What is Vector space: Definition and 539 Discussions

A vector space (also called a linear space) is a set of objects called vectors, which may be added together and multiplied ("scaled") by numbers, called scalars. Scalars are often taken to be real numbers, but there are also vector spaces with scalar multiplication by complex numbers, rational numbers, or generally any field. The operations of vector addition and scalar multiplication must satisfy certain requirements, called vector axioms (listed below in § Definition). To specify that the scalars are real or complex numbers, the terms real vector space and complex vector space are often used.
Certain sets of Euclidean vectors are common examples of a vector space. They represent physical quantities such as forces, where any two forces (of the same type) can be added to yield a third, and the multiplication of a force vector by a real multiplier is another force vector. In the same way (but in a more geometric sense), vectors representing displacements in the plane or three-dimensional space also form vector spaces. Vectors in vector spaces do not necessarily have to be arrow-like objects as they appear in the mentioned examples: vectors are regarded as abstract mathematical objects with particular properties, which in some cases can be visualized as arrows.
Vector spaces are the subject of linear algebra and are well characterized by their dimension, which, roughly speaking, specifies the number of independent directions in the space. Infinite-dimensional vector spaces arise naturally in mathematical analysis as function spaces, whose vectors are functions. These vector spaces are generally endowed with some additional structure such as a topology, which allows the consideration of issues of proximity and continuity. Among these topologies, those that are defined by a norm or inner product are more commonly used (being equipped with a notion of distance between two vectors). This is particularly the case of Banach spaces and Hilbert spaces, which are fundamental in mathematical analysis.
Historically, the first ideas leading to vector spaces can be traced back as far as the 17th century's analytic geometry, matrices, systems of linear equations and Euclidean vectors. The modern, more abstract treatment, first formulated by Giuseppe Peano in 1888, encompasses more general objects than Euclidean space, but much of the theory can be seen as an extension of classical geometric ideas like lines, planes and their higher-dimensional analogs.
Today, vector spaces are applied throughout mathematics, science and engineering. They are the appropriate linear-algebraic notion to deal with systems of linear equations. They offer a framework for Fourier expansion, which is employed in image compression routines, and they provide an environment that can be used for solution techniques for partial differential equations. Furthermore, vector spaces furnish an abstract, coordinate-free way of dealing with geometrical and physical objects such as tensors. This in turn allows the examination of local properties of manifolds by linearization techniques. Vector spaces may be generalized in several ways, leading to more advanced notions in geometry and abstract algebra.
This article deals mainly with finite-dimensional vector spaces. However, many of the principles are also valid for infinite-dimensional vector spaces.

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  1. M

    What Are Some Examples of Isomorphic Vector Spaces with Different Dimensions?

    I came across this problem today and haven't been able to figure it out... Give an example of a vector space V which isomorphic to a proper subspace W, i.e. V != W. It seems to me that V can't have a finite basis, but can't think of any examples regardless...any thoughts?
  2. P

    Vector Space Axioms: 4 Rules to Redefine

    I am trying to shorten and generalize the the definition of a vector space to redefine it in such a way that only four axioms are required. The axioms must hold for all vectors u, v and w are in V and all scalars c and d. I believe the four would be: 1. u + v is in V, 2. u + 0 = u 3. u...
  3. M

    Understanding Vector Spaces: Exploring Real Valued Functions on Arbitrary Sets

    Hello all. While looking at vector spaces leading up to multilinear mappings i am having trouble right at the start with the idea of the set of all real valued functions on an arbitrary set which vanish at all but a finite number of points. The author ( Wasserman, Tensors and Manifolds ) does...
  4. K

    Are These Matrices a Basis for M2x2(R)?

    Homework Statement Determine whether the following 2 x 2 matrices form a basis of the vector space M2x2(R) of all (2x2)-matrices over R: A1= 1 0 0 0 A2= 2 2 0 0 A3= 3 2 1 0 A4= 4 3 2 1 Homework Equations The Attempt at a Solution So for them to be...
  5. M

    Understanding Quotient Vector Space: Collapsing to Zero

    Hello all I have read about quotient spaces of a vector space in several books and have an understanding of what they are. Looking up Quotient Vector Space in Wiki it says :- The quotient of a vector space V by a subspace N is a vector space obtained by "collapsing" N to zero. I...
  6. T

    V is vector space of all antisimetric 3x3 matrices

    Homework Statement V is vector space of all antisimetric 3x3 matrices. Find the coordinates of the matrix A= \left| \begin{array}{ccc} \ 0 & 1 & -2 \\ -1 & 0 & -3 \\ 2 & 3 & 0 \end{array} \right|\] relative to the base E_1= \left|...
  7. A

    Proving Vector Space Subspace Union: Tips and Assistance"

    Hello Well i hv just started vector spaces and well am finding difficulty in proving this hoffman and kunze problem could some 1 help me :( Question : W1 and W2 be sub-spaces of vector space V such that set-theoritic union of W1 and W2 is also a Subspace . Proove that one of the subspace...
  8. A

    Is R a Vector Space with Defined Operations? | Homework Statement

    Homework Statement Let R denote the set of real numbers. Define scalar multiplication by \alpha x = \alpha x which is simply regular scalar multiplication, and vector addition is defined as x \oplus y = max(x,y). Is R a vector space with these operations? Homework Equations Some given...
  9. K

    Proving vector space, associativity

    Homework Statement Im doing a problem where I am trying to show that an abelian group with a scalar multiplication is a vector field. I am trying to show associativity right now and just have a question: im trying to show that exp(b.c.lnx) = b.exp(c.lnx) But I am not very sure of my logs...
  10. J

    Proving Vector Space of F[x]/(g(x)) with Degree n

    Homework Statement Show that F[x]/( g(x) ) is a n-dimensional vector space. where g is in F[x], and g has degree n. Its clear that F[x]/( g(x) ) is a vector space and that B= (1,x^{2},...,x^{n-1}) spans F[x]/( g(x) ), but I am having trouble showing that B is linearly independent...
  11. J

    Proving Vector Space Dimensionality of F[x]/(g(x))

    Homework Statement Show that F[x]/( g(x) ) is a n-dimensional vector space. where g is in F[x], and g has degree n. Its clear that F[x]/( g(x) ) is a vector space and that B= (1,x^{2},...,x^{n-1}) spans F[x]/( g(x) ), but I am having trouble showing that B is linearly independent
  12. B

    How Does Orthogonality and Matrix Transformation Affect Vector Spaces?

    Question 1 Let u, v1,v2 ... vn be vectors in R^{n}. Show that if u is orthogonal to v1,v2 ...vn then u is orthogonal to every vector in span{v1,v2...vn} My attempt if u is orthogonal to v1,v2 ...vn then (u.v1)+(u.v2)+...+(u.vn)=0 Let w be a vector in span{v1,v2...vn} therefore...
  13. W

    Difference between a vector space and a field?

    I'm just wondering what are the differences between vector spaces and fields. From what I understand by the definitions, both of these are collections of objects where additions and scalar multiplications can be performed. I can't seem to see the difference between vector spaces and fields.
  14. T

    Vector Space Algebra of Minkowski Space

    Consider the Minkowski space of 4 dimensions with signature (- + + +). How does the vector space algebra work here? More specifically given 3 space like orthonormal vectors how do we define fourth vector orthogonal to these vectors? I am looking for an appropriate vector product like it is in...
  15. M

    Least amount of structure for vector space.

    Hello all. Back to basics again. When defining a set of geometric vectors for a vector space of n dimensions how can we define such a set without a certain amount of structure already defined upon the n dimensional space. We presumably need some concept of direction to determine linear...
  16. E

    Vector Space Requirements for Functions that Vanish at x=0 and x=L

    Homework Statement Do functions that vanish at the end points x=0 and x=L form a vector space ? How about periodic functions obeying f(L)=f(0)? How about functions that obey f(0)=4 ? If the functions do not qualify , list the things that go wrong . Homework Equations All axioms...
  17. M

    Maximal Subspaces in Vector Spaces: Using Zorn's Lemma to Prove Existence

    Maximal subspace Problem: Prove that every vector space V has maximal subspace, i.e. a proper subspace that is not properly contained in a proper subspace of V. I let A be the collection of all proper subspaces of V, but I can't prove that every totally ordered subcollection of A has an...
  18. M

    Concept of a basis for a vector space

    concept of a "basis" for a vector space I do not understand the concept of a "basis" for a vector space. Here's an example from my practice final exam: Suppose U and V are subspaces of the real vector space W and {u1} is a basis for U and {v1} is a basis for V. If U intersection V = {0}...
  19. M

    What is the Proper Subspace Hierarchy in a Vector Space with Infinite Subsets?

    Homework Statement Let {W_1,W_2,W_3,...} be a collection of proper subspaces of V (i.e. W_i not=V) such that W_i is a subset of W_(i+1) for all i. Prove that U(W_i) (i from 1 to infinity) is a proper subspace of V The Attempt at a Solution I've already proven that U(W_i) is a subspace of...
  20. M

    Vector space over the rationals

    Hello all. I came across this problem in Halmos, Finite-Dimensional Vector Spaces, page 16. Is the set R of all real numbers a finite-dimensional vector space over the field Q of all rational numbers. There is a reference to a previous example which says that with the usual rules of...
  21. E

    Solving a Vector Space Problem: (a,b,1) Not a Vector Space

    [SOLVED] a simple vector space problem Homework Statement Consider the set of all entities of the form (a,b,c) where the entries are real numbers . Addition and scalar multiplication are defined as follows : (a,b,c) + (d,e,f) = (a+d,b+e,c+f) z*(a,b,c) = (za,zb,zc) Show that vectors...
  22. A

    Cardinality of a basis of an infinite-dimensional vector space

    I am reading "The linear algebra a beginning graduate student ought to know" by Golan, and I encountered a puzzling statement: Let V be a vector space (not necessarily finitely generated) over a field F. Prove that there exists a bijective function between any two bases of V. Hint: Use...
  23. A

    Why y=2x+1 is not a vector space?

    I'm trying to solve a problem ice109 recommended. I'm trying to show how y=2x+1 is not a vector space. Here I go. Let u=(x,2x+1) v=(x',2x'+1) w=(x",2x"+1) 1. If u and v are objects in V, then u + v is in V. u+v=(x+x',2x+2x'+2) fails because 2 is not in V? 2. u + v = v + u passes...
  24. C

    Vector space of polynomials problem

    [b]1. Consider the vector space of polynomials 1+x^3 , 1-x+x^2, 2x, 1+x^2 Are they linearly dependent or independent? dimension of vecotr space spanned by these vectors? [b]3. I have tried to solve this by letting a1 = 1+x^3 a2 = 1-x+x^2 a3 = 2x a4 = 1+x^2 Then I let (alpha)a1 +...
  25. A

    How can I tell if this is a vector space?

    1. Homework Statement A set of objects is given, together with operations of addition and scalar multiplication. Determine which sets are vector spaces under the given operations. For those that are not vector spaces, list all axioms that fail to hold. (x,y,z) + (x',y',z') =...
  26. E

    Is W a subspace of the vector space?

    W={(x1,x2,x3):x^{2}_{1}+x^{2}_{2}+x^{2}_{3}=0} , V=R^3 Is W a subspace of the vector space? from what i understand for subspace to be a subspace it has to have two conditions: 1.must be closed under addition 2.must be closed under multiplication so... I pick a vector s=(s1,s2,s3) and a second...
  27. M

    Free Vector Space Explained: Geroch & Matheinste

    Hello everyone. I came across the term free vector space in a book on mathematical physics by Geroch but cannot find them in any other of my books. Can someone give me an explanation of how a free vector space differs from a standard vector space. Geroch says that any set can be made into a...
  28. E

    Determine whether the set is a vector space

    15. Determine wheter the set is a vector space. The set of all fifth-degree polynomials with the standard operations. AXIOMS 1.u+v is in V 2.u+v=v+u 3.u+(v+w)=(u+v)+w 4.u+0=u 5.u+(-u)=0 6. cu is in V 7.c(u+v)=cu+cv 8.(c+d)u=cu+cd 9.c(du)=(cd)u 10.1(u)=u the back of my book says that axioms...
  29. E

    Vector Space: Fifth-Degree Polynomials

    15. Determine wheter the set is a vector space. The set of all fifth-degree polynomials with the standard operations. AXIOMS 1.u+v is in V 2.u+v=v+u 3.u+(v+w)=(u+v)+w 4.u+0=u 5.u+(-u)=0 6. cu is in V 7.c(u+v)=cu+cv 8.(c+d)u=cu+cd 9.c(du)=(cd)u 10.1(u)=u the axioms that fail are...
  30. R

    Linear Algebra: Vector Space proof

    Linear Algebra: Vector Space proof... I'm really having trouble comprehending this problem. This is not exactly a "homework problem" but I need a good, formal definition of this to help with some other problems. Let (Vectors) V1, V2,...,Vk be vectors in vector space V. Then the set W of all...
  31. F

    Proof Vector Space of Shift Maps is Isomorphic to R2

    Homework Statement Show that the space of all shift maps is indeed a vector space over R and that there is a linear bijection between it and R2 Homework Equations 10 Axioms of vector spaces Definition of bijection (1-1, onto) For 1-1: f(a) = f(b) -> a = b. The Attempt at a...
  32. J

    What Happens When a Group Leaves a Subset of a Countably Infinite Set Stable?

    If G\subset \textrm{End}(V), and W\subset V is a subspace of a vector space V, and somebody says "G leaves W stable", does it mean GW=W or GW\subset W or something else?
  33. Q

    Complexification of a vector space

    Hello all, I've just learned a bit about the complexification of a real vector space V to include scalar multiplication by complex numbers. A bit of confusion has ensued, which I am hoping someone can help me with conceptually: 1) how does one generate a basis for the new space Vc? It seems...
  34. M

    Vector Space Example: Dimension, Basis, and Inner Product | Homework Statement

    Homework Statement I have been going through some past exam papers and have come across this vector space question that I cannot find relevant examples for. Consider the vector space V of n-th order polynomials p(x) = a0 + a1x + a2x^2 +· · ·+anx^n, where a0,a1,a2, ...,an are real numbers, and...
  35. J

    Vector space dimension of little-l 2

    Homework Statement I'm trying to understand why \ell_2^\infty as a vector space over \mathbb{C}, has uncountable dimension. Homework Equations The Attempt at a Solution Firstly, I'm not really clear on the meaning of basis in infinite dimensions. Is it still true that any element...
  36. S

    Spanning Vector Spaces with Trigonometric Functions

    Homework Statement Is there any difference between the vector space spanned by the set cos(t),sin(t) and the vector space spanned by the set cos(t)+sin(t),cos(t)-sin(t)? Homework Equations The Attempt at a Solution Not really a homework question but it will help me answer a...
  37. O

    Don't understand this simple vector space problem

    Don't understand this reasoning with respect to linear operators. Let S and T be linear operators on the finite dimensional vector space V. Then assuming the composition ST is invertible, we get \text{null} \; S \subset \text{null} \; ST Why is that? I thought hard about it but I simply...
  38. E

    Degree 3 Polynomials and Vector Spaces: Understanding Bases and Coordinates

    So I have an assignment due in a few hours and I am pretty happy with it, aside from the fact that I am completely lost on the following section: - The polynomials of degree 3, denoted P3, form a vector space. 1. Show that when added, two general polynomials of degree 3 will always produce...
  39. H

    Finding a Basis for Vector Space V (Real Coeff. Polys. of Degree < 3)

    I am in a problem seminar class and I have not taken Linear Algebra in over 4 years so I am having a lot of problems with this. Please help...:eek: Homework Statement Let P be the set of all polynomials with real coefficients and of degree less than 3. Thus, P = {f:f(x)= a(sub0)...
  40. Q

    Standard representation of a vector space

    Hi everyone, Can anyone explain the following to me? Given a basis beta for an n-dimensional vector space V over the field F, "the standard representation of V with respect to beta is the function phi_beta(x)=[x]_beta for each x in V." This is from my textbook. It then proceeds to give...
  41. M

    Positive Quadrant Vector Space

    Homework Statement Show that the positive quadrant Q = ( (x,y) | x,y > 0 ) \in \mathbb{R}^2 is a vector space. Homework Equations Addition is redefined by (x_1,y_1) + (x_2,y_2) = (x_1 x_2, y_1 y_2) and scalar multiplication by c(x,y) = (x^c , y^c) The Attempt at a Solution There...
  42. MathematicalPhysicist

    A vector space and linear independent set.

    let V be a vector space and K a nonempty subset of V prove/disprove : K is linear independent set iff for every T such that T is a proper subset of K, span(T) is a proper subset of spanK. im having difficulty finding a counter example, so i think this statement is correct, but how to prove...
  43. J

    Show this is a projection on a vector space

    Homework Statement Let V=Mn(F) be the space of all nxn matrices over F; define TA=(1/2)(A+transpose(A)) for A in V. Verify that T is not only a linear operator on V, but is also a projection. Homework Equations A is a projection when A squared=A. The Attempt at a Solution I don't...
  44. U

    Differences Between Vector Spaces and Fields Explained

    What is the different between a vector space and a field? Seems to me that they both are the same thing
  45. R

    How can I prove that W contains all elementary matrices?

    Please help me proove the following: Let V be a vector space over all n-by-n square matrices. Let W be a non-trivial subspace of V satisfying the following condition: if A is an element of W and B is an element of V then AB, BA are both elements of W. Proove that W = V. And here is what...
  46. P

    Linear Algebra: Vector space axioms

    Homework Statement One of the fundamental axioms that must hold true for a set of elements to be considered a vector space is as follows: 1*x = x I was given a particular space: The set of all polynomials of degree greater than or equal to three, and zero, and asked to evaluate whether or...
  47. P

    Vector space for cross products?

    What vector space are cross products done in?
  48. E

    Vector Space Help: Understanding Notation & Polynomials

    Vector space help please.. Hi, Just started a linear algebra course recently but I am confused with the notation used :confused: http://i9.tinypic.com/2w4za50.jpg I am unsure how to proceed with this question. Can someone help? The part highlighted, what does it mean? 2x2 matrix of...
  49. M

    Vector Space Analysis of Polynomials & Matrices

    I am supposed to determine whether or not the following two sets constitute a vector space. 1) The set of all polynomials degree two. 2) The set of all diagonal 2 x 2 matrices. For the first one, it will not be a vector space because it does not satisfy the closure property. Also the...
  50. S

    Vector Space, (not calc i guess)

    We're working on vector spaces right now and this one problem is iving me a bit of trouble. Is the following a vector space? The set of all polynomials of the form n_2x^2 + n_1x + n_0 where n_0,n_1,n_2 \epsilon Z (integers)Now I'm pretty sure that this is going to end up NOT being a vector...
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