4 citations · 10 across the 7 of their papers we have counts for
7 papers
Radial positive definite functions and spectral theory of the Schrödinger operators with point interactions
N. Goloshchapova, M. Malamud, V. Zastavnyi
We complete the classical Schoenberg representation theorem for radial positive definite functions. We apply this result to study spectral properties of self-adjoint realizations o…
On exponential type entire functions without zeros in the open lower half-plane
Viktor P. Zastavnyi
We obtain sufficient conditions for an exponential type entire function not to have zeros in the open lower half-plane. An exact inequality containing the real and imaginary parts…
Exact estimation of an approximation of some classes of differentiable functions by convolution operators
Viktor P. Zastavnyi
Nikol'skii known theorem for the kernels satisfying a condition , is proved and for kernels from wider class. Explicit formulas for calculating the value of an approximation…
Asymptotic expansions of several series and their application
Viktor P. Zastavnyi
Asymptotic expansions of series and $\sum_{k=0}^\infty ε^k(k+a)^γ/ (x(k+a)^α+1)^μ}$ in powers of as are found, where …
Space-time covariance functions with compact support
Viktor P. Zastavnyi, Emilio Porcu
We characterize completely the Gneiting class of space-time covariance functions and give more relaxed conditions on the involved functions. We then show necessary conditions for t…
On a paper of Ž. Tomovski and R. Hilfer
Viktor P. Zastavnyi
The proof of the inequalities for alternating Mathieu type series in Journal of Mathematical Inequalities (2008) by Ž. Tomovski and R. Hilfer contains a mistake. Here we give the v…