BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Orbital perturbation theory in Schwarzschild space-time DTSTART;VALUE=DATE-TIME:20240926T133000Z DTEND;VALUE=DATE-TIME:20240926T135000Z DTSTAMP;VALUE=DATE-TIME:20260606T012124Z UID:indico-contribution-76-327@indico.bitp.kiev.ua DESCRIPTION:Speakers: Oleksii Yanchyshen (Bogolyubov Institute for Theoret ical Physics)\nIn our work\, we obtain a set of Gaussian orbital perturbat ion equations in the Schwarzschild space-time in terms of Weierstrass elli ptic functions\, and solve it for several external forces in linear approx imation. We consider forces defined from: the cosmological constant in the Schwarzschild–de Sitter space-time\, various quantum gravity correction s\, angular momentum from the Kerr space-time and some others. From this w e obtain several observables\, in particular\, we consider a simple "kludg e" scheme for gravitational waveforms.\n\nhttps://indico.bitp.kiev.ua/even t/13/contributions/327/ LOCATION:Bogolyubov Institute for Theoretical Physics (Section 1-4)\, Inst itute of Mathematics (Section 5) 322 URL:https://indico.bitp.kiev.ua/event/13/contributions/327/ END:VEVENT BEGIN:VEVENT SUMMARY:Milky Way globular clusters in cosmological timescale. Probability of the interaction with the Galactic center DTSTART;VALUE=DATE-TIME:20240926T131000Z DTEND;VALUE=DATE-TIME:20240926T133000Z DTSTAMP;VALUE=DATE-TIME:20260606T012124Z UID:indico-contribution-76-320@indico.bitp.kiev.ua DESCRIPTION:Speakers: Marina Ishchenko (MAO NAS Ukraine\, 2 Fesenkov Astro physical Institute\, Observatory 23\, 050020 Almaty\, Kazakhstan 3 Nicolau s Copernicus Astronomical Centre Polish Academy of Sciences\, ul. Bartycka 18\, 00-716 Warsaw\, Poland)\nThe main idea of the work is to carry out t he dynamic evolution of the orbits of Globular Cluster (GC) subsystems sam ple lookback time up to 10 Gyr. This allows us to estimate the possibility of GCs interaction with the Galactic center that dynamically changed in t he past. To reproduce the structure of the Galaxy in time\, we used extern al potentials which dynamically changed in a past and now their characteri stics are similar to the physical values of the Milky Way at the present d ay (mass and size of disk and halo). External potentials were selected fro m the large-scale cosmological database IllustrisTNG-100 (TNG-TVP). In the se potentials\, we reproduced the orbits of 147 GCs from Gaia DR3 in 10 Gy r lookback time using our own high-order N-body parallel dynamic code phi- GPU code. To identify clusters that have interaction with the Galactic cen ter\, we used the criteria of relative distance: it must be less than 100 pc. Applying this simple criteria\, we obtained statistically significant rates of close passages of the GCs with the Galactic center. We identified ten GCs\, including NGC 6401\, Pal 6\, NGC 6681\, NGC 6712\, NGC 6287\, N GC 6642\, NGC 6981\, HP 1\, NGC 1904\, and NGC 362\, with a high probabili ty of close passages near the Galactic center in all four TNG-TVPs\, parti cularly the first six with a probability of around 100%.\n\nhttps://indico .bitp.kiev.ua/event/13/contributions/320/ LOCATION:Bogolyubov Institute for Theoretical Physics (Section 1-4)\, Inst itute of Mathematics (Section 5) 322 URL:https://indico.bitp.kiev.ua/event/13/contributions/320/ END:VEVENT BEGIN:VEVENT SUMMARY:Initial value problem in the case of multivalued dispersion equati ons DTSTART;VALUE=DATE-TIME:20240926T125000Z DTEND;VALUE=DATE-TIME:20240926T131000Z DTSTAMP;VALUE=DATE-TIME:20260606T012124Z UID:indico-contribution-76-330@indico.bitp.kiev.ua DESCRIPTION:Speakers: Serhii Kukhtaruk (V. E. Lashkaryov Institute of Semi conductor Physics NAS of Ukraine)\nDispersion equations and relations are the key subjects of linear theories involving waves and collective excitat ions. However\, in some systems\, dispersion equations contain multivalued functions and their solutions are ambiguous. To resolve such uncertainty we suggest analyzing the initial value problem that gives the unambiguous solution. \nAs an example\, we considered the excitation of the Dirac plas mons in graphene on a polar substrate and analyzed a strong coupling betwe en plasmons in graphene and surface optical phonons of the substrate. Due to square-root singularity in graphene polarizability [1]\, the dispersion equation for this system contains branch points on the plane of complex f requency\, $\\omega$. The use of the initial value problem gives a unique solution and clarifies the physical picture of coupled oscillations. Parti cularly\, we found that lower plasmon-phonon mode\, which in terms of disp ersion can have a good quality factor\, is almost absent in excitation spe ctra. The main physical reason for the mode collapse is the suppression of space-time-dependent electric fields near $\\omega=v_F k$\, where $v_F$ i s the Fermi velocity and $k$ is the plasmon wavenumber [2]. The evidence o f the collapse can be seen in the relevant experiments [3\, 4].\n\n[1] S. M. Kukhtaruk and V. A. Kochelap\, Phys. Rev. B **92**\, 041409(R) (2015).\ n[2] S. M. Kukhtaruk\, V. A. Kochelap\, V. N. Sokolov\, K. W. Kim\, Physic a E: Low-dimensional Systems and Nanostructures\, **79**\, 26\, (2016).\n[ 3] R. J. Koch\, T. Haensel\, S. I.-U. Ahmed\, Th. Seyller\, and J. A. Scha efer\, Phys. Status Solidi C **7**\, 394 (2010). \n[4] R. J. Koch\, Th. Se yller\, and J. A. Schaefer\, Phys. Rev. B **82**\, 201413(R) (2010).\n\nht tps://indico.bitp.kiev.ua/event/13/contributions/330/ LOCATION:Bogolyubov Institute for Theoretical Physics (Section 1-4)\, Inst itute of Mathematics (Section 5) 322 URL:https://indico.bitp.kiev.ua/event/13/contributions/330/ END:VEVENT BEGIN:VEVENT SUMMARY:Pauli resonances in single- and many-channel systems DTSTART;VALUE=DATE-TIME:20240926T121000Z DTEND;VALUE=DATE-TIME:20240926T123000Z DTSTAMP;VALUE=DATE-TIME:20260606T012124Z UID:indico-contribution-76-365@indico.bitp.kiev.ua DESCRIPTION:Speakers: Victor Vasilevsky (Bogolyubov Institute for Theoreti cal Physics)\nIn this report\, we present results of systematic investigat ions of peculiarities of redundant solutions of the resonating group metho d (RGM)\, which are known as the Pauli resonance states. Such resonance s tates appear when one tries to use more advanced (more precise) wave funct ions describing internal structure of interacting clusters. It is generall y recognized that the Pauli resonance states are spurious solutions which blur real physical quantities such as phase shifts\, cross sections. Their appearance cannot be attributed to enlarging of centrifugal and Coulomb b arriers\, they also appear in a single-channel approximation and thus the Pauli resonance cannot be considered as the Feshbach resonances.\nThe subj ect of our investigations is continuos spectrum states of light nuclei $^ {6}$Li\, $^{7}$Li\, $^{8}$Be\, $^{9}$Be and $^{10}$B\, which are consid ered as two-cluster systems. Special attention is paid to the Pauli resona nce states which appear in interaction of $^{6}$Li with neutrons\, deuter ons\, tritons and alpha particles. All investigations are carried out in a three-cluster microscopic model\, which was formulated in Ref. [1]. In th is model dominant three-cluster configuration is transformed into a set of binary channels. One of the constituents of the binary channel is conside red as a two-cluster subsystem. Spectrum of bound states and corresponding wave functions of the subsystem are obtained by solving the two-cluster S chrödinger equation. This allows us to use more adequate wave functions d escribing the internal structure of the two-cluster subsystem. This is rat her important for two-cluster subsystems with a small separation energy\, such as deuteron\, $^{6}$Li and so on. Within the model\, Gaussian functi ons are used to describe relative motion of clusters in bound states of a two-cluster subsystem and oscillator functions are utilized to expand wave function of continuous spectrum states of compound nucleus. At the first stage of our investigation\, we use single-channel approximation in order to detect and analyze the Pauli resonance states.\nIt is found that the Pa uli resonance states in selected nuclei lie in the energy range between 11 and 45 MeV\, and their widths are varied from 8 keV to 8 MeV. The most d ense area of resonance states are concentrated in the interval 16 \n\nhttp s://indico.bitp.kiev.ua/event/13/contributions/365/ LOCATION:Bogolyubov Institute for Theoretical Physics (Section 1-4)\, Inst itute of Mathematics (Section 5) 322 URL:https://indico.bitp.kiev.ua/event/13/contributions/365/ END:VEVENT BEGIN:VEVENT SUMMARY:Elastic form factors of light alpha-cluster nuclei DTSTART;VALUE=DATE-TIME:20240926T115000Z DTEND;VALUE=DATE-TIME:20240926T121000Z DTSTAMP;VALUE=DATE-TIME:20260606T012124Z UID:indico-contribution-76-323@indico.bitp.kiev.ua DESCRIPTION:Speakers: Borys Grinyuk (Bogolyubov Institute for Theoretical Physics)\nWithin the α-particle model\, the structure of $^{12}C$\, $^{16 }O$\, and $^{20}Ne$ nuclei is studied. With the use of the variational met hod with Gaussian basis\, the wave functions are found for three-\, four-\ , and five-particle systems consisting from α-particles. The charge densi ty distributions and elastic form factors of $^{12}C$\, $^{16}O$\, and $^{ 20}Ne$ nuclei are calculated within the Helm approximation.\n\nhttps://ind ico.bitp.kiev.ua/event/13/contributions/323/ LOCATION:Bogolyubov Institute for Theoretical Physics (Section 1-4)\, Inst itute of Mathematics (Section 5) 322 URL:https://indico.bitp.kiev.ua/event/13/contributions/323/ END:VEVENT BEGIN:VEVENT SUMMARY:Towards relations between compaction and compressibility of hard s phere mixtures DTSTART;VALUE=DATE-TIME:20240926T113000Z DTEND;VALUE=DATE-TIME:20240926T115000Z DTSTAMP;VALUE=DATE-TIME:20260606T012124Z UID:indico-contribution-76-312@indico.bitp.kiev.ua DESCRIPTION:Speakers: Oleg Gerasymov (Odesa Mechnikov National University )\nThe study of the influence of local properties of multi-particle congl omerations on their macroscopic properties is one among of the traditional ly relevant problems of statistical physics. Parameterization of local pro perties can be carried out in various ways\, for example\, in terms of ord ering parameter tensors\, Euler invariants\, Voronoi tessellations and oth ers. While the macroscopic properties discussed above are the usual ones i n statistical physics and thermodynamics\, like compressibility\, heat cap acity\, thermal conductivity\, and others. In this paper\, we study the in fluence of the compaction factor (packing) on the property of compressibil ity using the example of a model conglomeration of solid spheres\, startin g with a mono-disperse system and further\, for multi-component mixtures. Using the known equations of state of the Carnahan-Starling type and their generalizations to the case of poly-disperse mixtures\, the inverse probl em of the influence of the proper parameters of the system (mixture) on th e degree of compaction (packing) is considered. Non-monotonicity in the be havior of the packing parameter and the possibility of achieving its maxim um value using a consistent selection of relations of the sizes of compone nts and their molar fractions are shown. Application of the above-describe d approach to two different physical systems - a binary liquid mixture and a two-component granular system - showed quite good agreement between the ory and experiment (especially in the case of a granular system). The prop osed approach can be generalized without fundamental difficulties to the c ase of multi-particle conglomerations with an arbitrary number of componen ts.\n\nhttps://indico.bitp.kiev.ua/event/13/contributions/312/ LOCATION:Bogolyubov Institute for Theoretical Physics (Section 1-4)\, Inst itute of Mathematics (Section 5) 322 URL:https://indico.bitp.kiev.ua/event/13/contributions/312/ END:VEVENT END:VCALENDAR