Undergrad About the existence of Hamel basis for vector spaces

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SUMMARY

The discussion centers on the existence of a Hamel basis for vector spaces, emphasizing that every vector space admits an algebraic (Hamel) basis if the Axiom of Choice (AC) is assumed. However, if AC is excluded, there are instances, such as the vector space ##\mathbb{R}_\mathbb{Q}##, where a Hamel basis cannot be explicitly constructed, leading to the conclusion that while every vector space theoretically has a Hamel basis, the proof relies on the acceptance of AC. The equivalence between the Axiom of Choice and the existence of a Hamel basis is established, highlighting the complexities involved in set theory without AC.

PREREQUISITES
  • Understanding of vector spaces and their properties
  • Familiarity with the Axiom of Choice (AC) and its implications
  • Knowledge of Zorn's Lemma and its role in proving the existence of bases
  • Basic concepts of set theory, particularly Zermelo-Fraenkel (ZF) set theory
NEXT STEPS
  • Explore the implications of the Axiom of Choice on set theory and vector spaces
  • Study Zorn's Lemma in detail and its applications in linear algebra
  • Investigate the properties of the vector space ##\mathbb{R}_\mathbb{Q}## and its basis
  • Examine the relationship between the Axiom of Choice and other mathematical concepts, such as Lebesgue measurability
USEFUL FOR

Mathematicians, particularly those specializing in linear algebra, set theory, and foundational mathematics, as well as students seeking to understand the implications of the Axiom of Choice on vector spaces.

  • #31
A well-formed formula (wff) is (syntactically) provable if and only if it is valid. This defines the relation between (Semantic) truth and (Syntactic) provability. I'm not aware of how the term 'hold' is used, by there are wff's in Sentence Logic that are contingent. And, yes, every provable statement in FOL os Sentence Logic is a Tautology; true in every model.
 
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  • #32
WWGD said:
A well-formed formula (wff) is (syntactically) provable if and only if it is valid. This defines the relation between (Semantic) truth and (Syntactic) provability. I'm not aware of how the term 'hold' is used, by there are wff's in Sentence Logic that are contingent. And, yes, every provable statement in FOL or Sentence Logic is a Tautology; true in every model.
Ok, a well-formed formula (wff) is (syntactically) provable if and only if it is valid since we're assuming a sound and (semantically) complete logic system (like FOL or Sentential (or propositional) logic are).

What does it mean that in Sentential logic there are contingent wffs ?
 
  • #33
cianfa72 said:
Ok, a well-formed formula (wff) is (syntactically) provable if and only if it is valid since we're assuming a sound and (semantically) complete logic system (like FOL or Sentential (or propositional) logic are).

What does it mean that in Sentential logic there are contingent wffs ?
Statements that aren't tautologies, like ##A \rightarrow B ##, which is not true when A is true and B is false.
 

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