inverse image
Noun
Meaning
inverse image (plural inverse images)
The set of points that map to a given point (or set of points) under a specified function.
Under the function given by
f
(
x
)
=
x
2
{\displaystyle f(x)=x^{2}}
, the inverse image of 4 is
{
−
2
,
2
}
{\displaystyle \{-2,2\}}
, as is the inverse image of
{
4
}
{\displaystyle \{4\}}
.
Synonyms
Examples
Equivalently, f is continuous if the inverse image of every open set is open.sfn This is an attempt to capture the intuition that there are no "jumps" or "separations" in the function.
Continuous functions and homeomorphisms main A function or map from one topological space to another is called continuous if the inverse image of any open set is open.
Given a homomorphism from an arbitrary semigroup to a semilattice, each inverse image is a (possibly empty) semigroup.
Thus the inverse image would be a 1-manifold with boundary.
We conclude that left adjoint to the inverse image functor is given by the direct image.