Showing the Dual Basis is a basis

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SUMMARY

The discussion centers on the concept of dual spaces in linear algebra, specifically the dual basis of a vector space \( V \) and its relationship to linear functionals. The proof that the dual basis forms a basis for the dual space \( V^* \) is established through the characterization \( \alpha^i(e_j)=\delta_j^i \). Additionally, the Riesz representation theorem is highlighted, which states that for any linear functional \( T: V \rightarrow \mathbb{R} \), there exists a vector \( t \) such that \( T(u)=\langle t,u \rangle \). The proof of this theorem can be approached using the Gram-Schmidt process.

PREREQUISITES
  • Understanding of vector spaces and linear transformations
  • Familiarity with the concept of dual spaces and dual bases
  • Knowledge of inner product spaces and the notation \( \langle \cdot, \cdot \rangle \)
  • Basic understanding of the Gram-Schmidt process
NEXT STEPS
  • Study the Riesz representation theorem in detail
  • Review the proof of the dual basis forming a basis for \( V^* \)
  • Learn the Gram-Schmidt process and its applications in generating orthonormal bases
  • Explore resources that provide examples of dual spaces and their properties
USEFUL FOR

Students of linear algebra, mathematicians studying functional analysis, and educators teaching concepts related to dual spaces and linear functionals.

joypav
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I am working through a book with my professor and we read a section on the dual space, $V^*$.
It gives the basis dual to the basis of $V$ and proves that this is in fact a basis for $V^*$.
Characterized by $\alpha^i(e_j)=\delta_j^i$

I understand the proof given. But he said a different statement...
If $T: V \rightarrow \Bbb{R}$ is linear, then there is a vector $t$ so that $T(u)=<t,u>$. ($<\cdot, \cdot>$ is the inner product)

He said this is equivalent to showing that the dual basis forms a basis, and that it can be proven using the Gram-Schmidt process. I was wondering what that proof looks like? Even just an outline... I don't need all the details.
 
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Hi joypav,

The result your advisor mentioned is the Riesz representation theorem. There are many books, websites, and papers that you can look to for its statement and proof. Have a look at one and feel free to follow up with any questions.
 

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