Galois Theory

Description: Test your understanding of Galois Theory, a branch of abstract algebra that studies field extensions and their automorphisms.
Number of Questions: 14
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Tags: galois theory field extensions automorphisms solvability irreducibility
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What is the fundamental theorem of Galois theory?

  1. Every finite extension of a field is normal.

  2. Every finite normal extension of a field is separable.

  3. The Galois group of a finite extension of a field is isomorphic to the group of automorphisms of the extension.

  4. All of the above.


Correct Option: D
Explanation:

The fundamental theorem of Galois theory is a powerful result that connects field extensions and their automorphisms.

What is a Galois extension?

  1. A finite extension of a field that is normal and separable.

  2. A finite extension of a field that is normal but not necessarily separable.

  3. A finite extension of a field that is separable but not necessarily normal.

  4. A finite extension of a field that is neither normal nor separable.


Correct Option: A
Explanation:

A Galois extension is a finite extension of a field that is both normal and separable.

What is the Galois group of a field extension?

  1. The group of all automorphisms of the extension.

  2. The group of all automorphisms of the extension that fix the base field.

  3. The group of all automorphisms of the extension that fix the base field and its subfields.

  4. The group of all automorphisms of the extension that fix the base field and its subfields and their subfields.


Correct Option: A
Explanation:

The Galois group of a field extension is the group of all automorphisms of the extension.

What is the order of the Galois group of a Galois extension?

  1. The degree of the extension.

  2. The number of elements in the extension.

  3. The number of automorphisms of the extension.

  4. The number of automorphisms of the extension that fix the base field.


Correct Option: A
Explanation:

The order of the Galois group of a Galois extension is the degree of the extension.

What is the solvability of a polynomial?

  1. The ability to express its roots in terms of radicals.

  2. The ability to express its roots in terms of elementary functions.

  3. The ability to express its roots in terms of algebraic functions.

  4. The ability to express its roots in terms of transcendental functions.


Correct Option: A
Explanation:

The solvability of a polynomial is the ability to express its roots in terms of radicals.

What is the Galois group of a polynomial?

  1. The group of all automorphisms of the splitting field of the polynomial.

  2. The group of all automorphisms of the splitting field of the polynomial that fix the base field.

  3. The group of all automorphisms of the splitting field of the polynomial that fix the base field and its subfields.

  4. The group of all automorphisms of the splitting field of the polynomial that fix the base field and its subfields and their subfields.


Correct Option: A
Explanation:

The Galois group of a polynomial is the group of all automorphisms of the splitting field of the polynomial.

What is the irreducibility of a polynomial?

  1. The inability to factor the polynomial into a product of two non-constant polynomials.

  2. The inability to factor the polynomial into a product of two non-linear polynomials.

  3. The inability to factor the polynomial into a product of two non-quadratic polynomials.

  4. The inability to factor the polynomial into a product of two non-cubic polynomials.


Correct Option: A
Explanation:

The irreducibility of a polynomial is the inability to factor the polynomial into a product of two non-constant polynomials.

What is the Eisenstein criterion for irreducibility?

  1. If a polynomial has an integer coefficient, a leading coefficient of 1, and a constant term that is not divisible by the leading coefficient, then it is irreducible over the integers.

  2. If a polynomial has a rational coefficient, a leading coefficient of 1, and a constant term that is not divisible by the leading coefficient, then it is irreducible over the rationals.

  3. If a polynomial has a real coefficient, a leading coefficient of 1, and a constant term that is not divisible by the leading coefficient, then it is irreducible over the reals.

  4. If a polynomial has a complex coefficient, a leading coefficient of 1, and a constant term that is not divisible by the leading coefficient, then it is irreducible over the complex numbers.


Correct Option: A
Explanation:

The Eisenstein criterion for irreducibility is a test for determining whether a polynomial with integer coefficients is irreducible over the integers.

What is the primitive element theorem?

  1. Every finite field extension has a primitive element.

  2. Every finite Galois extension has a primitive element.

  3. Every finite normal extension has a primitive element.

  4. Every finite separable extension has a primitive element.


Correct Option: B
Explanation:

The primitive element theorem states that every finite Galois extension has a primitive element.

What is the Kronecker-Weber theorem?

  1. Every abelian extension of the rationals is contained in a cyclotomic field.

  2. Every abelian extension of the rationals is contained in a quadratic field.

  3. Every abelian extension of the rationals is contained in a cubic field.

  4. Every abelian extension of the rationals is contained in a quartic field.


Correct Option: A
Explanation:

The Kronecker-Weber theorem states that every abelian extension of the rationals is contained in a cyclotomic field.

What is the Hilbert irreducibility theorem?

  1. Every polynomial with integer coefficients that is irreducible over the rationals is also irreducible over the integers.

  2. Every polynomial with rational coefficients that is irreducible over the rationals is also irreducible over the integers.

  3. Every polynomial with real coefficients that is irreducible over the rationals is also irreducible over the integers.

  4. Every polynomial with complex coefficients that is irreducible over the rationals is also irreducible over the integers.


Correct Option: A
Explanation:

The Hilbert irreducibility theorem states that every polynomial with integer coefficients that is irreducible over the rationals is also irreducible over the integers.

What is the Artin-Whaples theorem?

  1. Every finite Galois extension of the rationals is solvable.

  2. Every finite Galois extension of the rationals is solvable by radicals.

  3. Every finite Galois extension of the rationals is solvable by elementary functions.

  4. Every finite Galois extension of the rationals is solvable by algebraic functions.


Correct Option: A
Explanation:

The Artin-Whaples theorem states that every finite Galois extension of the rationals is solvable.

What is the Galois correspondence?

  1. A bijection between the subgroups of the Galois group of a Galois extension and the subfields of the extension.

  2. A bijection between the subgroups of the Galois group of a Galois extension and the quotient fields of the extension.

  3. A bijection between the subgroups of the Galois group of a Galois extension and the subrings of the extension.

  4. A bijection between the subgroups of the Galois group of a Galois extension and the ideals of the extension.


Correct Option: A
Explanation:

The Galois correspondence is a bijection between the subgroups of the Galois group of a Galois extension and the subfields of the extension.

What is the inverse Galois problem?

  1. Given a group, construct a Galois extension whose Galois group is isomorphic to the given group.

  2. Given a group, construct a field extension whose Galois group is isomorphic to the given group.

  3. Given a group, construct a ring extension whose Galois group is isomorphic to the given group.

  4. Given a group, construct a module extension whose Galois group is isomorphic to the given group.


Correct Option: A
Explanation:

The inverse Galois problem is the problem of constructing a Galois extension whose Galois group is isomorphic to a given group.

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