Large cardinals

इस पर आधारित

24 अनिवार्य पूर्वापेक्षाएँ (बिल्कुल नीचे तक)

आप सीखेंगे

• Define inaccessible and measurable cardinals and show that V_κ satisfies ZFC when κ is inaccessible.
• Explain why ZFC cannot prove that an inaccessible cardinal exists (if ZFC is consistent), and what 'consistency strength' means.
• Describe how measurable cardinals correspond to non-trivial elementary embeddings j : V → M.

परिभाषा

• κ is (strongly) inaccessible if it is uncountable, regular, and 2^λ < κ for every λ < κ.
• κ is measurable if there is a κ-complete non-principal ultrafilter on κ.
• A theory T has at least the consistency strength of S if the consistency of T implies the consistency of S, provably in a weak base theory.

प्रमेय

• If κ is inaccessible then V_κ is a model of ZFC.
• Scott (1961): if a measurable cardinal exists, then V ≠ L.
• Every measurable cardinal is inaccessible and is a limit of inaccessible cardinals.

आम भ्रांतियाँ

• Thinking large cardinals are merely very big numbers; their significance lies in consistency strength and their consequences, for instance for sets of reals.
• Assuming large-cardinal axioms are known to be consistent; their consistency cannot be proved in ZFC and rests on mathematical evidence and judgement.

वैकल्पिक खोजें

• Higher categories Grothendieck universes, which correspond to inaccessible cardinals, are a common way of handling size issues in category theory.
• ← ZFC: axiomatic set theory
• ← Ordinals and cardinals
• ← Gödel's incompleteness theorems
• ← Descriptive set theory

आगे पढ़ने के लिए

• Akihiro Kanamori, The Higher Infinite (1994)
• Thomas Jech, Set Theory (Third Millennium Edition) (2003)