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Abel's theorem in problems and solutions - School of Mathematics

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180 Problems <strong>of</strong> Chapter 2<br />

this curve under the mapp<strong>in</strong>g <strong>and</strong> let be chosen. If<br />

the variation <strong>of</strong> is equal to then the variation <strong>of</strong> is<br />

equal to (cf., 289). Consequently One may<br />

choose for the branch for the branch <strong>and</strong><br />

for the branch<br />

a)<br />

Answer.<br />

b)<br />

Answer.<br />

c)<br />

Answer.<br />

d)<br />

Answer.<br />

e)<br />

Answer.<br />

292. As for the function one proves that after mak<strong>in</strong>g the<br />

cut from the po<strong>in</strong>t to <strong>in</strong>f<strong>in</strong>ity, for example along the negative side<br />

<strong>of</strong> the real axis, the function turns out to be decomposed <strong>in</strong>to three<br />

s<strong>in</strong>gle-valued cont<strong>in</strong>uous branches. Dur<strong>in</strong>g a simple counterclockwise turn<br />

around the po<strong>in</strong>t varies by dur<strong>in</strong>g a double turn by<br />

<strong>and</strong> only after a triple turn around the po<strong>in</strong>t does the value<br />

<strong>of</strong> the function come back to its <strong>in</strong>itial value. The scheme <strong>of</strong> the<br />

Riemann surface <strong>of</strong> the function has thus the form shown <strong>in</strong> Figure<br />

69. The Riemann surface is represented <strong>in</strong> Figure 70 2 .<br />

FIGURE 69<br />

293. Suppose first that the curve C does not pass through the po<strong>in</strong>t<br />

Let be a function which describes the cont<strong>in</strong>uous variation <strong>of</strong><br />

(cf., Theorem 6, §2.7), <strong>and</strong> let Thus <strong>and</strong><br />

2 To know the mean<strong>in</strong>g <strong>of</strong> the details <strong>of</strong> this figure see the section: Draw<strong>in</strong>gs <strong>of</strong><br />

Riemann surfaces.

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