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  2. Euclidean vector - Wikipedia

    en.wikipedia.org/wiki/Euclidean_vector

    Two examples (r = −1 and r = 2) are given below: The scalar multiplications −a and 2a of a vector a. Scalar multiplication is distributive over vector addition in the following sense: r(a + b) = ra + rb for all vectors a and b and all scalars r. One can also show that a − b = a + (−1)b.

  3. Invariant subspace problem - Wikipedia

    en.wikipedia.org/wiki/Invariant_subspace_problem

    Every operator on a non-trivial complex finite dimensional vector space has an eigenvector, solving the invariant subspace problem for these spaces. In the field of mathematics known as functional analysis , the invariant subspace problem is a partially unresolved problem asking whether every bounded operator on a complex Banach space sends ...

  4. Hilbert's sixteenth problem - Wikipedia

    en.wikipedia.org/wiki/Hilbert's_sixteenth_problem

    The determination of the upper bound for the number of limit cycles in two-dimensional polynomial vector fields of degree n and an investigation of their relative positions. The first problem is yet unsolved for n = 8. Therefore, this problem is what usually is meant when talking about Hilbert's sixteenth problem in real algebraic geometry.

  5. Linear independence - Wikipedia

    en.wikipedia.org/wiki/Linear_independence

    That is to say, the north vector cannot be described in terms of the east vector, and vice versa. The third "5 miles northeast" vector is a linear combination of the other two vectors, and it makes the set of vectors linearly dependent, that is, one of the three vectors is unnecessary to define a specific location on a plane.

  6. Cyclic subspace - Wikipedia

    en.wikipedia.org/wiki/Cyclic_subspace

    The cyclic subspace associated with a vector v in a vector space V and a linear transformation T of V is called the T-cyclic subspace generated by v. The concept of a cyclic subspace is a basic component in the formulation of the cyclic decomposition theorem in linear algebra.

  7. Linear subspace - Wikipedia

    en.wikipedia.org/wiki/Linear_subspace

    If V is a vector space over a field K, a subset W of V is a linear subspace of V if it is a vector space over K for the operations of V.Equivalently, a linear subspace of V is a nonempty subset W such that, whenever w 1, w 2 are elements of W and α, β are elements of K, it follows that αw 1 + βw 2 is in W.

  8. Invariant subspace - Wikipedia

    en.wikipedia.org/wiki/Invariant_subspace

    Any eigenvector for T spans a 1-dimensional invariant subspace, and vice-versa. In particular, a nonzero invariant vector (i.e. a fixed point of T) spans an invariant subspace of dimension 1. As a consequence of the fundamental theorem of algebra, every linear operator on a nonzero finite-dimensional complex vector space has an eigenvector ...

  9. Hairy ball theorem - Wikipedia

    en.wikipedia.org/wiki/Hairy_ball_theorem

    The hairy ball theorem of algebraic topology (sometimes called the hedgehog theorem in Europe) [1] states that there is no nonvanishing continuous tangent vector field on even-dimensional n-spheres. [2] [3] For the ordinary sphere, or 2‑sphere, if f is a continuous function that assigns a vector in ℝ 3 to every point p on a sphere such that ...