Aaron Levin, Michigan State University
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PDL C-401
In 2003, Bugeaud, Corvaja, and Zannier gave an (essentially sharp) upper bound for the greatest common divisor gcd(a^n-1,b^n-1), where a and b are fixed integers and n varies over the positive integers. In contrast to the elementary statement of their result, the proof required deep results from Diophantine approximation. I will discuss a higher-dimensional generalization of their result and some related problems, all centered around greatest common divisors.