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In abstract algebra, a partially ordered ring is a ring (''A'', +, · ), together with a ''compatible partial order'', i.e. a partial order on the underlying set ''A'' that is compatible with the ring operations in the sense that it satisfies: : implies and : and imply that for all . Various extensions of this definition exist that constrain the ring, the partial order, or both. For example, an Archimedean partially ordered ring is a partially ordered ring where 's partially ordered additive group is Archimedean. An ordered ring, also called a totally ordered ring, is a partially ordered ring where is additionally a total order.〔〔 An l-ring, or lattice-ordered ring, is a partially ordered ring where is additionally a lattice order. == Properties == The additive group of a partially ordered ring is always a partially ordered group. The set of non-negative elements of a partially ordered ring (the set of elements ''x'' for which , also called the positive cone of the ring) is closed under addition and multiplication, i.e., if ''P'' is the set of non-negative elements of a partially ordered ring, then , and . Furthermore, . The mapping of the compatible partial order on a ring ''A'' to the set of its non-negative elements is one-to-one;〔 that is, the compatible partial order uniquely determines the set of non-negative elements, and a set of elements uniquely determines the compatible partial order if one exists. If ''S'' is a subset of a ring ''A'', and: # # # # then the relation where iff defines a compatible partial order on ''A'' (''ie.'' is a partially ordered ring).〔 In any l-ring, the ''absolute value'' of an element ''x'' can be defined to be , where denotes the maximal element. For any ''x'' and ''y'', : holds. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Partially ordered ring」の詳細全文を読む スポンサード リンク
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