Extend the functional by continuity (Functional analysis)

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SUMMARY

The discussion focuses on extending a bounded linear operator T0 from a dense linear subspace E of a normed vector space X to a Banach space Y. The key conclusion is that T0 can be extended to a continuous operator T without increasing its norm. The method involves demonstrating that if a sequence (xn) converges to x, then T0(xn) forms a Cauchy sequence, allowing the definition of a limit function f(x) that is a well-defined bounded linear function, leveraging the uniform continuity of T0.

PREREQUISITES
  • Understanding of normed vector spaces
  • Familiarity with Banach spaces
  • Knowledge of bounded linear operators
  • Concept of uniform continuity
NEXT STEPS
  • Study the properties of dense linear subspaces in normed vector spaces
  • Learn about the Hahn-Banach theorem for extending linear operators
  • Explore the concept of Cauchy sequences in the context of functional analysis
  • Investigate uniform continuity and its implications for bounded linear functions
USEFUL FOR

Mathematicians, particularly those specializing in functional analysis, graduate students studying advanced calculus, and anyone interested in the properties of linear operators in Banach spaces.

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Homework Statement



Let E be a dense linear subspace of a normed vector space X, and let Y be a
Banach space. Suppose T0 [itex]\in[/itex] £(E, Y) is a bounded linear operator from E to Y.
Show that T0 can be extended to T[itex]\in[/itex] £(E, Y) (by continuity) without increasing its norm.

The Attempt at a Solution


Someone kindly gave me a hint. I am trying to work out the details. The deadline is approaching. So I put the question here just in case. Thanks.
For this particular problem you want to show that if (xn) converges to x then T0(xn) is a Cauchy sequence and then define f(x) as the limit of the sequence. Finally you need to show that the map is a well-defined bounded linear function.
 
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Use that T0 is uniform continuous.
 
Thank you!
 

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