Differential equations with piecewise constant argument, which were firstly considered by Cooke and Wiener 1 , and Shah and Wiener 2 , usually describe hybrid dynamical systems a combination of continuous and discrete and so combine properties of both differential and difference equations. Over the years, great attention has been paid to the study of the existence of almost-periodic-type soluti...

We prove the complete asymptotic expansion of the integrated density of states of a Schrödinger operator H = −∆+b acting in R when the potential b is either smooth periodic, or generic quasi-periodic (finite linear combination of exponentials), or belongs to a wide class of almost-periodic functions.

In this paper, we prove an individual homogenization result for a class of almost periodic nonlinear parabolic operators. The spatial and temporal heterogeneities are almost periodic functions in the sense of Besicovitch. The latter allows discontinuities and suitable for many applications. First, we derive stability and comparison estimates for sequences of G-convergent nonlinear parabolic ope...

We devise a new geometric approach to study the propagation of disturbance compactly supported data in reaction-diffusion equations. The method builds a bridge between the propagation of disturbance and of almost planar solutions. It applies to very general reaction-diffusion equations. The main consequences we derive in this paper are: a new proof of the classical Freidlin-Gärtner formula for ...

In this paper, we systematically study the dynamics of a nonautonomous predator–prey system with the Beddington–DeAngelis functional response. The explorations involve the permanence, extinction, global asymptotic stability (general nonautonomous case); the existence, uniqueness and stability of a positive (almost) periodic solution and a boundary (almost) periodic solution for the periodic (al...

In [16], [17], [18], the global regularity conjecture for wave maps from two-dimensional Minkowski space R to hyperbolic space H was reduced to the problem of constructing a minimal-energy blowup solution which is almost periodic modulo symmetries in the event that the conjecture fails. In this paper, we show that this problem can be reduced further, to that of showing that solutions at the cri...

This paper concerns with a class of delayed Nicholson’s blowflies model with a nonlinear density-dependent mortality term. Under appropriate conditions, we establish some criteria to ensure that the solutions of this model converge globally exponentially to a positive almost periodic solution. Moreover, we give some examples and numerical simulations to illustrate our main results.

Sturmian words are balanced, almost periodic, self-similar and hierarchical infinite sequences that have been studied in music theory in connection with diatonic scale theory and related subjects.[3][5] Carey and Camplitt 1996 give a brief but suggestive rhythmic example in which these properties are made manifest in a particularly visceral manner. The present paper expands upon this example, c...

A sequence {an} in a group G is a T -sequence if there is a Hausdorff group topology τ on G such that an τ −→ 0. In this paper, we provide several sufficient conditions for a sequence in an abelian group to be a T -sequence, and investigate special sequences in the Prüfer groups Z(p∞). We show that for p 6= 2, there is a Hausdorff group topology τ on Z(p∞) that is determined by a T -sequence, w...

Let G(x) = [ eIm 0 c−1e−iνx + c0 + c1e e−iλxIm ] , where cj ∈ Cm×m, α, ν > 0 and α+ ν = λ. For rational α/ν such matrices G are periodic, and their Wiener-Hopf factorization with respect to the real line R always exists and can be constructed explicitly. For irrational α/ν, a certain modification (called an almost periodic factorization) can be considered instead. The case of invertible c0 and ...