On almost orthogonal series
摘要
In this work we prove analogues of Bessel inequality and Riesz–Fischer theorem in Hilbert spaces. We apply our generalized Bessel inequality to the Hilbert spaces associated with the Normal, Beta, Gamma and several discrete probability distributions to show how to generate certain types of inequalities for special functions systematically. In particular, from the Normal distribution we obtain inequalities for certain q-special functions; from the Beta distribution we derive inequalities for various hypergeometric functions; and from discrete distributions we establish inequalities for Dirichlet series.