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DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES

THEORY SEMINAR

                    -Wednesday, October 14, 1992

J.  S.  Devitt, University of Saskatchewan (visiting University of
Waterloo),   will   speak   on  "Algorithmic  issues  in  the
characterization of similarity solutions for systems of
partial differential equations"

TIME:                 1:30-2:30 p.m.

ROOM:                 DC 1304

ABSTRACT

The  methods  commonly used to solve systems of partial
differential  equations  often  begin  by  looking  for
transformations  of the coordinate system for which the
original equations invariant.  Systematic computational
methods  exist  for  characterizing  certain  types  of
similarity   transformations.    One   common  approach
involves   constructing   and   applying   an  extended
differential  operator  while  another reformulates the
problem  in  the language of differential forms and the
construction of differential ideals.

The  liesymm  package  in  Maple  fully  automates  the
     -------  -------
Harrison-Estabrook   procedure   for  constructing  the
determining  equations  of  the  isometry  group.  This
approach   uses   Cartan's   formulation  in  terms  of
differential forms and requires algebraic manipulations
that  differ  signficantly  from  the world of rational
polynomial manipulation.

In  this  talk  we  will  investigate  some of the data
structures  and algorithms required to work effectively
in this environment.  While we will include an overview
of  the algebra involved the material will be presented
primarily  as  a  case  study  and  will  focus  on the
computational issues that arise.