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On the existence of ψ-integrals

Rendiconti del Circolo Matematico di Palermo, 1972
The approximating sums for the Riemann-Stieltjes integral are formed with the integrand function evaluated at an arbitrary point in each subdivision interval. The ψ-integral uses the idea of achoice function to select a particular point in each of these intervals.
Baker, James D., Shive, Robert A. jun.
openaire   +2 more sources

Approximation of the $$ \bar \Psi $$-integrals of functions defined on the real axis by Fourier operators

Ukrainian Mathematical Journal, 2004
Summary: We find asymptotic formulas for the least upper bounds of the deviations of Fourier operators on classes of functions locally summable on the entire real axis and defined by \(\overline{\Psi}\)-integrals. On these classes, we also obtain asymptotic equalities for the upper bounds of functionals that characterize the simultaneous approximation ...
Stepanets', O. I., Sokolenko, I. V.
openaire   +1 more source

Approximation of $$\overline \psi$$ -Integrals of Periodic Functions by de la Vallée-Poussin Sums (Low Smoothness)

Ukrainian Mathematical Journal, 2001
Under certain conditions on the sequences \(\overline{\psi}=(\{\psi_1(k)\}, \{\psi_2(k)\}),\) \(\Lambda=\{\lambda_k^{(n)}\}\), \(k,n=0,1,2,...\), the asymptotic formulas for the quantities \[ {\mathcal E}(C_\infty^{\overline{\psi}};U_n)= \sup_{f\in C_\infty^{\overline{\psi}}} \|f(x)-U_n(f,x,\Lambda)\|_{C} \] are obtained as \(n\to\infty\).
Rukasov, V. I., Chajchenko, S. O.
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Approximation of Classes of $${\bar \psi }$$ -Integrals of Periodic Functions of Many Variables by Rectangular Linear Means of Their Fourier Series

Ukrainian Mathematical Journal, 2005
Summary: We obtain asymptotic equalities for deviations of rectangular linear means of Fourier series on classes of \(\overline{\psi}\)-integrals of functions of many variables.
Rukasov, V. I.   +2 more
openaire   +1 more source

Approximation of $$\bar \psi $$ -integrals of periodic functions by fourier sums (small smoothness). II

Ukrainian Mathematical Journal, 1998
Let \(L\) be the space of \(2\pi\)-periodic integrable functions. Let \(S[f]= {a_{0}/2}+\sum\limits_{k=1}^{\infty} (a_{k}\cos kx+b_{k}\sin kx)\equiv\sum\limits_{k=1}^{\infty}A_{k}(f;x)\) be the Fourier series of the function \(f\in L\), \(S_{n}(f;x)=\sum\limits_{k=1}^{n} A_{k}(f;x)\), and let \(\rho_{n}(f;x)=f(x)-S_{n-1}(f;x)\). Let \(\bar\psi=(\psi_{1}
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Rate of convergence of Fourier series on the classes of $$\bar \Psi $$ -integrals-integrals

Ukrainian Mathematical Journal, 1997
We introduce the notion of $$\bar \Psi $$ -integrals of 2π-periodic summable functions f, f e L, on the basis of which the space L is decomposed into subsets (classes) $$L^{\bar \Psi } $$
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Approximation of $$\bar \psi - Integrals$$ of periodic functions by Fourier sums (small smoothness). IIof periodic functions by Fourier sums (small smoothness). II

Ukrainian Mathematical Journal, 1998
We investigate the rate of convergence of Fourier series on the classes \(L^{\bar \psi } \)N in the uniform and integral metrics. The results obtained are extended to the case where the classes \(L^{\bar \psi } \)N are the classes of convolutions of functions from N with kernels with slowly decreasing coefficients.
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Constructing Integrable Lindblad Superoperators

Physical Review Letters, 2021
Balázs Pozsgay   +2 more
exaly  

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