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In this paper we give a simple definition of Dirac structures on
modules and on vector bundles which includes the existing ones,
and complex structures on vector bundles, as special cases. Among
other thing we prove:\\ 1) Each two Dirac structures on a
(Hermitian) module \emph{M} are (isometrically)
isomorphic(Hermitian) modules. Moreover, the set of all Dirac
structures on \emph{M}is in one-to-one correspondence with
Aut(M).\\ 2) Let \emph{M} be a smooth manifold, and let $\eta$ be
a (Hermitian) vector bundle over \emph{M}. Then, to each Dirac
structure on $\eta$, there corresponds a unique Dirac structure on
the (Hermitian) $\emph{C}^{\infty}(\emph{M})-module$ of its
sections. Conversely, to each Dirac structure on a Hermitian
finitely generated projective $\emph{C}^{\infty}(\emph{M})-module$
there corresponds a unique Dirac structure on the associated
(Hermitian) vector bundle over \emph{M}.\\ 3) Let \emph{M} be a
Hilbert \emph{R}-module. Then to each Dirac structure on
\emph{M}and to each state of \emph{R} there corresponds a unique
Dirac structure on the associated Hilbert space.
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