Cauchy sequence
E239283
A Cauchy sequence is a sequence whose terms become arbitrarily close to each other as the sequence progresses, providing a fundamental criterion for convergence in metric and normed spaces.
All labels observed (2)
Statements (46)
| Predicate | Object |
|---|---|
| instanceOf |
mathematical concept
ⓘ
sequence ⓘ |
| characterizes | convergence in complete metric spaces ⓘ |
| codomain | metric space ⓘ |
| contrastsWith | pointwise definition of limit ⓘ |
| definedIn |
metric space
ⓘ
normed vector space ⓘ topological vector space ⓘ |
| domain | elements of a metric space ⓘ |
| exampleOf | sequence defined by internal closeness rather than external limit point ⓘ |
| field |
functional analysis
ⓘ
mathematical analysis ⓘ topology ⓘ |
| generalizationOf |
Cauchy sequence of complex numbers
ⓘ
Cauchy sequence of real numbers ⓘ |
| hasCategory |
foundational concept in metric space theory
ⓘ
foundational concept in real analysis ⓘ |
| hasDefinition |
Cauchy sequence
self-linksurface differs
ⓘ
surface form:
A sequence (x_n) in a metric space (X,d) is Cauchy if for every ε > 0 there exists N such that for all m,n ≥ N, d(x_m,x_n) < ε.
|
| hasEquivalentFormulation |
for every ε > 0 there exists N such that for all k ≥ 0, d(x_{N+k},x_N) < ε
ⓘ
for every ε > 0 there exists N such that for all n ≥ N, d(x_n,x_N) < ε ⓘ |
| hasHistoricalRole | formalization of convergence in analysis ⓘ |
| hasLogicalForm | ∀ε>0 ∃N ∀m,n≥N : d(x_m,x_n)<ε ⓘ |
| hasProperty |
every convergent sequence in a metric space is Cauchy
ⓘ
in a complete metric space every Cauchy sequence converges ⓘ in an incomplete metric space a Cauchy sequence may fail to converge ⓘ in ℚ with the usual metric some Cauchy sequences do not converge in ℚ ⓘ in ℝ with the usual metric every Cauchy sequence converges ⓘ |
| hasType | sequence indexed by natural numbers ⓘ |
| implies | bounded sequence in a metric space ⓘ |
| namedAfter | Augustin-Louis Cauchy ⓘ |
| relatedTo |
Cauchy completion
ⓘ
Cauchy criterion for series ⓘ Cauchy filter ⓘ Cauchy net ⓘ complete metric space ⓘ convergent sequence ⓘ |
| requiresStructure |
distance function
ⓘ
metric ⓘ |
| usedAs | criterion for convergence ⓘ |
| usedIn |
Banach space theory
ⓘ
Hilbert space theory ⓘ analysis of series and infinite products ⓘ construction of real numbers from rationals ⓘ definition of completeness of a metric space ⓘ proofs of convergence theorems ⓘ |
| usedToDefine | completion of a metric space via equivalence classes of Cauchy sequences ⓘ |
Referenced by (3)
Full triples — surface form annotated when it differs from this entity's canonical label.
subject surface form:
Augustin-Louis Cauchy
this entity surface form:
A sequence (x_n) in a metric space (X,d) is Cauchy if for every ε > 0 there exists N such that for all m,n ≥ N, d(x_m,x_n) < ε.