Inverse function theorem over matrices

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Discussion Overview

The discussion revolves around the application of the inverse function theorem to functions defined over matrices, specifically examining the function f : M_{n\times n} \to M_{n\times n} where f(X) = X^2. Participants explore the validity of the theorem at the identity matrix and the implications of matrix proximity to the identity matrix.

Discussion Character

  • Exploratory, Technical explanation, Homework-related

Main Points Raised

  • One participant questions the validity of the inverse function theorem at the identity matrix and seeks to understand how to compute the Jacobian for the function f(X) = X^2.
  • Another participant agrees that matrices can be interpreted as vectors but challenges the notion of using a "new dot product" for matrix multiplication, suggesting that matrix multiplication follows its own rules.
  • A participant seeks clarification on the assertion that if a matrix Y is near the identity, then there exists a unique matrix X such that X^2 = Y, with another participant stating that this claim is false.
  • There is a suggestion that the problem may be more appropriate for a homework forum, indicating a potential context for the discussion.

Areas of Agreement / Disagreement

Participants express differing views on the uniqueness of the matrix X such that X^2 = Y when Y is near the identity matrix, with at least one participant asserting that the claim is false.

Contextual Notes

The discussion includes assumptions about the interpretation of matrices as vectors and the implications of defining a new product for matrix multiplication, which remain unresolved.

brunob
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Hi there!
I'm back again with functions over matrices.
I have a function f : M_{n\times n} \to M_{n\times n} / f(X) = X^2.

Is valid the inverse function theorem for the Id matrix? It talks about the Jacobian at the Id, but I have no idea how get a Jacobian of that function. Can I see that matrices as vectors and redefine the function as f : R^{n^2} \to R^{n^2} / f(x) = x^2 using a new dot product?
Also, how can I prove that if a matrix Y is near to Id then \exists ! X / X^2 = Y ?

Thanks!
 
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Yes, you can interpret the matrices as vectors. I'm not sure what you mean by "a new dot product". The square of a matrix would not be given by the dot product of the corresponding vector with itself; instead each component of resultant vector would be given by the formula for matrix multiplication.

brunob said:
Also, how can I prove that if a matrix Y is near to Id then \exists ! X / X^2 = Y ?
Thanks!

Is this to be interpreted as "if Y is near the identity, then there exists only one X such that X^2 = Y" ? If so this is false.
 
Thanks for your response MisterX.
What I mean with "a new dot product" is defining a product between vectors that represents the matrix multiplication.

Uhmm, yes that's it, it's an extra exercice they give me in my calculus II course. Why you say it's false?
 
brunob said:
Thanks for your response MisterX.
What I mean with "a new dot product" is defining a product between vectors that represents the matrix multiplication.

Uhmm, yes that's it, it's an extra exercice they give me in my calculus II course. Why you say it's false?

Then it belongs in the homework forums. Please post there.
 

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