## Differential and Integral Equations

- Differential Integral Equations
- Volume 24, Number 7/8 (2011), 767-786.

### Periodic solutions of damped hyperbolic equations at resonance: a translation along trajectories approach

#### Abstract

We develop an abstract averaging method for a periodic problem $$\left\{ \begin{array}{ll} \ddot u(t) + \beta \dot u(t) + A u + F(t,u(t)) = 0 , \ \ \ t\in [0,T] \\ u(0)=u(T), \dot u(0) = \dot u(T) , \end{array}\right. $$ where $A:D(A)\to X$ is a self-adjoint operator on a Hilbert space $X$ with compact resolvent and $\alpha>0$ such that $A+\alpha$ is strongly $m$-accretive, $\beta>0$ and $F:\mathbb R\times X^{1/2}\to X$, with $X^{1/2}$ being the fractional space of $A+\alpha$, is compact and $T$-periodic in the first variable. The so-called resonant case is considered, i.e., when ${\mathrm{Ker}}\, A\neq \{0\}$ and $F$ is bounded. By use of the topological degree applied to the translation along trajectories operator, effective conditions guaranteeing the existence of $T$-periodic solutions are given. The general result is applied to a damped hyperbolic partial differential equation and the Landesman-Lazer type criterion is derived.

#### Article information

**Source**

Differential Integral Equations, Volume 24, Number 7/8 (2011), 767-786.

**Dates**

First available in Project Euclid: 27 December 2012

**Permanent link to this document**

https://projecteuclid.org/euclid.die/1356628832

**Mathematical Reviews number (MathSciNet)**

MR2830707

**Zentralblatt MATH identifier**

1247.47078

**Subjects**

Primary: 47J35: Nonlinear evolution equations [See also 34G20, 35K90, 35L90, 35Qxx, 35R20, 37Kxx, 37Lxx, 47H20, 58D25] 47J15: Abstract bifurcation theory [See also 34C23, 37Gxx, 58E07, 58E09] 37L05: General theory, nonlinear semigroups, evolution equations

#### Citation

Ćwiszewski, Aleksander. Periodic solutions of damped hyperbolic equations at resonance: a translation along trajectories approach. Differential Integral Equations 24 (2011), no. 7/8, 767--786. https://projecteuclid.org/euclid.die/1356628832