What is Separable: Definition and 196 Discussions

In mathematics, a topological space is called separable if it contains a countable, dense subset; that is, there exists a sequence



{

x

n



}

n
=
1


∞




{\displaystyle \{x_{n}\}_{n=1}^{\infty }}
of elements of the space such that every nonempty open subset of the space contains at least one element of the sequence.
Like the other axioms of countability, separability is a "limitation on size", not necessarily in terms of cardinality (though, in the presence of the Hausdorff axiom, this does turn out to be the case; see below) but in a more subtle topological sense. In particular, every continuous function on a separable space whose image is a subset of a Hausdorff space is determined by its values on the countable dense subset.
Contrast separability with the related notion of second countability, which is in general stronger but equivalent on the class of metrizable spaces.

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  1. P

    MHB Separable Element: Minimal Polynomial Question

    if a\inK be seperable element over the field F,let f(x) be minimal plynomial of a over F.let degree of f(x) be n, We know f(x) will be seperable over F, BUT is it necessary that f(x) will be MINIMAL POLYNOMIAL of other n-1 roots. if so, what is the reason?
  2. T

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  3. T

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  4. C

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  5. E

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  7. L

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  9. alexsylvanus

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  10. M

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  11. P

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  12. K

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  13. P

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  14. T

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  15. J

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  16. F

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  17. F

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  18. W

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  19. H

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  20. M

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  21. mesa

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  22. G

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  25. K

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  27. J

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  29. T

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  32. P

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  33. D

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  34. I

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  38. N

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  39. dkotschessaa

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  40. C

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  44. R

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  46. Somefantastik

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  47. J

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  48. H

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  49. T

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  50. N

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