BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Towards understanding of condensed matter via study granular syste ms DTSTART;VALUE=DATE-TIME:20191223T144500Z DTEND;VALUE=DATE-TIME:20191223T150500Z DTSTAMP;VALUE=DATE-TIME:20260419T010656Z UID:indico-contribution-21-147@indico.bitp.kiev.ua DESCRIPTION:Speakers: Andrii Spivak (Odesa State Environmental University) \nGranular materials under the external perturbations show a diversity of structural transformations which characterized by different symmetries. Th eir rigorous classification in terms of phase transitions seems very attra ctable (nevertheless\, still questionable). Intriguing question is: can we use the information extracted from studying of structural transformations characters in granular materials to describe any details about the local symmetry of the condensed matter\, which displayed during the typical phas e–transformations? Here\, there are several analogies as well as discrep ancies are waiting for us: Local structure\, Phase transitions\, Landau-Gi nzburg kinetics\, Lindeman criteria for crystallization\, Equation of stat e.\n$~~~~~~$We would like to outline some results of our research directed to study of structurization\, which occurs during packing processes in ge ntly agitated granular (micro-mechanical) systems [1-5]. The focus will be done on developing and investigation of hard-spheres (discs) packing mode ls. The results of this research\, in our opinion\, in principle can provi de an understanding of some characters of the local structure and bulk pro perties not only of granular matter\, but also a regular phases of condens ed matter (e.g.\, molecular liquids and solutions\, colloids\, glasses). T he problem of densest packing are formally belong to pure mathematical are a. But inspite of this objectives to study structural and physical propert ies of perturbed granular systems a variety of physical theoretical model s which are partially based on phenomenological information (direct observ ation) have been developed. The packing of hard-particles can be described by geometric approach\, which provides a practical and universal methods of quantitative characterization of the local (as well as global) packing via symmetry categories.\n$~~~~~~$We will consider a packing of a large co nglomeration of hard particles confined by a finite-sized container. Bound aries as well as exclusion-volume effects (under the negligible dissipatio n) would be described by simple packing parameters (like compactivity). Pr operties of the states of such systems (for instance 2D hard discs) will b e studied theoretically and after then compared with the results of direct observations. Obtained results will be analyzed with respect to reminisce nces with some properties of the typical phases of condensed matter.\n\n[1 ]. Gerasimov O.I.\, Idomskyy V.A.\, Schram P.P.-J.M. Compaction of granula r graphite in a vertically vibrating container with restricted geometry. C ondens. Matter Phys. 4 (1)\, 161-164 (2001). DOI: https://doi.org/10.5488/ CMP.4.1.161\n[2]. Gerasimov O.I.\, Schram P.P.-J.M. Differential equation of state of a model system with a singular measure: application to granula r materials in steady states. Physica A 312 (1-2)\, 172-180 (2002). DOI: h ttps://doi.org/10.1016/S0378-4371(02)00851-8\n[3]. Gerasymov O.I.\, Zagoro dny A.G.\, Somov M.M. Toward the Analysis of the Structure of Granular Mat erials. Ukr. J. Phys. 58 (1)\, 32-39 (2013). DOI: https://doi.org/10.1540 7/ujpe58.01.0032\n[4]. Gerasymov O.I.\, Spivak A.Ya. Kinetic model of comp action in granular materials. Ukr. J. Phys. 60 (3)\, 253-257 (2015). DOI: https://doi.org/10.15407/ujpe60.03.0253\n[5]. Schockmel J.\, Vandewalle N. \, Opsomer E.\, Lumay G. Frustrated crystallization of a monolayer of magn etized beads under geometrical confinement. Phys. Rev. E 95 (6)\, 062120 (2017). DOI: https://doi.org/10.1103/PhysRevE.95.062120\n\nhttps://indico. bitp.kiev.ua/event/4/contributions/147/ LOCATION:Bogolyubov Institute for Theoretical Physics of the National Acad emy of Sciences of Ukraine 322 URL:https://indico.bitp.kiev.ua/event/4/contributions/147/ END:VEVENT BEGIN:VEVENT SUMMARY:The influence of the three-particle interaction on critical phenom ena of the Bose-Hubbard Model DTSTART;VALUE=DATE-TIME:20191223T142500Z DTEND;VALUE=DATE-TIME:20191223T144500Z DTSTAMP;VALUE=DATE-TIME:20260419T010656Z UID:indico-contribution-21-141@indico.bitp.kiev.ua DESCRIPTION:Speakers: Oleksii Kryvchikov (B.Verkin Institute for Low Tempe rature Physics and Engineering of the National Academy of Sciences of Ukra ine)\nThe critical behavior of a mixture of two types of ultracold bosons on the optical lattice was studied. The system can be described by the Bos e-Hubbard model. It is known that the system can be in a superfluid or in a Mott insulator state\, depending on the hopping parameter and chemical p otential. The interaction between different types of particles drastically changes the phase diagram. In particular\, the transitions between mixed and superfluid states appear. The presence of a three-particle interaction leads to an increase in the Mott insulator region of the phase diagram. I n particular\, bosons with a higher hopping value can be still in the Mott insulator phase. The results are obtained in the framework of the mean-fi eld approximation for a wide range of parameters.\n\nhttps://indico.bitp.k iev.ua/event/4/contributions/141/ LOCATION:Bogolyubov Institute for Theoretical Physics of the National Acad emy of Sciences of Ukraine 322 URL:https://indico.bitp.kiev.ua/event/4/contributions/141/ END:VEVENT BEGIN:VEVENT SUMMARY:First passage time distribution for spiking neuron with fast inhib itory feedback stimulated with renewal stream DTSTART;VALUE=DATE-TIME:20191223T150500Z DTEND;VALUE=DATE-TIME:20191223T152500Z DTSTAMP;VALUE=DATE-TIME:20260419T010656Z UID:indico-contribution-21-140@indico.bitp.kiev.ua DESCRIPTION:Speakers: Olha Shchur (Bogolyubov Institute for Theoretical Ph ysics of the National Academy of Sciences of Ukraine\, Kyiv)\nWe consider a class of spiking neuron models defined by a set of conditions typical f or basic threshold-type models\, such as leaky integrate-and-fire model an d some artificial neurons. A series of impulses\, representing a point re newal process\, is applied to a neuron. Each output impulse is fed back to the neuron after a fixed time delay\, $\\Delta$. This impulse acts as an impulse received through a fast inhibitory (GABA$_a$) synapse.\n$~~~~~~~~ $In our previous work [1]\, we have obtained a general relation in case of input Poisson stream for calculating exactly the probability density func tion (PDF) $p(t)$ for the distribution of the first passage time of crossi ng the threshold.\n$~~~~~~~~$In the present work\, we have obtained a simi lar results but applicable in case of any renewal input stream. The calcul ation is based on the known PDF $p^0(t)$ for the same neuron without feedb ack and the PDF of interspike intervals for input stream\, $p^{in}(t)$.\n \n[1]. Vidybida\, A.\, Shchur\, O. Relation between firing statistics of s piking neuron with delayed fast inhibitory feedback and without feedback\, *Fluctuation and Noise Letters*\, 17(01):1850005 (2018).\n\nhttps://indic o.bitp.kiev.ua/event/4/contributions/140/ LOCATION:Bogolyubov Institute for Theoretical Physics of the National Acad emy of Sciences of Ukraine 322 URL:https://indico.bitp.kiev.ua/event/4/contributions/140/ END:VEVENT BEGIN:VEVENT SUMMARY:Transverse energy transfer by Alfven waves in toroidal plasmas DTSTART;VALUE=DATE-TIME:20191223T140500Z DTEND;VALUE=DATE-TIME:20191223T142500Z DTSTAMP;VALUE=DATE-TIME:20260419T010656Z UID:indico-contribution-21-159@indico.bitp.kiev.ua DESCRIPTION:Speakers: M.H. Tyshchenko (Institute for Nuclear Research of t he National Academy of Sciences of Ukraine\, Kyiv)\nDestabilized magnetohy drodynamic (MHD) eigenmodes can transfer the energy and momentum from the region where particles (e.g.\, fast ions) drive the plasma instability to another region\, where the destabilized waves are damped. This phenomenon named “spatial channeling” (SC) was predicted in [1\,2]. A key element of the SC is that the energy and momentum of particles driving the instab ility are transferred by the waves (eigenmodes)\, not by the diffusion or heat conduction. In this work the physics of the transverse energy transfe r by Alfven waves in toroidal plasmas is elucidated. It is found that\, in contrast to the classical Alfven waves in infinite plasmas\, the Alfven w aves in toroidal systems produce plasma compression due to coupling with f ast magnetoacoustic waves\, which provides the energy transfer. The radial group velocities of the traveling waves constituting the Global Alfven Ei genmodes and Toroidicity-induced Alfven Eigenmodes are calculated. It is s hown that equation for Alfven eigenmodes derived in the approximation of v anishing wave field along the equilibrium magnetic field reproduce the lon gitudinal magnetic field of the wave and lead to correct transverse energy flux. The obtained results explain how Alfven eigenmodes can provide the spatial energy channeling. The results of this work are published in [3]. \nThis work was supported by the Project No. PL15/18 of the National Acade my of Sciences of Ukraine and the Project No. 6392 of the Science and Tech nology Center in Ukraine (STCU).\n\n[1] Ya. I. Kolesnichenko\, Yu. V. Yako venko\, and V. V. Lutsenko\, Phys. Rev. Lett. **104**\, 075001 (2010)\n[2] Ya. I. Kolesnichenko\, Yu. V. Yakovenko\, V. V. Lutsenko\, R. B. White\, and A. Weller\, et al.\, Nucl. Fusion **50**\, 084011 (2010)\n[3] Ya. I.Ko lesnichenko\, Yu. V. Yakovenko\, and M. H. Tyshchenko\, Phys. Plasmas **25 **\, 122508 (2018)\n\nhttps://indico.bitp.kiev.ua/event/4/contributions/15 9/ LOCATION:Bogolyubov Institute for Theoretical Physics of the National Acad emy of Sciences of Ukraine 322 URL:https://indico.bitp.kiev.ua/event/4/contributions/159/ END:VEVENT END:VCALENDAR