<span class=strong>Tutorial/demonstration session</span>

Thursday, October 26, 2006 - 4:00pm - 7:00pm
Lind 400
No Abstract
  • 4ti2 – Computing with Lattices, Cones, and Subspaces
    Peter Malkin (Université Catholique de Louvain)
    In this demonstration, we present the main functionality of the software package 4ti2. Using 4ti2, we can compute Hilbert bases, Graver bases, Groebner bases, and Markov bases of lattices, and the rays of a cone and the circuits of a linear subspace. 4ti2 also has functions to optimize integer linear programs.
  • SINGULAR – A Tool for Algebraic Geometry
    Hans Schöenemann (Universität Kaiserslautern)

    Scenario for SINGULAR presentation

    1 Overview on SINGULAR

    I will give a short overview of the abilities of Singular,
    with special emphasis on the
    new features of Singular version 3.0.

    2 Applications

    The main part of the presentation will concentrate on the following tools for algebraic geometry:

    2.1 Non-commutative Extension (G-algebras)

    We demonstrate Singular's non-commutative extension
    and show an application of it to compute the cohomology of twists of a sheaf
    F on Pn associated to coker(M) for M being a graded module.s
    It uses the Tate resolution over the exterior algebra.

    The normalization will be computed for a reduced ring
    The result is a list of rings of the form
    Ri /Ii.
    The normalization of R/I is the product of the
    factor rings of the rings in the list divided out by the ideals.

    2.3 Primary Decomposition

    There are two algorithms implemented in Singular
    which provide primary decomposition:
    primdecGTZ, based on Gianni/Trager/Zacharias (written by Gerhard Pfister) and primdecSY, based on Shimoyama/Yokoyama (written by Wolfram Decker and Hans Schoenemann).
    We will demonstrate some examples of both.

    2.4 Absolute Factorization And Absolute
    Primary Decomposition

    The absolute factorization of a multivariate polynomial
    f with
    coefficients in a field K of characteristic zero computes a suitable
    field extension L (of K) and computes an absolutely irreducible factor of f in that extension.

    These routines are used to compute an absolute primary decomposition:
    the routines return an list of he absolute prime components together
    with its number of conjugates.

  • Demonstration of HomLab
    Charles Wampler (General Motors Corporation)
    HomLab, a suite of Matlab routines, was created for learning about the numerical solution of polynomial systems using homotopy continuation.The
    package is distributed for use with the book Sommese and Wampler, The Numerical Solution of Systems of Polynomials Arising in Engineering and Science, World Scientific, 2005. In addition to the main software package, the HomLab distribution includes codes to be used in working the exercises at the end of each chapter.

    While created for use with the book, HomLab is a general-purpose solver, fast enough for moderately-sized systems. It provides the capability to find all isolated solutions and to provide witness points on positive-dimensional solution sets. Parameter continuation is available for tracking nonsingular isolated solutions through a parameterized family of polynomials, eliminating the overhead that otherwise would be imposed by degenerate and positive-dimensional components.

    The software can be downloaded at
    The HomLab User's Manual appears as Appendix C of Sommese and Wampler.

  • Solving Large Overdetermined Systems with CRACK
    Thomas Wolf (Brock University)
    Starting as an automatic tools to integrate overdetermined
    systems of linear PDEs, CRACK developed in recent years to a package
    that is also well suited for polynomially non-linear systems.
    Newer algorithms, like one for reducing the number of terms are
    essentially different from the Groebner basis algorithm and thus a
    useful addition which make the package especially suited for solving
    large and heavily overdetermined systems. In the talk and demo an
    overview shall be given, featuring, for example, the recent extension
    that allows to dynamically generate the system to be solved during its
    solution process. This became necessary for a computation in discrete
    differential geometry where the polynomial consistency conditions for a
    3-dimensional face formula involve 1017 terms.
  • Software for Partial Differential Equations
    Gregory Reid (University of Western Ontario)
    In this talk symbolic software will be described for overdetermined systems of Partial Differential Equations.

    The symbolic software is the rifsimp package which is available in distributed
    Maple (since Maple 7). It is tightly integrated and automatically called in many applications of Maple (e.g. its ODE and PDE solving routines). It was programmed by Allan Wittkopf.

    Examples and applications of the use of this software will be given. Some problems will also be used so that participants can try them during the session.
    Examples include: determination of initial data uniqueley determining solutions
    of PDE; determination of normal forms for PDE; determination of formal power series for PDE; determination of symmetries of PDE; integration of PDE.

    Strategies for tackling difficult problems and examples of their use.
  • Computing Tropical Varieties in Gfan
    Anders Jensen (Aarhus University)
    We will demonstrate how the Gfan software can be used for computing Groebner
    fans and tropical varieties of polynomial ideals. For Groebner fans we will see
    how to do computations up to symmetry, draw the fans and do interactive Groebner
    walks. Tropical computations are more involved. The following problems can be
    handled by Gfan: intersecting tropical hypersurfaces, computing tropical bases
    of curves and traversing tropical varieties of prime ideals. These will all be
    demonstrated. We will discuss the most common problems one encounters with the
    tropical part of the software: finding a starting cone, specifying symmetries,
    selecting an appropriate output format and reading the output.