Difference between revisions of "Interior"

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==Definition==
 
==Definition==
 
Given a set {{M|U\subseteq X}} and an arbitrary [[metric space]], {{M|(X,d)}} or [[topological space]], {{M|(X,\mathcal{J})}} the ''interior'' of {{M|U}}, denoted {{M|\text{Int}(U)}} is defined as{{rITTGG}}{{rITTBM}}:
 
Given a set {{M|U\subseteq X}} and an arbitrary [[metric space]], {{M|(X,d)}} or [[topological space]], {{M|(X,\mathcal{J})}} the ''interior'' of {{M|U}}, denoted {{M|\text{Int}(U)}} is defined as{{rITTGG}}{{rITTBM}}:

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Definition

Given a set UX and an arbitrary metric space, (X,d) or topological space, (X,J) the interior of U, denoted Int(U) is defined as[1][2]:

  • Int(U):={xX| x is interior to U} - (see interior point for the definition of what it means to be interior to)

Note that, unlike interior point which is basically a synonym for neighbourhood (taking the definition of neighbourhood as discussed on its page) the interior is a meaningful and distinct definition. In accordance with the topological definition of interior point (requiring that U be a neighbourhood to some xX) we see that:

  • Int(U) is the set of all points U is a neighbourhood to.

Immediate properties

Let UX be an arbitrary subset of a topological space (X,J) (as all metric spaces are topological, they are included), then:

[Expand]

Claim 1: Int(U) is open

See also

References

  1. <cite_references_link_accessibility_label> Introduction to Topology - Theodore W. Gamelin & Robert Everist Greene
  2. <cite_references_link_accessibility_label> Introduction to Topology - Bert Mendelson