A Note on Average of Roots of Unity

作者:Panraksa Chatchawan*; Ruengrot Pornrat
来源:American Mathematical Monthly, 2017, 124(2): 170-174.
DOI:10.4169/amer.math.monthly.124.2.170

摘要

We consider the problem of characterizing all functions f defined on the set of integers modulo n with the property that an average of some nth roots of unity determined by f is always an algebraic integer. Examples of such functions with this property are linear functions. We show that, when n is a prime number, the converse also holds. That is, any function with this property is representable by a linear polynomial. Finally, we give an application of the main result to the problem of determining self-perfect isometries for the cyclic group of prime order p.

  • 出版日期2017-2

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