Define R/Q: How to Add in Quotient Groups

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Discussion Overview

The discussion revolves around the definition and properties of the quotient group R/Q under addition, exploring the nature of cosets and their disjointness. Participants are examining how to describe these cosets and the implications of boundedness on their representation.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks to define R\Q under addition, expressing confusion about boundedness and repetition of elements.
  • Another participant explains that the operation on cosets is defined as [x] + [y] = [x+y], where [z] denotes the equivalence class of z.
  • A participant notes that while R/Z consists of disjoint sets, they question the conditions under which cosets in R/Q can also be disjoint.
  • Another participant asserts that the group is not cyclic and cannot be generated by a single element, challenging the notion of repetition in cosets.
  • A later reply expresses a desire for a "nice" description of disjoint cosets whose union covers the real numbers, linking this to the representation of real numbers through bounded intervals.
  • There is a discussion about the uniqueness of representing real numbers through the addition of integers and rational numbers, questioning whether a similar method applies to irrational numbers.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the groups and the properties of cosets, with no consensus reached regarding the conditions for disjointness or the representation of elements in R/Q.

Contextual Notes

There are unresolved questions regarding the definitions of boundedness and the implications for the representation of cosets. The discussion also touches on the uniqueness of representations in relation to different sets of numbers.

matness
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how to define R\Q?(under addition)
R\Q={a+Q:? <a<?}
a€R but if it is not bounded then it will repeat
please help me
n
 
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you define [x]+[y] to be [x+y] wehre [z] means the equivalence class of y (ie the coset y+Q)
 
quotient group is the set of cosets y+Q but if i take y€R the sets begin to repeat (it is a cyclic group, isn't it?)i
for example R\Z ={x+Z: 0<x<1} is set of disjoint sets
so can we also find conditions for y to be disjoint and nice?
 
of course the groups isn't cyclic, it isn't even countable os can't have a singel generator. i struggle to understand your question. what "sets" begin to repeat? plus all cosets are disjoint or equal. do you simply want a "nice" way of describing the equivalence classes? i doubt there is one.
 
mattgrime:<do you simply want a "nice" way of describing the equivalence classes?>
probably. sorry for misremembering the defn for cyclic groups

what i want to know is a description for set of disjoint (but not same) cosets such that their union is real numbers.

the R\Q question crossed my mind because of the description R\Z ={x+Z: 0<x<1} if x were bounded as 0<x<2 some of the elements of the R\Z would be same That is what i mean by "repetition".
but i could'nt describe a set for R\Q in the same way

All of these seemed to me related to counting. when counting real numbers(it is a bit utopian) adding a number € Z and a real number between 0 and 1 is enough. (e.g. 3.4=3+0.4 and this representation is unique using this method)
but same method using rational numbers does not work ,
can we say adding a number € Q and an irrational number between 0 and 1 is enough .
(a real number is more than enough)

thanks in advance
 

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