Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2025/ii/paper-4/20g/e/solution

Start with any generator and use the decomposition from part (d). For each , choose an integer such that
and put
Since is a unit, . Moreover,
The vector lies in the fixed compact parallelepiped
Hence there is a constant such that every real coordinate of every is at most , and every complex coordinate is at most .
For a real embedding ,
For a chosen complex embedding , the weighted coordinate gives
The conjugate embedding has the same modulus. Exponentiating and taking any proves the archimedean balancing of a principal ideal generator:
for every embedding , with depending only on .

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