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+ <#GAPDoc Label="AppExampleAlgebras">
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+
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+ <Section >
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+ <Heading >
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+ The function
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+ </Heading >
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+ For your convenience, &SBStrips; comes bundled with <M >5</M > SB algebras
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+ built in. We detail these algebras in this appendix. They may be obtained by
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+ calling <Ref Func =" SBStripsExampleAlgebra" />. <P />
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+
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+ <ManSection >
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+ <Func Name =" SBStripsExampleAlgebra" Arg =" n" />
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+ <Description >
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+ Arguments: <A >n</A >, an integer between <C >1</C > and <C >5</C > inclusive
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+ <Br />
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+ </Description >
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+ <Returns >
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+ a SB algebra
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+ <P />
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+ </Returns >
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+ <Description >
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+ Calling this function with argument <C >1</C >, <C >2</C >, <C >3</C >,
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+ <C >4</C > or <C >5</C > respectively returns the algebras described in
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+ subsections <Ref Subsect =" ExAlg1" />, <Ref Subsect =" ExAlg2" />, <Ref
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+ Subsect =" ExAlg3" />, <Ref Subsect =" ExAlg4" /> or <Ref Subsect =" ExAlg5" />.
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+ </Description >
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+ </ManSection >
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+ </Section >
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+
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+ <Section >
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+ <Heading >
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+ The algebras
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+ </Heading >
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+
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+ Each algebra is of the form <M >KQ/\langle \rho \rangle</M >, where <M >K</M >
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+ is the field <C >Rationals</C > in &GAP; and where <M >Q</M > and <M >\rho</M > are
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+ respectively a quiver and a set of relations. These change from example to
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+ example.
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+ <P />
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+
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+ The &LaTeX; version of this documentation provides pictures of each quiver.
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+
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+ <Subsection Label =" ExAlg1" >
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+ <Heading >
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+ Algebra <M >1</M >
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+ </Heading >
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+
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+ The quiver and relations of this algebra are specified to &QPA; as follows.
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+ <Example ><![CDATA[
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+ gap> quiv := Quiver(
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+ > 2,
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+ > [ [ 1, 1, "a" ], [ 1, 2, "b" ], [ 2, 1, "c" ], [ 2, 2, "d" ] ]
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+ > );
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+ <quiver with 2 vertices and 4 arrows>
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+ pa := PathAlgebra( Rationals, quiv );
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+ <Rationals[<quiver with 2 vertices and 4 arrows>]>
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+ gap> rels := [
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+ > pa.a * pa.a, pa.b * pa.d, pa.c * pa.b, pa.d * pa.c,
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+ > pa.c * pa.a * pa.b, (pa.d)^4,
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+ > pa.a * pa.b * pa.c - pa.b * pa.c * pa.a
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+ > ];
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+ [ (1)*a^2, (1)*b*d, (1)*c*b, (1)*d*c, (1)*c*a*b,
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+ (1)*d^4, (1)*a*b*c+(-1)*b*c*a ]
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+ ]]> </Example >
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+ <Alt Only =" LaTeX" >
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+ Here is a picture of the quiver.
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+ <Display >
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+ \begin{tikzcd}
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+ 1 \ar[loop left, "a"] \ar[r, bend left, "b"]
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+ & 2 \ar[l, bend left, "c"] \ar[loop right, "d"]
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+ \end{tikzcd}
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+ </Display >
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+ <P />
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+ </Alt >
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+ The relations of this algebra are chosen so that the nonzero paths of
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+ length <M >2</M > are: <C >a*b</C >, <C >b*c</C >, <C >c*a</C >, <C >d*d</C >.
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+ <P />
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+
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+ The simple module associated to vertex <C >v2</C > has infinite syzygy type.
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+ </Subsection >
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+
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+ <Subsection Label =" ExAlg2" >
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+ <Heading >
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+ Algebra <M >2</M >
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+ </Heading >
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+
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+ The quiver and relations of this algebra are specified to &QPA; as follows.
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+ <Example ><![CDATA[
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+ gap> quiv := Quiver(
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+ > 3,
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+ > [ [ 1, 2, "a" ], [ 2, 3, "b" ], [ 3, 1, "c" ] ]
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+ > );
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+ <quiver with 3 vertices and 3 arrows>
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+ gap> pa := PathAlgebra( Rationals, quiv );
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+ <Rationals[<quiver with 3 vertices and 3 arrows>]>
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+ gap> rels := NthPowerOfArrowIdeal( pa, 4 );
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+ [ (1)*a*b*c*a, (1)*b*c*a*b, (1)*c*a*b*c ]
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+ ]]> </Example >
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+ <Alt Only =" LaTeX" >
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+ Here is a picture of the quiver.
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+ <Display >
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+ \begin{tikzcd}
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+ 1 \ar[r, "a"]
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+ & 2 \ar[r, "b"]
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+ \ar[loop below, phantom, ""{coordinate, name=X} ]
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+ & 3 \ar[ll, "c", rounded corners,
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+ to path={
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+ -- ([xshift=1.5ex]\tikztostart.east)
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+ |- (X)[pos=1]\tikztonodes
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+ -| ([xshift=-1.5ex]\tikztotarget.west)
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+ -- (\tikztotarget.west)
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+ }
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+ ]
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+ \end{tikzcd}
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+ </Display >
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+ <P />
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+ </Alt >
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+ (In other words, this quiver is the <M >3</M >-cycle quiver, and the
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+ relations are the paths of length <M >4</M >.) The nonzero paths of length
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+ <M >2</M > are: <C >a*b</C >, <C >b*c</C >, <C >c*a</C >.
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+ <P />
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+
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+ This algebra is a Nakayama algebra, and so has finite representation type.
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+ <E >A fortiori</E >, it is syzygy-finite.
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+ </Subsection >
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+
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+ <Subsection Label =" ExAlg3" >
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+ <Heading >
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+ Algebra <M >3</M >
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+ </Heading >
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+
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+ The quiver and relations of this algebra are specified to &QPA; as follows.
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+ <Example ><![CDATA[
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+ gap> quiv := Quiver(
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+ > 4,
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+ > [ [1,2,"a"], [2,3,"b"], [3,4,"c"], [4,1,"d"], [4,4,"e"], [1,2,"f"],
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+ > [2,3,"g"], [3,1,"h"] ]
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+ > );
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+ <quiver with 4 vertices and 8 arrows>
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+ gap> pa := PathAlgebra( Rationals, quiv );
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+ <Rationals[<quiver with 4 vertices and 8 arrows>]>
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+ gap> rels := [
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+ > pa.a * pa.g, pa.b * pa.h, pa.c * pa.e, pa.d * pa.f,
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+ > pa.e * pa.d, pa.f * pa.b, pa.g * pa.c, pa.h * pa.a,
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+ > pa.a * pa.b * pa.c * pa.d * pa.a - ( pa.f * pa.g * pa.h )^2 * pa.f,
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+ > pa.d * pa.a * pa.b * pa.c - ( pa.e )^3,
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+ > pa.c * pa.d * pa.a * pa.b * pa.c,
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+ > ( pa.h * pa.f * pa.g )^2 * pa.h
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+ > ];
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+ [ (1)*a*g, (1)*b*h, (1)*c*e, (1)*d*f, (1)*e*d, (1)*f*b, (1)*g*c,
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+ (1)*h*a, (1)*a*b*c*d*a+(-1)*f*g*h*f*g*h*f, (-1)*e^3+(1)*d*a*b*c,
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+ (1)*c*d*a*b*c, (1)*h*f*g*h*f*g*h ]
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+ ]]> </Example >
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+ <Alt Only =" LaTeX" >
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+ Here is a picture of the quiver.
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+ <Display >
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+ \begin{tikzcd}
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+ 1 \ar[r, bend left, "a"] \ar[r, "f"']
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+ & 2 \ar[d, bend left, "b"] \ar[d, "g"']
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+ \\
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+ 4 \ar[u, bend left, "d"] \ar[loop left, "e"]
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+ & 3 \ar[l, bend left, "c"] \ar[ul, "h"]
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+ \end{tikzcd}
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+ </Display >
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+ <P />
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+ </Alt >
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+
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+ The relations of this algebra are chosen so that the nonzero paths of
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+ length <M >2</M > are: <C >a*b</C >, <C >b*c</C >, <C >c*d</C >, <C >d*a</C >,
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+ <C >e*e</C >, <C >f*g</C >, <C >g*h</C > and <C >h*f</C >.
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+ </Subsection >
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+
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+ <Subsection Label =" ExAlg4" >
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+ <Heading >
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+ Algebra <M >4</M >
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+ </Heading >
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+
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+ The quiver and relations of this algebra are specified to &QPA; as follows.
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+ <Example ><![CDATA[
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+ gap> quiv := Quiver(
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+ > 8,
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+ > [ [ 1, 1, "a" ], [ 1, 2, "b" ], [ 2, 2, "c" ], [ 2, 3, "d" ],
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+ > [ 3, 4, "e" ], [ 4, 3, "f" ], [ 3, 4, "g" ], [ 4, 5, "h" ],
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+ > [ 5, 6, "i" ], [ 6, 5, "j" ], [ 5, 7, "k" ], [ 7, 6, "l" ],
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+ > [ 6, 7, "m" ], [ 7, 8, "n" ], [ 8, 8, "o" ], [ 8, 1, "p" ] ]
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+ > );
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+ <quiver with 8 vertices and 16 arrows>
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+ gap> pa := PathAlgebra( Rationals, quiv );
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+ <Rationals[<quiver with 8 vertices and 16 arrows>]>
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+ gap> rels := [
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+ > pa.a * pa.a, pa.b * pa.d, pa.c * pa.c, pa.d * pa.g, pa.e * pa.h,
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+ > pa.f * pa.e, pa.g * pa.f, pa.h * pa.k, pa.i * pa.m, pa.j * pa.i,
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+ > pa.k * pa.n, pa.l * pa.j,
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+ > pa.m * pa.l, pa.n * pa.p, pa.o * pa.o, pa.p * pa.b,
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+ > pa.a * pa.b * pa.c * pa.d,
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+ > pa.e * pa.f * pa.g * pa.h,
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+ > pa.g * pa.h * pa.i * pa.j * pa.k,
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+ > pa.c * pa.d * pa.e - pa.d * pa.e * pa.f * pa.g,
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+ > pa.f * pa.g * pa.h * pa.i - pa.h * pa.i * pa.j * pa.k * pa.l,
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+ > pa.j * pa.k * pa.l * pa.m * pa.n - pa.m * pa.n * pa.o,
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+ > pa.o * pa.p * pa.a * pa.b - pa.p * pa.a * pa.b * pa.c
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+ > ];
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+ ]]> </Example >
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+ The relations of this algebra are chosen so that the nonzero paths of
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+ length <M >2</M > are: <C >a*b</C >, <C >b*c</C >, <C >c*d</C >, <C >d*e</C >,
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+ <C >e*f</C >, <C >f*g</C >, <C >g*h</C >, <C >h*i</C >, <C >i*j</C >, <C >j*k</C >,
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+ <C >k*l</C >, <C >l*m</C >, <C >m*n</C >, <C >n*o</C >, <C >o*p</C > and <C >p*a</C >.
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+ </Subsection >
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+
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+ <Subsection Label =" ExAlg5" >
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+ <Heading >
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+ Algebra <M >5</M >
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+ </Heading >
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+
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+ The quiver and relations of this algebra are specified to &QPA; as follows.
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+ <Example ><![CDATA[
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+ gap> quiv := Quiver(
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+ > 4,
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+ > [ [ 1, 2, "a" ], [ 2, 3, "b" ], [ 3, 4, "c" ], [ 4, 1, "d" ],
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+ > [ 1, 2, "e" ], [ 2, 3, "f" ], [ 3, 1, "g" ], [ 4, 4, "h" ] ]
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+ > );
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+ <quiver with 4 vertices and 8 arrows>
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+ gap> pa := PathAlgebra( Rationals, quiv5 );
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+ <Rationals[<quiver with 4 vertices and 8 arrows>]>
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+ gap> rels := [
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+ > pa.a * pa.f, pa.b * pa.g, pa.c * pa.h, pa.d * pa.e, pa.e * pa.b,
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+ > pa.f * pa.c, pa.g * pa.a, pa.h * pa.d,
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+ > pa.b * pa.c * pa.d * pa.a * pa.b * pa.c,
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+ > pa.d * pa.a * pa.b * pa.c * pa.d * pa.a,
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+ > ( pa.h )^6,
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+ > pa.a * pa.b * pa.c * pa.d * pa.a * pa.b -
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+ > pa.e * pa.f * pa.g * pa.e * pa.f * pa.g * pa.e * pa.f,
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+ > pa.c * pa.d * pa.a * pa.b * pa.c * pa.d -
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+ > pa.g * pa.e * pa.f * pa.g * pa.e * pa.f * pa.g
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+ > ];
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+ [ (1)*a*f, (1)*b*g, (1)*c*h, (1)*d*e, (1)*e*b, (1)*f*c, (1)*g*a,
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+ (1)*h*d, (1)*b*c*d*a*b*c, (1)*d*a*b*c*d*a, (1)*h^6,
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+ (1)*a*b*c*d*a*b+(-1)*e*f*g*e*f*g*e*f,
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+ (1)*c*d*a*b*c*d+(-1)*g*e*f*g*e*f*g ]
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+ ]]> </Example >
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+ The relations of this algebra are chosen so that the nonzero paths of
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+ length <M >2</M > are: <C >a*b</C >, <C >b*c</C >, <C >c*d</C >, <C >d*a</C >,
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+ <C >e*f</C >, <C >f*g</C >, <C >g*e</C >, <C >h*h</C >.
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+ </Subsection >
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+ </Section >
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+
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+ <#/GAPDoc>
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