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overspill

 
(ō'vər-spĭl') pronunciation
intr.v., -spilled, or -spilt (-spĭlt), -spill·ing, -spills.
To spill over.

n. (ō'vər-spĭl')
  1. The act of spilling over.
  2. Something that spills over: an overspill of milk.
  3. Chiefly British. Movement of people from overcrowded cities to less populated areas.

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The population which is dispersed from large cities to relieve congestion and overcrowding, and, possibly, unemployment. It occurs with redevelopment in the city where new building is at much lower densities so that some people—the overspill—cannot be housed in the city.

In non-standard analysis, a branch of mathematics, overspill (referred to as overflow by Goldblatt (1998, p. 129)) is a widely used proof technique. It is based on the fact that the set of standard natural numbers N is not an internal subset of the internal set *N of hypernatural numbers.

By applying the induction principle for the standard integers N and the transfer principle we get the principle of internal induction:

For any internal subset A of *N, if

  1. 1 is an element of A, and
  2. for every element n of A, n + 1 also belongs to A,

then

A = *N

If N were an internal set, then instantiating the internal induction principle with N, it would follow N = *N which is known not to be the case.

The overspill principle has a number of useful consequences:

  • The set of standard hyperreals is not internal.
  • The set of bounded hyperreals is not internal.
  • The set of infinitesimal hyperreals is not internal.

In particular:

  • If an internal set contains all infinitesimal non-negative hyperreals, it contains a positive non-infinitesimal (or appreciable) hyperreal.
  • If an internal set contains N it contains an unbounded element of *N.

Example

These facts can be used to prove the equivalence of the following two conditions for an internal hyperreal-valued function ƒ defined on *R.

 \forall  \epsilon >\!\!\!> 0,  \exists \delta >\!\!\!> 0, |h| \leq \delta \implies |f(x+h) - f(x)| \leq \varepsilon

and

 \forall  h \cong 0,  \ |f(x+h) - f(x)| \cong 0

The proof that the second fact implies the first uses overspill, since given a non-infinitesimal positive ε,

 \forall \mbox{ positive } \delta \cong 0, \ (|h| \leq \delta \implies |f(x+h) - f(x)| < \varepsilon).\,

Applying overspill, we obtain a positive appreciable δ with the requisite properties.

These equivalent conditions express the property known in non-standard analysis as S-continuity of ƒ at x. S-continuity is referred to as an external property, since its extension (e.g. the set of pairs (ƒ, x) such that ƒ is S-continuous at x) is not an internal set.

References

  • Robert Goldblatt (1998). Lectures on the hyperreals. An introduction to nonstandard analysis. Springer.

Translations:

Overspill

Top

Dansk (Danish)
n. - overskud, befolkningsoverskud
v. intr. - løbe over

Nederlands (Dutch)
het gemorste, overbevolking (die wegtrekt)

Français (French)
n. - excédent de population
v. intr. - avoir un excédent de population, déborder de

Deutsch (German)
n. - Bevölkerungsüberschuß, Übergelaufenes
v. - überlaufen

Ελληνική (Greek)
n. - πλεονάζων πληθυσμός (εξαπλούμενος σε περίχωρα), υπερπληθυσμός, πλεονάζουσα ποσότητα υγρού που ξεχειλίζει από δοχείο
v. - ξεχειλίζω

Italiano (Italian)
sovrappopolazione

Português (Portuguese)
n. - transbordamento (m), excedente populacional, emigrantes (m)

Русский (Russian)
перенаселенность, переливание через край

Español (Spanish)
n. - exceso de población, traslado de población, derrame
v. intr. - derramar

Svenska (Swedish)
n. - befolkningsöverskott
v. - svämma över

中文(简体)(Chinese (Simplified))
溢落的东西, 过剩人口, 溢出

中文(繁體)(Chinese (Traditional))
n. - 溢落的東西, 過剩人口
v. intr. - 溢出

한국어 (Korean)
n. - 넘침, 넘친 물, 과잉인구
v. intr. - 넘치다

日本語 (Japanese)
n. - あふれ出し, 剰余
v. - あふれる

العربيه (Arabic)
‏(الاسم) انتقال السكان الى مناطق أقل ازدحاما (فعل) ينتقل الى مكان أقل ازدحاما‏

עברית (Hebrew)
n. - ‮כמות עודפת, הכמות שגלשה, האוכלוסיה העודפת המהגרת למקום אחר (בריטניה)‬
v. intr. - ‮גלש אל מעבר ל-‬


 
 
Related topics:
satellite town
Banbury (city, England)
Basingstoke (city, England)

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