We prove the multiplicity of periodic solutions for an equation in a separable Hilbert space $H$, with $T$-periodic dependence in time, of the type $$ ddot x+{cal A}x+ abla_xV(t,x)=e(t),. $$ Here, ${cal A}$ is a semi-negative definite bounded selfadjoint operator, with nontrivial null-space ${cal N}({cal A})$, the function $V(t,x)$ is bounded above, periodic in $x$ along a basis of ${cal N}({cal A})$, with $ abla_xV$ having its image in a compact set, and $e(t)$ has mean value in ${cal N}({cal A})^perp$. Our results generalize several well-known theorems in the finite-dimensional setting, as well as a recent existence result by Boscaggin, Fonda and Garrione.
Multiple periodic solutions of infinite-dimensional pendulum-like equations
Alessandro Fonda;
2020-01-01
Abstract
We prove the multiplicity of periodic solutions for an equation in a separable Hilbert space $H$, with $T$-periodic dependence in time, of the type $$ ddot x+{cal A}x+ abla_xV(t,x)=e(t),. $$ Here, ${cal A}$ is a semi-negative definite bounded selfadjoint operator, with nontrivial null-space ${cal N}({cal A})$, the function $V(t,x)$ is bounded above, periodic in $x$ along a basis of ${cal N}({cal A})$, with $ abla_xV$ having its image in a compact set, and $e(t)$ has mean value in ${cal N}({cal A})^perp$. Our results generalize several well-known theorems in the finite-dimensional setting, as well as a recent existence result by Boscaggin, Fonda and Garrione.File | Dimensione | Formato | |
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2020_Fonda-Mawhin-Willem_PAFA.pdf
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