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#W isorms.xml
#Y Copyright (C) 2015 James D. Mitchell
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## Licensing information can be found in the README file of this package.
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<#GAPDoc Label="IsRMSIsoByTriple">
<ManSection>
<Filt Name = "IsRMSIsoByTriple"Type = "Category"/>
<Filt Name = "IsRZMSIsoByTriple"Type = "Category"/>
<Description>
The isomorphisms between finite Rees matrix or 0-matrix semigroups
<C>S</C> and <C>T</C> over groups <C>G</C> and <C>H</C>, respectively,
specified by a triple consisting of:
<Enum>
<Item>
an isomorphism of the underlying graph of <C>S</C> to the underlying
graph of of <C>T</C>
</Item>
<Item>
an isomorphism from <C>G</C> to <C>H</C>
</Item>
<Item>
a function from <C>Rows(S)</C> union <C>Columns(S)</C> to <C>H</C>
</Item>
</Enum>
belong to the categories <C>IsRMSIsoByTriple</C> and
<C>IsRZMSIsoByTriple</C>. Basic operators for such isomorphism are given
in <Ref Subsect = "Operators for isomorphisms of Rees (0-)matrix semigroups"/>,
and basic operations are:
<#GAPDoc Label="RMSIsoByTriple">
<ManSection>
<Oper Name = "RMSIsoByTriple" Arg = "R1, R2, triple"/>
<Oper Name = "RZMSIsoByTriple" Arg = "R1, R2, triple"/>
<Returns>An isomorphism.</Returns>
<Description>
If <A>R1</A> and <A>R2</A> are isomorphic regular Rees 0-matrix semigroups
whose underlying semigroups are groups then <C>RZMSIsoByTriple</C> returns
the isomorphism between <A>R1</A> and <A>R2</A> defined by <A>triple</A>,
which should be a list consisting of the following:
<List>
<Item>
<C><A>triple</A>[1]</C> should be a permutation describing an
isomorphism from the graph of <A>R1</A> to the graph of <A>R2</A>,
i.e. it should satisfy
<C>OnDigraphs(RZMSDigraph(<A>R1</A>), <A>triple</A>[1])
= RZMSDigraph(<A>R2</A>)</C>.
</Item>
<Item>
<C><A>triple</A>[2]</C> should be an isomorphism from the underlying
group of <A>R1</A> to the underlying group of <A>R2</A> (see
<Ref Attr="UnderlyingSemigroup"
Label="for a Rees 0-matrix semigroup"
BookName="ref"/>).
</Item>
<Item>
<C><A>triple</A>[3]</C> should be a list of elements from the
underlying group of <A>R2</A>. If the
<Ref Attr="Matrix" BookName="ref"/>
of <A>R1</A> has <M>m</M> columns
and <M>n</M> rows, then the list should have length <M>m + n</M>,
where the first <M>m</M> entries should correspond to the columns of
<A>R1</A>'s matrix, and the last n entries should correspond to
the rows. These column and row entries should correspond to the
<M>u_i</M> and <M>v_\lambda</M> elements in Theorem 3.4.1 of
<Cite Key = "Howie1995aa"/>.
</Item>
</List>
If <A>triple</A> describes a valid isomorphism from <A>R1</A> to <A>R2</A>
then this will return an object in the category
<Ref Filt="IsRZMSIsoByTriple"/>; otherwise an error will be returned. <P/>
If <A>R1</A> and <A>R2</A> are instead Rees matrix semigroups (without
zero) then <C>RMSIsoByTriple</C> should be used instead. This operation
is used in the same way, but it should be noted that since an RMS's graph
is a complete bipartite graph, <C><A>triple</A>[1]</C> can be any
permutation on <C>[1 .. m + n]</C>, so long as no point in <C>[1 .. m]</C>
is mapped to a point in <C>[m + 1 .. m + n]</C>. <P/>
<#GAPDoc Label="ELM_LIST">
<ManSection>
<Oper Name = "ELM_LIST" Label = "for IsRMSIsoByTriple"
Arg = "map, pos"/>
<Returns>
A component of an isomorphism of Rees (0-)matrix semigroups by triple.
</Returns>
<Description>
<C>ELM_LIST(<A>map</A>, <A>i</A>)</C> returns the <C>i</C>th component of
the Rees (0-)matrix semigroup isomorphism by triple <A>map</A> when
<C>i = 1, 2, 3</C>.
<P/>
The components of an isomorphism of Rees (0-)matrix semigroups by triple
are:
<Enum>
<Item>
An isomorphism of the underlying graphs of the source and range of
<A>map</A>, respectively.
</Item>
<Item>
An isomorphism of the underlying groups of the source and range of
<A>map</A>, respectively.
</Item>
<Item>
An function from the union of the rows and columns of the source of
<A>map</A> to the underlying group of the range of <A>map</A>.
</Item>
</Enum>
</Description>
</ManSection>
<#/GAPDoc>
<#GAPDoc Label="CompositionMapping2">
<ManSection>
<Oper Name = "CompositionMapping2" Label = "for IsRMSIsoByTriple"
Arg = "map1, map2"/>
<Oper Name = "CompositionMapping2" Label = "for IsRZMSIsoByTriple"
Arg = "map1, map2"/>
<Returns>
A Rees (0-)matrix semigroup by triple.
</Returns>
<Description>
If <A>map1</A> and <A>map2</A> are isomorphisms of Rees matrix or
0-matrix semigroups specified by triples and the range of <A>map2</A> is
contained in the source of <A>map1</A>, then
<C>CompositionMapping2(<A>map1</A>, <A>map2</A>)</C> returns the
isomorphism from <C>Source(<A>map2</A>)</C> to <C>Range(<A>map1</A>)</C>
specified by the triple with components:
<#GAPDoc Label="ImagesElm">
<ManSection>
<Oper Name = "ImagesElm" Label = "for IsRMSIsoByTriple" Arg = "map, pt"/>
<Oper Name = "ImagesRepresentative" Label = "for IsRMSIsoByTriple"
Arg = "map, pt"/>
<Returns>
An element of a Rees (0-)matrix semigroup or a list containing such an element.
</Returns>
<Description>
If <A>map</A> is an isomorphism of Rees matrix or 0-matrix semigroups
specified by a triple and <A>pt</A> is an element of the source of
<A>map</A>, then <C>ImagesRepresentative(<A>map</A>, <A>pt</A>) =
<A>pt</A> ^ <A>map</A></C> returns the image of <A>pt</A> under
<A>map</A>.
<P/>
The image of <A>pt</A> under <A>map</A> of <C>Range(<A>map</A>)</C> is the element with components:
<#GAPDoc Label="CanonicalReesZeroMatrixSemigroup">
<ManSection>
<Attr Name = "CanonicalReesZeroMatrixSemigroup" Arg = "S"/>
<Attr Name = "CanonicalReesMatrixSemigroup" Arg = "S"/>
<Returns>
A Rees zero matrix semigroup.
</Returns>
<Description>
If <A>S</A> is a Rees 0-matrix semigroup then
<C>CanonicalReesZeroMatrixSemigroup</C> returns an isomorphic Rees
0-matrix semigroup <C>T</C> with the same
<Ref Attr="UnderlyingSemigroup" Label="for a Rees 0-matrix semigroup"
BookName="ref"/>
as <A>S</A> but the
<Ref Attr="Matrix" BookName="ref"/>
of <C>T</C> has been canonicalized. The output
<C>T</C> is canonical in the sense that for any two inputs
which are isomorphic Rees zero matrix semigroups the output of this
function is the same.<P/>
<C>CanonicalReesMatrixSemigroup</C> works the same but for Rees matrix
semigroups.
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