BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Molecular dynamics analysis of particle number fluctuations of a f irst-order phase transition DTSTART;VALUE=DATE-TIME:20240117T144000Z DTEND;VALUE=DATE-TIME:20240117T150000Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-270@indico.bitp.kiev.ua DESCRIPTION:Speakers: Volodymyr Kuznietsov (University of Houston)\nWe stu dy the critical point effects on particle number fluctuations both in the crossover ($T > T_{\\rm c}$) and mixed phase ($T \n\nhttps://indico.bitp.k iev.ua/event/11/contributions/270/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/270/ END:VEVENT BEGIN:VEVENT SUMMARY:Quantum van der Waals theory of nuclear matter with quarkyonic pha se DTSTART;VALUE=DATE-TIME:20240117T142000Z DTEND;VALUE=DATE-TIME:20240117T144000Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-273@indico.bitp.kiev.ua DESCRIPTION:Speakers: Roman Poberezhnyuk (Bogolyubov Institute for Theoret ical Physics of the National Academy of Sciences of Ukraine)\nWe extend th e Quantum van der Waals description of isospin symmetric nuclear matter at zero temperature to a high baryon density region by incorporating the con tinuous transition to quark matter in accordance with the recently propose d quarkyonic approach. The resulting equation of state exhibits the nucle ar liquid-gas transition at $n_B \\leq \\rho_0$ and undergoes a transition to quarkyonic matter at densities $n_B \\approx 1.5-2 \\rho_0$ that are r eachable in intermediate energy heavy-ion collisions. The transition is ac companied by a peak in the sound velocity. The results depend only mildly on the chosen excluded volume mechanism but do require the introduction of an infrared regulator $\\Lambda$ to avoid an acausal sound velocity. We a lso consider the recently proposed baryquark matter scenario for the reali zation of the Pauli exclusion principle\, which yields a similar equation of state and turns out to be energetically favored in all the considered s etups.\n\nhttps://indico.bitp.kiev.ua/event/11/contributions/273/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/273/ END:VEVENT BEGIN:VEVENT SUMMARY:Constraints on the parameters of the neutrino extension of the Sta ndard Model DTSTART;VALUE=DATE-TIME:20240117T140000Z DTEND;VALUE=DATE-TIME:20240117T142000Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-272@indico.bitp.kiev.ua DESCRIPTION:Speakers: Oleksandr Khasai (Bogolyubov Institute for Theoretic al Physics of the National Academy of Sciences of Ukraine)\nThis work exam ines limitations on the neutrino extension parameters of the Standard Mode l of elementary particle physics. A simple relationship between the observ ed quantities\, elements of the matrices S and R was obtained\, which is v alid for non-zero masses of active neutrinos and for different values of m asses of heavy sterile neutrinos. Experimental constraints on the elements of the S and R matrices were improved\, and constraints on $U_{tot}^2$ d epending on the mass of a heavy neutrino with right chirality were obtaine d. The expression for the baryon asymmetry of the early Universe also was analyzed.\n\nhttps://indico.bitp.kiev.ua/event/11/contributions/272/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/272/ END:VEVENT BEGIN:VEVENT SUMMARY:Contribution of one-loop corrections in the decoupling limit of ge neralized Yukawa model DTSTART;VALUE=DATE-TIME:20240117T134000Z DTEND;VALUE=DATE-TIME:20240117T140000Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-283@indico.bitp.kiev.ua DESCRIPTION:Speakers: Mykyta Dmytriiev (Oles Honchar Dnipro National Unive rsity)\nThere exist many models of physics beyond the Standard model (SM) which introduce new heavy particles. Signals of such new states could be p arametrized either within a complete model of new physics or its low-energ y approximation. The latter consists of effective Lagrangian (EL)\, which describes effects of interactions with heavy particles on the dynamics of light fields when heavy states decouple. Parameters of this EL should be c onstrained in experimental data analysis. These constraints\, in turn\, ar e translated into limits on parameters of a corresponding complete model. This approach is employed in many researches. In our investigation we show that the EL considered in this treatment is valid only if loop correction s coming from the light sector of a corresponding complete model are negli gible in the decoupling limit.\n \nOur research is conducted for two scatt ering processes which take place in $s$- and $t$-channel\, respectively. T ransformational properties of fields and complex interactions within the S M are inessential for our analyzis. Hence\, we consider generalized Yukawa model instead of a complete SM extended with some new states. We begin wi th the following Lagrangian of a complete model:\n\n$$\\begin{equation}\n \\mathcal{L} = \\frac{1}{2}\\left(\\partial_{\\mu}\\phi\\right)^2 - \\f rac{1}{2}\\mu^2\\phi^2 + \\frac{1}{2}\\left(\\partial_{\\mu}\\chi\\right)^ 2 - \\frac{1}{2}\\Lambda^2\\chi^2 - \\lambda\\phi^4 - \\rho\\phi^2\\chi^2 - \\xi\\chi^4 +\n\\\\ +\\sum\\limits_{a=1\;2}\\bar{\\psi}_a\\left(i\\hat{\ \partial} - m_a - g_{\\phi}\\phi - g_{\\chi}\\chi\\right)\\psi_a\n\\end{eq uation}.~~ (1)$$\n\nThis model consists of two scalar fields $\\phi$ and $ \\chi$ and two fermionic fields $\\psi_1$ and $\\psi_2$. We put $\\chi$ bo son to be much heavier than the other particles of the model\, so $\\Lambd a\\gg \\mu\;\\\,m_1\;\\\,m_2$. We derived the following low-energy EL for this model in the limit when $\\chi$ boson decouples:\n\n$$\\begin{equatio n}\n \\mathcal{L}_{eff} = \\frac{1}{2}\\left(\\partial_{\\mu}\\phi\\rig ht)^2 - \\frac{1}{2}\\mu^2\\phi^2 - \\lambda\\phi^4 + \\sum\\limits_{a=1\; 2}\\bar{\\psi}_a\\left(i\\hat{\\partial} - m_a - g_{\\phi}\\phi\\right)\\p si_a + \\frac{g_{\\chi}^2}{2\\Lambda^2}\\left(\\bar{\\psi}_1\\psi_1 + \\ba r{\\psi}_2\\psi_2\\right)^2.\n\\end{equation}~ (2)$$\n\nHere the last term describes effective four-fermion interactions which approximate contribut ions of the heavy scalar in observables when $\\chi$ decouples. The other terms in (2) describe dynamics of the model light sector if $g_{\\chi} = 0 $.\n \nTwo scattering processes were considered within the complete model (1) and EFT (2) - these are $\\psi_1\\bar{\\psi_1} \\rightarrow \\psi_2\\b ar{\\psi_2}$ and $\\psi_1\\psi_2 \\rightarrow \\psi_1\\psi_2$. Cross-secti ons of these processes were derived within the complete model (1) in the i mproved Born approximation and within the EFT (2). Contributions of radiat ive corrections into the cross-sections of these processes were estimated in the decoupling limit. We investigated scenarios where $\\chi$ boson has a mass in the interval $20\\mu \\leq \\Lambda \\leq 200\\mu$.\n\n\n(a) Lo op corrections to the $\\phi$ boson mass\n\n (b) Diagram of one-loop mixin g of light and heavy scalars of\nthe model\n\nFIG. 1: One-loop diagrams wh ich become significant at low energies for some values of the model coupli ng.\n \n$~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~$ \nWe found out th at if $|g_{\\phi}|$ and $|g_{\\chi}|$ are small\, then the loop correction s are negligible and the EL (2) is applicable for description of the scatt ering processes at low energies. For the values of $m_1$\, $m_2$ and $\\mu $ chosen in our research this takes place if $|g_{\\phi}| 2.5$ then corre ctions displayed in Fig.(1a) have a magnitude of more than $10\\\,\\%$ of the $\\chi$ boson mass. These corrections suppress the contribution of the heavy scalar in a reaction cross-section. Hence\, if $|g_{\\chi}|$ is big \, then (2) significantly overestimates $\\chi$ boson contribution in a cr oss-section when $\\chi$ decouples.\n \nIf $|g_{\\phi}|$ is not small\, th en contribution of the scalar fields one-loop mixing is significant in bot h $s$- and $t$-channels. One-loop mixing of $\\phi$ and $\\chi$ is introdu ced by the diagram in Fig.(1b). In our model\, we get that if $|g_{\\phi}| > 1.5$\, then modulus of the contribution of scalars one-loop mixing in t he matrix elements of the considered reactions is bigger than $50\\\,\\%$ of the four-fermion interaction term modulus at $s > \\mu^2$ and $|t| > \\ mu^2$. This was observed in the limit when loop correction in Fig.(1a) is negligible.\n \nTo conclude\, in our research we have derived the conditio ns when radiative corrections to interactions with the heavy boson are neg ligible in the decoupling limit in cross-sections of reactions within the generalized Yukawa model. According to these conditions\, radiative correc tions become significant if the interactions between light fermions and ei ther light or decoupled scalar are not feeble. In such scenarios\, express ion (2) should not be used as the low-energy approximation of the model (1 ). The results obtained in this investigation could be applied to some mod els of new physics which extend the SM\, such as the two-Higgs-doublet mod el (2HDM). The latter has a limit when new heavy particles decouple. So\, low-energy EL exists for it. Contributions of radiative corrections into c ross-sections within the 2HDM should be estimated in the limit when heavy fields beyond the SM decouple. This is the problem left for the future.\n\ nhttps://indico.bitp.kiev.ua/event/11/contributions/283/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/283/ END:VEVENT BEGIN:VEVENT SUMMARY:Searches for axions in proton-proton and ion-ion collisions at ene rgies of 5.02 TEV and 13 TEV DTSTART;VALUE=DATE-TIME:20240117T130000Z DTEND;VALUE=DATE-TIME:20240117T132000Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-276@indico.bitp.kiev.ua DESCRIPTION:Speakers: Serhii Chernyshenko (Institute for Nuclear Research NAS of Ukraine)\nAs a part of the ATLAS Collaboration experimental measure ments of light-by-light\nscattering in Pb+Pb collisions during 2015 and 20 18 at an integrated luminosity of 2.2 nb-1 and energy of 5.02 TeV\, taking into account the obtained experimental constraints [1]\, we have modeled the production cross sections of axion production\, which is candidate for dark matter with subsequent decay into γγ. Candidates for light-by-ligh t scattering are selected in events with\ntwo photons\, pseudorapidity\, | ηγ | \n\nhttps://indico.bitp.kiev.ua/event/11/contributions/276/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/276/ END:VEVENT BEGIN:VEVENT SUMMARY:Dynamic Picture of Relativistic Heavy-Ion Collisions DTSTART;VALUE=DATE-TIME:20240117T124000Z DTEND;VALUE=DATE-TIME:20240117T130000Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-290@indico.bitp.kiev.ua DESCRIPTION:Speakers: Musfer Adzhymambetov (Bogolyubov Institute for Theor etical Physics of the National Academy of Sciences of Ukraine)\nCollider e xperiments serve as an unique tool to create and study new forms of strong ly interacting matter\, such as quark-gluon plasma (QGP). This state of ma tter is believed to have existed in the microseconds after the Big Bang wh en temperatures and energy densities were extremely high. However\, due to confinement under typical Earth conditions\, elementary particles of quan tum chromodynamics (QCD) exist only in colorless combinations within hadro ns. Lattice QCD calculations show that at zero chemical potential\, there is no phase transition between these two states of matter - QGP and hadron gas. However\, in baryon-rich regions of the QCD phase diagram\, a phase transition of finite order is expected to occur which ends with a critical point.\nOne of the primary goals of current and future experimental progr ams\, including RHIC BES and CBM\, is to search for the signal of the crit ical point in observables. Such studies demand a comparison with predictio ns of theoretical models. In this talk\, I will present a recently develop ed integrated Hydro-Kinetic model tailored to describe the full dynamics o f the system created in heavy-ion collisions at relatively low energies. A dditionally\, I will discuss an idea for searching for signals of the crit ical point through a comparison of model simulations and experimental data .\n\nhttps://indico.bitp.kiev.ua/event/11/contributions/290/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/290/ END:VEVENT BEGIN:VEVENT SUMMARY:Bremsstrahlung emission in proton-deuteron scattering and nucleon- nucleon forces DTSTART;VALUE=DATE-TIME:20240117T122000Z DTEND;VALUE=DATE-TIME:20240117T124000Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-271@indico.bitp.kiev.ua DESCRIPTION:Speakers: Kostiantyn Shaulskyi (Institute for Nuclear Research )\nWe will present the results of a study of the bremsstrahlung emission o f photons in a process of proton scattering on deuterons. Despite the long history of studies of the interaction of protons with deuterons and the e xistence of some studies on the subject in such reactions there are some i nteracting problems that need to be tackled. This stimulates us to develop a new model that allows us to gain more information about processes induc ed by the $p + d$ interaction and the properties of nuclear forces. Beside s\, this model is aimed at detailed analysis and interpretation of the exi sting experimental data on bremsstrahlung emission in these processes. The relative simplicity of the selected nuclei is explained by the fact that it is possible to demonstrate more clearly the effectiveness of the model. \n\nThe quantum model of photon emission developed by us is a continuation of the development of methods of bremsstrahlung emission in nuclear proce sses formulated in [1\, 2] (see references therein) with new incorporating ideas of cluster models [3\, 4] (see references therein). Within the fram ework of the model\, proton scattering on a deuteron is described as a sol ution of the quantum-mechanical three-nucleon problem with semi-realistic nucleon-nucleon potentials. This model is applied to study wave functions of continuous spectrum states in the $p + d$ system and then to calculate cross sections of photon emission. Based on this model\, a good descriptio n of the existing experimental emission data has been achieved [5\, 6]. Th e dependence of the cross sections of bremsstrahlung emission on the shape of the nucleon-nucleon potential is studied in details.\n\nWe have applie d our method to analyse results of experimental investigations [5\, 6] of gamma ray production in $p + d$ interactions. Our analysis revealed that t he results of the experiments [5\, 6] with chosen parameters (incident ene rgy of proton beam\, energy of detected photons) are insensitive to the pe culiarities of nuclear forces. However\, we have identified another energy region for experiments where it is possible to obtain information about t he properties of nuclear forces within the present method with higher accu racy. To make our analysis more complete\, we analyze bremsstrahlung prope rties in a wide range of proton beam energies and photon energies.\n\nResu lts of our model allow us to predict behavior of bremsstrahlung cross sect ions which can be used for planning of new experiments. The approach devel oped can be used to study the bremsstrahlung emission in a large variety o f nuclear scattering processes\, and also to determine effects of nuclear structure and nucleusnucleus interaction on a such emission.\n\n1. S.P. Ma ydanyuk. Enhancement of incoherent bremsstrahlung in proton-nucleus scatte ring in the ∆-\nresonance energy region. Phys. Rev. C107\, 024618 (2023) \, arXiv: 2203.07146.\n2. X. Liu et al. First investigations of hypernucle i in reactions via analysis of bremsstrahlung photons. Phys. Rev. C99\, 06 4614 (2019)\, arXiv: 1810.11942.\n3. V. Vasilevsky et al. Algebraic model for scattering in three s cluster systems. 1. Theoretical background. Phys . Rev. C63\, 034606 (2001).\n\nhttps://indico.bitp.kiev.ua/event/11/contri butions/271/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/271/ END:VEVENT BEGIN:VEVENT SUMMARY:Nature of Pauli resonances states in light nuclei DTSTART;VALUE=DATE-TIME:20240117T120000Z DTEND;VALUE=DATE-TIME:20240117T122000Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-282@indico.bitp.kiev.ua DESCRIPTION:Speakers: Nursultan Kalzhigitov (Al-Farabi Kazakh National Uni versity)\nThe resonating group method (RGM) [1] is a rigorous and self-con sistent realization of cluster model. It has been numerously proved the RG M is a powerful tool to study the structure of light atomic nuclei and nuc lear reactions of different types. Thus it equally well describes bound an d continuous spectrum states. The main advantages of the RGM is that it ta kes into account the internal structure of interacting nuclei (clusters) a nd correctly treats the Pauli principle. In the standard (initial) version of the RGM\, the internal structure of clusters was described by wave fun ctions of the many-particle shell model. Then\, many attempts have been ma de (undertaken) to use more realistic wave functions of clusters. They aim ed at a more correct description of interacting clusters and compound syst em as well. These attempts brought new interesting results. However\, they also gave a birth of a new problem\, which is called the Pauli resonances and which are considered as a redundant solutions of the RGM equations. I t was recognized\, the Pauli principle is the origin of the problem.\nIn o ur work\, we perform a systematic investigation of the Pauli resonance sta tes in the continuum spectrum of light atomic nuclei: $^6$Li\, $^7$Li\, $^ 8$Be\, $^9$Be and $^{10}$B. These nuclei are considered as two-cluster sys tems. One of the clusters of two-cluster system\, which is weakly bound\, is also considered as a two-cluster system. We especially interested in th e Pauli resonance states appearing in interaction of neutrons\, protons\, deuteron\, tritons and alpha particles with $^6$Li. For this purpose\, we employ of a microscopic three-cluster model\, formulated in [2]. This mode l uses square-integrable Gaussian and oscillator bases to expand wave func tion of relative motion of clusters. As a result\, the many-particle Schr ödinger equation is transformed into a set linear algebraic equations. It is numerously demonstrated that discrete algebraic form of two-cluster Ha miltonian is the best way to analyze effects of the Pauli principle.\nIt i s shown that the Pauli resonance states in selected nuclei lie in the ener gy range between 11 and 45 MeV\, and their widths are varied from 8 keV to 8 MeV. It is demonstrated that in main cases\, only one Pauli resonance emerges in continuous spectrum of two-cluster systems. We have also found several cases when two Pauli resonances are formed by interaction of two c lusters.\nAnalysis of wave functions of the Pauli resonance states and the many-particle Schrödinger equation in the discrete space allowed us to f ormulate an algorithm for elimination of Pauli resonance states. This algo rithm suggests new definition of so-called totally-forbidden and almost-fo rbidden Pauli states which are responsible for creation of the Pauli reson ances. It is demonstrated that the suggested algorithm completely eliminat es all Pauli resonance states.\n\n1. J.A. Wheeler\, Phys. Rev. 52\, 1107 ( 1937).\n2. V.S. Vasilevsky\, F. Arickx\, et al. Nucl. Phys. A. 824\, 37 ( 2009).\n\nhttps://indico.bitp.kiev.ua/event/11/contributions/282/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/282/ END:VEVENT BEGIN:VEVENT SUMMARY:Influence of the variable cross section on the domain wall dynamic s in curved ferromagnetic nanostripes DTSTART;VALUE=DATE-TIME:20240117T105000Z DTEND;VALUE=DATE-TIME:20240117T111000Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-266@indico.bitp.kiev.ua DESCRIPTION:Speakers: Dmytro Karakuts (Taras Shevchenko National Universit y of Kyiv\, 01601 Kyiv\, Ukraine)\nCurvilinear magnetism is an emerging fi eld which connects low-dimensional magnetic architectures with their geome trical properties to describe resulting novel phenomena. Nanoscale curved magnetic stripes are a crucial building block in the race for high-density and ultrafast magnetic memory\, and can substantially augment the perform ance of spintronic devices [1\,2].\n\nHere\, we aim to theoretically and n umerically study how changes in the cross-section area of the curved ferro magnetic nanostripe affect its magnetic structure. Namely\, we show that t ailoring of the gradient of the cross-section area can be used to control the motion of the domain wall. Although\, the magnetic response of the cur ved nanostripe is already well-studied\, in all previous studies cross sec tion of the nanowire was assumed to be constant. Only recently\, a new mic romagnetic framework emerged that allows the exploration of the changes in the magnetization dynamics caused by the cross-section area gradient [3]. \n\nHere\, we use the collective variable approach by adapting the q-Ф mo del to stripes with varying cross section. The description of the domain w all motion in ferromagnetic wires is investigated by considering the tempo ral evolution of the magnetization vector based on the Landau–Lifshitz –Gilbert equation. To derive the specific equations of motion for the co llective variables\, the Lagrange-Rayleight formalism is used\, where the dependency on the spatial variation of the cross-section area is factored in both the Lagrangian and the dissipative function.\n\nThe resulting equa tions of the domain wall motion are studied for three specific geometries: a straight stripe\, an arc of a circle and an Euler spiral. For the case of a straight stripe with absent curvature\, we show that the domain wall velocity is mainly determined by the cross-section gradient. For the case of constant curvature\, the asymptotic domain wall velocity is shown to ha ve two components: the first component is identical to the speed of the do main wall in the straight wire\, while the second one describes the coupli ng between the curvature and the cross-section gradient. For the case of t he wire\, whose curvature grows at a constant rate\, the asymptotic domain wall velocity has two contributions. The first one is the same as the vel ocity in the straight wire\, however\, the second one differs from the pre vious case and is determined solely by the rate of curvature growth. All a nalytical predictions are well­confirmed by the NMAG micromagnetic simula tions [4].\n\nThe gradient of the cross-section area of the curved ferroma gnetic nanostripe creates an internal driving force\, which in turn induce s the domain wall motion and can explain the recent experimental results [ 5]. We have shown how the dynamics of the domain wall motion can be modifi ed through tailoring the cross-section area of the nanostripe. Although we showcased our approach only for three specific geometries\, it is general and can be applied to a wide class of geometries.\n\n1. Curvilinear Micro magnetism: From Fundamentals to Applications\, edited by D. Makarov and D. Sheka\, Topics in Applied Physics Vol. 146 (Springer\, Cham\, 2022).\n2. D. D. Sheka\, O. V. Pylypovskyi\, O. M. Volkov\, K. V. Yershov\, V. P. Kra vchuk\, and D. Makarov\, Small 18\, 2105219 (2022).\n3. K. V. Yershov\, D. D. Sheka\, Phys. Rev. B 107\, L100415 (2023).\n4. T. Fischbacher\, M. Fra nchin\, G. Bordignon and H. Fangohr\, IEEE Transactions on Magnetics\, Vol . 43\, No. 6\, (2007).\n5. L. Skoric et al. ACS Nano 16\, 8860 (2022).\n\n https://indico.bitp.kiev.ua/event/11/contributions/266/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/266/ END:VEVENT BEGIN:VEVENT SUMMARY:Nonlinear wave phenomena in Josephson junctions DTSTART;VALUE=DATE-TIME:20240117T100500Z DTEND;VALUE=DATE-TIME:20240117T105000Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-287@indico.bitp.kiev.ua DESCRIPTION:Speakers: Yaroslav Zolotaryuk (Bogolyubov Institute for Theore tical Physics of the National Academy of Sciences of Ukraine)\nhttps://ind ico.bitp.kiev.ua/event/11/contributions/287/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/287/ END:VEVENT BEGIN:VEVENT SUMMARY:Spatial coherence of compact sources with respect to X-ray phase c ontrast imaging formation DTSTART;VALUE=DATE-TIME:20240117T092500Z DTEND;VALUE=DATE-TIME:20240117T094500Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-277@indico.bitp.kiev.ua DESCRIPTION:Speakers: Artur Ovcharenko (Institute of Applied Physics of th e NAS of Ukraine)\nSignificant successes and important results of research on synchrotron radiation sources raised a new urgent question\, namely th e development of bright compact radiation sources with coherence parameter s that allow the implementation of phase-informative methods. This is due to the growing demand for the use of new research methods based on X-ray r adiation in engineering\, materials science and medicine. The study concer ns the topical issue of implementation of diffraction research methods on compact radiation sources [1]. Taking into account phase information helps to increase the sensitivity and informativeness of the obtained images\, making their use more effective in a wide range of research and diagnostic tasks.\n\nThe aim is to determine the research capabilities of various ty pes of installations in solving specific applied problems\, as well as to develop applied calculation methods for planning and conducting X-ray phas e contrast experiments. X-ray phase contrast arises due to the difference in the phase of X-rays when they pass through objects with different refra ctive or absorption indices. One of the approaches for modeling X-ray phas e contrast is the Fresnel-Kirchhoff scalar diffraction theory [2-4]. This study presents a method for calculating phase-contrast images of test obje cts. A two-stage algorithm for calculating the X-ray phase contrast image from sources of different shapes and sizes has been developed. The evoluti on of the wave front along the source-object and object-screen path is tak en into account. The source-object and object-screen distances at which it is possible to observe phase-contrast images in the Fresnel region have b een found. Simulated images of test objects were obtained in the form of i ntensity contrast on the screen and its phase profile. As the calculations show\, increasing the thickness of certain sections of the test object le ads to changes in the phase distribution and intensity of the resulting im age. This is manifested in the form of the appearance of intensity maxima at the edges of the object\, where there is a fast change in its thickness \, as well as minima\, where the thickness is the largest\, which is expla ined by a greater deviation of X-rays from their original direction.\n\nTh e results of the research will be useful for the development of methods fo r studying the internal structure of materials\, as well as for solving pr oblems in medical diagnostics\, where X-ray phase contrast can help distin guish tissues with different physical properties\, for example\, in the st udy of soft tissues and organs.\n\n1. L. Quenot\, S. Bohic and E. Brun\, A ppl. Sci.\, 12(19)\, 9539\; (2022)\nhttps://doi.org/10.3390/app12199539\n2 . D. Paganin Coherent x-ray optics. Oxford University Press\, 2013\, 424 p p.\n3. V. Kolobrodov\, G. Timchyk\, Applied Diffraction Optics: Textbook\, K.: NTUU "KPI"\, 2014\, 312 pp.\n4. A. Pil-Ali et al.\, Proc. SPIE 11595\ , Medical Imaging 2021: Physics of Medical Imaging\, 115951N (15 February 2021)\; doi: 10.1117/12.2582225\n\nhttps://indico.bitp.kiev.ua/event/11/co ntributions/277/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/277/ END:VEVENT BEGIN:VEVENT SUMMARY:The Mutual Influence of Production Rate of Point Defects and Tempe rature on the Effects of Radiation-Induced Segregation in the Fe-20Cr-8Ni Alloy DTSTART;VALUE=DATE-TIME:20240117T090500Z DTEND;VALUE=DATE-TIME:20240117T092500Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-274@indico.bitp.kiev.ua DESCRIPTION:Speakers: Roman Skorokhod (Institute of Applied Physics of Nat ional Academy of Sciences of Ukraine\, Sumy\, Ukraine)\nIn this paper\, a computer simulation of radiation-induced segregation in the Fe-20Cr-8Ni al loy was carried out within the framework of the modified inverse Kirkendal l model [1-3]. The dependences of the concentrations of Cr and Ni atoms on the surface of the sample on the rate of production of point defects and temperature\, as well as the concentration profiles of Cr and Ni atoms and point defects\, were calculated. The influence of the rate of production of point defects and temperature on the concentration profiles of componen ts and point defects is analyzed in detail. It is shown that the effect of the increase in the rate of production of point defects on the concentrat ion profiles of the alloy components can be compensated with a sufficientl y high accuracy by a relatively small increase in temperature (fig. 1). Th is effect is explained by the competition of two mechanisms: (i) increasin g the irradiation of the alloy leads to a narrowing of the concentration p rofiles\; (ii) an increase in temperature leads to a broadening of concent ration profiles.\n\nFig. 1. Concentration profiles of Cr and Ni in the Fe- 20Cr-8Ni alloy under irradiation.\n\n1. G.S. Was\, *Fundamentals of Radiat ion Materials Science. Metals and Alloys* (2nd ed.) (New York: Springer: 2 017).\n2. R.V. Skorokhod\, O.M. Buhay\, V.M. Bilyk\, V.L. Denysenko and O. V. Koropov\, *East European Journal of Physics*\, **5**\, No. 1: 61–69 ( 2018) (in Ukrainian).\n3. R.V. Skorokhod and O.V. Koropov\, *Metallofiz. N oveishie Tekhnol.*\, **44**\, No. 6: 691—711 (2022) (in Ukrainian).\n\nh ttps://indico.bitp.kiev.ua/event/11/contributions/274/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/274/ END:VEVENT BEGIN:VEVENT SUMMARY:Revealing inaccuracies of the GFN1-xTB semi-empirical method with machine-learning toolset DTSTART;VALUE=DATE-TIME:20240117T084500Z DTEND;VALUE=DATE-TIME:20240117T090500Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-275@indico.bitp.kiev.ua DESCRIPTION:Speakers: Andrii Terets (1) Faculty of Physics\, Taras Shevche nko National University of Kyiv. 2) Chuiko Institute of Surface Chemistry \, NAS of Ukraine\,)\nThe change in conformation during biological functio ning is a characteristic feature of biomolecules. The presence of various conformers complicates their physics-based modeling\, as the properties of each conformer need to be determined separately. Moreover\, the relative energies of the conformers become an additional quantity of interest becau se they determine the probability of each conformation in a real system.\n \nAlthough ab initio quantum-mechanical methods are the most accurate for determining the physical properties of molecules\, their computational cos ts become prohibitive when applied to biomolecules with a large number of atoms and/or a large number of conformations. Semi-empirical quantum mecha nical methods\, particularly those based on the tight-binding approximatio n in density functional theory (DFTB)\, significantly reduce computational requirements by utilizing parameterized models for the elements of the Fo ck or Kohn-Sham matrices. However\, due to such simplifications\, the resu lting method can show low accuracy in some cases\, despite performing accu rately in other cases.\n\nIn this work\, we demonstrate that machine learn ing (ML) methods such as graph neural networks and ensemble models can be employed to predict errors in determining the relative energies of conform ers by the semi-empirical method GFN1-xTB from the DFTB family\, based sol ely on the molecular structural formula as input.\n\nThe developed ML ense mble model achieves an accuracy of about 80% in determining whether a give n molecule is 'challenging' for GFN1-xTB. This approach can be used to fin d the molecules that most vividly highlight the shortcomings of the physic al model underlying the GFN1-xTB method. We demonstrate that for the 190 m olecules selected using the developed model\, the average error in relativ e energies of their conformers obtained by the GFN1-xTB method is 4.2 kcal /mol\, in contrast to 1.8 kcal/mol when the same number of test molecules are selected randomly. This indicates that the ML toolset indeed allows fo r the identification of challenging molecules and can therefore be useful in improving the approximations utilized by semi-empirical methods.\n\nhtt ps://indico.bitp.kiev.ua/event/11/contributions/275/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/275/ END:VEVENT BEGIN:VEVENT SUMMARY:Application of machine learning approaches to the generation of or ganic compounds and prediction of their properties DTSTART;VALUE=DATE-TIME:20240117T080000Z DTEND;VALUE=DATE-TIME:20240117T084500Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-288@indico.bitp.kiev.ua DESCRIPTION:Speakers: Maksym Druchok (Institute for Condensed Matter Physi cs of the National Academy of Sciences of Ukraine)\nhttps://indico.bitp.ki ev.ua/event/11/contributions/288/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/288/ END:VEVENT BEGIN:VEVENT SUMMARY:Perturbation equations for Schwarzschild geodesics DTSTART;VALUE=DATE-TIME:20240116T144500Z DTEND;VALUE=DATE-TIME:20240116T150500Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-268@indico.bitp.kiev.ua DESCRIPTION:Speakers: Oleksii Yanchyshen (Bogolyubov Institute for Theoret ical Physics)\nIn our work we consider geodesic equations in Schwarzschild space-time with arbitrary external forces and obtain Gaussian perturbatio n equations for osculating elements in terms of Weierstrass elliptic funct ions. As an application\, we solve the perturbation equations analytically in linear approximation for forces induced by the presence of the cosmolo gical constant in the Schwarzschild-de Sitter metric\, which we compared w ith a known analytical solution. Also\, we solve the perturbation equation s for hybrid Schwarzschild/post-Newtonian $2.5$ order self-forces.\n\nhttp s://indico.bitp.kiev.ua/event/11/contributions/268/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/268/ END:VEVENT BEGIN:VEVENT SUMMARY:Long-time asymptotic series for the Painleve II equation: Riemann- Hilbert approach DTSTART;VALUE=DATE-TIME:20240116T142500Z DTEND;VALUE=DATE-TIME:20240116T144500Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-267@indico.bitp.kiev.ua DESCRIPTION:Speakers: Yurii Zhuravlov (Bogolyubov Institute for Theoretica l Physics of the National Academy of Sciences of Ukraine)\nWe elaborate a systematic way to obtain higher order contributions in the nonlinear steep est descent method for Riemann-Hilbert problem associated with homogeneous Painleve II equation. The problem is reformulated as a matrix factorizati on problem on two circles and can be solved perturbatively reducing it to finite systems of algebraic linear equations. The method is applied to fin d explicitly long-time asymptotic behaviour for tau function of Painleve I I equation.\n\nhttps://indico.bitp.kiev.ua/event/11/contributions/267/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/267/ END:VEVENT BEGIN:VEVENT SUMMARY:Andreev reflection in scanning tunneling spectroscopy of unconvent ional superconductors DTSTART;VALUE=DATE-TIME:20240116T140500Z DTEND;VALUE=DATE-TIME:20240116T142500Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-263@indico.bitp.kiev.ua DESCRIPTION:Speakers: Pavlo Sukhachov (University of California\, Santa Cr uz)\nMotivated by recent experimental observations of unconventional super conductivity in the twisted bilayer and trilayer graphene\, we develop a t heory of point-contact tunneling into superconductors with arbitrary gap s tructures and for arbitrary transmission coefficients of the contact. Expl oiting the dependence of Andreev reflections on the position of the STM ti p relative to lattice symmetry points\, we show that the nature of the ord er parameter can be extracted by combining weak- and strong-tunneling limi ts of differential conductance. This provides complementary information ab out the superconducting gap structure beyond the tunneling density of stat es\, strongly facilitating the ability to extract the gap symmetry and its relation to the underlying crystalline lattice. We use the developed theo ry to discuss recent experimental results on superconductivity in twisted bilayer graphene.\n\nhttps://indico.bitp.kiev.ua/event/11/contributions/26 3/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/263/ END:VEVENT BEGIN:VEVENT SUMMARY:Theory of low-frequency electron fluctuations in a quasi-ballistic FET DTSTART;VALUE=DATE-TIME:20240116T132500Z DTEND;VALUE=DATE-TIME:20240116T134500Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-264@indico.bitp.kiev.ua DESCRIPTION:Speakers: Mykola Yelisieiev (Institute of Semiconductor Physic s\, NAS of Ukraine\, Kyiv\, Ukraine)\nWe investigated the electronic proce sses in a field effect transistor channel using shallow water approximatio ns to obtain the analytical expressions for electron and field distributio ns\, as well as electric fluctuations using the Langevin approach. We cons idered the current-voltage characteristic of the transistor in the station ary mode. For the non-stationary case\, we obtained the spatial distributi ons of the spectral fluctuations density for different parameters of the c hannel\, and the dependence of these values on the stationary parameters. We considered two modes of measuring transistor characteristics with a fix ed voltage or current.\n\nhttps://indico.bitp.kiev.ua/event/11/contributi ons/264/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/264/ END:VEVENT BEGIN:VEVENT SUMMARY:Optimization of quantum logic gates based on nonadiabatic Landau-Z ener-Stückelberg-Majorana transitions DTSTART;VALUE=DATE-TIME:20240116T130500Z DTEND;VALUE=DATE-TIME:20240116T132500Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-278@indico.bitp.kiev.ua DESCRIPTION:Speakers: Oleh Ivakhnenko (B. Verkin ILTPE of NASU | RIKEN\, J apan)\nQuantum logic gates applied to qubits are basic elements of the cir cuit model used for quantum computations. Usually\, quantum gates are real ized by a resonant excitation\, resulting in Rabi oscillations\, which lea d to a periodic excitation of the qubit. It has certain limitations and co mplications\, like neglecting counter-rotating terms. We investigate an al ternative way for quantum control and performing of quantum logic gates wi th Landau-Zener-Stückelberg-Majorana (LZSM) transitions [1\,2\,3] using n onadiabatic driving and alternation of the two stages of evolution: adiaba tic evolution and non-adiabatic transitions. We investigate mechanisms\, d ynamics\, and ways to optimize single-qubit LZSM gates [1\,3]. We apply th e adiabatic-impulse model to describe multiple LZSM transitions [1\,3]\, w hich we use to create LZSM-based quantum logic gates. Any single-qubit ope ration can be realized with only two LZSM transitions with an adjustable t ime of free evolution time before and after those transitions. To gain bet ter fidelity and reduce quantum gates performing time\, we can use multipl e LZSM transitions. LZSM-based quantum logic gates in comparison with Rabi oscillations based gates allow us to reduce gate time with keeping fideli ty high\, enabling us to perform more gates before the impact from decoher ence and relaxation becomes significant. Fig.1 shows the dynamics for the NOT (X) gate realized by double LZSM transitions.\nAcknowledgments: This r esearch was funded by the Army Research Office and was supported by Grant No. 911NF-20-1-0261\, RIKEN International Program Associate.\n\n1. A. Ryzh ov\, O. Ivakhnenko\, S. Shevchenko\, «Alternative fast quantum logic gate s using nonadiabatic Landau-Zener-Stückelberg-Majorana transitions»\, Ar Xiv:2310.17932\, 2023 \n2. D. Campbell\, et al.\, «Universal nonadiabatic control of small-gap superconducting qubits»\, Phys. Rev. X\, 2020 10\, 041051 \n3. O. V. Ivakhnenko\, S. N. Shevchenko and F. Nori «Nonadiabatic Landau-Zener-Stückelberg-Majorana transitions\, dynamics\, and interfere nce»\, Phys. Rep.\, 2023\, 995\, 1.\n\n\nFig. 1. Dynamics for the NOT (X) gate with ground initial state with double LZSM transitions: (a) dynamics on the Bloch sphere\, (b) dynamics of Bloch coordinates.\n\nhttps://indic o.bitp.kiev.ua/event/11/contributions/278/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/278/ END:VEVENT BEGIN:VEVENT SUMMARY:Theoretical study of a transmon-type qubit connected to a semi-inf inite transmission line DTSTART;VALUE=DATE-TIME:20240116T124500Z DTEND;VALUE=DATE-TIME:20240116T130500Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-284@indico.bitp.kiev.ua DESCRIPTION:Speakers: Maksym Liul (B. Verkin ILTPE of NASU)\nThe research is dedicated to a detailed theoretical study of dynamic processes that occ ur during the interaction of a transmon-type qubit connected to a semi-inf inite transmission line with two signals: pump and probe. By manipulating the frequencies and amplitudes of the signals it is possible to explore th e system behavior. We use the Lindblad equation formalism to make our calc ulations. From the solution of the Lindblad equation one can get upper cha rge level occupation probability as a function of pump and probe signals p arameters (amplitudes and frequencies) and build these dependencies. \nIn Ref. [1] the authors mentioned that the experimentally measured reflection coefficient corresponds to upper charge level occupation probability in t he theory. In Ref. [2] the theoretical model describing the system was dev eloped and approved experimentally. The current research is an extension o f the corresponding article: here we build the dependencies which were not considered before. Particularly we studied the steady state\, by plotting the dependence of upper charge level occupation probability on the probe frequency and the pump frequency. For studying dynamics the upper charge l evel occupation probability was built as a function of (a) time and the pr obe frequency\; (b) time and the probe frequency. The obtained plots provi de a deeper insight into the underlying physical processes and could be va luable for guiding future experiments. Additionally\, we address the Lindb lad equation using Lindblad superoperators in different bases. In our opin ion\, this comparative analysis holds significant methodological importanc e.\n\nAcknowledgments\nThe author was partially supported by the grant fro m the National Academy of Sciences of Ukraine for research works of young scientists (1/H-2023\, 0123U103073).\n\n1. P. Y. Wen\, O. V. Ivakhnenko\, M. A. Nakonechnyi\, B. Suri\, J.-J. Lin\, W.-J. Lin\, J. C. Chen\, S. N. S hevchenko\, F. Nori\, and I.-C. Hoi\, Landau-Zener-Stückelberg-Majorana i nterferometry of a superconducting qubit in front of a mirror\, Phys. Rev. B 102\, 075448 (2020).\n2. M. P. Liul\, C.-H. Chien\, C.-Y. Chen\, P. Y. Wen\, J. C. Chen\, Y.-H. Lin\, S. N. Shevchenko\, F. Nori\, and I.-C. Hoi\ , “Coherent dynamics of a photon-dressed qubit\,” Phys. Rev. B 107\, 1 95441 (2023).\n\nhttps://indico.bitp.kiev.ua/event/11/contributions/284/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/284/ END:VEVENT BEGIN:VEVENT SUMMARY:History and modern trends in thermoelectric and thermomagnetic phe nomena DTSTART;VALUE=DATE-TIME:20240116T120000Z DTEND;VALUE=DATE-TIME:20240116T124500Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-286@indico.bitp.kiev.ua DESCRIPTION:Speakers: Sergei Sharapov (Bogolyubov Institute for Theoretica l Physics of the National Academy of Sciences of Ukraine)\nhttps://indico. bitp.kiev.ua/event/11/contributions/286/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/286/ END:VEVENT BEGIN:VEVENT SUMMARY:How partition function zeros help find out the finite-size scaling above the upper critical dimension DTSTART;VALUE=DATE-TIME:20240116T093000Z DTEND;VALUE=DATE-TIME:20240116T095000Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-285@indico.bitp.kiev.ua DESCRIPTION:Speakers: Yulian Honchar (Institute for Condensed Matter Physi cs of the National Academy of Sciences of Ukraine\, Lviv\; Centre for Flui ds and Complex Systems\, Coventry University\,Coventry CV1 5FB\, UK\; L4 C ollaboration and Doctoral College for the Statistical Physics of Complex S ystems\, Lviv-Leipzig-Lorraine-Coventry\, Europe)\nFor many years the ques tion of finite-size scaling above the upper critical dimension dc was a so urce of many new theoretical results as well as new and interesting works in computer simulations\, see [1] for a review . While in the thermodynami c limit system’s scaling behaviour is mean-field\, for the finitesize sy stems two scaling regimes are being considered. Simple approach is a trivi al renormalization group fixed point\, obtained by setting all fields to z ero\, called Gaussian fixed point\, or G-scaling. Second scaling regime in troduces a new scaling exponent $q = max(1\, d/d_c)$\, that governs the sc aling of correlation length $\\xi$ with system size L\, it is called Q-sc aling. The latter was confirmed for periodic boundary conditions\, both at the infinite system’s critical temperature and at the pseudocritical po ints. For lattices with free boundary conditions the shifting and rounding of the susceptibility peak that occurs at the pseudocritical point are bi g enough to position the pseudocriticality far from the critical point of the infinite system. This leads to both scaling regimes emerge\, so theory predicted G-scaling at $T_c$ and Q-scaling at $T_L$. Numerical validation of the finite-size scaling for free boundary conditions was not clear\, a s the boundary effects are too strong to observe the scaling picture accur ately. In this work we show the shortcomings of the regular computer simul ations methods and improve the quality of the finite-size scaling using th e Lee-Yang zeros technique. Using the partition function zeros provides us with the more accurate scaling picture with smaller lattice sizes at hand [2].\n\n1. Berche\, B.\; Ellis\, T.\; Holovatch\, Yu.\; Kenna\, R. Phase Transitions above\nthe Upper Critical Dimension. SciPost Phys. Lect. Notes 2022\, 60. DOI:\n10.21468/SciPostPhysLectNotes.60\n2. Honchar Yu.\, Berch e B.\, Holovatch Yu.\, Kenna R. When correlations exceed\nsystem size: fin ite-size scaling in free boundary conditions above the upper\ncritical dim ension. // preprint ArXiv:. - 2023. - arXiv:2311.11721. (to\nappear in Con dens.Matter Phys 2024\, 1) DOI:10.48550/arXiv.2311.11721\n\nhttps://indico .bitp.kiev.ua/event/11/contributions/285/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/285/ END:VEVENT BEGIN:VEVENT SUMMARY:Phase behavior of ionic liquids in disordered porous media DTSTART;VALUE=DATE-TIME:20240116T080500Z DTEND;VALUE=DATE-TIME:20240116T085000Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-289@indico.bitp.kiev.ua DESCRIPTION:Speakers: Taras Patsahan (Institute for Condensed Matter Physi cs of the National Academy of Sciences of Ukraine)\nhttps://indico.bitp.k iev.ua/event/11/contributions/289/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/289/ END:VEVENT BEGIN:VEVENT SUMMARY:Towards the influence of compaction on the compressibility of a mo del bi-component mixture DTSTART;VALUE=DATE-TIME:20240116T091000Z DTEND;VALUE=DATE-TIME:20240116T093000Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-280@indico.bitp.kiev.ua DESCRIPTION:Speakers: Heorhiy Kudashkin (Odesa State Environmental Univers ity)\nThere are well-defined indications\, following from experimental stu dies of compressibility (adiabatic compressibility is measured using sound speed measurements\, and then isothermal compressibility is restored)\, t o the existence of a dependence of the compressibility of simple bi-compon ent mixtures not only on the molar fractions of the components [1]. It can be assumed that this parameter may be the compaction (packaging) paramete r [2].\nIn this way\, this work examines the question of the influence of the packing parameter on the compressibility of a model two-component mixt ure. For this purpose\, it is proposed to use extensions of the model equa tions of state (for example\, the van der Waals equation is chosen) for th e case of a two-component mixture together with an equation for compressib ility\, following from the Carnahan-Starling-Mansoori theory [3]\, which o perates precisely with the compactization factor.\nAnalytical expressions have been obtained to express the compressibility of a binary mixture thro ugh the molar fractions of the components and the compaction of the entire bi-component system. Using the obtained analytical expressions\, three-di mensional phase diagrams have been constructed in the axes compressibility \, the molar fraction of one of the components\, and the compaction of the mixture\, allowing one to track the joint influence of these parameters o n the equation of state model bi-component system.\nAs a result of studyin g the obtained phase diagrams\, it was established that the influence of i nternal parameters (molar composition\, compaction) is carried out jointly and consistently (multi-parameter). Mole composition and compaction\, for model systems (such as the hard ball model) are among the carefully contr olled parameters and thus\, the proposed model for describing compressibil ity is suitable for use to parameterize the results of empirical studies o f the dependence of the compressibility of simple binary mixtures (liquid\ , or granular) to the theoretical description of which the concept of hard spheres is applicable.\n\nREFERENCES\n\n1. F. Aliotta et al.\, J. Phys. Chem.\, 2007. 126\, 224508. https://doi.org/10.1063/1.2745292\n2. O. I. Ge rasymov et al.\, Tightening (Compaction) of Bi-Component Micromechanical ( Granular) System. Sci. innov.\, 2021. V. 17\, no. 4. P. 79—88.\nhttps:// doi.org/10.15407/scine17.04.079\n3. G. A. Mansoori\, N. F. Carnahan\, K.E. Starling\, T. W. Leland Jr. Equilibrium Thermodynamic Properties of the M ixture of Hard Spheres. The Journal of Chemical Physics\, 1971. 54(4)\, 15 23—1525. https://doi.org/10.1063/1.1675048.\n\nhttps://indico.bitp.kiev. ua/event/11/contributions/280/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/280/ END:VEVENT BEGIN:VEVENT SUMMARY:Towards the modeling of impurity migration in a heterogeneous medi a DTSTART;VALUE=DATE-TIME:20240116T085000Z DTEND;VALUE=DATE-TIME:20240116T091000Z DTSTAMP;VALUE=DATE-TIME:20260916T084415Z UID:indico-contribution-11-281@indico.bitp.kiev.ua DESCRIPTION:Speakers: Liudmyla Sidletskaya (Odesa State Environmental Univ ersity)\nOne of the primary tasks of ensuring the safety of objects in con tact with polluting objects (for example\, radiation waste) is to assess t he risks associated with the possible spread of impurities over long dista nces. Experiments that were carried out on a real natural scale\, in which the migration of an impurity injected into a layer including a network of migration channels was studied under natural conditions\, showed that in such heterogeneous media\, the tracer concentration profiles are significa ntly asymmetric. In particular\, they have an asymmetry strongly shifted t owards the flow\, in which the decrease in the impurity concentration does not correspond to the classical Fickian law of molecular diffusion and oc curs not according to an exponential law\, but rather according to a power law [1\,2]. Such an anomalous nature of the dispersion of impurities (for example\, radionuclides or other polluting components\, such as heavy met al atoms) during natural filtration in highly heterogeneous layers is dang erous due to the possibility of their migration over longer distances than follows from estimates made based on of the classical diffusion model.\nM odels with fractional spatial derivatives used in theoretical works to des cribe such experiments are\, as a rule\, limited to the one-dimensional ca se and are not directly applicable to the calculation of natural processes in three-dimensional anisotropic media. To solve this problem\, a concept for using multidimensional stochastic random walk models can be proposed\ , including modeling Lévy flights in the space of alpha-stable random pro cesses [3].\nAlpha-stable random processes are processes characterized by infinitely divisible scenarios (trajectories)\, which are\, in a certain s ense\, an attractor for all other processes.\nIf\, for example\, we consid er the well-known Kolmogorov equation [4] as a control equation in the one -dimensional case for different values of the control parameter\, then for some certain values of it\, it reduces to the usual diffusion equation. A t the same time\, there is such an interval of numerical values of the con trol parameter in which it turns into the diffusion equation with fraction al derivatives (fractional diffusion equation). And\, if the process chara cterized by the Gaussian distribution describes a random walk of a particl e that does not make long (super-diffusive) movements\, then under certain conditions we obtain distributions that describe so-called “Lévy fligh ts”\, which are suitable for modeling the movement of impurities through a system of channels in a given medium (matrix).\nIn the context describe d above\, for the problems of parameterization of experimental measurement data\, this work directly proposes a phenomenological expression for the impurity concentration function\, which depends on a small number of param eters and allows the description of the migration process in both classica l diffusion and large-scale (super-diffusion) modes.\n\n1. Xiaoying Zhang\ , Funing Ma \, Zhenxue Dai\, Ju Wang\, Liang Chen\, Hui Ling\, Mohamad Rez a Soltanian Radionuclide transport in multi-scale fractured rocks: A revie w Journal of Hazardous Materials Volume 424\, Part C\, 15 February 2022\, 127550.\n2. Li\, Y.\; Wu\, F.\; Li\, X.\; Tan\, X. Experimental study on w aterflood development in large–scale karst structures. J. Petrol. Sci. E ng.\, 2019. 175. 193–202.\n3. Fa K.S\, Lenzi E.K Power law diffusion coe fficient and anomalous diffusion: Analysis of solutions and first passage time. Phys Rev E\, 2003. 67:061105.\n4. Y. He\, S. Burov\, R. Metzler\, E. Barkai. Random Time-Scale Invariant Diffusion and Transport Coefficients. Phys Rev Lett\, 2008. 101:058101.\n\nhttps://indico.bitp.kiev.ua/event/11 /contributions/281/ LOCATION:BITP & Zoom URL:https://indico.bitp.kiev.ua/event/11/contributions/281/ END:VEVENT END:VCALENDAR