What is the meaning of A^(⊥) in a mathematical context?

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Discussion Overview

The discussion revolves around the interpretation of the notation A^(⊥) in a mathematical context, particularly focusing on its meaning in relation to sets and the concept of perpendicularity in linear algebra. Participants explore the implications of the notation in terms of direct sums and scalar product spaces.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about the meaning of the perpendicular symbol in the context of the notation x ∈ R ⊕ R⊥, suggesting that R is a set.
  • Another participant clarifies that the upside down capital T represents perpendicularity, explaining its relevance in both geometry and linear algebra.
  • A different participant reiterates the notation x ∈ R ⊕ R⊥, noting that it is typically read as "R perp."
  • One participant explains that the "oplus" denotes a direct sum, indicating that x can be uniquely expressed as a sum of elements from R and R⊥.
  • Another participant posits that if "R" refers to the real line, then "R perp" represents a line perpendicular to it, and their direct sum forms a plane containing both lines.

Areas of Agreement / Disagreement

Participants present various interpretations of the notation and its implications, with no consensus reached on a singular understanding of A^(⊥) or its applications.

Contextual Notes

Some assumptions about the definitions of R and the nature of the scalar product space remain unspecified, which may affect the interpretations presented.

mikeph
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I'm looking at a condition in a maths paper that I don't understand, essentially it is:

x ∈ R ⊕ R

R is a set I think, but I'm not sure what the perpendicular symbol means.

Also am I correct in thinking the circled plus means that x must be in either R or R (but not both)?

Thanks
 
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The upside down capital T means <perpendicular>, both in elementary geometry and in linear algebra (or functional analysis). A to the power T upside dowm is the subset B of M made up of all y in M, such that whatever x from the subset A of M, <x,y> = 0, where (M,<,>) is a scalar product space.
 
MikeyW said:
I'm looking at a condition in a maths paper that I don't understand, essentially it is:

x ∈ R ⊕ R
It's usually read as "R perp".
 
If "R" is the real line, then "R perp" is a line perpendicular to it. Their direct sum is the plane containing the two lines.
 

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