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Field Extension

Field Extension. The main study of Field Theory By: Valerie Toothman. What is a Field Extension?. Abstract Algebra Main object of study in field theory The General idea is to start with a field and construct a larger field that contains that original field and satisfies additional properties.

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Field Extension

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  1. Field Extension The main study of Field Theory By: Valerie Toothman

  2. What is a Field Extension? • Abstract Algebra • Main object of study in field theory • The General idea is to start with a field and construct a larger field that contains that original field and satisfies additional properties

  3. Definitions • Field - any set of elements that satisfies the field axioms

  4. Definitions • Subfield – Let L be a field and K be a subset of L. If the subset K of L is closed under the field operations inherited from L, then the subset K of L is a subfield of L. • Extension Field- If K is a subfield of L then the larger field L is said to be the extension field of K. • Notation – L/K (L over K) signifies that L is an extension field of K • Degree – The field L can be considered as a vector space over the field K. The dimension of this vector space is the degree denoted by [L:K]

  5. Example • The field of complex numbers C is an extension field of the field of real numbers R, and R in turn is an extension field of the field of rational numbers Q. • C- a+bi where a is real a number • R – includes all rational numbers • So we say C/R , R/Q, and C/Q

  6. Example • The set Q(√2) = {a + b√2 | a, b ∈ Q} is an extension field of Q. • Degree - √2 is a root of -2 which cannot be factored in Q[x] so we use {1, √2} as a basis. Therefore the degree is 2

  7. One Happy Family! Field Extension Algebraic Extension Finite Extension Galois Extension (Normal and Separable extension)

  8. Galois Theory • Galois theory- the study of algebraic extensions of a field. Algebraic extensions is a kind of field extension (L/K) that for every element of L is a root of some non-zero polynomial with coefficients in K. • In General it provides a connection between field theory and group theory by Roots of a given polynomial.

  9. The Theory of Field extensions (including Galois theory) • Leads to impossibility proofs of classical problems such as angle trisection and squaring the circle with a compass and straightedge

  10. Field Extensions The main study of Field Theory By: Valerie Toothman

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