Finding Fixed Points of a Mobius transformation

In summary, a Mobius transformation is a type of rational function that maps the complex plane onto itself. It has the form of f(z) = (az + b)/(cz + d), where a, b, c, and d are complex numbers and z is the input value. A fixed point of a Mobius transformation is a point on the complex plane that remains unchanged after the transformation is applied. To find fixed points, you can set f(z) = z and solve for z, or use the equation ad - bc = 0. Fixed points are important in understanding the behavior and structure of a Mobius transformation, and there can be at most two fixed points.
  • #1
tazzzdo
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Homework Statement



Find all the fixed points to the following Mobius transformation.

Homework Equations



m(z) = (2z + 5)/(3z - 1)

The Attempt at a Solution



Aren't all fixed points going to map to themselves? So shouldn't it be solving for m(z) = z and coming up with roots of a quadratic equation?
 
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  • #2
Well, I don't know what "it" should be doing but that is what I recommend you do.
 
  • #3
I meant I* lol. Thanks.
 

1. What is a Mobius transformation?

A Mobius transformation is a type of rational function that maps the complex plane onto itself. It takes the form of f(z) = (az + b)/(cz + d), where a, b, c, and d are complex numbers and z is the input value. It is also known as a linear fractional transformation.

2. What is a fixed point of a Mobius transformation?

A fixed point of a Mobius transformation is a point on the complex plane that remains unchanged after the transformation is applied. In other words, if z is a fixed point, then f(z) = z. This means that the point is mapped onto itself, and it does not move under the transformation.

3. How do you find fixed points of a Mobius transformation?

To find the fixed points of a Mobius transformation, you can set f(z) = z and solve for z. This will give you two possible solutions, which represent the two fixed points of the transformation. Alternatively, you can use the fact that the fixed points are the roots of the quadratic equation ad - bc = 0, where a, b, c, and d are the coefficients of the transformation function.

4. Why are fixed points important in Mobius transformations?

Fixed points are important in Mobius transformations because they help us understand how the transformation behaves. If a point is a fixed point, it means that it is mapped onto itself, and it does not move under the transformation. This can provide insights into the symmetry and structure of the transformation, and it can also help us find other important points on the complex plane.

5. Can a Mobius transformation have more than two fixed points?

No, a Mobius transformation can have at most two fixed points. This is because it is a rational function of degree 1, which means that it can have at most one root. Since the fixed points are the roots of the quadratic equation ad - bc = 0, there can be at most two fixed points. However, it is possible for a Mobius transformation to have only one fixed point or no fixed points at all.

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