  The basis for the field theory are properties of the closed exterior
differential forms (skew-symmetric differential forms defined on manifolds with
the closed metric forms), which reflect properties of the conservation laws for
physical fields. It is possible to classify physical fields and interactions.
So, the (0-form) corresponds to the strong interaction, the (1-form)
corresponds to the weak interaction, the (2-form) coorresponds to the
electromagnetic interaction, and the (3-form) corresponds to the gravitational
interaction. This is the basis of unified field theory. As a general field
theory it can be a theory, which not only decribes possible physical fields and
relation between them, but also discloses a mechanism of forming physical
fields and the causality of such processes. It occurs that as the basis of such
a theory it can become the theory of skew-symmetric differential forms defined
on manifolds with unclosed metric forms. These differential forms, which were
named the evolutionary ones, reflrect the properties of the conservation laws
for material media (the balance conservation laws for energy, linear and
angular momentum, and mass) and disclose a mechanism of the evolutionary
processes in material media. It is in such processes the physical structures
that form physical fields originate. The theory of exterior and evolutionary
skew-symmetric differential forms discloses the causality of physical
processes, establishes a relation between physical fields and material media
and allows to introduce a classification of physical fields and interactions.
