# Division rings¶

class sage.categories.division_rings.DivisionRings(base_category)

The category of division rings

A division ring (or skew field) is a not necessarily commutative ring where all non-zero elements have multiplicative inverses

EXAMPLES:

sage: DivisionRings()
Category of division rings
sage: DivisionRings().super_categories()
[Category of domains]

Commutative
class ElementMethods
Finite_extra_super_categories()

Return extraneous super categories for DivisionRings().Finite().

EXAMPLES:

Any field is a division ring:

sage: Fields().is_subcategory(DivisionRings())
True


This methods specifies that, by Weddeburn theorem, the reciprocal holds in the finite case: a finite division ring is commutative and thus a field:

sage: DivisionRings().Finite_extra_super_categories()
(Category of commutative magmas,)
sage: DivisionRings().Finite()
Category of finite enumerated fields


Warning

This is not implemented in DivisionRings.Finite.extra_super_categories because the categories of finite division rings and of finite fields coincide. See the section Deduction rules in the documentation of axioms.

class ParentMethods
extra_super_categories()

Return the Domains category.

This method specifies that a division ring has no zero divisors, i.e. is a domain.

sage: DivisionRings().extra_super_categories()