Fall 2011

Course number: 21876

Meeting MW 5:30 - 6:45

GMCS 307

San Diego State University

Last Class: Wed. Dec. 7.

Final Exam: Fri. Dec. 16, 1:00-3:00.

Other times: by appointment.

SCHEDULE | |

ASSIGNMENTS | |

Notes on prerequisite material.(pdf) | |

Notes on Groebner bases.(pdf) | |

Notes on modules.(pdf) | |

Problems for the exam and notes on UFDs.(pdf) |

We will study algebraic geometry, one of the oldest and richest areas of mathematics. During the 20th century, the theoretical and very abstract side of the subject was prominent, but with the availability of computers, the computational roots have been reinvigorated. This course will develop the theory behind the computational tools.

What is algebraic geometry? Think back to high-school algebra where
you graphed polynomial equations and perhaps found the intersection
of plane curves defined by a line and a parabola or more general
curves defined by polynomials.
Now think about higher dimensional space and consider intersections of
hyper-surfaces defined by polynomial equations.
Such objects are called *algebraic sets* or *algebraic varieties*.
What is the dimension? How many components are there? What is the
simplest way to describe the intersection? These are some
fundamental questions of algebraic geometry.

The fundamental result in algebraic geometry is the algebra-geometry
"dictionary" which gives a precise relationship between geometrical
objects and algebraic ones: between *varieties* in n-dimensional
space and *radical
ideals* in the polynomial ring in n variables.
The fundamental tools in computational algebraic geometry are Grobner
bases for ideals and Buchberger's algorithm.
Grobner bases are a generalization of the greatest
common divisor of integers.
Just as the Euclidean algorithm may be used to
compute the gcd, Buchberger's algorithm is used to compute a Grobner
basis for an ideal.

In the last few decades, numerous applications of algebraic geometry have been discovered: in coding theory, cryptography, robotics, object recognition, engineering, genomics etc. Some links that show the scope of recent work are: The Society for Industrial and Applied Mathematics Activity Group on Algebraic Geometry, The Special Semester on Grobner Bases and Related Methods; The Thematic Year on Applications of Algebraic Geometry at the Institute for Mathematics and Its Applications; and the work of Bernd Sturmfels. Powerful computational software has also been developed. See for example Sage , Macaulay 2, Singular, and Magma. These computational tools are of great importance in application.

Cox, Little, O'Shea * Ideals, Varieties, and Algorithms: An
Introduction to Computational Algebraic Geometry and Commutative
Algebra* 2nd Ed., Springer-Verlag, 1997, or 3rd edition 2007.

William A. Stein et al. Sage Mathematics Software The Sage Development Team, 2011, http:www.sagemath.org

The text is a well written book that is one of the standard references in computational algebraic geometry. I will cover the core material on Grobner bases (chapters 1-3), the algebra-geometry dictionary (chapter 4) and, in less detail, functions on a variety (chapter 7), and projective space (chapter 8). Student interest will also guide the course.

Sage is an open source mathematics software package that incorporates numerous other open-source packages into a unified package. The Sage tutorial will help you get started.

- Properties of the Integers: The division theorem and divisibility, the Euclidean algorithm, unique factorization, modular arithmetic.
- Polynomial Ring in One Variable: The division theorem, greatest common divisor, the Euclidean algorithm, unique factorization. The correspondence between factors and roots. Polynomial rings modulo a polynomial.
- Commutative Rings and ideals: The general language of rings and ideals. Integral domains, the quotient of an integral domain by an ideal, homomorphisms.
- Linear Algebra: nullspace, subspace, dimension, basis.

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