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Puiseux's Theorem


Puiseux's theorem states that the local branches of a complex algebraic curve admit convergent Puiseux expansions. If P(z,w) is a nonzero polynomial with polynomial degree d>0 in w, each local solution near z=z_0 can be written

 w(z)=sum_(k=k_0)^inftya_k(z-z_0)^(k/n),
(1)

where n is a positive integer and k_0 is an integer. The series converges for sufficiently small nonzero z-z_0 on a chosen branch of (z-z_0)^(1/n) (McMullen 2026, pp. 44-45). Thus, after z-z_0=t^n, a branch with finite limit w_0 has a power series parametrization

z=z_0+t^n
(2)
w=w_0+sum_(k=1)^(infty)a_kt^k.
(3)

Branches tending to infinity have a Laurent series with finitely many negative powers instead.


See also

Algebraic Curve, Algebraic Function, Laurent Series, Puiseux Series

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References

Coolidge, J. L. A Treatise on Algebraic Plane Curves. New York: Dover, p. 207, 1959.McMullen, C. T. "Riemann Surfaces." Harvard University, Math 213b, Apr. 28, 2026. https://abel.math.harvard.edu/~ctm/math213b/home/course/course.pdf.Puiseux, V. "Recherches sur les fonctions algébriques." J. Math. Pures Appl. 15, 365-480, 1850. https://www.numdam.org/item/JMPA_1850_1_15__365_0/.

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Puiseux's Theorem

Cite this as:

Weisstein, Eric W. "Puiseux's Theorem." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/PuiseuxsTheorem.html

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