Re: Dense subspace of L2 (R)



On 31-07-2009 21:55, Gauster wrote:

What's the easiest way to prove that the functions x^n.e^(-x^2/2)
span a subspace that is dense in L2 (R) ?

I don't know if this is the easiest way, but it is not hard to prove
that, for each continuous function _f_ from R into R with compact
support and for each r > 0, there is a linear combination _g_ of
functions of the form x^n.e^(-x^2/2) such that ||f - g||_2 < r. Since
the set of continuous function from R into R with compact support is
dense in L^2(R), this is enough.

Best regards,

Jose Carlos Santos
.



Relevant Pages

  • Re: Category theory and complete objects
    ... > complete to a closure operator. ... > completions in. ... If X is not compact, ... >> can be done and is Hausdorff, then X will be dense in this space. ...
    (sci.math)
  • compact support
    ... I'm trying to figure out what compact support is; ... of points in the domain where the function does not equal zero. ... I'm not sure what closure means. ...
    (sci.math)
  • Re: Where to start
    ... DataTable in a ListView. ... since Sorted ListViews are not supported on Compact. ... No direct support for Sql-Server but the DataBase class should work ...
    (microsoft.public.dotnet.languages.csharp)
  • Re: Where to start
    ... DataTable in a ListView. ... since Sorted ListViews are not supported on Compact. ... No direct support for Sql-Server but the DataBase class should work ...
    (microsoft.public.dotnet.framework.compactframework)
  • Re: The example of outer regular but not inner regular measure!
    ... If f is the continuous function with compact support, ... linear functional of f to approach to infinite. ... take a infinite sequence of neighborhood consisting fixed V whose ...
    (sci.math)

Quantcast