Equivalence Relation and the Unit Circle: Understanding R/Z and S^1

In summary, the conversation discusses the equivalence relation on R/Z and how it relates to S^1 or the unit circle. The book claims R/Z is equivalent to S^1, while the speaker argues it is actually (0,1). They also discuss the length of the interval and how it relates to the circumference of the unit circle.
  • #1
pivoxa15
2,255
1

Homework Statement


If Z acts on R by n.x=n+x then R/Z is just S^1. CLaims the book

But I think R/Z is (0,1)


The Attempt at a Solution


Any number greater than or equal to 1 is dealt with by the equivalence relation. How does the unit circle come into it? We are dealing only with one dimensional space here.
 
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  • #2
Because the points x=0 and x'=1 are identified as the same point in R/Z?
 
  • #3
pivoxa15 said:

Homework Statement


If Z acts on R by n.x=n+x then R/Z is just S^1. CLaims the book

But I think R/Z is (0,1)


The Attempt at a Solution


Any number greater than or equal to 1 is dealt with by the equivalence relation. How does the unit circle come into it? We are dealing only with one dimensional space here.
That's the whole point- the equivalence relation makes 0 and 1 equivalent- you are bending [0,1] (not (0,1)) back on itself so it becomes a circle.
 
  • #4
Actually the interval should be [0,1) so if you include 1 then 1 is 0 so it bends back on itself. However they described it as S^1. Why S^1? That is the unit circle with radius 1. So has circumference 2pi. But our interval has length 2pi?
 

1. What is an equivalence relation?

An equivalence relation is a type of relation between two objects that follows three properties: reflexivity, symmetry, and transitivity. This means that the relation is reflexive, which means every element is related to itself, symmetric, which means if x is related to y, then y is also related to x, and transitive, which means if x is related to y and y is related to z, then x is also related to z.

2. How does the equivalence relation apply to the unit circle?

In the context of the unit circle, the equivalence relation refers to the relationship between points on the circle that have the same distance from the origin. This means that any two points on the unit circle that have the same distance from the origin are considered equivalent under this relation.

3. What is R/Z in relation to the unit circle?

R/Z, or the quotient group of the real numbers by the integers, is a mathematical concept used to describe the equivalence classes on the unit circle. Essentially, it represents the set of all possible angles on the unit circle, where each angle is related to another angle by a multiple of 2π.

4. What is the significance of R/Z and S^1 in mathematics?

R/Z and S^1 are both important concepts in mathematics because they help us understand the structure and properties of the unit circle. They also have applications in various fields such as geometry, trigonometry, and complex analysis.

5. How can understanding equivalence relations on the unit circle be useful in real-world applications?

Equivalence relations on the unit circle can be applied in various real-world scenarios, such as navigation, astronomy, and engineering. For example, understanding the symmetry and transitivity of points on the unit circle can help us determine the shortest distance between two points, which is useful in navigation and calculating trajectories in engineering.

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