The typical Mathematics Ph.D. student takes courses in the first and second year, at the same time exploring some more advanced mathematics with the goal of finding a research area. Ideally, by around the beginning of the third year, the student has found an area to specialize in and a thesis advisor. This timeline varies for each student.
The department has no “qualifying exam” or “preliminary exam”. We do insist that every student develop a basic broad mastery of mathematics, but we ensure this more by courses than by exams; see the section on degree requirements below.
There is no expectation that students will be “weeded out”. In fact, the program has very little attrition.