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In algebra , a primordial element is a particular kind of a vector in a vector space .
Let
V
{\displaystyle V}
be a vector space over a field
F
{\displaystyle \mathbb {F} }
and let
(
e
i
)
i
∈
I
{\displaystyle \left(e_{i}\right)_{i\in I}}
be an
I
{\displaystyle I}
-indexed basis of vectors for
V
.
{\displaystyle V.}
By the definition of a basis, every vector
v
∈
V
{\displaystyle v\in V}
can be expressed uniquely as
v
=
∑
i
∈
I
a
i
(
v
)
e
i
{\displaystyle v=\sum _{i\in I}a_{i}(v)e_{i}}
for some
I
{\displaystyle I}
-indexed family of scalars
(
a
i
)
i
∈
I
{\displaystyle \left(a_{i}\right)_{i\in I}}
where all but finitely many
a
i
{\displaystyle a_{i}}
are zero.
Let
I
(
v
)
=
{
i
∈
I
:
a
i
(
v
)
≠
0
}
{\displaystyle I(v)=\left\{i\in I:a_{i}(v)\neq 0\right\}}
denote the set of all indices for which the expression of
v
{\displaystyle v}
has a nonzero coefficient.
Given a subspace
W
{\displaystyle W}
of
V
,
{\displaystyle V,}
a nonzero vector
p
∈
W
{\displaystyle p\in W}
is said to be primordial if it has both of the following two properties:[ 1]
I
(
p
)
{\displaystyle I(p)}
is minimal among the sets
I
(
w
)
,
{\displaystyle I(w),}
where
0
≠
w
∈
W
,
{\displaystyle 0\neq w\in W,}
and
a
i
(
p
)
=
1
{\displaystyle a_{i}(p)=1}
for some index
i
.
{\displaystyle i.}
Linear equations Matrices
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Characteristic polynomial
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(0,1)-matrix
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Matrix decompositions Relations and computations Vector spaces Structures Multilinear algebra Affine and projective Numerical linear algebra