Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2022/iii/paper-152/1/c/solution

Let and generate the distinguished cone. If a complete fan had exactly one further ray with primitive generator and were smooth away from , the other two cones would be smooth. Completeness puts on the other side of the two boundary rays, so after choosing cyclic orientation . Smoothness would require
hence . This has no integer solution for . Thus no proper toric variety can satisfy the three conditions from the PDF.

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