Infinity and one norm question

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    Infinity Norm
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Discussion Overview

The discussion revolves around the properties of the one and infinity norms of complex vectors, particularly in relation to their conjugate transposes. Participants explore why these norms are not equal for complex vectors, contrasting this with the behavior observed in the 2-norm.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions why the one and infinity norms of a complex vector x differ from those of its conjugate transpose x*.
  • Another participant asks for clarification on the definition of the infinity norm of x*.
  • A participant provides a definition of the infinity norm of x* as the maximum of the absolute values of the components of the conjugate transpose.
  • There is a suggestion that the one and infinity norms may not be equal for complex vectors, but could be equal for real vectors.
  • A participant discusses the absolute value of a complex number and its relationship to the norms, indicating a potential connection to the norms' properties.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the equality of the norms for complex vectors, with some suggesting they may be equal for real vectors. The discussion does not reach a consensus on the implications of these properties.

Contextual Notes

Participants do not fully resolve the implications of their definitions and observations, leaving some assumptions and conditions unaddressed.

Visceral
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Hi,

I was wondering why the one and infinity norm of a complex vector x are not equal to the the one and infinity norm of x* (the conjugate transpose of x)? This seems to be true for the 2-norm, but I am not sure why for these other norms.
 
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What is your definition of infinity norm of x*?
 
the infinity norm of x* = (x1*, x2*, ... , xn*)^T is

max|xj*| where 1≤j≤n

if that makes sense. Sorry, not good with latex on here. I think I might see now the infinity and one norm of a complex vector x may not be equal. However, they are equal if x is a real vector correct?
 
If z = x+iy is a complex number (x,y\in \mathbb R), then |z^*|= |x-iy| = x^2+ (-y^2)=x^2+y^2=|z|.
 

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