• Some Fourier inequalities for orthogonal systems in Lorentz–Zygmund spaces 

      Akishev, Gabdolla; Persson, Lars Erik; Seger, Andreas (Journal article; Peer reviewed, 2019-06-13)
      A number of classical inequalities and convergence results related to Fourier coefficients with respect to unbounded orthogonal systems are generalized and complemented. All results are given in the case of Lorentz–Zygmund spaces.
    • Some New Fourier and Jackson–Nikol’skii Type Inequalities in Unbounded Orthonormal Systems 

      Singh, Harpal; Persson, Lars-Erik; Akishev, Gabdolla (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-09-16)
      We consider the generalized Lorentz space L_ψ,q defined via a continuous and concave function ψ and the Fourier series of a function with respect to an unbounded orthonormal system. Some new Fourier and Jackson-Nikol’skii type inequalities in this frame are stated, proved and discussed. In particular, the derived results generalize and unify several well-known results but also some new applications ...
    • Some new Fourier inequalities for unbounded orthogonal systems in Lorentz-Zygmund spaces 

      Akishev, Gabdolla; Lukkassen, Dag; Persson, Lars Erik (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-20)
      In this paper we prove some essential complements of the paper (J. Inequal. Appl. 2019:171, 2019) on the same theme. We prove some new Fourier inequalities in the case of the Lorentz–Zygmund function spaces L q,r (logL ) α Lq,r(log⁡L)α involved and in the case with an unbounded orthonormal system. More exactly, in this paper we prove and discuss some new Fourier inequalities of this type for ...