Wednesday, 10 May 2017

functional analysis - Can we embed XotimesY into the space of bounded, linear operators XtoY?

Let




  • F{C,R}


  • X and Y be normed F-vector spaces

  • X denote the topological dual space of X

  • L(X,Y) denote the space of bounded, linear operators from X to Y

  • B(X×Y,F) be the space of bilinear forms on X×Y

  • XY denote the tensor product of X and Y




Can we show that XY can be embedded into L(X,Y), i.e. that there is a





  1. injective,

  2. continuous and

  3. open



mapping ι:XYι(XY)?




Clearly, we would need to choose a norm on XY:=span{φy:(φ,y)X×Y}, where (φy)(A):=A(φ,y)for BB(X×Y,F). I think that the projective norm π(u):=inf will do it.





My idea is to define (\iota u)(x):=\sum_{i=1}^n\varphi_i(x)y_i\;\;\;\text{for }x\in X\tag 1 for u\in X'\otimes Y with u=\sum_{i=1}^n\varphi_i\otimes y_i.




This \iota is obviously linear. Maybe we can show that it is bounded too (i.e. a bounded, linear operator). This would yield (2.). How can we show this and how can we show (1.) and (3.)?

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