Mobius transformation proving equivalence class

In summary: Mobius transformation s such that c = s°p°s^{-1}. This can be done by letting s = q°r. Then, c = (q°r)°p°(q°r)^{-1} = q°(r°p°r^{-1})°q^{-1} = q°b°q^{-1}, which is in the equivalence class of p.In summary, we have shown that the given equation forms an equivalence class, as it satisfies the three properties listed in the homework equations. This means that m is in the equivalence class
  • #1
d2j2003
58
0

Homework Statement


I have to show that if there is a mobius transformation p such that m=p°n°p[itex]^{-1}[/itex]
forms an equivalence class.

Homework Equations


need to show that aRa, if aRb then bRa, and if aRb and bRc then aRc


The Attempt at a Solution



well.. for aRa I somehow need to show that m=p°m°p[itex]^{-1}[/itex] right? so if we just say m=p°p°m°p[itex]^{-1}[/itex] °p[itex]^{-1}[/itex] then this is of the correct form... if we say (p°p)=q then m=q°m°q[itex]^{-1}[/itex] which is of the correct form so mRm am I moving in the right direction?

Thanks in advance
 
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  • #2
for any help!

let me offer some guidance on how to approach this problem.

First, let's define our terms. A Mobius transformation is a function that maps the extended complex plane (including infinity) to itself. It is represented by the formula p(z) = (az+b)/(cz+d), where a, b, c, and d are complex numbers and ad-bc ≠ 0. This transformation can be composed with other Mobius transformations to form a new transformation.

Now, let's look at the given equation m = p°n°p^{-1}. This means that m is the result of applying the Mobius transformation p to the result of applying the Mobius transformation n to the inverse of p. In other words, m is in the equivalence class of p.

To show that this forms an equivalence class, we need to demonstrate the three properties listed in the homework equations. Let's start with aRa. This means that m = p°m°p^{-1}. We can rewrite this as p(m) = (p°p)(m)(p^{-1}°p^{-1}), which simplifies to p(m) = q(m)q^{-1}, where q = p°p. This shows that m is in the equivalence class of q, which is the composition of two Mobius transformations and is itself a Mobius transformation.

Next, let's consider the property aRb. This means that if aRb, then bRa. In this case, if m is in the equivalence class of p, then there exists a Mobius transformation q such that m = q°p°q^{-1}. In order for b to be in the equivalence class of p, we need to show that there exists a Mobius transformation r such that b = r°p°r^{-1}. This can be achieved by letting r = q^{-1}. Then, b = q^{-1}°(q°p°q^{-1})°q = (q^{-1}°q)°p°(q^{-1}°q) = p. This shows that b is in the equivalence class of p.

Finally, we need to show the property aRb and bRc then aRc. This means that if a is in the equivalence class of p and b is in the equivalence class of p, then c is also in the equivalence class of p. In other words,
 

Related to Mobius transformation proving equivalence class

1. What is a Mobius transformation?

A Mobius transformation is a function that maps points from one complex plane to another complex plane using a linear fractional transformation, also known as a Mobius transformation. It is defined as f(z) = (az + b) / (cz + d), where a, b, c, and d are complex numbers and ad - bc ≠ 0.

2. How does a Mobius transformation prove equivalence class?

A Mobius transformation proves equivalence class by showing that any two points in the complex plane can be mapped to each other by a Mobius transformation, as long as they are in the same equivalence class. This means that the transformation preserves the equivalence relation between points, and thus, the equivalence class remains the same.

3. Can a Mobius transformation change the shape of a figure?

Yes, a Mobius transformation can change the shape of a figure. Since it is a conformal mapping, it preserves angles between intersecting curves, but it can still stretch, shrink, or rotate the figure.

4. How can a Mobius transformation be used to prove geometric properties?

Mobius transformations can be used to prove geometric properties by transforming a geometric figure into a simpler form, such as a circle or a straight line. These simpler forms often have well-known properties, making it easier to prove the properties of the original figure.

5. Are all Mobius transformations reversible?

No, not all Mobius transformations are reversible. A Mobius transformation is reversible only if its inverse function also exists, which is true only if ad - bc ≠ 0. If ad - bc = 0, then the transformation is not reversible and is known as a degenerate transformation.

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