|
In topology and related areas of mathematics, the neighbourhood system, complete system of neighborhoods, or neighbourhood filter for a point ''x'' is the collection of all neighbourhoods for the point ''x''. == Basis == A neighbourhood basis or local basis for a point ''x'' is a filter base of the neighbourhood filter, i.e. a subset : such that :. That is, for any neighbourhood we can find a neighbourhood in the neighbourhood basis that is contained in . Conversely, as with any filter base, the local basis allows to get back the corresponding neighbourhood filter as .〔 (See Chapter 2, Section 4)〕 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「neighbourhood system」の詳細全文を読む スポンサード リンク
|