Fields

class sage.categories.fields.Fields(s=None)

Bases: sage.categories.category_singleton.Category_singleton

The category of (commutative) fields, i.e. commutative rings where all non-zero elements have multiplicative inverses

EXAMPLES:

sage: K = Fields()
sage: K
Category of fields
sage: Fields().super_categories()
[Category of euclidean domains, Category of unique factorization domains, Category of division rings]

sage: K(IntegerRing())
Rational Field
sage: K(PolynomialRing(GF(3), 'x'))
Fraction Field of Univariate Polynomial Ring in x over
Finite Field of size 3
sage: K(RealField())
Real Field with 53 bits of precision

TESTS:

sage: TestSuite(Fields()).run()
class ElementMethods
gcd(other)

Greatest common divisor.

NOTE:

Since we are in a field and the greatest common divisor is only determined up to a unit, it is correct to either return zero or one. Note that fraction fields of unique factorization domains provide a more sophisticated gcd.

EXAMPLES:

sage: GF(5)(1).gcd(GF(5)(1))
1
sage: GF(5)(1).gcd(GF(5)(0))
1
sage: GF(5)(0).gcd(GF(5)(0))
0

For fields of characteristic zero (i.e., containing the integers as a sub-ring), evaluation in the integer ring is attempted. This is for backwards compatibility:

sage: gcd(6.0,8); gcd(6.0,8).parent()
2
Integer Ring

If this fails, we resort to the default we see above:

sage: gcd(6.0*CC.0,8*CC.0); gcd(6.0*CC.0,8*CC.0).parent()
1.00000000000000
Complex Field with 53 bits of precision

AUTHOR:

  • Simon King (2011-02): Trac ticket #10771
is_unit()

Returns True if self has a multiplicative inverse.

EXAMPLES:

sage: QQ(2).is_unit()
True
sage: QQ(0).is_unit()
False
lcm(other)

Least common multiple.

NOTE:

Since we are in a field and the least common multiple is only determined up to a unit, it is correct to either return zero or one. Note that fraction fields of unique factorization domains provide a more sophisticated lcm.

EXAMPLES:

sage: GF(2)(1).lcm(GF(2)(0))
0
sage: GF(2)(1).lcm(GF(2)(1))
1

If the field contains the integer ring, it is first attempted to compute the gcd there:

sage: lcm(15.0,12.0); lcm(15.0,12.0).parent()
60
Integer Ring

If this fails, we resort to the default we see above:

sage: lcm(6.0*CC.0,8*CC.0); lcm(6.0*CC.0,8*CC.0).parent()
1.00000000000000
Complex Field with 53 bits of precision
sage: lcm(15.2,12.0)
1.00000000000000

AUTHOR:

  • Simon King (2011-02): Trac ticket #10771
class Fields.ParentMethods
fraction_field()

Returns the fraction field of self, which is self.

EXAMPLES:

sage: QQ.fraction_field() is QQ
True
is_field(proof=True)

Returns True as self is a field.

EXAMPLES:

sage: QQ.is_field()
True
is_integral_domain()

Returns True, as fields are integral domains.

EXAMPLES:

sage: QQ.is_integral_domain()
True
is_integrally_closed()

Return True, as per IntegralDomain.is_integraly_closed(): for every field \(F\), \(F\) is its own field of fractions, hence every element of \(F\) is integral over \(F\).

EXAMPLES:

sage: QQ.is_integrally_closed()
True
sage: QQbar.is_integrally_closed()
True
sage: Z5 = GF(5); Z5
Finite Field of size 5
sage: Z5.is_integrally_closed()
True
Fields.super_categories()

EXAMPLES:

sage: Fields().super_categories()
[Category of euclidean domains, Category of unique factorization domains, Category of division rings]

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