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monoid(...,Join=>...) -- specify how to handle degrees in the coefficient ring

Synopsis

Description

The Join option specifies whether the degrees in the new monoid ring will be obtained by joining the degrees in the coefficient with the degrees in the monoid.

By default, (multi)degrees are concatenated when forming polynomial rings over polynomial rings, as can be seen by examining the corresponding flattened monoid, which displays information about all of the variables.

i1 : QQ[x][y]

o1 = QQ[x][y]

o1 : PolynomialRing
i2 : oo.FlatMonoid

o2 = monoid[y, x, Degrees => {{1}, {0}}, Heft => {2:1}, MonomialOrder => {MonomialSize => 32}]
                              {0}  {1}                                   {GRevLex => {1}    }
                                                                         {Position => Up    }
                                                                         {GRevLex => {1}    }

o2 : GeneralOrderedMonoid
i3 : QQ[x][y][z]

o3 = QQ[x][y][z]

o3 : PolynomialRing
i4 : oo.FlatMonoid

o4 = monoid[z, y, x, Degrees => {{1}, {0}, {0}}, Heft => {3:1}, MonomialOrder => {MonomialSize => 32}]
                                 {0}  {1}  {0}                                   {GRevLex => {1}    }
                                 {0}  {0}  {1}                                   {Position => Up    }
                                                                                 {2:(GRevLex => {1})}

o4 : GeneralOrderedMonoid

That behavior can be overridden with the monoid(...,Join=>...) option.

i5 : QQ[x][y, Join => false]

o5 = QQ[x][y]

o5 : PolynomialRing
i6 : oo.FlatMonoid

o6 = monoid[y, x, Degrees => {2:1}, Heft => {1}, Join => false, MonomialOrder => {MonomialSize => 32}]
                                                                                 {GRevLex => {1}    }
                                                                                 {Position => Up    }
                                                                                 {GRevLex => {1}    }

o6 : GeneralOrderedMonoid

This option may also be used when creating a new ring from an existing ring, creating a tensor product ring, or symmetric algebra.

Further information

See also

Functions with optional argument named Join :