src/HOL/Algebra/README.html
author paulson
Thu May 01 11:54:18 2003 +0200 (2003-05-01)
changeset 13944 9b34607cd83e
parent 7998 3d0c34795831
child 13949 0ce528cd6f19
permissions -rw-r--r--
new proofs about direct products, etc.
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<HTML><HEAD><TITLE>HOL/Algebra/README.html</TITLE></HEAD><BODY>
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<H2>Algebra: Theories of Rings and Polynomials</H2>
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<P>This development of univariate polynomials is separated into an
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abstract development of rings and the development of polynomials
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itself. The formalisation is based on [Jacobson1985], and polynomials
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have a sparse, mathematical representation. These theories were
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developed as a base for the integration of a computer algebra system
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to Isabelle [Ballarin1999], and was designed to match implementations
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of these domains in some typed computer algebra systems.  Summary:
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<P><EM>Rings:</EM>
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  Classes of rings are represented by axiomatic type classes. The
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  following are available:
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<PRE>
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  ringS:	Syntactic class
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  ring:		Commutative rings with one (including a summation
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		operator, which is needed for the polynomials)
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  domain:	Integral domains
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  factorial:	Factorial domains (divisor chain condition is missing)
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  pid:		Principal ideal domains
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  field:	Fields
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</PRE>
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  Also, some facts about ring homomorphisms and ideals are mechanised.
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<P><EM>Polynomials:</EM>
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  Polynomials have a natural, mathematical representation. Facts about
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  the following topics are provided:
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<MENU>
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<LI>Degree function
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<LI> Universal Property, evaluation homomorphism
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<LI>Long division (existence and uniqueness)
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<LI>Polynomials over a ring form a ring
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<LI>Polynomials over an integral domain form an integral domain
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</MENU>
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 <P>Still missing are
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    Polynomials over a factorial domain form a factorial domain
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    (difficult), and polynomials over a field form a pid.
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<P>[Jacobson1985] Nathan Jacobson, Basic Algebra I, Freeman, 1985.
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<P>[Ballarin1999] Clemens Ballarin, Computer Algebra and Theorem Proving,
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  Author's <A HREF="http://iaks-www.ira.uka.de/iaks-calmet/ballarin/publications.html">PhD thesis</A>, 1999.
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<H2>GroupTheory -- Group Theory using Locales, including Sylow's Theorem</H2>
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<P>This directory presents proofs about group theory, by
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Florian Kammüller.  (Later, Larry Paulson simplified some of the proofs.)
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These theories use locales and were indeed the original motivation for
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locales.  However, this treatment of groups must still be regarded as
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experimental.  We can expect to see refinements in the future.
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Here is an outline of the directory's contents:
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<UL> <LI>Theory <A HREF="Group.html"><CODE>Group</CODE></A> defines
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semigroups, groups, homomorphisms and the subgroup relation.  It also defines
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the product of two groups.  It defines the factorization of a group and shows
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that the factorization a normal subgroup is a group.
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<LI>Theory <A HREF="Bij.html"><CODE>Bij</CODE></A>
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defines bijections over sets and operations on them and shows that they
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are a group.  It shows that automorphisms form a group.
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<LI>Theory <A HREF="Ring.html"><CODE>Ring</CODE></A> defines rings and proves
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a few basic theorems.  Ring automorphisms are shown to form a group.
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<LI>Theory <A HREF="Sylow.html"><CODE>Sylow</CODE></A>
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contains a proof of the first Sylow theorem.
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<LI>Theory <A HREF="Summation.html"><CODE>Summation</CODE></A> Extends
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abelian groups by a summation operator for finite sets (provided by
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Clemens Ballarin).
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</UL>
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<HR>
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<P>Last modified on $Date$
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<ADDRESS>
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<P><A HREF="http://iaks-www.ira.uka.de/iaks-calmet/ballarin">Clemens Ballarin</A>.  Karlsruhe, October 1999
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<A NAME="ballarin@ira.uka.de" HREF="mailto:ballarin@ira.uka.de">ballarin@ira.uka.de</A>
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</ADDRESS>
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