%0 Journal Article %T Periodicity of mild solutions to higher order differential equations in Banach spaces %A Thanh Lan Nguyen %J Electronic Journal of Differential Equations %D 2004 %I Texas State University %X We give necessary and sufficient conditions for the periodicity of mild solutions to the the higher order differential equation $u^{(n)}(t)=Au(t)+f(t)$, $0le t le T$, in a Banach space $E$. Applications are made to the cases, when $A$ generates a $C_0$-semigroup or a cosine family, and when $E$ is a Hilbert space. %K Abstract Cauchy problems %K Fourier series %K periodic mild solutions %K semigroups and cosine families. %U http://ejde.math.txstate.edu/Volumes/2004/79/abstr.html