Algebraic Closure, Embeddings, and Separability — Examples
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✓ 11 results · all verified · 11 also independently AI-judged
Every result on this page is machine-checked by a proof checker and read in full and owner-audited; the judge is an additional, independent cross-model AI review of the proofs; all 11 also cleared it.
1 · Prerequisites
Abstract Algebra
- Algebraic Closure, Embeddings, and Separability
- Algebraic Extensions, Extension Degree, and Finite Fields
- Binary Operations, Monoids, Groups and Subgroups
- Cosets, Index and Lagrange's Theorem
- Cyclic Groups and Direct Products
- Divisibility, Euclidean Domains, Principal Ideal Domains and Unique Factorisation
- Group Homomorphisms and the Isomorphism Theorems
- Ideals, Quotient Rings and the Isomorphism Theorems for Rings
- Normal Subgroups and Quotient Groups
- Polynomial Rings, the Division Algorithm and Roots
- Rings, Subrings, Integral Domains and Fields
- Simple Field Extensions and the Construction of the Complex Numbers
- Splitting Fields
- The Field of Fractions and Localisation
- The Fundamental Theorem of Finite Abelian Groups
Linear Algebra
Number Theory
Real Analysis
2 · Logical flowchart
3 · Items
Example
Assuming Choice, real algebraic numbers embed properly in an algebraic closure of ℚ
Example
Fₚ is the union of its finite subfields and is an infinite algebraic extension
Example
ℚ(³√2) has three embeddings into ℚ̄ but only one ℚ-automorphism
Example
ℚ(√2,√3) has four embeddings into ℚ̄
Example
xᵖ-t is irreducible and inseparable over Fₚ(t)
Counterexample
Fₚ(s,t)/Fₚ(sᵖ,tᵖ) has degree p², infinitely many intermediate fields, and no primitive element
Example
⋃_n≥0Fₚ(t^1/pⁿ) is an infinite perfect field of characteristic p
False statement
FALSE: every irreducible polynomial over a field is separable
False statement
FALSE: every finite extension satisfies [K:F]ₛ=[K:F]
False statement
FALSE: every algebraic extension is simple
False statement
FALSE: an algebraic closure is unique up to a unique base-field isomorphism
Sources
- P. L. Clark, Field Theory, Corollary 3.4
- J. S. Milne, Fields and Galois Theory, finite fields and algebraic closures
- P. L. Clark, Field Theory, Chapter 4
- J. S. Milne, Fields and Galois Theory, Chapters 2 to 6
- J. S. Milne, Fields and Galois Theory, Chapters 3 and 5
- P. L. Clark, Field Theory, Chapter 5
- J. S. Milne, Fields and Galois Theory, Chapter 6