A Cohen type inequality for Laguerre-Sobolev expansions with a mass point outside their oscillatory regime Articles uri icon

publication date

  • January 2014

start page

  • 994

end page

  • 1006


  • 6


  • 38

International Standard Serial Number (ISSN)

  • 1300-0098

Electronic International Standard Serial Number (EISSN)

  • 1303-6149


  • Let consider the Sobolev type inner product \langle f, g\rangle_S = \int_0^{\infty} f(x)g(x)d \mu (x) + Mf(c)g(c) + Nf^{\prime}(c) g^{\prime}(c), where d\mu (x) = x^{\alpha} e^{-x}dx, \alpha > -1, is the Laguerre measure, c < 0, and M, N \geq 0. In this paper we get a Cohen-type inequality for Fourier expansions in terms of the orthonormal polynomials associated with the above Sobolev inner product. Then, as an immediate consequence, we deduce the divergence of Fourier expansions and Cesàro means of order \delta in terms of this kind of Laguerre--Sobolev polynomials.


  • Mathematics


  • sobolev-type orthogonal polynomials; cohen-type inequality; fourier-sobolev expansions