Proof of expanding algebraic functions by Puiseux series

In summary, The basic result in algebraic geometry states that all algebraic functions of one variable can be represented by fractional power series. This can be proven by setting the denominator of the power series to be the factorial of the degree of the polynomial and showing that the coefficients can be solved for. The problem of showing convergence can be addressed by demonstrating that the series converges in the specified domain.
  • #1
jackmell
1,807
54
Hi,

I'm told that a basic result in algebraic geometry is that all algebraic functions [itex]w(z)[/itex] of one variable given by the equation:

[tex]f(w,z)=a_n(z)w^n+a_{n-1}(z)w^{n-1}+\cdots+a_0(z)=0[/tex]

can be written in terms of fractional power series of the form:

[tex]w(z)=\sum_{n=-\infty}^{\infty}a_n \left(z^{1/d}\right)^n[/tex]

Might someone here suggest an accessible reference that goes over the proof or perhaps take a moment to explain some of the basic ideas behind the proof to me?

Thanks,
Jack
 
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  • #2
My gut feeling is just set d=n! (or to the lcm of 1, 2, .., n), plug in, and show that you can solve for the coefficients.
 
  • #3
Hurkyl said:
My gut feeling is just set d=n! (or to the lcm of 1, 2, .., n), plug in, and show that you can solve for the coefficients.

Afraid I don't follow that Hurkyl. My main question is how do I show the existence of such a power series representation and then show that it actually converges to the function in the specified domain.
 

Related to Proof of expanding algebraic functions by Puiseux series

1. What is a Puiseux series?

A Puiseux series is a type of power series expansion used to represent algebraic functions that cannot be expressed as a Taylor series. It is particularly useful for functions with fractional or negative powers.

2. What is the significance of expanding an algebraic function by Puiseux series?

Expanding an algebraic function by Puiseux series allows us to better understand the behavior of the function near singular points or branch points, where it cannot be expressed as a Taylor series. This expansion also provides a more precise representation of the function compared to other methods.

3. How is a Puiseux series expansion calculated?

A Puiseux series expansion is calculated by finding the coefficients of the series using a recursive formula or by using the Newton-Puiseux algorithm. This involves computing the coefficients of the series one by one using the derivatives of the function at the expansion point.

4. What are the limitations of Puiseux series expansions?

One limitation of Puiseux series expansions is that they only provide a local representation of the function, meaning they are only valid in a small neighborhood around the expansion point. Additionally, calculating the coefficients of the series can be challenging for more complex functions.

5. How are Puiseux series expansions used in real-world applications?

Puiseux series expansions are used in various fields of mathematics and science, such as in the study of singularities in complex analysis, in algebraic geometry, and in physics to model physical phenomena. They are also used in computer algebra systems to approximate and manipulate algebraic functions.

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