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orderedQQn -- Construct an ordered module $\QQ^n$

Synopsis

Description

For an overview see Ordered modules. Let $R$ be a polynomial ring with $n$ variables $x_1 \dots x_n$. Then the corresponding ordered $\QQ^n$ module has the following ordering. Suppose that $v, w \in \QQ^n$. Let $d \in \ZZ$ be a positive integer and $c \in \ZZ^n_{\ge 0}$ be a vector such that $dv + c$ and $dw + c$ have non-negative entries. Then $v < w$ if and only if $x^{dv + c} > x^{dw + c}$ in $R$. Note that this property does not depend on the choices of $c$ and $d$, so we obtain a well-defined order on $\QQ^n$.

i1 : R = QQ[x_1 .. x_3, MonomialOrder => Lex]

o1 = R

o1 : PolynomialRing
i2 : M = orderedQQn R

       3
o2 = QQ

o2 : Ordered QQ^3 module
i3 : v = 1/2 * M_0 - 1/3 * M_1

o3 = |  1/2 |
     | -1/3 |
     |   0  |

o3 : Ordered QQ^3 module
i4 : w = 1/2 * M_0 + 1/4 * M_2

o4 = | 1/2 |
     |  0  |
     | 1/4 |

o4 : Ordered QQ^3 module
i5 : v < w

o5 = true

Instead of supplying a polynomial ring, we may supply the rank $n$ of the module along with a monomial order. The constructor creates the ring $R$ with $n$ variables and the given monomial order to construct the OrderedQQn module

i6 : N = orderedQQn(3, {Lex})

       3
o6 = QQ

o6 : Ordered QQ^3 module
i7 : R = N.cache.Ring

o7 = R

o7 : PolynomialRing
i8 : N' = orderedQQn R

       3
o8 = QQ

o8 : Ordered QQ^3 module
i9 : N == N'

o9 = true

$N$ and $N'$ are the same module because they are built from the same ring. See OrderedQQn == OrderedQQn.

See also

Ways to use orderedQQn :

For the programmer

The object orderedQQn is a method function.