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Use of complex analysis for deriving lower bounds for trigonometric polynomials
A. S. Belov Ivanovo State University
Abstract:
It is shown that for any distinct natural numbers k1,…,kn and arbitrary real numbers a1,…,an the following inequality holds:
−minxn∑j=1aj(cos(kjx)−sin(kjx))⩾B(11+lnnn∑j=1a2j)1/2,n∈N,
where B is a positive absolute constant (for example, B=1/8). An example shows that in this inequality the order with respect ton, i.e., the factor (1+lnn)−1/2, cannot be improved. A more elegant analog of Pichorides' inequality and some other lower bounds for trigonometric sums have been obtained.
Received: 12.04.1997
Citation:
A. S. Belov, “Use of complex analysis for deriving lower bounds for trigonometric polynomials”, Mat. Zametki, 63:6 (1998), 803–811; Math. Notes, 63:6 (1998), 709–716
Linking options:
https://www.mathnet.ru/eng/mzm1350https://doi.org/10.4213/mzm1350 https://www.mathnet.ru/eng/mzm/v63/i6/p803
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Abstract page: | 628 | Full-text PDF : | 262 | References: | 96 | First page: | 1 |
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