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Are there complex functions with finite, nonzero branch points?

  1. Aug 28, 2014 #1
    I just completed a brief introduction to branch points in complex analysis, and I find it difficult to imagine/come up with functions with nonzero branch points.

    My difficulty is this: for the point to be considered a branch point, f(r,θ) and f(r,θ+2π) must be different for ANY closed path. If the branch point is zero, you can arbitrarily shrink the path and still be sweeping from 0 to 2π. If your branch point is anything but the origin, then as the path becomes arbitrarily small, so does the angle you sweep over. In such a case, how can you get multiple values for the same input?

    Thanks in advance for any answers to this problem.
  2. jcsd
  3. Aug 28, 2014 #2


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    What if you just translate a function with branch point at 0?
  4. Aug 30, 2014 #3


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    You mean for any closed path with a winding number around zero. This is specific for a branch point at zero. For a branch point somewhere else, the closed paths to consider are those with a winding number around that other point, not around zero.
  5. Sep 3, 2014 #4
    fuserofworlds: look for Riemann surfaces in textbooks or the Internet. They provide a conceptual explanation of branching functions.
  6. Sep 3, 2014 #5


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    Hint: find the branch points of [itex] \sqrt{(z-a)(z-b)}[/itex] for [itex]a \neq b[/itex] and neither [itex]a[/itex] or [itex]b[/itex] are zero.

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