Radical of an element of a unique factorization normalization monoid #
This file defines a radical of an element a
of a unique factorization normalization
monoid, which is defined as a product of normalized prime factors of a
without duplication.
This is different from the radical of an ideal.
Main declarations #
radical
: The radical of an elementa
in a unique factorization monoid is the product of its prime factors.radical_eq_of_associated
: Ifa
andb
are associates, i.e.a * u = b
for some unitu
, thenradical a = radical b
.radical_unit_mul
: Multiplying unit does not change the radical.radical_dvd_self
:radical a
dividesa
.radical_pow
:radical (a ^ n) = radical a
for anyn ≥ 1
radical_of_prime
: Radical of a prime element is equal to its normalizationradical_pow_of_prime
: Radical of a power of prime element is equal to its normalizationradical_mul
: Radical is multiplicative for two relatively prime elements.radical_prod
: Radical is multiplicative for finitely many relatively prime elements.
For unique factorization domains #
For Euclidean domains #
EuclideanDomain.divRadical
: For an elementa
in an Euclidean domain,a / radical a
.EuclideanDomain.divRadical_mul
:divRadical
of a product is the product ofdivRadical
s.IsCoprime.divRadical
:divRadical
of coprime elements are coprime.
For natural numbers #
UniqueFactorizationMonoid.primeFactors_eq_natPrimeFactors
: The prime factors of a natural number are the same as the prime factors defined inNat.primeFactors
.Nat.radical_le_self
: The radical of a natural number is less than or equal to the number itself.Nat.two_le_radical
: If a natural number is at least 2, then its radical is at least 2.
TODO #
The finite set of prime factors of an element in a unique factorization monoid.
Equations
Instances For
If x
is a unit, then the finset of prime factors of x
is empty.
The converse is true with a nonzero assumption, see normalizedFactors_eq_zero_iff
.
The finset of prime factors of x
is empty if and only if x
is a unit.
The converse is true without the nonzero assumption, see primeFactors_of_isUnit
.
Relatively prime elements have disjoint prime factors (as finsets).
Radical of an element a
in a unique factorization monoid is the product of
the prime factors of a
.
Equations
Instances For
Alias of UniqueFactorizationMonoid.radical_zero
.
Alias of UniqueFactorizationMonoid.radical_one
.
If a
is a radical element, then it divides its radical.
An irreducible a
divides the radical of b
if and only if it divides b
itself.
Note this generalises to radical elements a
, see UniqueFactorizationMonoid.dvd_radical_iff
.
If a
divides b
, then the radical of a
divides the radical of b
. The theorem requires
that b ≠ 0
, since radical 0 = 1
but a ∣ 0
holds for every a
.
If a
is a radical element, then a
divides the radical of b
if and only if it divides b
.
Note the forward implication holds without the b ≠ 0
assumption via radical_dvd_self
.
Radical is multiplicative for relatively prime elements.
Theorems for UFDs
Coprime elements have disjoint prime factors (as multisets).
Coprime elements have disjoint prime factors (as finsets).
Radical is multiplicative for coprime elements.
Division of an element by its radical in an Euclidean domain.