Elements of bounded height in number fields#
Sage functions to list all elements of a given number field with height less than a specified bound.
AUTHORS:
John Doyle (2013): initial version
David Krumm (2013): initial version
TJ Combs (2018): added Doyle-Krumm algorithm - 4
Raghukul Raman (2018): added Doyle-Krumm algorithm - 4
REFERENCES:
[DK2013]
- sage.rings.number_field.bdd_height.bdd_height(K, height_bound, tolerance=0.01, precision=53)#
Compute all elements in the number field \(K\) which have relative multiplicative height at most
height_bound.The function can only be called for number fields \(K\) with positive unit rank. An error will occur if \(K\) is \(QQ\) or an imaginary quadratic field.
This algorithm computes 2 lists: L containing elements x in \(K\) such that H_k(x) <= B, and a list L’ containing elements x in \(K\) that, due to floating point issues, may be slightly larger then the bound. This can be controlled by lowering the tolerance.
In current implementation both lists (L,L’) are merged and returned in form of iterator.
ALGORITHM:
This is an implementation of the revised algorithm (Algorithm 4) in [DK2013].
INPUT:
height_bound– real numbertolerance– (default: 0.01) a rational number in (0,1]precision– (default: 53) positive integer
OUTPUT:
an iterator of number field elements
EXAMPLES:
There are no elements of negative height:
sage: from sage.rings.number_field.bdd_height import bdd_height sage: K.<g> = NumberField(x^5 - x + 7) sage: list(bdd_height(K,-3)) []
The only nonzero elements of height 1 are the roots of unity:
sage: from sage.rings.number_field.bdd_height import bdd_height sage: K.<g> = QuadraticField(3) sage: list(bdd_height(K,1)) [0, -1, 1]
sage: from sage.rings.number_field.bdd_height import bdd_height sage: K.<g> = QuadraticField(36865) sage: len(list(bdd_height(K,101))) # long time (4 s) 131
sage: from sage.rings.number_field.bdd_height import bdd_height sage: K.<g> = NumberField(x^6 + 2) sage: len(list(bdd_height(K,60))) # long time (5 s) 1899
sage: from sage.rings.number_field.bdd_height import bdd_height sage: K.<g> = NumberField(x^4 - x^3 - 3*x^2 + x + 1) sage: len(list(bdd_height(K,10))) 99
- sage.rings.number_field.bdd_height.bdd_height_iq(K, height_bound)#
Compute all elements in the imaginary quadratic field \(K\) which have relative multiplicative height at most
height_bound.The function will only be called with \(K\) an imaginary quadratic field.
If called with \(K\) not an imaginary quadratic, the function will likely yield incorrect output.
ALGORITHM:
This is an implementation of Algorithm 5 in [DK2013].
INPUT:
\(K\) – an imaginary quadratic number field
height_bound– a real number
OUTPUT:
an iterator of number field elements
EXAMPLES:
sage: from sage.rings.number_field.bdd_height import bdd_height_iq sage: K.<a> = NumberField(x^2 + 191) sage: for t in bdd_height_iq(K,8): ....: print(exp(2*t.global_height())) 1.00000000000000 1.00000000000000 1.00000000000000 4.00000000000000 4.00000000000000 4.00000000000000 4.00000000000000 8.00000000000000 8.00000000000000 8.00000000000000 8.00000000000000 8.00000000000000 8.00000000000000 8.00000000000000 8.00000000000000
There are 175 elements of height at most 10 in \(QQ(\sqrt(-3))\):
sage: from sage.rings.number_field.bdd_height import bdd_height_iq sage: K.<a> = NumberField(x^2 + 3) sage: len(list(bdd_height_iq(K,10))) 175
The only elements of multiplicative height 1 in a number field are 0 and the roots of unity:
sage: from sage.rings.number_field.bdd_height import bdd_height_iq sage: K.<a> = NumberField(x^2 + x + 1) sage: list(bdd_height_iq(K,1)) [0, a + 1, a, -1, -a - 1, -a, 1]
A number field has no elements of multiplicative height less than 1:
sage: from sage.rings.number_field.bdd_height import bdd_height_iq sage: K.<a> = NumberField(x^2 + 5) sage: list(bdd_height_iq(K,0.9)) []
- sage.rings.number_field.bdd_height.bdd_norm_pr_gens_iq(K, norm_list)#
Compute generators for all principal ideals in an imaginary quadratic field \(K\) whose norms are in
norm_list.The only keys for the output dictionary are integers n appearing in
norm_list.The function will only be called with \(K\) an imaginary quadratic field.
The function will return a dictionary for other number fields, but it may be incorrect.
INPUT:
\(K\) – an imaginary quadratic number field
norm_list– a list of positive integers
OUTPUT:
a dictionary of number field elements, keyed by norm
EXAMPLES:
In \(QQ(i)\), there is one principal ideal of norm 4, two principal ideals of norm 5, but no principal ideals of norm 7:
sage: from sage.rings.number_field.bdd_height import bdd_norm_pr_gens_iq sage: K.<g> = NumberField(x^2 + 1) sage: L = range(10) sage: bdd_pr_ideals = bdd_norm_pr_gens_iq(K, L) sage: bdd_pr_ideals[4] [2] sage: bdd_pr_ideals[5] [-g - 2, -g + 2] sage: bdd_pr_ideals[7] []
There are no ideals in the ring of integers with negative norm:
sage: from sage.rings.number_field.bdd_height import bdd_norm_pr_gens_iq sage: K.<g> = NumberField(x^2 + 10) sage: L = range(-5,-1) sage: bdd_pr_ideals = bdd_norm_pr_gens_iq(K,L) sage: bdd_pr_ideals {-5: [], -4: [], -3: [], -2: []}
Calling a key that is not in the input
norm_listraises a KeyError:sage: from sage.rings.number_field.bdd_height import bdd_norm_pr_gens_iq sage: K.<g> = NumberField(x^2 + 20) sage: L = range(100) sage: bdd_pr_ideals = bdd_norm_pr_gens_iq(K, L) sage: bdd_pr_ideals[100] Traceback (most recent call last): ... KeyError: 100
- sage.rings.number_field.bdd_height.bdd_norm_pr_ideal_gens(K, norm_list)#
Compute generators for all principal ideals in a number field \(K\) whose norms are in
norm_list.INPUT:
\(K\) – a number field
norm_list– a list of positive integers
OUTPUT:
a dictionary of number field elements, keyed by norm
EXAMPLES:
There is only one principal ideal of norm 1, and it is generated by the element 1:
sage: from sage.rings.number_field.bdd_height import bdd_norm_pr_ideal_gens sage: K.<g> = QuadraticField(101) sage: bdd_norm_pr_ideal_gens(K, [1]) {1: [1]}
sage: from sage.rings.number_field.bdd_height import bdd_norm_pr_ideal_gens sage: K.<g> = QuadraticField(123) sage: bdd_norm_pr_ideal_gens(K, range(5)) {0: [0], 1: [1], 2: [g + 11], 3: [], 4: [2]}
sage: from sage.rings.number_field.bdd_height import bdd_norm_pr_ideal_gens sage: K.<g> = NumberField(x^5 - x + 19) sage: b = bdd_norm_pr_ideal_gens(K, range(30)) sage: key = ZZ(28) sage: b[key] [157*g^4 - 139*g^3 - 369*g^2 + 848*g + 158, g^4 + g^3 - g - 7]
- sage.rings.number_field.bdd_height.integer_points_in_polytope(matrix, interval_radius)#
Return the set of integer points in the polytope obtained by acting on a cube by a linear transformation.
Given an r-by-r matrix
matrixand a real numberinterval_radius, this function finds all integer lattice points in the polytope obtained by transforming the cube [-interval_radius,interval_radius]^r via the linear map induced bymatrix.INPUT:
matrix– a square matrix of real numbersinterval_radius– a real number
OUTPUT:
a list of tuples of integers
EXAMPLES:
Stretch the interval [-1,1] by a factor of 2 and find the integers in the resulting interval:
sage: from sage.rings.number_field.bdd_height import integer_points_in_polytope sage: m = matrix([2]) sage: r = 1 sage: integer_points_in_polytope(m,r) [(-2), (-1), (0), (1), (2)]
Integer points inside a parallelogram:
sage: from sage.rings.number_field.bdd_height import integer_points_in_polytope sage: m = matrix([[1, 2],[3, 4]]) sage: r = RealField()(1.3) sage: integer_points_in_polytope(m,r) [(-3, -7), (-2, -5), (-2, -4), (-1, -3), (-1, -2), (-1, -1), (0, -1), (0, 0), (0, 1), (1, 1), (1, 2), (1, 3), (2, 4), (2, 5), (3, 7)]
Integer points inside a parallelepiped:
sage: from sage.rings.number_field.bdd_height import integer_points_in_polytope sage: m = matrix([[1.2,3.7,0.2],[-5.3,-.43,3],[1.2,4.7,-2.1]]) sage: r = 2.2 sage: L = integer_points_in_polytope(m,r) sage: len(L) 4143
If
interval_radiusis 0, the output should include only the zero tuple:sage: from sage.rings.number_field.bdd_height import integer_points_in_polytope sage: m = matrix([[1,2,3,7],[4,5,6,2],[7,8,9,3],[0,3,4,5]]) sage: integer_points_in_polytope(m,0) [(0, 0, 0, 0)]