查询词典 cofinality

The cofinality of any ordinal ''α'' is a regular ordinal, i.e. the cofinality of the cofinality of ''α'' is the same as the cofinality of ''α''.

任何序数''α''的共尾性是正规序数，就是说''α''的共尾性的共尾性同于''α''的共尾性。

The cofinality of a set of ordinals or any other well ordered set is the cofinality of the order type of that set.

序数或任何其他良序集合的集合的共尾性是这个集合的序类型的共尾性。

For example, the cofinality of ω is ω, because the sequence ω·''m''( where ''m'' ranges over the natural numbers ) tends to ω; but, more generally, any countable limit ordinal has cofinality ω.

例如，ω的共尾性是ω，因为序列ω·''m''(这里的''m''取值于自然数之上)趋向于ω；但是，更加一般的说，任何可数极限序数都有共尾性ω。

So the cofinality operation is

所以共尾性运算是

All superclasses of closed unbounded classes are stationary and stationary classes are unbounded, but there are stationary classes which are not closed and there are stationary classes which have no closed unbounded subclass ( such as the class of all limit ordinals with countable cofinality ).

所有闭合无界类的超类是固定的并且固定类是无界的，但是有着不闭合的固定类并且有着没有闭合无界子类的固定类(比如带有可数共尾性的所有极限序数的类)。

In the days of sailing vessels the crew were afraid they would be becalmed on the ocean.

在使用帆船的时代，船员们担心他们会因为无风而无法在海洋上航行。

As long as foreign donors pay the PA's salary bill, few expect a new intifada.

只要外国继续为巴权力机构的薪水买单，希望发动新暴动的人便寥寥无几。