Stepanov ergodic perturbations for nonautonomous evolution equations in Banach spaces

On the almost periodicity of nonautonomous evolution equations and application to Lotka-Volterra systems

Consider the nonautonomous semilinear evolution equation of type: $(\star) \; u'(t)=A(t)u(t)+f(t,u(t)), \; t \in \mathbb{R},$ where $ A(t), \ t\in \mathbb{R} $ is a family of closed linear operators in a Banach space $X$, the nonlinear term $f$, acting on some real interpolation spaces, is assumed to be almost periodic just in a weak sense (i.e. in Stepanov sense) with respect to $t$ and Lipschitzian in bounded sets with respect to the second variable. We prove the existence and uniqueness of almost periodic solutions in the strong sense (Bohr sense) for equation $ (\star) $ using the exponent…

S-asymptotically omega-periodic solution for a nonlinear differential equation with piecewise constant argument via S-asymptotically omega-periodic functions in the Stepanov sense

In this paper, we show the existence of function which is not S-asymptotically omega-periodic, but which is S-asymptotically omega-periodic in the Stepanov sense. We give sufficient conditions for the existence and uniqueness of S-asymptotically omega-periodic solutions for a nonautonomous differential equation with piecewise constant argument in a Banach space when omega is an integer. This is done using the Banach fixed point Theorem. An example involving the heat operator is discussed as an illustration of the theory.

Long time behavior of random and nonautonomous Fisher-KPP equations. Part II. Transition fronts

In the current series of two papers, we study the long time behavior of the following random Fisher-KPP equation $$ u_t =u_{xx}+a(θ_tω)u(1-u),\quad x\in\R, \eqno(1) $$ where $ω\inΩ$, $(Ω, \mathcal{F},\mathbb{P})$ is a given probability space, $θ_t$ is an ergodic metric dynamical system on $Ω$, and $a(ω)>0$ for every $ω\inΩ$. We also study the long time behavior of the following nonautonomous Fisher-KPP equation, $$ u_t=u_{xx}+a_0(t)u(1-u),\quad x\in\R, \eqno(2) $$ where $a_0(t)$ is a positive locally Hölder continuous function. In the first part of the series, we studied the stability of posit…

Long time behavior of random and nonautonomous Fisher-KPP equations. Part I. Stability of equilibria and spreading speeds

In the current series of two papers, we study the long time behavior of the following random Fisher-KPP equation $$ u_t =u_{xx}+a(θ_tω)u(1-u),\quad x\in\mathbb{R} $$ where $ω\inΩ$, $(Ω, \mathcal{F},\mathbb{P})$ is a given probability space, $θ_t$ is an ergodic metric dynamical system on $Ω$, and $a(ω)>0$ for every $ω\inΩ$. We also study the long time behavior of the following nonautonomous Fisher-KPP equation, $$ u_t=u_{xx}+a_0(t)u(1-u),\quad x\in\mathbb{R}$$ where $a_0(t)$ is a positive locally Hölder continuous function. In this first part of the series, we investigate the stability of posit…

具有时变非对称核的非局部Fisher-KPP方程的传播速度

Spreading speeds for nonlocal Fisher--KPP equations with time-dependent asymmetric kernels

研究非自治非局部Fisher-KPP方程的传播速度，在核函数指数有界且存在均匀均值条件下，证明左右传播速度由线性决定公式给出。