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Why there's no L^2[-inf,inf] space?

  1. Feb 2, 2015 #1
    Hello,

    Maybe it's a silly question, but why the space ##L^2[a,b]## has always to have bounded limits? Why can't we define the space of functions ##f(x)## where ##x \in \mathbb{R}## and ##\int_{-\infty}^\infty |f(x)|^2 dx \le M## for some ## M \in \mathbb{R^+}##? As far as I know the sum of two square integrable functions is still a square integrable function, even if it's domain is not bounded; and the rest of properties of Hilbert spaces hold. So why it's not well defined?

    Thank you
     
  2. jcsd
  3. Feb 2, 2015 #2
    The space ##L^2(\mathbb R)## is well defined, who told you that it is not?
     
  4. Feb 3, 2015 #3
    Thank you, I think it was a misunderstanding.
     
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