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  2. 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.

  3. Linear subspace - Wikipedia

    en.wikipedia.org/wiki/Linear_subspace

    In R 3, the intersection of two distinct two-dimensional subspaces is one-dimensional. Given subspaces U and W of a vector space V, then their intersection U ∩ W := {v ∈ V : v is an element of both U and W} is also a subspace of V. [10] Proof: Let v and w be elements of U ∩ W. Then v and w belong to both U and W.

  4. 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 ...

  5. Bin packing problem - Wikipedia

    en.wikipedia.org/wiki/Bin_packing_problem

    In the guillotine cutting problem, both the items and the "bins" are two-dimensional rectangles rather than one-dimensional numbers, and the items have to be cut from the bin using end-to-end cuts. In the selfish bin packing problem, each item is a player who wants to minimize its cost. [53]

  6. Phase plane - Wikipedia

    en.wikipedia.org/wiki/Phase_plane

    A two-dimensional system of linear differential equations can be written in the form: [1] = + = + which can be organized into a matrix equation: [] = [] [] =.where A is the 2 × 2 coefficient matrix above, and v = (x, y) is a coordinate vector of two independent variables.

  7. Linear map - Wikipedia

    en.wikipedia.org/wiki/Linear_map

    If and are finite-dimensional vector spaces over a field F, of respective dimensions m and n, then the function that maps linear maps : to n × m matrices in the way described in § Matrices (below) is a linear map, and even a linear isomorphism.

  8. Hilbert space - Wikipedia

    en.wikipedia.org/wiki/Hilbert_space

    More precisely, an orthonormal basis is a Hamel basis if and only if the Hilbert space is a finite-dimensional vector space. [90] Completeness of an orthonormal system of vectors of a Hilbert space can be equivalently restated as: for every v ∈ H, if v, e k = 0 for all k ∈ B, then v = 0.

  9. 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 ...