A difficult exercise
While proctoring the make-up exam for my class, I thought of an exercise related to my group theory posts on direct and free products that should cause even the more experienced mathematicians in the audience a bit of difficulty.
Consider four groups ,
,
, and
, and four homomorphisms:
Use these to construct two homomorphisms from to
, and show that they’re the same.
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This is mainly an expository blath, with occasional high-level excursions, humorous observations, rants, and musings. The main-line exposition should be accessible to the “Generally Interested Lay Audience”, as long as you trace the links back towards the basics. Check the sidebar for specific topics (under “Categories”).
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Is it time for a hint?
Where to find the second homomorphism?
One comes from each universal property. One from the product and one from the coproduct.