Main Definitions
If A is an infinite set of regular cardinals, D is an ultrafilter on A, then we let denote the cofinality of the ordered set of functions where the ordering is defined as follows. if . pcf(A) is the set of cofinalities that occur if we consider all ultrafilters on A, that is,
Read more about this topic: PCF Theory
Famous quotes containing the words main and/or definitions:
“But the main things about a man are his eyes and his feet. He should be able to see the world and go after it.”
—Alfred Döblin (1878–1957)
“The loosening, for some people, of rigid role definitions for men and women has shown that dads can be great at calming babies—if they take the time and make the effort to learn how. It’s that time and effort that not only teaches the dad how to calm the babies, but also turns him into a parent, just as the time and effort the mother puts into the babies turns her into a parent.”
—Pamela Patrick Novotny (20th century)