Published online by Cambridge University Press: 20 November 2018
An $R$-module
$M$ is called a multiplication module if for each submodule
$N$ of
$M,\,N\,=\,IM$ for some ideal
$I$ of
$R$. As defined for a commutative ring
$R$, an
$R$-module
$M$ is said to be semiprimitive if the intersection of maximal submodules of
$M$ is zero. The maximal spectra of a semiprimitive multiplication module
$M$ are studied. The isolated points of
$\text{Max}\left( M \right)$ are characterized algebraically. The relationships among the maximal spectra of
$M$,
$\text{Soc}\left( M \right)$ and
$\text{Ass}\left( M \right)$ are studied. It is shown that
$\text{Soc}\left( M \right)$ is exactly the set of all elements of
$M$ which belongs to every maximal submodule of
$M$ except for a finite number. If
$\text{Max}\left( M \right)$ is infinite,
$\text{Max}\left( M \right)$ is a one-point compactification of a discrete space if and only if
$M$ is Gelfand and for some maximal submodule
$K$,
$\text{Soc}\left( M \right)$ is the intersection of all prime submodules of
$M$ contained in
$K$. When
$M$ is a semiprimitive Gelfand module, we prove that every intersection of essential submodules of
$M$ is an essential submodule if and only if
$\text{Max}\left( M \right)$ is an almost discrete space. The set of uniform submodules of
$M$ and the set of minimal submodules of
$M$ coincide.
$\text{Ann}\left( \text{Soc}\left( M \right) \right)M$ is a summand submodule of
$M$ if and only if
$\text{Max}\left( M \right)$ is the union of two disjoint open subspaces
$A$ and
$N$, where
$A$ is almost discrete and
$N$ is dense in itself. In particular,
$\text{Ann}\left( \text{Soc}\left( M \right) \right)\,=\,\text{Ann}\left( M \right)$ if and only if
$\text{Max}\left( M \right)$ is almost discrete.