Fractional ideals
A fractional ideal in the number field $K$ is a $Z_K$-module $A$ such that there exists an integer $d>0$ which $dA$ is an (integral) ideal in $Z_K$. Due to the Dedekind property of $Z_K$, the ideals for a multiplicative group.
Fractional ideals are represented as an integral ideal and an additional denominator. They are of type NfOrdFracIdl
.
Creation
fractional_ideal
— Methodfractional_ideal(O::NfAbsOrd, A::ZZMatrix, b::ZZRingElem, A_in_hnf::Bool = false) -> NfAbsOrdFracIdl
Creates the fractional ideal of $\mathcal O$ with basis matrix $A/b$. If A_in_hnf
is set, then it is assumed that $A$ is already in lower left HNF.
fractional_ideal
— Methodfractional_ideal(O::NfAbsOrd, A::ZZMatrix, b::ZZRingElem, A_in_hnf::Bool = false) -> NfAbsOrdFracIdl
Creates the fractional ideal of $\mathcal O$ with basis matrix $A/b$. If A_in_hnf
is set, then it is assumed that $A$ is already in lower left HNF.
fractional_ideal
— Methodfractional_ideal(O::NfAbsOrd, A::FakeFmpqMat, A_in_hnf::Bool = false) -> NfAbsOrdFracIdl
Creates the fractional ideal of $\mathcal O$ with basis matrix $A$. If A_in_hnf
is set, then it is assumed that the numerator of $A$ is already in lower left HNF.
fractional_ideal
— Methodfractional_ideal(O::NfOrd, I::NfAbsOrdIdl) -> NfOrdFracIdl
The fractional ideal of $O$ generated by a $Z$-basis of $I$.
fractional_ideal(O::NfAbsOrd, I::NfAbsOrdIdl) -> NfAbsOrdFracIdl
Turns the ideal $I$ into a fractional ideal of $\mathcal O$.
fractional_ideal
— Methodfractional_ideal(O::NfAbsOrd, I::NfAbsOrdIdl, b::ZZRingElem) -> NfAbsOrdFracIdl
Creates the fractional ideal $I/b$ of $\mathcal O$.
fractional_ideal
— Methodfractional_ideal(O::NfAbsOrd, a::nf_elem) -> NfAbsOrdFracIdl
Creates the principal fractional ideal $(a)$ of $\mathcal O$.
fractional_ideal
— Methodfractional_ideal(O::NfAbsOrd, a::NfAbsOrdElem) -> NfAbsOrdFracIdl
Creates the principal fractional ideal $(a)$ of $\mathcal O$.
inv
— Method inv(a::LocElem{T}, checked::Bool = true) where {T <: RingElem}
Returns the inverse element of $a$ if $a$ is a unit. If 'checked = false' the invertibility of $a$ is not checked and the corresponding inverse element of the Fraction Field is returned.
inv(A::NfAbsOrdIdl) -> NfOrdFracIdl
Computes the inverse of $A$, that is, the fractional ideal $B$ such that $AB = \mathcal O_K$.
Arithmetic
All the normal operations are provided as well.
inv
— Method inv(a::LocElem{T}, checked::Bool = true) where {T <: RingElem}
Returns the inverse element of $a$ if $a$ is a unit. If 'checked = false' the invertibility of $a$ is not checked and the corresponding inverse element of the Fraction Field is returned.
inv(A::NfAbsOrdFracIdl) -> NfAbsOrdFracIdl
Returns the fractional ideal $B$ such that $AB = \mathcal O$.
integral_split
— Methodintegral_split(A::NfAbsOrdFracIdl) -> NfAbsOrdIdl, NfAbsOrdIdl
Computes the unique coprime integral ideals $N$ and $D$ s.th. $A = ND^{-1}$
numerator
— Methodnumerator(a::NfRelOrdFracIdl) -> NfRelOrdIdl
Returns the ideal $d*a$ where $d$ is the denominator of $a$.
denominator
— Methoddenominator(a::NfRelOrdFracIdl) -> ZZRingElem
Returns the smallest positive integer $d$ such that $da$ is contained in the order of $a$.
Miscaellenous
order
— Methodorder(a::NfAbsOrdFracIdl) -> NfAbsOrd
The order that was used to define the ideal $a$.
basis_matrix
— Methodbasis_matrix(I::NfAbsOrdFracIdl) -> FakeFmpqMat
Returns the basis matrix of $I$ with respect to the basis of the order.
basis_mat_inv
— Methodbasis_mat_inv(I::NfAbsOrdFracIdl) -> FakeFmpqMat
Returns the inverse of the basis matrix of $I$.
basis_mat_inv(A::GenOrdIdl) -> FakeFracFldMat
Return the inverse of the basis matrix of $A$.
basis
— Methodbasis(I::NfAbsOrdFracIdl) -> Vector{nf_elem}
Returns the $\mathbf Z$-basis of $I$.
norm
— Methodnorm(I::NfAbsOrdFracIdl) -> QQFieldElem
Returns the norm of $I$.
norm(a::NfRelOrdIdl) -> NfOrdIdl
Returns the norm of $a$.
norm(a::NfRelOrdFracIdl{T, S}) -> S
Returns the norm of $a$.
norm(a::AlgAssAbsOrdIdl, O::AlgAssAbsOrd; copy::Bool = true) -> QQFieldElem
Returns the norm of $a$ considered as an (possibly fractional) ideal of $O$.
norm(a::AlgAssRelOrdIdl{S, T, U}, O::AlgAssRelOrd{S, T, U}; copy::Bool = true)
where { S, T, U } -> T
Returns the norm of $a$ considered as an (possibly fractional) ideal of $O$.