Definition:Uniform

Definition

Let $B$ be an object.

Let $P$ be a property of $B$.

Then $P$ is said to be uniform if and only if $P$ is constant throughout the whole of $B$.

Examples

Uniform Convergence

Let $\sequence {f_n}$ be a sequence of real functions defined on $D \subseteq \R$.

Let:

$\forall \epsilon \in \R_{>0}: \exists N \in \R: \forall n \ge N, \forall x \in D: \size {\map {f_n} x - \map f x} < \epsilon$

That is:

$\ds \forall \epsilon \in \R_{>0}: \exists N \in \R: \forall n \ge N: \sup_{x \mathop \in D} \size {\map {f_n} x - \map f x} < \epsilon$

Then $\sequence {f_n}$ converges to $f$ uniformly on $D$ as $n \to \infty$.

Uniform Continuity

Let $I \subseteq \R$ be a real interval.

A real function $f: I \to \R$ is said to be uniformly continuous on $I$ if and only if:

for every $\epsilon > 0$ there exists $\delta > 0$ such that the following property holds:

for every $x, y \in I$ such that $\size {x - y} < \delta$ it happens that $\size {\map f x - \map f y} < \epsilon$.

Formally: $f: I \to \R$ is uniformly continuous if and only if the following property holds:

$\forall \epsilon > 0: \exists \delta > 0: \paren {x, y \in I, \size {x - y} < \delta \implies \size {\map f x - \map f y} < \epsilon}$

Continuous Uniform Distribution

Let $X$ be a continuous random variable on a probability space $\struct {\Omega, \Sigma, \Pr}$.

Let $a, b \in \R$ such that $a < b$.

$X$ is said to be uniformly distributed on the closed real interval $\closedint a b$ if and only if it has probability density function:

$\map {f_X} x = \begin{cases} \dfrac 1 {b - a} & a \le x \le b \\ 0 & \text{otherwise} \end{cases}$

This is written:

$X \sim \ContinuousUniform a b$

Discrete Uniform Distribution

Let $X$ be a discrete random variable on a probability space.

Then $X$ has a discrete uniform distribution with parameter $n$ if and only if:

$\Img X = \set {1, 2, \ldots, n}$

$\map \Pr {X = k} = \dfrac 1 n$

That is, there is a number of outcomes with an equal probability of occurrence.

This is written:

$X \sim \DiscreteUniform n$

Uniform Lamina

A uniform lamina is a lamina whose (area) density is constant.

Sources

• 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): uniform