Abstract Algebra Test 2 True/False
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Questions and Answers

Every permutation is a one to one function.

True

Every function is a permutation if and only if it is one to one.

False

Every function from a finite set onto itself must be one to one.

True

Every group G is isomorphic to a subgroup of S sub G.

<p>True</p> Signup and view all the answers

Every subgroup of an abelian group is abelian.

<p>True</p> Signup and view all the answers

Every element of a group generates a cyclic subgroup of the group.

<p>True</p> Signup and view all the answers

The symmetric group S10 has 10 elements.

<p>False</p> Signup and view all the answers

The symmetric group S3 is cyclic.

<p>False</p> Signup and view all the answers

Sn is not cyclic for any n.

<p>False</p> Signup and view all the answers

Every group is isomorphic to some group of permutations.

<p>True</p> Signup and view all the answers

Every permutation is a cycle.

<p>False</p> Signup and view all the answers

Every cycle is a permutation.

<p>True</p> Signup and view all the answers

Every nontrivial subgroup H of S9 containing some odd permutation contains a transposition.

<p>False</p> Signup and view all the answers

A5 has 120 elements.

<p>False</p> Signup and view all the answers

Sn is not cyclic for any n greater than or equal to one.

<p>False</p> Signup and view all the answers

A3 is a commutative group.

<p>True</p> Signup and view all the answers

S7 is isomorphic to the subgroup of all those elements of S8 that leave the number 8 fixed.

<p>True</p> Signup and view all the answers

S7 is isomorphic to the subgroup of all those elements of S8 that leave the number 5 fixed.

<p>True</p> Signup and view all the answers

The odd permutations in S8 form a subgroup of S8.

<p>False</p> Signup and view all the answers

Every subgroup of every group has left cosets.

<p>True</p> Signup and view all the answers

The number of left cosets of a subgroup of a finite group divides the order of the group.

<p>True</p> Signup and view all the answers

Every group of prime order is abelian.

<p>True</p> Signup and view all the answers

One cannot have left cosets of a finite subgroup of an infinite group.

<p>False</p> Signup and view all the answers

A subgroup of a group is a left cosets of itself.

<p>True</p> Signup and view all the answers

Only subgroups of finite groups have left cosets.

<p>False</p> Signup and view all the answers

An is of index 2 in Sn for n>1.

<p>True</p> Signup and view all the answers

The theorem of Lagrange is a nice result.

<p>True</p> Signup and view all the answers

Every finite group contains an element of every order that divides the order of the group.

<p>False</p> Signup and view all the answers

Every finite cyclic group contains an element of every order that divides the order of the group.

<p>True</p> Signup and view all the answers

If G1 and G2 are any groups, then G1 x G2 is always isomorphic to G2 x G1.

<p>True</p> Signup and view all the answers

Computation in an external direct product of groups is easy if you know how to compute in each component group.

<p>True</p> Signup and view all the answers

Groups of finite order must be used to form an external direct product.

<p>False</p> Signup and view all the answers

A group of prime order could not be the internal direct product of two proper nontrivial subgroups.

<p>True</p> Signup and view all the answers

Z2 x Z4 is isomorphic to Z8.

<p>False</p> Signup and view all the answers

Z2 x Z4 is isomorphic to S8.

<p>False</p> Signup and view all the answers

Z3 x Z8 is isomorphic to S4.

<p>False</p> Signup and view all the answers

Every element in Z4 x Z8 has order 8.

<p>False</p> Signup and view all the answers

The order of Z12 x Z15 is 60.

<p>False</p> Signup and view all the answers

Zm x Zn has mn elements whether m and n are relatively prime or not.

<p>True</p> Signup and view all the answers

Every abelian group of prime order is cyclic.

<p>True</p> Signup and view all the answers

Every abelian group of prime power order is cyclic.

<p>False</p> Signup and view all the answers

Z8 is generated by {4, 6}.

<p>False</p> Signup and view all the answers

Z8 is generated by {4, 5, 6}.

<p>True</p> Signup and view all the answers

Any two finitely generated abelian groups with the same Betti number are isomorphic.

<p>False</p> Signup and view all the answers

Every abelian group of order divisible by 5 contains a cyclic subgroup of order 5.

<p>True</p> Signup and view all the answers

Every abelian group of order divisible by 4 contains a cyclic subgroup of order 4.

<p>False</p> Signup and view all the answers

Every abelian group of order divisible by 6 contains a cyclic subgroup of order 6.

<p>False</p> Signup and view all the answers

Study Notes

Permutations and Functions

  • Every permutation functions as a one-to-one function, maintaining unique mappings.
  • Not every function qualifies as a permutation even if it is one-to-one, thus functions can exist without being permutations.
  • A function that maps a finite set onto itself must be one-to-one to ensure every element is paired uniquely.

Groups and Subgroups

  • Every group ( G ) can be represented as a subgroup within some symmetric group ( S_n ).
  • All subgroups of abelian groups retain the property of being abelian.
  • Any group element generates a cyclic subgroup, confirming the cyclical nature of group elements.

Symmetric Groups

  • The symmetric group ( S_{10} ) does not contain 10 elements; it actually has ( 10! ) elements.
  • The symmetric group ( S_3 ) is not cyclic, as it cannot be generated by a single element.
  • For ( n \geq 1 ), ( S_n ) is not cyclic due to its structure.

Isomorphism in Groups

  • Every group is isomorphic to some group of permutations, indicating a structural similarity.
  • Not every permutation is a cycle; permutations can exhibit more complex structures.
  • Every cycle qualifies as a permutation, reinforcing the relationship between cycles and permutations.

Cosets and Subgroups

  • All subgroups possess left cosets, leading to a structured approach in group theory.
  • The number of left cosets of a subgroup within a finite group divides the order of that group, establishing a foundational principle in group theory.
  • Groups of prime order are inherently abelian.

Direct Products and Elements

  • An isomorphic relationship exists between ( G_1 \times G_2 ) and ( G_2 \times G_1 ) for any groups ( G_1 ) and ( G_2 ).
  • Working with external direct products is manageable if one understands computations within each component group.
  • Finite-order groups are not a prerequisite for forming an external direct product, which can also involve infinite groups.

Group Orders and Structure

  • A group of prime order cannot be expressed as the internal direct product of two proper nontrivial subgroups due to its simplicity.
  • The group ( \mathbb{Z}_2 \times \mathbb{Z}_4 ) does not isomorphically match ( \mathbb{Z}_8 ) or ( S_8 ).
  • The structure ( \mathbb{Z}_m \times \mathbb{Z}_n ) possesses ( mn ) elements regardless of whether ( m ) and ( n ) are relatively prime.

Cyclic Structures and Betti Numbers

  • Every abelian group of prime order exhibits cyclic behavior, leading to simple structures.
  • However, not all abelian groups of prime power order are cyclic, indicating complexity in higher powers.
  • The group ( \mathbb{Z}_8 ) can be generated by the elements {4, 5, 6}, emphasizing its cyclic nature.

Subgroups Based on Order

  • An abelian group whose order is divisible by 5 must contain at least one cyclic subgroup of order 5.
  • Conversely, groups whose order is divisible by 4 or 6 do not necessarily contain cyclic subgroups of those respective orders, highlighting exceptions in subgroup structures.

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Test your knowledge of Abstract Algebra with these true/false flashcards. Each card covers fundamental concepts such as permutations, functions, and groups. Challenge yourself and see how well you understand the intricate relationships in algebra!

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