7. Cantor's Theorem
This chapter discusses Cantor's theorem and the concept of cardinality in sets. It establishes that the cardinality of any set is strictly less than the cardinality of its power set, and provides various proofs, particularly using the diagonalization argument. The chapter concludes by revealing that there are infinitely many infinities, reflecting the nature of different cardinalities within infinite sets.
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What we have learnt
- Cantor's theorem states that the cardinality of a set is strictly less than its power set.
- The proof involves showing a contradiction through the diagonalization argument.
- There are infinitely many different sizes of infinity, creating a hierarchy of cardinalities.
Key Concepts
- -- Cantor's Theorem
- A theorem stating that for any set A, the cardinality of A is strictly less than the cardinality of its power set P(A).
- -- Cardinality
- A measure of the 'number of elements' in a set, used to compare the sizes of different sets.
- -- Diagonalization Argument
- A proof technique used to show that certain sets are uncountable by constructing a subset that cannot be mapped to an existing set.
- -- Power Set
- The set of all subsets of a given set A, denoted as P(A).
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