where Φ maps conformally onto the exterior of the unit disc (Nevai (1979)). We provide a new and direct proof for this and some related results due to Nevai, and apply it to convergence acceleration of diagonal Padé approximants.     

Bounds for a domain containing all compact invariant sets of the system describing the laser–plasma interaction

In this paper we consider the localization problem of compact invariant sets of the system describing the laser–plasma interaction. We establish that this system has an ellipsoidal localization for simple restrictions imposed on its parameters. Then we improve this localization by applying other localizing functions. In addition, we give sufficient conditions under which the origin is the unique compact invariant set.     

Quantum decoherence and El Naschie’s complex temporality

It is well-known that the Schrödinger equation reduces to a classical diffusion equation by means of Wick rotation (t → it), suggesting a correspondence between quantum and classical mechanics. Nonetheless, this result does not admit a clear conceptual interpretation. In the framework of his fractal space-time theory, El Naschie showed that great conceptual advantage could be achieved by extending the imaginary time, it, to a perfectly symmetric, complex conjugate time 0 ± it. In this note we show through a simple analysis, involving formal analytic continuation (t → 0 ± it), that El Naschie’s time complexification provides the basis for a physical interpretation of the correspondence between quantum and classical mechanics in terms of quantum decoherence. We find that decoherent states inevitably arise due to time symmetry breaking as we go from the micro Cantorian space-time, where the two symmetric times, 0 + it and 0 − it, coexist to our 4-dimensional smooth space-time, where t is the only time.     

Viewing sets of mutually unbiased bases as arcs in finite projective planes

This note is a short conceptual elaboration of the conjecture of Saniga et al. [J. Opt. B: Quantum Semiclass 6 (2004) L19–L20] by regarding a set of mutually unbiased bases (MUBs) in a d-dimensional Hilbert space as an analogue of an arc in a (finite) projective plane of order d. Complete sets of MUBs thus correspond to (d + 1)-arcs, i.e., ovals. In the Desarguesian case, the existence of two principally distinct kinds of ovals for d = 2ⁿ and n  3, viz. conics and non-conics, implies the existence of two qualitatively different groups of the complete sets of MUBs for the Hilbert spaces of corresponding dimensions. A principally new class of complete sets of MUBs are those having their analogues in ovals in non-Desarguesian projective planes; the lowest dimension when this happens is d = 9.     

Convergence of approximate solutions for waves in a stratified fluid with approximated density distribution

Equations defining in linear approximation the wave motions in an arbitrarily stratified fluid are derived. Investigation of convergence of wave solutions with approximations ρ_n (z) of the mean density profile ρ_o (z) shows that uniform convergence of ρ_n (z) to ρ_o (z) is the sufficient condition of convergence of wave equation solutions. The convergence of solutions is uniform on sets of upper bound wave numbers and lower bound phase velocities of waves. Examples that show that when the continuous function ρ_o (z) is approximated by step-wide functions ρ_n (z) the convergence of solutions for internal waves is not uniform over the whole set of admissible wave numbers and phase velocities of waves.     

Bounds for compact invariant sets of the system describing dynamics of the nuclear spin generator

This paper is concerned with the localization problem of compact invariant sets of the system describing dynamics of the nuclear spin generator. We establish that all compact invariant sets of this system are located in the intersection of a ball with two frusta and compute its parameters. In addition, localization by using the two-parameter set of parabolic cylinders is described. Our results are obtained with help of the iteration theorem concerning a localization of compact invariant sets. One numerical example illustrating a localization of a chaotic attractor is presented as well.     

Fixed and periodic points in the probabilistic normed and metric spaces

In this paper, a fixed point theorem is proved, i.e., if A is a C-contraction in the Menger space (S, F) and E  S be such that is compact, then A has a fixed point. In addition, under the same condition, the existence of a periodic point of A is proved. Finally, a fixed point theorem in probabilistic normed spaces is proved.     

Explicit and exact special solutions for BBM-like B(m, n) equations with fully nonlinear dispersion

In this paper, the BBM-like equations with fully nonlinear dispersion, B(m, n) equations: u_t + (u^m)_x − (uⁿ)_xxt = 0 which exhibit solutions with compact support and with solitary patterns, are studied. The exact solitary-wave solutions with compact support and exact special solutions with solitary patterns of the equations are found by a new method. The special cases, B(2, 2) and B(3, 3), are used to illustrate the concrete scheme of our approach presented by this paper in B(m, n) equations. The nonlinear equations B(m, n) are addressed for two different cases, namely when m = n being odd and even integers. General formulas for the solutions of B(m, n) equations are established.     

Numerical results for positive solutions of a superlinear elliptic equation

In this work we present a numerical approach for finding positive solutions of the type −Δu = λf(u) for x  Ω, with Dirichlet boundary condition, where f is a superlinear function of u. We will show in which range of λ, this problem achieves multiple numerical solutions and what is the behavior of the branches of solutions.     

Localization of invariant compacta of autonomous systems

A class of problems that may be characterized as localization problems are becoming increasingly popular in qualitative theory of differential equations [1–15]. The specific formulations differ, but geometrically all search for phase space subsets with desired properties, e.g., contain certain solutions of the system of differential equations. Such problems include construction of positive invariant sets that contain certain separatrices of the Lorenz system [1], analysis of asymptotic behavior of solutions of the Lorenz system and determination of sets that contain the Lorenz attractor [2–5, 14], as well as determination of sets containing all periodic trajectories [6–13], separatrices, and other trajectories [10, 11]. Such sets may be naturally called localizing sets and it is obviously interesting to study methods and results that produce exact or nearly exact localizing sets for each phase space structure. In this article we focus on localization of the invariant compact sets in the phase space of a differential equation system, specifically the problem of finding phase space subsets that contain all the invariant compacta of the system. Invariant compact sets are equilibria, periodic trajectories, separatrices, limit cycles, invariant tori, and other sets and their finite unions. These sets and their properties largely determine the phase space structure and the qualitative behavior of solutions of the differential equation system.