MonomialIdeal -- the class of all monomial ideals handled by the engine

Description

Monomial ideals are kinds of ideals, but many algorithms are much faster. Generally, any routines available for ideals are also available for monomial ideals.

i1 : R = QQ[a..d];

i2 : I = monomialIdeal(a*b*c,b*c*d,a^2*d,b^3*c)

                            3    2
o2 = monomialIdeal (a*b*c, b c, a d, b*c*d)

o2 : MonomialIdeal of R

i3 : I^2

                     2 2 2     4 2   6 2   3        2 3        2 2    4 2  
o3 = monomialIdeal (a b c , a*b c , b c , a b*c*d, a b c*d, a*b c d, b c d,
     ------------------------------------------------------------------------
      4 2   2     2   2 2 2
     a d , a b*c*d , b c d )

o3 : MonomialIdeal of R

i4 : I + monomialIdeal(b*c)

                          2
o4 = monomialIdeal (b*c, a d)

o4 : MonomialIdeal of R

i5 : I : monomialIdeal(b*c)

                        2
o5 = monomialIdeal (a, b , d)

o5 : MonomialIdeal of R

i6 : radical I

o6 = monomialIdeal (b*c, a*d)

o6 : MonomialIdeal of R

i7 : associatedPrimes I

o7 = {monomialIdeal (a, b), monomialIdeal (a, c), monomialIdeal (b, d),
     ------------------------------------------------------------------------
     monomialIdeal (c, d), monomialIdeal (a, b, d)}

o7 : List

i8 : primaryDecomposition I

                      2                      2                           
o8 = {monomialIdeal (a , b), monomialIdeal (a , c), monomialIdeal (b, d),
     ------------------------------------------------------------------------
                                              3
     monomialIdeal (c, d), monomialIdeal (a, b , d)}

o8 : List

Specialized functions only available for monomial ideals

borel(MonomialIdeal) -- make a Borel fixed submodule
isBorel(MonomialIdeal) -- whether an ideal is fixed by upper triangular changes of coordinates
MonomialIdeal - MonomialIdeal -- monomial ideal difference
dual(MonomialIdeal) -- the Alexander dual of a monomial ideal
independentSets -- some size-maximal independent subsets of variables modulo an ideal
irreducibleDecomposition -- express a monomial ideal as an intersection of irreducible monomial ideals
standardPairs -- find the standard pairs of a monomial ideal

i9 : borel I

                     3   2      2   3   2           2      2     2   2  
o9 = monomialIdeal (a , a b, a*b , b , a c, a*b*c, b c, a*c , b*c , a d,
     ------------------------------------------------------------------------
             2
     a*b*d, b d, a*c*d, b*c*d)

o9 : MonomialIdeal of R

i10 : isBorel I

o10 = false

i11 : I - monomialIdeal(b^3*c,b^4)

                             2
o11 = monomialIdeal (a*b*c, a d, b*c*d)

o11 : MonomialIdeal of R

i12 : standardPairs I

                                                                           
o12 = {{1, {c, d}}, {a, {c, d}}, {1, {d, b}}, {a, {d, b}}, {1, {c, a}}, {1,
      -----------------------------------------------------------------------
                           2
      {b, a}}, {b, {c}}, {b , {c}}}

o12 : List

i13 : independentSets I

o13 = {a*b, a*c, b*d, c*d}

o13 : List

i14 : dual I

                        3        2      3
o14 = monomialIdeal (a*b , a*c, a b*d, b d, c*d)

o14 : MonomialIdeal of R

The ring of a monomial ideal must be a commutative polynomial ring. This ring must not be a skew commuting ring, and/or a quotient ring.

monomialIdeal -- make a monomial ideal
monomialSubideal -- find the largest monomial ideal in an ideal
independentSets(MonomialIdeal) -- see independentSets -- some size-maximal independent subsets of variables modulo an ideal
standardPairs(MonomialIdeal) -- see standardPairs -- find the standard pairs of a monomial ideal
polarize(MonomialIdeal) -- see polarize -- compute the polarization of a monomial ideal
codim(MonomialIdeal) -- compute the codimension
MonomialIdeal - MonomialIdeal -- monomial ideal difference
dual(MonomialIdeal,List) -- the Alexander dual
dual(MonomialIdeal,RingElement) -- the Alexander dual
dual(MonomialIdeal) -- the Alexander dual of a monomial ideal
lcm(MonomialIdeal) -- least common multiple of all minimal generators

Functions and methods returning a monomial ideal:

MonomialIdeal * MonomialIdeal -- see * -- a binary operator, usually used for multiplication
MonomialIdeal * Ring -- see * -- a binary operator, usually used for multiplication
Ring * MonomialIdeal -- see * -- a binary operator, usually used for multiplication
RingElement * MonomialIdeal -- see * -- a binary operator, usually used for multiplication
MonomialIdeal + MonomialIdeal -- see + -- a unary or binary operator, usually used for addition
borel(MonomialIdeal) -- see borel(Matrix) -- make a Borel fixed submodule
MonomialIdeal ^ Array -- see Ideal ^ Array -- bracket power of an ideal
MonomialIdeal ^ ZZ -- see Ideal ^ ZZ -- power of an ideal
mingens(MonomialIdeal) -- see mingens(Module) -- minimal generator matrix
monomialIdeal -- make a monomial ideal
MonomialIdeal - MonomialIdeal -- monomial ideal difference
MonomialIdeal : RingElement
monomialIdeal(String) (missing documentation)
quotient(MonomialIdeal,RingElement)
saturate(MonomialIdeal,RingElement) -- see saturate -- saturation of ideal or submodule
trim(MonomialIdeal) -- see trim -- minimize generators and relations

Methods that use a monomial ideal:

ZZ % MonomialIdeal -- see % -- a binary operator, usually used for remainder and reduction
ZZ // MonomialIdeal -- see // -- a binary operator, usually used for quotient
codim(MonomialIdeal) -- compute the codimension
dim(MonomialIdeal) -- see dim(Ideal) -- compute the Krull dimension
dual(MonomialIdeal) -- the Alexander dual of a monomial ideal
dual(MonomialIdeal,List) -- the Alexander dual
dual(MonomialIdeal,RingElement) -- the Alexander dual
generators(MonomialIdeal) -- see generators(Ideal) -- the generator matrix of an ideal
ideal(MonomialIdeal) -- convert a monomial ideal to an ideal
independentSets(MonomialIdeal) -- see independentSets -- some size-maximal independent subsets of variables modulo an ideal
isBorel(MonomialIdeal) -- see isBorel -- whether an ideal is fixed by upper triangular changes of coordinates
isMonomialIdeal(MonomialIdeal) -- see isMonomialIdeal -- whether something is a monomial ideal
isSquareFree(MonomialIdeal) -- see isSquareFree -- whether something is square free monomial ideal
lcm(MonomialIdeal) -- least common multiple of all minimal generators
Matrix % MonomialIdeal -- see methods for normal forms and remainder -- normal form of ring elements and matrices
RingElement % MonomialIdeal -- see methods for normal forms and remainder -- normal form of ring elements and matrices
monomialIdeal(MonomialIdeal) -- see monomialIdeal(Ideal) -- monomial ideal of lead monomials of a Gröbner basis
numgens(MonomialIdeal) -- see numgens(Ring) -- number of generators of a polynomial ring
poincare(MonomialIdeal) -- see poincare -- assemble degrees of a ring, module, or ideal into a polynomial
polarize(MonomialIdeal) -- see polarize -- compute the polarization of a monomial ideal
Matrix // MonomialIdeal -- see quotient(Matrix,Matrix) -- factor a map through another with the same target
RingElement // MonomialIdeal -- see quotient(Matrix,Matrix) -- factor a map through another with the same target
standardPairs(MonomialIdeal) -- see standardPairs -- find the standard pairs of a monomial ideal
standardPairs(MonomialIdeal,List) -- see standardPairs -- find the standard pairs of a monomial ideal

For the programmer

The object MonomialIdeal is a type, with ancestor classes Ideal < HashTable < Thing.