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Turán's method
Number theory in mathematics From Wikipedia, the free encyclopedia
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In mathematics, Turán's method provides lower bounds for exponential sums and complex power sums. The method has been applied to problems in equidistribution.
![]() | This article includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations. (December 2013) |
The method applies to sums of the form
where the b and z are complex numbers and ν runs over a range of integers. There are two main results, depending on the size of the complex numbers z.
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Turán's first theorem
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The first result applies to sums sν where for all n. For any range of ν of length N, say ν = M + 1, ..., M + N, there is some ν with |sν| at least c(M, N)|s0| where
The sum here may be replaced by the weaker but simpler .
We may deduce the Fabry gap theorem from this result.
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Turán's second theorem
The second result applies to sums sν where for all n. Assume that the z are ordered in decreasing absolute value and scaled so that |z1| = 1. Then there is some ν with
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See also
- Turán's theorem in graph theory
References
- Montgomery, Hugh L. (1994). Ten lectures on the interface between analytic number theory and harmonic analysis. Regional Conference Series in Mathematics. Vol. 84. Providence, RI: American Mathematical Society. ISBN 0-8218-0737-4. Zbl 0814.11001.
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