Homomorphism in Group Theory
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Questions and Answers

Which property is demonstrated by the function f when it is shown to be one-to-one?

  • f is an isomorphism between G1 and G2
  • f(a) = f(b) implies a = b (correct)
  • f(a) = e2 for some element e2
  • f(a-1) = [f(a)]-1 for all a in G1
  • According to the properties of a homomorphism, what must hold true for the identity elements e1 and e2?

  • f(e1) must be different from e2
  • e2 must be greater than e1
  • f(e1) must equal a for some a in G2
  • f(e1) must equal e2 (correct)
  • What can be concluded if a function f from G1 to G2 is determined to be a bijection?

  • It is not a subgroup of G2
  • It fails to satisfy homomorphism properties
  • Only some elements in G2 will have pre-images in G1
  • There exists an inverse function f^-1 from G2 to G1 (correct)
  • If H1 is a subgroup of G1 and f is a homomorphism, what can be concluded about H2 = f(H1)?

    <p>H2 is guaranteed to be a subgroup of G2</p> Signup and view all the answers

    In the context of the theorem for homomorphism, what is true about the inverse of an isomorphism?

    <p>It is also a homomorphism</p> Signup and view all the answers

    What defines a cyclic group?

    <p>Every element can be expressed as a fixed element raised to an integer power.</p> Signup and view all the answers

    In the context of cyclic groups, what can be said about the order of an element and its role as a generator?

    <p>The order of the generator must equal the order of the group.</p> Signup and view all the answers

    What characterizes an isomorphism?

    <p>It is a function that preserves group operation and is a bijection.</p> Signup and view all the answers

    Which statement about homomorphisms is true?

    <p>They preserve the group operation.</p> Signup and view all the answers

    Which of the following accurately describes a permutation group?

    <p>A group where elements are permutations of a nonempty set and the operation is function composition.</p> Signup and view all the answers

    For an infinite cyclic group, how many generators can exist?

    <p>Two.</p> Signup and view all the answers

    What is the relationship between groups in terms of isomorphism?

    <p>Isomorphic groups have the same number of elements and operations.</p> Signup and view all the answers

    Which of the following mappings can be shown as an isomorphism?

    <p>A mapping from positive real numbers under multiplication to real numbers under addition.</p> Signup and view all the answers

    What is true about the right coset of a subgroup H in G where a is an element of G?

    <p>It is the set {a * h | h ∈ H}</p> Signup and view all the answers

    How does an isomorphism relate to the structure of groups G1 and G2?

    <p>It is a function that preserves operations and is a bijection.</p> Signup and view all the answers

    According to Lagrange's Theorem, which statement is correct regarding the order of a subgroup H of G?

    <p>The order of H divides the order of G.</p> Signup and view all the answers

    If f is a homomorphism from group G1 to group G2, what can be inferred about the operation f(a) for any elements a in G1?

    <p>f(a * b) = f(a) * f(b) for any a, b in G1.</p> Signup and view all the answers

    What can be concluded if H1 is a subgroup of G1 and H2 = f(H1) under a homomorphism f?

    <p>H2 is a subgroup of G2.</p> Signup and view all the answers

    What defines the left coset of a subgroup H in G for an element a in G?

    <p>The set {a * h | h ∈ H}</p> Signup and view all the answers

    If f(a) represents the image of an element a under an isomorphism f, what is true about the inverse image?

    <p>f(f^{-1}(x)) = x for any x in G2.</p> Signup and view all the answers

    Given two groups G1 and G2 and a function f that is an isomorphism, which property must hold for all elements x, y in G2?

    <p>x * y = f(a) * f(b) for some a, b in G1.</p> Signup and view all the answers

    Study Notes

    One-to-one Functions and Isomorphisms

    • If a function f is one-to-one, it means that each element in the domain maps to a unique element in the codomain. This implies that no two distinct elements in the domain map to the same element in the codomain.

    Homomorphism Properties

    • For any homomorphism f from G1 to G2, the identity elements e1 and e2 satisfy the equation f(e1) = e2. In other words, the identity element in G1 maps to the identity element in G2.

    Bijections and Isomorphism

    • If a function f from G1 to G2 is a bijection, it means that it is both one-to-one and onto. This implies that every element in G2 has a unique preimage in G1. A bijective homomorphism is an isomorphism.
    • An isomorphism indicates that two groups have the same structure, even if they are composed of different elements.

    Subgroups and Homomorphisms

    • If H1 is a subgroup of G1 and f is a homomorphism, then H2 = f(H1) is a subgroup of G2. This means that the image of a subgroup under a homomorphism is also a subgroup.

    Inverse of an Isomorphism

    • The inverse of an isomorphism is also an isomorphism. This highlights the symmetry of the relationship between isomorphic groups.

    Cyclic Groups

    • A cyclic group is a group generated by a single element. This implies that all elements in the group can be expressed as powers of this generator.

    Order and Generators of Cyclic Groups

    • In a cyclic group, the order of an element is the number of times it must be multiplied by itself to get the identity element.
    • An element is known as a generator of a cyclic group if its order is equal to the order of the group.

    Isomorphism Definition

    • An isomorphism is a bijective homomorphism between two groups that preserves the operation. This means that the operation in the first group is mapped to the same operation in the second group.

    Homomorphism Properties

    • Homomorphisms always map the identity element of the first group to the identity element of the second group.

    Permutation Groups

    • A permutation group is a group whose elements are permutations of a set. Each element in the group corresponds to a unique way of rearranging the elements of the set.

    Generators in Infinite Cyclic Groups

    • An infinite cyclic group has infinitely many generators. This is because any element that has infinite order can be used as a generator.

    Isomorphism and Group Relationship

    • Isomorphic groups have the same structure and are essentially identical, despite possibly containing different elements. They behave in the same way under their respective operations.

    Example Isomorphisms

    • Mappings that preserve the operation and are bijective can be demonstrated as isomorphisms.

    Right Cosets

    • The right coset of a subgroup H in G for an element a in G is defined by the set of all elements of the form ha, where h is an element of H.

    Isomorphism and Group Structure

    • An isomorphism preserves the structure of groups G1 and G2. This means that they have the same algebraic properties such as associativity, identity elements, and inverses.

    Lagrange's Theorem and Subgroup Order

    • According to Lagrange's Theorem, the order of a subgroup H of a group G is always a divisor of the order of the group G.

    Homomorphism and Operation Preservation

    • If f is a homomorphism from group G1 to group G2, then for any elements a in G1, f(a) corresponds to the image of a under the mapping f, and the operation in G2 is preserved.

    Subgroup Images under Homomorphisms

    • If H1 is a subgroup of G1 and H2 = f(H1) under a homomorphism f, then H2 is also a subgroup of G2.

    Left Cosets

    • The left coset of a subgroup H in G for an element a in G is defined by the set of all elements of the form ah, where h is an element of H.

    Inverse Images under Isomorphisms

    • Under an isomorphism f, the inverse image of an element in G2 is unique and corresponds to the preimage of that element in G1.

    Isomorphism Property for Elements

    • If f is an isomorphism between groups G1 and G2, then for all elements x, y in G2, f(x) * f(y) = f(x * y). This reflects the preservation of the group operation under the isomorphism.

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    Description

    This quiz covers the concept of homomorphisms in group theory, exploring the definitions, examples, and theorems related to bijections and isomorphisms. Test your understanding of these crucial topics in abstract algebra and their implications in mathematics.

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