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"Think Globally, Act Locally" Remember this slogan?
Is it possible to synthesis a global solution from a bunch of local ones? Consider
this question in the context of Diophantine Equations. The answer in the degree 1 case starts us on a
journey through modular arithmetic to Hensel's creation, the p-adic numbers -- enabling us to define
"locally". Historically, the answer in the degree 2 case, the Hasse-Minkowski Theorem, legitimized
the use of p-adic numbers. All this sets the stage for the degree 3 case where local solvability DOES
NOT imply global solvability. We will mention Selmer's beautiful example,
3x3+4y3+5z3 = 0 , but focus on Reichardt's example 2x2 =
1-17y4 . Elementary methods allow us to prove that this is locally solvable, but not
globally solvable. The only puzzle is "What is inherently global about the 'not globally solvable'
argument?"
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