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. D

    Why is the dimension of the vector space , 0?

    In other words, why is dim[{0}]=0. My math professor explained that since the 0 vector is just a POINT in R2 that the zero subspace doesn't have a basis and therefore has dimension zero. This is not satisfactory. For example, I know R2 has a dimension 2, P_n has dimension n+1, M_(2,2) has...
  2. K

    Normed vector space: convex set

    Homework Statement Show that the closed unit ball {x E V:||x||≤1} of a normed vector space, (V,||.||), is convex, meaning that if ||x||≤1 and ||y||≤1, then every point on the line segment between x and y has norm at most 1. (hint: describe the line segment algebraically in terms of x and y...
  3. B

    Basis for Vector Space: Understanding the Exceptional Case

    Homework Statement My notes has the following statement, but I seem to have forgotten to write down the conclusion of the statement before my professor erased it from the board. "Any vector space V there will be a basis except for 1 type of space: " Any ideas as to what that 1 type of...
  4. J

    Homeomorphism between a 1-dim vector space and R

    im trying to get a homeomorphism between a 1-dim vector space and R, but independent of the basis. Any ideas?
  5. V

    Is Span{W} a Subspace of Vector Space V?

    Homework Statement Suppose V is a vector space with operations + and * (under the usual operations) and W = {w1, w2, ... , wn} is a subset of V with n vectors. Show Span{W} is a subspace of V. The attempt at a solution I know that to show a set is a subspace, we need to show...
  6. F

    Is Composition by a Mapping a Linear Isomorphism in Vector Spaces?

    Homework Statement Sorry for the vague title! Let R denote the set of real numbers, and F(S,R) denote the set of all functions from a set S to R. Part 1: Let \phi be any mapping from a set A to a set B. Show that composition by \phi is a linear mapping from F(B,R) to F(A,R). That is...
  7. D

    Vector Space Axiom: Can this be done easier?

    I think, in case it is wrong, I proved the the first vector space axiom for 3 x 3 magic squares; however, there has to be an easier way to do what I did. This pdf has been removed. Go to page 2 of the discussion for an updated version. I attached a pdf file due to I can create the...
  8. D

    Vector Space Axioms: Proving Axiom 1

    Since I can't copy and paste from maple into this message w/out losing formatting, I attached a pdf with all the work. I am having trouble proving axiom 1 of two general magic square matrices added together; plus, I am not sure if my set notation is entirely correct.
  9. C

    Prove Finite Dimensional Normed Vector Space is Differentiable

    Homework Statement Let V be a finite dimensional normed vector space and let U= L(V)*, the set of invertible elements in L(V). Show, f:U-->U defined by f(T)= T-1 is differentiable at each T in U and moreover, Df(T)H = -T-1HT-1 where Df(T)= f'(T). Homework Equations Apparently...
  10. D

    Solving for x in Vector Space (1,2)^T; (-1,1)^T

    Find the basis of the vector space (1,2)^T; (-1,1)^T When I solve the matrix, I obtain x1=0 and x2=0 x=(0,0)^T. Can a basis be two 0 column vectors? Thanks for the help.
  11. M

    Proving Equal Ranks in Linear Maps: The Case of T^2 = TT and T(V) = V

    Homework Statement let T(V)=V be a linear map, where V is a finite-dimensional vector space. Then T^2 is defined to be the composite TT of T with itself, and similarly T^(i+1) = TT^i for all i >=1. Suppose Rank (T) = Rank (T^2) Homework Equations a) prove that Im(T) = Im(T^2) b) for...
  12. B

    Show functions of this form are a vector space etc

    Show that the functions (c_{1}+c_{2}sin^{2}x+c_{3}cos^2{x}) form a vector space. Find a basis of it. What is its dimension? My answer is that it's a vector space because: (c_{1}+c_{2}sin^{2}x+c_{3}cos^2{x})+(c'_{1}+c'_{2}sin^{2}x+c'_{3}cos^2{x})...
  13. M

    Dimension of Hom(K)(U,V) and Basis of the Vector Space

    Homework Statement Let U and V be vector spaces of dimensions of n and m over K and let Hom(subscriptK)(U,V) be the vector space over K of all linear maps from U to V. Find the dimension and describe a basis of Hom(subscriptK)(U,V). (You may find it helpful to use the correspondence with mxn...
  14. D

    Is ℝ+ a Vector Space with Scalar Multiplication and Addition?

    I am not sure if my #4 holds and I don't know how to approach #7. My Axioms are below the general axioms. {∀ x ϵ ℝ+ : x>0} Define the operation of scalar multiplication, denoted ∘, by α∘x = x^α, x ϵ ℝ+ and α ϵ ℝ. Define the operation of addition, denoted ⊕, by x ⊕ y = x·y, x, y ϵ ℝ+. Thus...
  15. T

    How Do You Calculate the Magnitude of a Constant Vector in Different Dimensions?

    Homework Statement Calculate ||1,1,1||in R3 Calculate ||1,1,1,1|| in R4. Calculate ||1,1,...,1|| in Rn. Homework Equations All I have in this problem is that, Where do I start? The Attempt at a Solution
  16. D

    Axiom 6 Vector Space: Proving ℝ+ is a Vector Space

    {∀ x ϵ ℝ+ : x>0} Define the operation of scalar multiplication, denoted ∘, by α∘x = x^α, x ϵ ℝ+ and α ϵ ℝ. Define the operation of addition, denoted ⊕, by x ⊕ y = x·y, x, y ϵ ℝ+. Thus, for this system, the scalar product of -3 times 1/2 is given by: -3∘1/2 = (1/2)^-3 = 8 and the sum of 2 and...
  17. D

    Defining Scalar and Addition Operations in ℝ+

    {∀ x ϵ ℝ+ : x>0} Define the operation of scalar multiplication, denoted ∘, by α∘x = x^α, x ϵ ℝ+ and α ϵ ℝ. Define the operation of addition, denoted ⊕, by x ⊕ y = x·y, x, y ϵ ℝ+. Thus, for this system, the scalar product of -3 times 1/2 is given by: -3∘(1/2)= (1/2)^-3 = 8 and the sum of 2 and 5...
  18. J

    Hermitian matrix vector space over R proof

    Homework Statement I need to prove that the hermitian matrix is a vector space over R Homework Equations The Attempt at a Solution I know the following: If a hermitian matrix has aij = conjugate(aji) then its easy to prove that the sum of two hermitian matrices A,B give a hermitian...
  19. S

    Proving Vector Space Axioms: (-1)u=-u

    Hi. please anyone help me with vector spaces and the way to prove the axioms. like proving that (-1)u=-u in a vector space.
  20. M

    What Are the Rank and Nullity of a Linear Transformation?

    Homework Statement find the rank and nullity of the linear transformation T:U -> V and find the basis of the kernel and the image of T Homework Equations U=R[x]<=5 V=R[x]<=5 (polynomials of degree at most 5 over R), T(f)=f'''' (4th derivative) The Attempt at a Solution Rank = 2...
  21. M

    Understanding the Basis of a Zero Vector Space

    Homework Statement erm, I just want to know, what is the basis for a zero vector space? Homework Equations The Attempt at a Solution is it the zero vector itself? but if that's the case, then the constant alpha could be anything other than zero, which means the zero vector is not...
  22. I

    What Is the Dimension of Subspaces U and W in a Vector Space V?

    Homework Statement V=R^{4}\ and\ a^{\rightarrow}, b^{\rightarrow}, c^{\rightarrow}, d^{\rightarrow}, e^{\rightarrow} \in V. (I'll drop the vector signs for easier typing...) a = (2,0,3,0), b = (2,1,0,0), c = (-2,0,3,0), d = (1,1,-2,-2), e = (3,1,-5,-2) Let\ U \subseteq V be\...
  23. M

    Solving for Vector Space V: Find Dimension & Basis

    Homework Statement Find the dimnesion and a basis of vector space V Homework Equations V is the set of all vectors (a,b,c) in R^3 with a+2b-4c=0 The Attempt at a Solution (4c-2b,b,c) = b(-2,1,0) + c(4,0,1) so {(-2,1,0),(4,0,1)} is the basis of the SUBSPACE of V right? how do I...
  24. N

    Need help with vector space multiple choice

    Determine whether the given set S is a subspace of the vector space V. A. V=P5, and S is the subset of P5 consisting of those polynomials satisfying p(1)>p(0). B. V is the vector space of all real-valued functions defined on the interval [a,b], and S is the subset of V consisting of those...
  25. M

    Prove that the additive inverse -v of an element v in a vector space is unique.

    Homework Statement Prove that the additive inverse -v of an element v in a vector space is unique. Homework Equations Additive Inverse in V For each v in V, there is an element -v in V such that v + (-v) = 0. The Attempt at a Solution Assume that the additive inverse is not...
  26. Z

    Prove that the additive identity in a vector space is unique

    Homework Statement Prove that the additive identity in a vector space is unique Homework Equations Additive identity There is an element 0 in V such that v + 0 = v for all v in V The Attempt at a Solution Assume that the additive identity is NOT unique, then there exists y...
  27. mnb96

    Perpendicularity on complex vector space

    Hi, given a complex vector space with a hermitian inner product, how is the cosine of the angle between two vectors defined? I tried to follow a similar reasoning as in the real case and I got the following: cos(\theta)=\mathcal{R}e \frac{ \left\langle u,v\right\rangle}{\left\|u\right\|...
  28. M

    Transformations in vector space

    dear all,we know that active transformation refers to action of changing vectors keeping the operators unchanged whereas passive transformation refers to change of operator components keeping vectors unchanged. what i cannot understand(i am just starting quantum mechanics)is in the former if we...
  29. S

    What's a vector space and not?

    He gets only the positive vectors. But I don't get which is not a vector space. What I understand is vector space maybe a R^2, R^3 or R^n. Can anyone here explain it more clearly? I don't get what he said. http://www.youtube.com/watch?v=JibVXBElKL0" @ 29:55
  30. N

    Vector Space Basis: Standard or Odd?

    In short: does every vector space have a "standard" basis in the sense as it is usually defined i.e. the set {(0,1),(1,0)} for R2? And another example is the standard basis for P3 which is the set {1,t,t2}. But for more abstract or odd vector spaces such as the space of linear transformations...
  31. M

    Is this matrix a vector space?

    Homework Statement a b c 0 b 8 0 0 c Homework Equations 10 axioms to determine vector space: 1. If u and v are objects in V, then u + v is in V. 2. u + v = v + u 3. u + (v + w) = (u + v) + w 4. There is an object 0 in V, called a zero vector for V, such that 0...
  32. C

    Linear algebra: cyclic vector space

    Homework Statement Prove that V is cyclic relative to a linear transformation T, T:V->V if and only if the minimal polynomial of T is the same as the characteristic polynomial of T. Homework Equations The Attempt at a Solution i have finished the => direction (proved that if...
  33. H

    Does the Set T Form a Vector Space Under Given Operations?

    Homework Statement Let T be the set of all ordered triples of real numbers (x,y,z) such that xyz=0 with the usual operations of addition and scalar multiplication for R^3, namely, vector addition:(x,y,z)+(x',y',z')=(x+x',y+y',z+z') scalar multiplication: k(x,y,z)=(kx,ky,kz) Determine...
  34. N

    Why 3x3 Matrices Don't Form a Vector Space Over Reals

    Homework Statement The set of all nonsingular 3x3 matrices does not form a vector space over the real numbers under addition. Why? Homework Equations A vector space over F, under addition, is a nonempty set V such that A1 Addition is associative A2 Existence of 0 A3 Existence of negative A4...
  35. R

    Linear independent vector space

    I have a quick question about vector spaces. Consider the vector space of all polynomials of degree < 1. If the leading coefficient (the number that multiplies x^{N-1}) is 1, does the set still constitute a vector space? I am thinking that it doesn't because the coefficient multiplying...
  36. A

    Proof set of one-forms is a vector space

    Hi, I am currently working through 'Schutz-First course in General Relativity' problem sets. Question 2 of Chapter 3, asks me to prove the set of one forms is a vector space. Earlier in the chapter, he defines: \tilde{s}=\tilde{p}+\tilde{q} \tilde{r}=\alpha \tilde{p} To be...
  37. A

    Linear Algebra - Is this set a vector space [Easy?]

    Homework Statement Does this set describe a vector space? Te set of all solutions (x,y) of the equation 2x + 3y = 0 with addition and multiplication by scalars defined as in R^2.Homework EquationsAssociativity of addition u + (v + w) = (u + v) + w. Commutativity of addition v + w = w + v...
  38. K

    Vector Space vs Field F Vector Space

    Hello, I'm studying linear algebra and wanted to know what is the difference between a "vector space" and a "vector space over field F". I know that a vector space over field F satisfies the 8 axioms, but does a vector space satisfy this also?
  39. M

    Calculating Distance and Innerproduct in 4-D Minkowski Vector Space

    Homework Statement In the 4-D Minkowski vector space [you can think of this as the locations of events in space-time given by (t, x, y, z)] consider the vectors pointing to the following events: (4ns, -1m, 2, 7) and (2ns, 3m, 1m, 9m) (a) Find the distance between the events. (b) Find the...
  40. C

    Complex solutions to a differential equation a vector space?

    Homework Statement Is the set of all complex solutions to the differential equation \frac{d^2 y}{d x^2} + 2\frac{d y}{d x} - 3 y = 0 If so, find a basis, the dimension, and give the zero vector Homework Equations The Attempt at a Solution I solved the equation and got the...
  41. C

    Vector Space Proof: Is V a Vector Space?

    vector space proof?? Let V = ((a1,a2): a1,a2 \in R). For (a1,a2), (b1,b2) \in V and c \in R, define (a1,a2) + (b1,b2) = (a1 + 2b1, a2 + 3b2) and c(a1,a2) = (ca1, ca2). Is V a vector space over R with these operations? Justify your answer. Does this set hold for all the eigth...
  42. J

    Is the Set of Functions with a Zero Integral a Subspace of C[a,b]?

    Homework Statement Determine whether or not the given set is a subspace of the indicated vector space: Functions f such that [integral from a to b]f(x)dx = 0; C[a,b] (not sure how to do the coding for integrals) Homework Equations to be a subspace it must follow these axioms: (i) if x and y...
  43. G

    Vector Space Homework: Proving Axioms of V for a, u

    Homework Statement Show that if V is a vector space, a is any scalar and u is a member of V then 1) (-1)x = -x 2) a(-u) = -au 3) -(-u) = u Homework Equations The ten axioms of vector space. The Attempt at a Solution I have solved a0 = 0, but I couldn't figure out how to start answering these...
  44. B

    Vector Space Q: Is Additive Identity Unique?

    Just wondering. Suppose we some plane, any plane like S = \{ (x_1, x_2, x_3) \in F^{3} \ : \ x_1 + 5x_2 + 3x_3 = 0 \} where F is either \mathbb{R} or \mathbb{C} . We know that S is a vector space (passes the origin). We know that (0,0,0) is the additive identity and it should be unique by...
  45. B

    Finding a basis of a vector space

    1. The problem statement Let W = {(x, y, z, t): x + y + 2z - t = 0} be a vector space under R^4. Find a basis of W over R. 2. The attempt at a solution To me I would think that the vector space itself could its own basis, but I know I'm probably way off. I also tried solving x = t - y...
  46. B

    Proving the Vector Space Property: cv = 0, v ≠ 0 → c = 0

    I'm considering the problem: Given c \in \bold{F}, v \in V where F is a field and V a vector space, show that cv = 0, v \neq 0 \ \Rightarrow \ c = 0 I've been wrapping my head around this one for a while now but I can't seem to get it. Proving that if cv = 0 and v \neq 0 implies v = 0 is...
  47. K

    Solution space of linear homogeneous PDE forms a vector space?

    Homework Statement Claim: The solution space of a linear homogeneous PDE Lu=0 (where L is a linear operator) forms a "vector space". Proof: Assume Lu=0 and Lv=0 (i.e. have two solutions) (i) By linearity, L(u+v)=Lu+Lv=0 (ii) By linearity, L(au)=a(Lu)=(a)(0)=0 => any linear...
  48. I

    Subspace of Normed Vector Space

    Let X be a normed vector space. If C is a closed subspace x is a point in X not in C, show that the set C+Fx is closed. (F is the underlying field of the vector space).
  49. W

    Number of subspaces of a vector space over a finite field

    Homework Statement Prove: If V is an n-dimensional vector space of a finite field, and if 0 <= m <= n, then the number of m-dimensional subspaces of V is the same as the number of (n-m)-dimensional subspaces. The Attempt at a Solution Well here's a sketch of my argument. Let U be an...
  50. P

    (Linear Algebra) Vector Space and Fields

    Homework Statement Let \omega = \frac{1}{2} + \frac{\sqrt7}{2}i(a) Verify that \omega^2 = \omega - 2 (b) Prove that F = \{a + b \omega : a, b \in \mathbb{Q} \} is a field, using the usual operations of addition and multiplication for complex numbers. (c) Recall that we can think of F as a...
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