Complex analysis: mapping a hyperbola onto a line

  • Thread starter Grothard
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Homework Statement



We want to create a map from (x,y) to (u,v) such that the right side (positive x) of the hyperbola x^2 - y^2 = 1 is mapped onto the line v = 0 AND all the points to the left of that hyperbola are mapped to above the line. The mapping should be one-to-one and conformal


Homework Equations



I think (but am not 100% sure) the map has to be from z = x+iy to w = u+iv, so it's important to define x and y in terms of z. I figured out that x = (z+conj(z))/2 and y = (z-conj(z))/2

The Attempt at a Solution



We can map y directly to u through u = y. That should be sufficient I think.
v = x^2 - y^2 - 1 does map the parabola onto the line (it makes v = 0) but it maps the points to the right of the parabola onto above the line, so we multiply by -1 to get v = y^2 - x^2 + 1. We can write everything as:

w = y + i(y^2 - x^2 + 1) and then substitute the x = (z+conj(z))/2 and y = (z-conj(z))/2 in to make it a function of z.

This seems to work for when x >= 0, but it fails to map some points on the left side of the y axis (all of which should be mapped to above the line v = 0). This is because the function x^2 - y^2 = 1 describes two parabolas, and we have to somehow mathematically disregard the left one. I'm not sure how to do that. Could somebody please help?
 

Answers and Replies

  • #2
Dick
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You aren't really dealing with this as a complex function yet. You have got that v(x,y)=x^2-y^2-1 if f(z)=u(x,y)+i*v(x,y) where z=x+iy.That's a start. Now shouldn't you think about using the Cauchy-Riemann equations to figure out what u(x,y) might be and then try to deduce what f(z) might be?
 

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