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Exponential Sum




e


Therefore a typical exponential sum may take the form

:∑ ''e''(''x''''n'')

summed over a finite sequence of Real Number s ''x''''n''.

If we allow some real coefficients ''a''''n'', to get the form

:∑ ''a''''n''''e''(''x''''n''),

it is the same as allowing exponents that are Complex Number s. Both forms are certainly useful in applications. A large part of Twentieth Century Analytic Number Theory was devoted to finding good estimates for these sums, a trend started by basic work of Hermann Weyl in Diophantine Approximation .


ESTIMATES


The main thrust of the subject is that a sum

S


is ''trivially'' estimated by the number ''N'' of terms. That is, the Absolute Value

  :''S'' O(&radic''N'')
  :''S'' o(''N'')