Projective Hierarchy
In the mathematical field of descriptive set theory, a subset of a Polish space is projective if it is for some positive integer . Here is
- if is analytic
- if the complement of, is
- if there is a Polish space and a subset such that is the projection of ; that is,
The choice of the Polish space in the third clause above is not very important; it could be replaced in the definition by a fixed uncountable Polish space, say Baire space or Cantor space or the real line.
Read more about Projective Hierarchy: Relationship To The Analytical Hierarchy
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“In the world of the celebrity, the hierarchy of publicity has replaced the hierarchy of descent and even of great wealth.”
—C. Wright Mills (1916–1962)