If you ask Karl Mahlburg about his mathematical breakthrough, he will, typically, smile a very shy smile, duck his head, and say something self- effacing.
But Mahlburg, a 25-year-old UW-Madison graduate student, has solved what may be the last part of a historic mathematical problem that has challenged the brightest minds in the field of number theory for 75 years. It is a feat that has drawn praise from the elite in the math world.