Перегляд за Автор "Brilenkov, Maksym"

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  • Ескіз
    Документ
    Effect of the Cubic Torus Topology on Cosmological Perturbations
    (2021) Eingorn, Maxim; Canay, Ezgi; Metcalf, Jacob M.; Brilenkov, Maksym; Zhuk, Oleksandr I.; Жук, Олександр Іванович; Жук, Александр Иванович
    We study the effect of the cubic torus topology of the Universe on scalar cosmological perturbations which define the gravitational potential. We obtain three alternative forms of the solution for both the gravitational potential produced by point-like masses, and the corresponding force. The first solution includes the expansion of delta-functions into Fourier series, exploiting periodic boundary conditions. The second one is composed of summed solutions of the Helmholtz equation for the original mass and its images. Each of these summed solutions is the Yukawa potential. In the third formula, we express the Yukawa potentials via Ewald sums. We show that for the present Universe, both the bare summation of Yukawa potentials and the Yukawa-Ewald sums require smaller numbers of terms to yield the numerical values of the potential and the force up to desired accuracy. Nevertheless, the Yukawa formula is yet preferable owing to its much simpler structure.
  • Ескіз
    Документ
    Gravitational Interaction in the Chimney Lattice Universe †
    (2021) Eingorn, Maxim; McLaughlin II, Andrew; Canay, Ezgi; Brilenkov, Maksym; Zhuk, Oleksandr I.; Жук, Олександр Іванович; Жук, Александр Иванович
    We investigate the influence of the chimney topology T T R of the Universe on the gravitational potential and force that are generated by point-like massive bodies. We obtain three distinct expressions for the solutions. One follows from Fourier expansion of delta functions into series using periodicity in two toroidal dimensions. The second one is the summation of solutions of the Helmholtz equation, for a source mass and its infinitely many images, which are in the form of Yukawa potentials. The third alternative solution for the potential is formulated via the Ewald sums method applied to Yukawa-type potentials. We show that, for the present Universe, the formulas involving plain summation of Yukawa potentials are preferable for computational purposes, as they require a smaller number of terms in the series to reach adequate precision.