Integrodifferential equations of neutral type with \(L^p\)-phase spaces

We prove a new variation of constants formula for the mild solutions of a class of functional integrodifferential equations of neutral type with \(L^p\) $L^p$ -phase space. Additionally, we compute the spectrum of the generator of the \(C_0\) $C_0$ -semigroup in a relevant product Banach space linked to these equations. Furthermore, conditions that indicate the positivity of this semigroup are established.