ISSN:

1078-0947

eISSN:

1553-5231

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## Discrete & Continuous Dynamical Systems

June 2013 , Volume 33 , Issue 6

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2013, 33(6): 2241-2251
doi: 10.3934/dcds.2013.33.2241

*+*[Abstract](1839)*+*[PDF](332.6KB)**Abstract:**

We consider sufficient conditions to determine the global dynamics for equivariant maps of the plane with a unique fixed point which is also hyperbolic. When the map is equivariant under the action of a compact Lie group, it is possible to describe the local dynamics. In particular, if the group contains a reflection, there is a line invariant by the map. This allows us to use results based on the theory of free homeomorphisms to describe the global dynamical behaviour. We briefly discuss the case when reflections are absent, for which global dynamics may not follow from local dynamics near the unique fixed point.

2013, 33(6): 2253-2270
doi: 10.3934/dcds.2013.33.2253

*+*[Abstract](2187)*+*[PDF](449.8KB)**Abstract:**

We relate the symbolic extension entropy of a partially hyperbolic dynamical system to the entropy appearing at small scales in local center manifolds. In particular, we prove the existence of symbolic extensions for $\mathcal{C}^2$ partially hyperbolic diffeomorphisms with a $2$-dimensional center bundle. 200 words.

2013, 33(6): 2271-2297
doi: 10.3934/dcds.2013.33.2271

*+*[Abstract](3147)*+*[PDF](473.5KB)**Abstract:**

We consider a system coupling the parabolic-parabolic chemotaxis equations to the incompressible Navier-Stokes equations in spatial dimensions two and three. We establish the local existence of regular solutions and present some blow-up criterions. For two dimensional chemotaxis-Navier-Stokes equations, regular solutions constructed locally in time are, in reality, extended globally under some assumptions pertinent to experimental observations in [21] on the consumption rate and chemotactic sensitivity. We also show the existence of global weak solutions in spatially three dimensions with stronger restriction on the consumption rate and chemotactic sensitivity.

2013, 33(6): 2299-2318
doi: 10.3934/dcds.2013.33.2299

*+*[Abstract](1902)*+*[PDF](421.7KB)**Abstract:**

Arising from one-particle distribution functions of stationary dissipative plasmas, we consider a coupled elliptic system with singular data in the plane. The existence and uniqueness of solutions to the Dirichlet boundary value problem are proved. In addition, the structure of other solutions, including blow-up solutions, is also clarified.

2013, 33(6): 2319-2347
doi: 10.3934/dcds.2013.33.2319

*+*[Abstract](2792)*+*[PDF](508.8KB)**Abstract:**

We prove Schauder estimates for a class of non-local elliptic operators with kernel $K(y)=a(y)/|y|^{d+\sigma}$ and either Dini or Hölder continuous data. Here $0 < \sigma < 2$ is a constant and $a$ is a bounded measurable function, which is not necessarily to be homogeneous, regular, or symmetric. As an application, we prove that the operators give isomorphisms between the Lipschitz--Zygmund spaces $\Lambda^{\alpha+\sigma}$ and $\Lambda^\alpha$ for any $\alpha>0$. Several local estimates and an extension to operators with kernels $K(x,y)$ are also discussed.

2013, 33(6): 2349-2368
doi: 10.3934/dcds.2013.33.2349

*+*[Abstract](3161)*+*[PDF](503.5KB)**Abstract:**

In this paper, we consider the phenomena of the thermal runaway and the asymptotic runaway in a nonlocal nonlinear model, which is raised from the thermal-electricity and it is so-called an Ohmic heating model. The model prescribes the dimensionless temperature when the electric current flows through two conductors, subject to a fixed potential difference. The electrical resistivity of the one of the conductors depends on the temperature and the other one remains constant. The problem will be mathematically formulated to a quasilinear nonlocal parabolic equation with Dirichlet boundary condition. An analysis of the problem shows that the solution of the problem exists globally, provided that the conductor with constant resistivity is connected. Furthermore, for some special temperature-resistivity relations, the unique stationary solution is shown to be global asymptotically stable. The results assert a physical fact that the thermal produced by the Ohmic heating process will runaway from the surfaces of the conductor, the temperature of the conductor remains bounded and solution of the system converges asymptotically to the unique equilibrium.

2013, 33(6): 2369-2387
doi: 10.3934/dcds.2013.33.2369

*+*[Abstract](2782)*+*[PDF](428.2KB)**Abstract:**

In this paper we study the scalar delay differential equation \linebreak $\dot{x}(t)=-ax(t) + bf(x(t-\tau))$ with feedback function $f(\xi)=\frac{1}{2}(|\xi+1|-|\xi-1|)$ and with real parameters $a>0,\ \tau>0$ and $b\neq 0$, which can model a single neuron or a group of synchronized neurons. We give necessary and sufficient conditions for existence and uniqueness of periodic orbits with prescribed oscillation frequencies. We also investigate the period of the slowly oscillating periodic solution as a function of the delay. Based on the obtained results we state an analogous theorem concerning existence and uniqueness of periodic orbits of a certain type of system of delay differential equations. The proofs are based among others on theory of monotone systems and discrete Lyapunov functionals.

2013, 33(6): 2389-2401
doi: 10.3934/dcds.2013.33.2389

*+*[Abstract](2496)*+*[PDF](396.4KB)**Abstract:**

We investigate the orbital stability and instability of standing waves for two classes of Klein-Gordon equations in the semi-classical regime.

2013, 33(6): 2403-2421
doi: 10.3934/dcds.2013.33.2403

*+*[Abstract](2156)*+*[PDF](428.1KB)**Abstract:**

This paper studies the relationship between the return time $\tau_n$ and the Rényi Entropy Function of order $s$, $R(s)$. For a dynamical system with an invariant $\alpha$-mixing measure $\mu$ and a measurable partition, we consider the sum $W$ of measures of cylinders along orbit segments of length $\tau_n$ and relate that growth/decay rate to the R$\acute{\textrm{e}}$nyi Entropy. The key strategy is to introduce the hitting number $\nu_x(A) = | \{1 \leq i \leq \tau_n(x) : T^i(x) \in A\}|$, the number of times that $x$ hits the set $A$ when $x$ travels along its orbit of length $\tau_n(x)$, and write $W=\sum \nu_x(A) \mu(A)^s$, where the sum is taken over the $n$-cylinders. Then we show that $\nu_x(A) \approx \exp(n h_{\mu}) \mu(A)$ for most $n$-cylinders $A$. Hence $W \approx \exp(nh_{\mu}) \sum \mu(A)^{1+s}$, which relates $\tau_n(x)$ to $R(s)$, as the sum $\sum \mu(A)^{1+s} \approx \exp(-nsR(s))$.

2013, 33(6): 2423-2450
doi: 10.3934/dcds.2013.33.2423

*+*[Abstract](2685)*+*[PDF](562.4KB)**Abstract:**

In this paper we establish the existence of certain classes of solutions to the energy critical nonlinear wave equation in dimensions $3$ and $5$ assuming that the energy exceeds the ground state energy only by a small amount. No radial assumption is made. We find that there exist four sets in $\dot H^{1}\times L^{2}$ with nonempty interiors which correspond to all possible combinations of finite-time blowup on the one hand, and global existence and scattering to a free wave, on the other hand, as $t → ±∞$.

2013, 33(6): 2451-2467
doi: 10.3934/dcds.2013.33.2451

*+*[Abstract](2830)*+*[PDF](430.6KB)**Abstract:**

Positive topological entropy and distributional chaos are characterized for hereditary shifts. A hereditary shift has positive topological entropy if and only if it is DC$2$-chaotic (or equivalently, DC$3$-chaotic) if and only if it is not uniquely ergodic. A hereditary shift is DC$1$-chaotic if and only if it is not proximal (has more than one minimal set). As every spacing shift and every beta shift is hereditary the results apply to those classes of shifts. Two open problems on topological entropy and distributional chaos of spacing shifts from an article of Banks et al. are solved thanks to this characterization. Moreover, it is shown that a spacing shift $\Omega_P$ has positive topological entropy if and only if $\mathbb{N}\setminus P$ is a set of Poincaré recurrence. Using a result of Kříž an example of a proximal spacing shift with positive entropy is constructed. Connections between spacing shifts and difference sets are revealed and the methods of this paper are used to obtain new proofs of some results on difference sets.

2013, 33(6): 2469-2494
doi: 10.3934/dcds.2013.33.2469

*+*[Abstract](2165)*+*[PDF](503.6KB)**Abstract:**

We consider a nonlinear Dirichlet problem driven by the $p$-Laplace differential operator. We assume that the Carathéodory reaction term $f(z,x)$ exhibits an asymmetric behavior on the two semiaxes of $\mathbb{R}$. Namely, $f(z,\cdot)$ is $(p-1)$-linear near $-\infty$ and $(p-1)$-superlinear near $+\infty$, but without satisfying the well-known Ambrosetti--Rabinowitz condition (AR-condition). Combining variational methods based on critical point theory, with suitable truncation techniques and Morse theory, we show that the problem has at least three nontrivial smooth solutions, two of which have constant sign (one positive, the other negative).

2013, 33(6): 2495-2522
doi: 10.3934/dcds.2013.33.2495

*+*[Abstract](3500)*+*[PDF](690.3KB)**Abstract:**

This paper is concerned with two $n$-species stochastic cooperative systems. One is autonomous, the other is non-autonomous. For the first system, we prove that for each species, there is a constant which can be represented by the coefficients of the system. If the constant is negative, then the corresponding species will go to extinction with probability 1; If the constant is positive, then the corresponding species will be persistent with probability 1. For the second system, sufficient conditions for stochastic permanence and global attractivity are established. In addition, the upper- and lower-growth rates of the positive solution are investigated. Our results reveal that, firstly, the stochastic noise of one population is unfavorable for the persistence of all species; secondly, a population could be persistent even the growth rate of this population is less than the half of the intensity of the white noise.

2013, 33(6): 2523-2529
doi: 10.3934/dcds.2013.33.2523

*+*[Abstract](1906)*+*[PDF](284.9KB)**Abstract:**

We show that for odd-valued piecewise-constant skew products over a certain two parameter family of interval exchanges, the skew product is ergodic for a full-measure choice of parameters.

2013, 33(6): 2531-2546
doi: 10.3934/dcds.2013.33.2531

*+*[Abstract](2543)*+*[PDF](420.7KB)**Abstract:**

We prove that the Cauchy problem for the Chern-Simons-Higgs equations on the (2+1)-dimensional Minkowski space-time is globally well posed for initial data with finite energy. This improves a result of Chae and Choe, who proved global well-posedness for more regular data. Moreover, we prove local well-posedness even below the energy regularity, using the the null structure of the system in Lorenz gauge and bilinear space-time estimates for wave-Sobolev norms.

2013, 33(6): 2547-2564
doi: 10.3934/dcds.2013.33.2547

*+*[Abstract](2382)*+*[PDF](478.1KB)**Abstract:**

In this note, we investigate the localized multifractal spectrum of Birkhoff average in the beta-dynamical system $([0,1], T_{\beta})$ for general $\beta>1$, namely the dimension of the following level sets $$ \Big\{x\in [0,1]: \lim_{n\to \infty}\frac{1}{n}\sum_{j=0}^{n-1}\psi(T^jx)=f(x)\Big\}, $$ where $f$ and $\psi$ are two continuous functions defined on the unit interval $[0,1]$. Instead of a constant function in the classical multifractal cases, the function $f$ here varies with $x$. The method adopted in the proof indicates that the multifractal analysis of Birkhoff average in a general $\beta$-dynamical system can be achieved by approximating the system by its subsystems.

2013, 33(6): 2565-2592
doi: 10.3934/dcds.2013.33.2565

*+*[Abstract](2669)*+*[PDF](553.0KB)**Abstract:**

Our purpose is to show existence of weak solutions to unsteady flow of non-Newtonian incompressible nonhomogeneous fluids with nonstandard growth conditions of the stress tensor. We are motivated by the fluids of anisotropic behaviour and characterised by rapid shear thickening. Since we are interested in flows with the rheology more general than power-law-type, we describe the growth conditions with the help of an $x$--dependent convex function and formulate our problem in generalized Orlicz spaces.

2013, 33(6): 2593-2619
doi: 10.3934/dcds.2013.33.2593

*+*[Abstract](2502)*+*[PDF](443.8KB)**Abstract:**

In this paper we consider two-dimensional nonlinear quasi-periodic system with small perturbations. Assume that the unperturbed system has a hyperbolic-type degenerate equilibrium point and the frequency satisfies the Diophantine conditions. Using the KAM iteration we prove that for sufficiently small perturbations, the system can be reduced by a nonlinear quasi-periodic transformation to a suitable normal form with an equilibrium point at the origin. Hence, for the system we can obtain a small quasi-periodic solution.

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