Cancellation in an exponential sum
= Cancellation in an exponential sum
Cancellation occurs when different <complex numbers> in an <exponential sum> have directions that reduce the <absolute value> of their <sum>. For example, the <orthogonality of roots of unity> makes $\sum_{a=0}^{p-1}e(a/p)=0$ for every <integer> $p>1$, despite all terms having <absolute value> one.