Purchase Solution

Mobius transformation sharing fixed point commute

Not what you're looking for?

Ask Custom Question

Let T be a Mobius transformation, T doesn't equal to identity. Show that a Mobius transformation S commutes with T if S and T have the same fixed points.

Purchase this Solution

Solution Preview

Definition:
Mobius transformation can be defined as

T(z) = a(z+b)/(z+c), where a, b, and c are some complex numbers.

Let us parametrize the other Mobius transformation as

S(z) = A(z+B)/(z+C), where A, B, and C are some other complex numbers.

We are to prove that if T and S have the same fixed points, then T(S(z)) = S(T(z))

Let us now see what are the fixed points.

For T, if z is a fixed point, then

z = T(z) = a(z+b)/(z+c).

We can solve this by multiplying the equation by the denominator and getting the quadratic equation:
z^2 +(c-a)z - ab = 0.

There are two ways to proceed now, depending on whether you are familiar with Vieta formulae.

If you have not studied Vieta formulae, ...

Purchase this Solution


Free BrainMass Quizzes
Geometry - Real Life Application Problems

Understanding of how geometry applies to in real-world contexts

Know Your Linear Equations

Each question is a choice-summary multiple choice question that will present you with a linear equation and then make 4 statements about that equation. You must determine which of the 4 statements are true (if any) in regards to the equation.

Graphs and Functions

This quiz helps you easily identify a function and test your understanding of ranges, domains , function inverses and transformations.

Solving quadratic inequalities

This quiz test you on how well you are familiar with solving quadratic inequalities.

Exponential Expressions

In this quiz, you will have a chance to practice basic terminology of exponential expressions and how to evaluate them.