A vector space is a set of objects known as vectors that may be added together and multiplied by numbers, called scalars. Scalars are often taken to be real numbers, but they’re also are vector spaces with scalar multiplication by complex numbers, rational numbers, or generally any field. The processes of vector addition and scalar multiplication must fulfill definite requirements, called vector axioms. To specify that the scalars are real or complex numbers, the terms real vector space and sophisticated vector space are often used.

### Definition

A vector space over a field F may be a set V alongside two operations that satisfy the eight axioms listed below. Inside the next, V × V denotes the intersection of V with itself and → denotes a mapping from one set to a different.

The main operation, named vector addition or just addition +: V × V → V, receipts any two vectors v and w and assigns to them a 3rd vector which is usually written as v + w, and called the sum of those two vectors.

Another operation termed scalar multiplication •: F × V → V， takes any scalar a and any vector v and provides another vector av. (Similarly, the vector av is a component of the set V. Scalar multiplication isn’t to be confused with the inner product, also called scalar product or scalar product, which is a further structure present on some specific, but not all vector spaces. Scalar multiplication may be a multiplication of a vector by a scalar; the opposite may be a multiplication of two vectors producing a scalar.)

### Vector spaces with other structure

Beginning the determination of view of algebra, vector spaces are totally understood insofar as any vector space is characterized, up to isomorphism, by its dimension. However, vector spaces intrinsically don’t offer a framework to affect the question—crucial to analysis—whether a sequence of functions converges to a different function. Likewise, algebra isn’t adapted to affect infinite series, since the addition operation allows only finitely many terms to be added. Therefore, the requests of functional analysis need to see additional structures.

A vector space could also be given a partial order ≤, under which some vectors are often compared. For instance, n-dimensional real spaces Rn are often ordered by comparing their vectors component-wise. Ordered vector spaces, for instance, Riesz spaces, are fundamental to Lebesgue integration, which relies on the power to precise a function as a difference of two positive functions

f = f+ − f−,

where f+ indicates the positive a part off and f− the negative part

### Applications

Vector spaces have several applications as they happen often in common circumstances, namely wherever functions with values in some field are involved. They supply a framework to affect analytical and geometrical problems or are utilized in the Fourier transform. This list isn’t thorough: more applications exist, for instance in optimization. The minimax theorem of the theory of games stating the existence of a singular payoff when all players play optimally is often formulated and proven using vector spaces methods.

### Distributions

A distribution may be a linear map assigning variety to every “test” function, typically a smooth function with compact support, during a continuous way: within the above terminology, the space of distributions is that the dual of the test function space. The end space is gifted with a topology that takes under consideration not only f itself but also all its higher derivatives. A typical example is that the results of integrating a test function f over some domain Ω:

I (f) = ∫ Ω f (x) d x

When Ω = {p}, the set consisting of one point, this reduces to the Dirac distribution, denoted by δ, which associates to a test function f its value at the p: δ (f) = f (p). Distributions are a strong instrument to unravel differential equations. Meanwhile, all standard analytic notions similar derivatives are linear; they extend naturally to the space of distributions. Therefore, the equation in the query is frequently moved to a distribution space, which is greater than the underlying function space, in order that more flexible methods are available for solving the equation. For instance, Green’s functions and fundamental solutions are usually distributions instead of proper functions, and may then be wont to find solutions of the equation with prescribed boundary conditions. The found solution can then in some cases be proven to be actually a real function, and an answer to the first equation (for example, using the Lax–Milgram theorem, a consequence of the Riesz representation theorem)

### Vector bundles

A vector bundle maybe a family of vector spaces parameterized continuously by a mathematical space X. More precisely, a vector bundle over X may be a mathematical space E equipped with an endless map

π: E → X

Such that for each x in X, the fiber π−1(x) may be a vector space. The case dim V = 1 is named a line bundle.