Abstract Algebra: Proving Normal Subgroup and Isomorphisms

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SUMMARY

The discussion centers on proving that the set N = {(a, e2) | a ∈ G1} is a normal subgroup of the group G = G1 × G2, where e2 is the identity element of G2. It establishes that N is isomorphic to G1 by demonstrating a one-to-one mapping that preserves group operations. Furthermore, it concludes that the quotient group G/N is isomorphic to G2, confirming the relationships between these algebraic structures through isomorphism and normal subgroup properties.

PREREQUISITES
  • Understanding of group theory concepts, specifically normal subgroups.
  • Familiarity with the definition and properties of isomorphisms in abstract algebra.
  • Knowledge of Cartesian products of groups and their operations.
  • Ability to construct and analyze group homomorphisms.
NEXT STEPS
  • Study the properties of normal subgroups in group theory.
  • Learn how to construct isomorphisms between groups in abstract algebra.
  • Explore the concept of quotient groups and their significance in group theory.
  • Investigate examples of group homomorphisms and their applications.
USEFUL FOR

Students of abstract algebra, mathematicians focusing on group theory, and anyone seeking to deepen their understanding of normal subgroups and isomorphisms in algebraic structures.

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Homework Statement


If G1, G2 are two groups and G = G1 times G2 = {(a,b) such that a is an element of G1, b is and element of G2}, where we define (a,b)(c,d) = (ac, bd),

(a) Show that N = {(a, e2) such that a is an element of G1}, where e2 is the unit element of G2, is a normal subgroup of G.

(b) Show that N is isomorphic to G1.

(c) Show that G/N is isomorphic to G2.


Homework Equations





The Attempt at a Solution


I did part (a) but I do not know how to begin parts (b) and (c)
 
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understand what is the definition for isomorphism (ie. need to find a 1-1 mapping from elements in N to elements in G1 such that the multiplication table is the same)
 
(b) write down the only conceivable map, and show it is an isomorphism

(c) see (b).
 

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