Proving Cardinality of P(S) > S

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SUMMARY

The discussion centers on proving that the cardinality of the powerset P(S) is strictly greater than the cardinality of any set S. The user proposes a function T: S → P(S) defined by T(s) = {s}, establishing an injection and demonstrating that |S| ≤ |P(S)|. However, the user recognizes the need to prove strict inequality, indicating that no bijection exists between S and P(S). This highlights the fundamental concept of cardinality in set theory.

PREREQUISITES
  • Understanding of set theory concepts, particularly cardinality
  • Familiarity with injections and bijections in mathematical functions
  • Knowledge of powersets and their properties
  • Basic mathematical proof techniques
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  • Study Cantor's Theorem on the cardinality of powersets
  • Explore examples of injections and bijections in set theory
  • Learn about different sizes of infinity and their implications
  • Investigate the implications of cardinality in mathematical logic
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Mathematicians, students studying set theory, and anyone interested in understanding the foundations of cardinality and its implications in mathematics.

Mr Davis 97
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Homework Statement


Prove that the cardinality of ##P(S)## is greater than the cardinality of S, where S is any set.

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The Attempt at a Solution


It would seem that we could simply define ##T: S \rightarrow P(S)## such that ##T(s) = \{s \}##. This is clearly an injection, so ##|S| \le |P(S)|##. That seemed too easy though, so I feel like I am doing something wrong.
 
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Mr Davis 97 said:
That seemed too easy though, so I feel like I am doing something wrong.
I think you are asked to prove strict inequality of cardinalities.
 
Krylov said:
I think you are asked to prove strict inequality of cardinalities.
So I have to show that there exists no bijection between ##S## and its powerset?
 

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