22

I would like to present an application of Gröbner bases. The audience is a class of first year graduate students who are taking first year algebra.

Does anyone have suggestions on a specific application that the audience would appreciate?

Mykie
  • 7,245

4 Answers4

21

Since Gröbner basis algorithms may be considered as nonlinear generalizations of Gaussian elimination for systems of linear equations, they have very widespread applicability. Below is a random collection of applications of Gröbner bases.

Bill Dubuque
  • 282,220
  • I was unable to fix the last link over "phylogenetic tree construction", which points to springerlink.com. Perhaps you could take a look, whenever possible... – The Amplitwist Apr 28 '22 at 19:06
7

I learnt of a cool application here in Math.SE where I had asked a question to parametrize $$x=2t-4t^3$$ $$y=t^2-3t^4$$

There was no straightforward way to eliminate $t$, however a user pointed out

using a Gröbner basis routine such as that in Mathematica easily gives the implicit Cartesian equation $$27x^4-4x^2(36y+1)+16y(4y+1)^2=0$$

In Mathematica: GroebnerBasis[{x == 2t - 4t^3, y == t^2 - 3t^4}, {x, y}, t]

I doubt this would be fascinating to graduates though.

6

Here are the things I use Grobner bases for, which I certainly find interesting:

  1. Extending the univariate division algorithm to multivariate polynomials (although not a true euclidean division algorithm, it is still useful).

  2. (related) Computing generators for $I_1 + I_2$ where $I_1,I_2$ are ideals in a multivariate polynomial ring (say $\mathbb{C}$), and using this to determine $I(V_1\cap V_2)$ where $V_1$ and $V_2$ are affine varieties in $\mathbb{A}^n$ for $n > 1$.

I'm not sure if these interest you or the students you are presenting to, but hopefully it's at least a start.

Alex Becker
  • 61,883
  • 2
    I don't think you need Gröbner bases to find generators for $I_1+I_2$ -- any generators of $I_1$ and of $I_2$ can be combined to give generators of $I_1+I_2$. A slightly different answer that actually uses Gröbner bases is that Gröbner bases give a way to compute generators of the intersection $I_1 \cap I_2$. (Briefly, $I_1 \cap I_2 = ((1-t)I_1 + tI_2) \cap k[x]$, and this intersection, eliminating the extra variable $t$, can be computed with Gröbner bases in an elimination order.) – Zach Teitler Nov 10 '21 at 07:52
6
  • find intersection points of a couple of conics (pick the right coefficients to make it not so tedious to do all the manipulation)

  • describing the motion of a constrained single hinged robot arm or planetary epicycles (make a cardioid from two equations)

  • colorability of a graph (see A Crash Course... ) (when presented with the construction, very easy to see that the algorithm produces a solution)

Mitch
  • 8,837