Sets of homomorphisms between number fields#
- class sage.rings.number_field.homset.CyclotomicFieldHomset(R, S, category=None)[source]#
Bases:
NumberFieldHomset
Set of homomorphisms with domain a given cyclotomic field.
EXAMPLES:
sage: End(CyclotomicField(16)) Automorphism group of Cyclotomic Field of order 16 and degree 8
>>> from sage.all import * >>> End(CyclotomicField(Integer(16))) Automorphism group of Cyclotomic Field of order 16 and degree 8
- Element[source]#
alias of
CyclotomicFieldHomomorphism_im_gens
- list()[source]#
Return a list of all the elements of
self
(for which the domain is a cyclotomic field).EXAMPLES:
sage: K.<z> = CyclotomicField(12) sage: G = End(K); G Automorphism group of Cyclotomic Field of order 12 and degree 4 sage: [g(z) for g in G] [z, z^3 - z, -z, -z^3 + z] sage: x = polygen(ZZ, 'x') sage: L.<a, b> = NumberField([x^2 + x + 1, x^4 + 1]) sage: L Number Field in a with defining polynomial x^2 + x + 1 over its base field sage: Hom(CyclotomicField(12), L)[3] Ring morphism: From: Cyclotomic Field of order 12 and degree 4 To: Number Field in a with defining polynomial x^2 + x + 1 over its base field Defn: zeta12 |--> -b^2*a sage: list(Hom(CyclotomicField(5), K)) [] sage: Hom(CyclotomicField(11), L).list() []
>>> from sage.all import * >>> K = CyclotomicField(Integer(12), names=('z',)); (z,) = K._first_ngens(1) >>> G = End(K); G Automorphism group of Cyclotomic Field of order 12 and degree 4 >>> [g(z) for g in G] [z, z^3 - z, -z, -z^3 + z] >>> x = polygen(ZZ, 'x') >>> L = NumberField([x**Integer(2) + x + Integer(1), x**Integer(4) + Integer(1)], names=('a', 'b',)); (a, b,) = L._first_ngens(2) >>> L Number Field in a with defining polynomial x^2 + x + 1 over its base field >>> Hom(CyclotomicField(Integer(12)), L)[Integer(3)] Ring morphism: From: Cyclotomic Field of order 12 and degree 4 To: Number Field in a with defining polynomial x^2 + x + 1 over its base field Defn: zeta12 |--> -b^2*a >>> list(Hom(CyclotomicField(Integer(5)), K)) [] >>> Hom(CyclotomicField(Integer(11)), L).list() []
- class sage.rings.number_field.homset.NumberFieldHomset(R, S, category=None)[source]#
Bases:
RingHomset_generic
Set of homomorphisms with domain a given number field.
- Element[source]#
alias of
NumberFieldHomomorphism_im_gens
- cardinality()[source]#
Return the order of this set of field homomorphism.
EXAMPLES:
sage: x = polygen(ZZ, 'x') sage: k.<a> = NumberField(x^2 + 1) sage: End(k) Automorphism group of Number Field in a with defining polynomial x^2 + 1 sage: End(k).order() 2 sage: k.<a> = NumberField(x^3 + 2) sage: End(k).order() 1 sage: K.<a> = NumberField([x^3 + 2, x^2 + x + 1]) sage: End(K).order() 6
>>> from sage.all import * >>> x = polygen(ZZ, 'x') >>> k = NumberField(x**Integer(2) + Integer(1), names=('a',)); (a,) = k._first_ngens(1) >>> End(k) Automorphism group of Number Field in a with defining polynomial x^2 + 1 >>> End(k).order() 2 >>> k = NumberField(x**Integer(3) + Integer(2), names=('a',)); (a,) = k._first_ngens(1) >>> End(k).order() 1 >>> K = NumberField([x**Integer(3) + Integer(2), x**Integer(2) + x + Integer(1)], names=('a',)); (a,) = K._first_ngens(1) >>> End(K).order() 6
- list()[source]#
Return a list of all the elements of
self
.EXAMPLES:
sage: x = polygen(ZZ, 'x') sage: K.<a> = NumberField(x^3 - 3*x + 1) sage: End(K).list() [ Ring endomorphism of Number Field in a with defining polynomial x^3 - 3*x + 1 Defn: a |--> a, Ring endomorphism of Number Field in a with defining polynomial x^3 - 3*x + 1 Defn: a |--> a^2 - 2, Ring endomorphism of Number Field in a with defining polynomial x^3 - 3*x + 1 Defn: a |--> -a^2 - a + 2 ] sage: Hom(K, CyclotomicField(9))[0] # indirect doctest Ring morphism: From: Number Field in a with defining polynomial x^3 - 3*x + 1 To: Cyclotomic Field of order 9 and degree 6 Defn: a |--> -zeta9^4 + zeta9^2 - zeta9
>>> from sage.all import * >>> x = polygen(ZZ, 'x') >>> K = NumberField(x**Integer(3) - Integer(3)*x + Integer(1), names=('a',)); (a,) = K._first_ngens(1) >>> End(K).list() [ Ring endomorphism of Number Field in a with defining polynomial x^3 - 3*x + 1 Defn: a |--> a, Ring endomorphism of Number Field in a with defining polynomial x^3 - 3*x + 1 Defn: a |--> a^2 - 2, Ring endomorphism of Number Field in a with defining polynomial x^3 - 3*x + 1 Defn: a |--> -a^2 - a + 2 ] >>> Hom(K, CyclotomicField(Integer(9)))[Integer(0)] # indirect doctest Ring morphism: From: Number Field in a with defining polynomial x^3 - 3*x + 1 To: Cyclotomic Field of order 9 and degree 6 Defn: a |--> -zeta9^4 + zeta9^2 - zeta9
An example where the codomain is a relative extension:
sage: K.<a> = NumberField(x^3 - 2) sage: L.<b> = K.extension(x^2 + 3) sage: Hom(K, L).list() [ Ring morphism: From: Number Field in a with defining polynomial x^3 - 2 To: Number Field in b with defining polynomial x^2 + 3 over its base field Defn: a |--> a, Ring morphism: From: Number Field in a with defining polynomial x^3 - 2 To: Number Field in b with defining polynomial x^2 + 3 over its base field Defn: a |--> -1/2*a*b - 1/2*a, Ring morphism: From: Number Field in a with defining polynomial x^3 - 2 To: Number Field in b with defining polynomial x^2 + 3 over its base field Defn: a |--> 1/2*a*b - 1/2*a ]
>>> from sage.all import * >>> K = NumberField(x**Integer(3) - Integer(2), names=('a',)); (a,) = K._first_ngens(1) >>> L = K.extension(x**Integer(2) + Integer(3), names=('b',)); (b,) = L._first_ngens(1) >>> Hom(K, L).list() [ Ring morphism: From: Number Field in a with defining polynomial x^3 - 2 To: Number Field in b with defining polynomial x^2 + 3 over its base field Defn: a |--> a, Ring morphism: From: Number Field in a with defining polynomial x^3 - 2 To: Number Field in b with defining polynomial x^2 + 3 over its base field Defn: a |--> -1/2*a*b - 1/2*a, Ring morphism: From: Number Field in a with defining polynomial x^3 - 2 To: Number Field in b with defining polynomial x^2 + 3 over its base field Defn: a |--> 1/2*a*b - 1/2*a ]
- order()[source]#
Return the order of this set of field homomorphism.
EXAMPLES:
sage: x = polygen(ZZ, 'x') sage: k.<a> = NumberField(x^2 + 1) sage: End(k) Automorphism group of Number Field in a with defining polynomial x^2 + 1 sage: End(k).order() 2 sage: k.<a> = NumberField(x^3 + 2) sage: End(k).order() 1 sage: K.<a> = NumberField([x^3 + 2, x^2 + x + 1]) sage: End(K).order() 6
>>> from sage.all import * >>> x = polygen(ZZ, 'x') >>> k = NumberField(x**Integer(2) + Integer(1), names=('a',)); (a,) = k._first_ngens(1) >>> End(k) Automorphism group of Number Field in a with defining polynomial x^2 + 1 >>> End(k).order() 2 >>> k = NumberField(x**Integer(3) + Integer(2), names=('a',)); (a,) = k._first_ngens(1) >>> End(k).order() 1 >>> K = NumberField([x**Integer(3) + Integer(2), x**Integer(2) + x + Integer(1)], names=('a',)); (a,) = K._first_ngens(1) >>> End(K).order() 6
- class sage.rings.number_field.homset.RelativeNumberFieldHomset(R, S, category=None)[source]#
Bases:
NumberFieldHomset
Set of homomorphisms with domain a given relative number field.
EXAMPLES:
We construct a homomorphism from a relative field by giving the image of a generator:
sage: x = polygen(ZZ, 'x') sage: L.<cuberoot2, zeta3> = CyclotomicField(3).extension(x^3 - 2) sage: phi = L.hom([cuberoot2 * zeta3]); phi Relative number field endomorphism of Number Field in cuberoot2 with defining polynomial x^3 - 2 over its base field Defn: cuberoot2 |--> zeta3*cuberoot2 zeta3 |--> zeta3 sage: phi(cuberoot2 + zeta3) zeta3*cuberoot2 + zeta3
>>> from sage.all import * >>> x = polygen(ZZ, 'x') >>> L = CyclotomicField(Integer(3)).extension(x**Integer(3) - Integer(2), names=('cuberoot2', 'zeta3',)); (cuberoot2, zeta3,) = L._first_ngens(2) >>> phi = L.hom([cuberoot2 * zeta3]); phi Relative number field endomorphism of Number Field in cuberoot2 with defining polynomial x^3 - 2 over its base field Defn: cuberoot2 |--> zeta3*cuberoot2 zeta3 |--> zeta3 >>> phi(cuberoot2 + zeta3) zeta3*cuberoot2 + zeta3
In fact, this
phi
is a generator for the Kummer Galois group of this cyclic extension:sage: phi(phi(cuberoot2 + zeta3)) (-zeta3 - 1)*cuberoot2 + zeta3 sage: phi(phi(phi(cuberoot2 + zeta3))) cuberoot2 + zeta3
>>> from sage.all import * >>> phi(phi(cuberoot2 + zeta3)) (-zeta3 - 1)*cuberoot2 + zeta3 >>> phi(phi(phi(cuberoot2 + zeta3))) cuberoot2 + zeta3
- default_base_hom()[source]#
Pick an embedding of the base field of
self
into the codomain of this homset. This is done in an essentially arbitrary way.EXAMPLES:
sage: x = polygen(ZZ, 'x') sage: L.<a, b> = NumberField([x^3 - x + 1, x^2 + 23]) sage: M.<c> = NumberField(x^4 + 80*x^2 + 36) sage: Hom(L, M).default_base_hom() Ring morphism: From: Number Field in b with defining polynomial x^2 + 23 To: Number Field in c with defining polynomial x^4 + 80*x^2 + 36 Defn: b |--> 1/12*c^3 + 43/6*c
>>> from sage.all import * >>> x = polygen(ZZ, 'x') >>> L = NumberField([x**Integer(3) - x + Integer(1), x**Integer(2) + Integer(23)], names=('a', 'b',)); (a, b,) = L._first_ngens(2) >>> M = NumberField(x**Integer(4) + Integer(80)*x**Integer(2) + Integer(36), names=('c',)); (c,) = M._first_ngens(1) >>> Hom(L, M).default_base_hom() Ring morphism: From: Number Field in b with defining polynomial x^2 + 23 To: Number Field in c with defining polynomial x^4 + 80*x^2 + 36 Defn: b |--> 1/12*c^3 + 43/6*c
- list()[source]#
Return a list of all the elements of
self
(for which the domain is a relative number field).EXAMPLES:
sage: x = polygen(ZZ, 'x') sage: K.<a, b> = NumberField([x^2 + x + 1, x^3 + 2]) sage: End(K).list() [ Relative number field endomorphism of Number Field in a with defining polynomial x^2 + x + 1 over its base field Defn: a |--> a b |--> b, ... Relative number field endomorphism of Number Field in a with defining polynomial x^2 + x + 1 over its base field Defn: a |--> a b |--> -b*a - b ]
>>> from sage.all import * >>> x = polygen(ZZ, 'x') >>> K = NumberField([x**Integer(2) + x + Integer(1), x**Integer(3) + Integer(2)], names=('a', 'b',)); (a, b,) = K._first_ngens(2) >>> End(K).list() [ Relative number field endomorphism of Number Field in a with defining polynomial x^2 + x + 1 over its base field Defn: a |--> a b |--> b, ... Relative number field endomorphism of Number Field in a with defining polynomial x^2 + x + 1 over its base field Defn: a |--> a b |--> -b*a - b ]
An example with an absolute codomain:
sage: x = polygen(ZZ, 'x') sage: K.<a, b> = NumberField([x^2 - 3, x^2 + 2]) sage: Hom(K, CyclotomicField(24, 'z')).list() [ Relative number field morphism: From: Number Field in a with defining polynomial x^2 - 3 over its base field To: Cyclotomic Field of order 24 and degree 8 Defn: a |--> z^6 - 2*z^2 b |--> -z^5 - z^3 + z, ... Relative number field morphism: From: Number Field in a with defining polynomial x^2 - 3 over its base field To: Cyclotomic Field of order 24 and degree 8 Defn: a |--> -z^6 + 2*z^2 b |--> z^5 + z^3 - z ]
>>> from sage.all import * >>> x = polygen(ZZ, 'x') >>> K = NumberField([x**Integer(2) - Integer(3), x**Integer(2) + Integer(2)], names=('a', 'b',)); (a, b,) = K._first_ngens(2) >>> Hom(K, CyclotomicField(Integer(24), 'z')).list() [ Relative number field morphism: From: Number Field in a with defining polynomial x^2 - 3 over its base field To: Cyclotomic Field of order 24 and degree 8 Defn: a |--> z^6 - 2*z^2 b |--> -z^5 - z^3 + z, ... Relative number field morphism: From: Number Field in a with defining polynomial x^2 - 3 over its base field To: Cyclotomic Field of order 24 and degree 8 Defn: a |--> -z^6 + 2*z^2 b |--> z^5 + z^3 - z ]