Russian Academy of Sciences

Landau Institute for Theoretical Physics

In Print

Parallel SPH modeling using dynamic domain decomposition and load balancing displacement of Voronoi subdomains

14 June in 11:30

Maria S. Egorova, Sergey A. Dyachkov, Anatoliy N. Parshikov, Vasily V. Zhakhovsky

A highly adaptive load balancing algorithm for parallel simulations using particle methods, such as molecular dynamics and smoothed particle hydrodynamics (SPH), is developed. Our algorithm is based on the dynamic spatial decomposition of simulated material samples between Voronoi subdomains, where each subdomain with all its particles is handled by a single computational process which is typically run on a single CPU core of a multiprocessor computing cluster. The algorithm displaces the positions of neighbor Voronoi subdomains in accordance with the local load imbalance between the corresponding processes. It results in particle transfers from heavy-loaded processes to less-loaded ones. Iteration of the algorithm puts into alignment the processor loads. Convergence to a well-balanced decomposition from imbalanced one is improved by the usage of multi-body terms in the balancing displacements. The high adaptability of the balancing algorithm to simulation conditions is illustrated by SPH modeling of the dynamic behavior of materials under extreme conditions, which are characterized by large pressure and velocity gradients, as a result of which the spatial distribution of particles varies greatly in time. The higher parallel efficiency of our algorithm in such conditions is demonstrated by comparison with the corresponding static decomposition of the computational domain. Our algorithm shows almost perfect strong scalability in tests using from tens to several thousand processes.
Publications: arXiv:1805.05128v2 [physics.comp-ph] ; Computer Physics Communications, Volume 234, January 2019, Pages 112-125

Termal’nyi effekt Kholla kak topologicheskii invaraint

7 June in 11:30

Lev Spodyneiko

We show that derivatives of thermal Hall conductance of a 2d lattice quantum system with respect to parameters of the Hamiltonian are well-defined bulk quantities provided correlators of local observables are short-range. This is despite the fact that thermal Hall conductance itself has no meaning as a bulk transport coefficient. We use this to define a relative topological invariant for gapped 2d lattice quantum systems at zero temperature. Up to a numerical factor, it can be identified with the difference of chiral central charges for the corresponding edge modes. This establishes bulk-boundary correspondence for the chiral central charge. We also show that for Local Commuting Projector Hamiltonians relative thermal Hall conductance vanishes identically, while for free fermionic systems it is related to the electric Hall conductance via the Wiedemann-Franz law.

Dissipative and Hall viscosity of a disordered 2D electron gas

7 June in 11:30

I.S. Burmistrov

Hydrodynamic charge transport is at the center of recent research efforts. Of particular interest is the nondissipative Hall viscosity, which conveys topological information in clean gapped systems. The prevalence of disorder in the real world calls for a study of its effect on viscosity. Here we address this question, both analytically and numerically, in the context of a disordered noninteracting 2D electrons. Analytically, we employ the self-consistent Born approximation, explicitly taking into account the modification of the single-particle density of states and the elastic transport time due to the Landau quantization. The reported results interpolate smoothly between the limiting cases of weak (strong) magnetic field and strong (weak) disorder. In the regime of weak magnetic field our results describes the quantum (Shubnikov-de Haas type) oscillations of the dissipative and Hall viscosity. For strong magnetic fields we characterize the effects of the disorder-induced broadening of the Landau levels on the viscosity coefficients. This is supplemented by numerical calculations for a few filled Landau levels. Our results show that the Hall viscosity is surprisingly robust to disorder.

Formation and decay of eddy currents generated by crossed surface waves

31 May in 11:30

Parfenyev V.M., Filatov S.V., Brazhnikov M.Yu., Vergeles S.S., Levchenko A.A.

The mass-transport induced by crossed surface waves consists of the Stokes and Euler contributions which are very different in nature. The first contribution is a generalization of Stokes drift for a plane wave in ideal fluid and the second contribution arises due to the fluid viscosity and it is excited by a force applied in the viscous sublayer near the fluid surface. We study the formation and decay of the induced mass-transport theoretically and experimentally and demonstrate that both contributions have different time scales for typical experimental conditions. The evolution of the Euler contribution is described by a diffusion equation, where the fluid kinematic viscosity plays the role of the diffusion coefficient, while the Stokes contribution evolves faster, feeling the additional damping near the system boundaries. The difference becomes more pronounced if the fluid surface is contaminated. We model the effect of contamination by a thin insoluble liquid film presented on the fluid surface with the compression modulus being the only non-zero rheological parameter of the film. Then the Euler contribution into the mass-transport becomes parametrically larger and the evolution of the Stokes contribution becomes parametrically faster. The parameter is the same in both cases and it is equal to the quality factor of surfaces waves, which is modified by the presence of a surface film. We infer the value of the compression modulus of the film by fitting the results of transient measurements of eddy currents and demonstrate that the obtained value leads to the correct ratio of amplitudes of horizontal and vertical velocities of the wave motion and is in reasonable agreement with the measured dissipation rate of surface waves.

Bernoulli Experiment under Restart

31 May in 11:30

S. Belan

It is known that restart of the stochastic process can significantly reduce the expected time required to its completion. This effect is widely implemented to speed up the randomized search algorithms and can potentially be used to increase the rate of chemical reactions. However, complex stochastic processes often exhibit several possible scenarios of completion which are not equally desirable in terms of efficiency. In this talk I will discuss how restart affects the splitting probabilities of a Bernoulli-like stochastic process, i.e., of a process which can end with one of two outcomes. Special attention will be paid to the class of problems, where a carefully tuned restart rate maximizes the chances to obtain the desired outcome. Importantly, the analysis revealed universality displayed by the optimally restarted processes.

Spetsial’naya Kelerova geometriya i teorii Landau-Ginzburga

17 May in 11:30

Konstantin Aleshkin

Doklad po teme predstavlyaemoi k zashchite kandidatskoi dissertatsii.

Aspects of quarkonium propagation in a thermal medium as seen by string models

17 May in 11:30 (short)

Oleg Andreev

We use gauge/string duality to model a heavy quark-antiquark pair in a color singlet moving through a thermal plasma. In particular, we explore the effect of velocity on the string tension and Debye screening mass. Then we apply the results to the analysis of heavy quarkonium bound states. With some assumptions, we estimate the characteristic size of quarkonium and its dissociation temperature.

Realizatsiya fermionnykh modelei v sistemakh kholodnykh atomov

19 April in 11:30

S. I. Matveenko

Pokazano, chto topologicheskoe sverkhtekuchee sostoyanie s p-sparivaniem (p_x + i p_y) mozhet byt’ realizovano v dvumernoi opticheskoi reshetke fermionnykh polyarnykh molekul. Dlya sistem s odnosloinoi i dvukhsloinoi geometriei vychislennye temperatury fazovykh perekhodov v sverkhtekuchee sostoyanie okazalis’ eksperimental’no dostizhimymi, poryadka desyatkov nanokel’vinov. [A.K. Fedorov, S.I. Matveenko, V. I. Yudson, G.V. Shlyapnikov , "Novel p-wave superfluids of fermionic polar molecules", Sci. Rep. 6, 27448; (2016).]
Issledovana chislenno i analiticheski fazovaya diagramma dvusloinoi sistemy fermionnykh polyarnykh molekul s disbalansom molekulyarnykh plotnostei v sloyakh. Dlya disbalansa (effektivnogo magnitnogo polya), prevyshayushchego kriticheskoe znachenie, sistema perekhodit pri dostatochno nizkikh temperaturakh iz sostoyaniya odnorodnoi sverkhtekuchei zhidkosti v sostoyaniya Larkina-Ovchinnikova-Ful’de-Ferrella s periodicheskoi strukturoi parametra poryadka. V otlichie ot sluchaya kontaktnogo vzaimodeistviya s singletnym sparivaniem, dipol’-dipol’noe vzaimodeistvie generiruet nenulevuyu tripletnuyu sostavlyayushchuyu parametra poryadka. [Hao Lee, S. I. Matveenko, Daw-Wei Wang, G. V. Shlyapnikov, "Fulde-Ferrell-Larkin-Ovchinnikov state in bilayer dipolar systems", Phys.Rev. A, 96, 061602(R) (2017)].
Issledovana odnomernoi model’ dvukhkomponentnogo fermionnogo gaza s sil’nym kontaktnym ottalkivaniem chastits s protivopolozhnym spinom i nelokal’nym prityazheniem fermionov s odinakovym spinom. Model’ mozhet byt’ eksperimental’no realizovana v sisteme kholodnykh atomov. Pri etom parametry vzaimodeistviya mogut izmenyat’sya v shirokom diapazone s pomoshch’yu vneshnego magnitnogo polya. Ispol’zuya metody bozonizatsii i renormgruppy, naideno osnovnoe sostoyanie sistemy v zavisimosti ot parametrov vzaimodeistviya. Pokazano, chto pri kriticheskom znachenii nelokal’nogo vzaimodeistviya proiskhodit fazovyi perekhod pervogo roda v sostoyanie s nenulevoi namagnichennost’yu. [D. V. Kurlov, S. I. Matveenko, V. Gritsev, G. V. Shlyapnikov, "One-dimensional two-component fermions with contact even-wave repulsion and SU(2) breaking near-resonant odd-wave attraction", Phys. Rev. A, (prinyata v pechat’)].

Some exact solutions of the Volterra lattice

19 April in 11:30

V.E. Adler, A.B. Shabat

We study solutions of the Volterra lattice satisfying the stationary equation for its non-autonomous symmetry. It is shown that the dynamics in $t$ and $n$ are governed by the continuous and discrete Painlev\'e equations, respectively. The class of initial data leading to regular solutions is described. For the lattice on the half-line, these solutions are expressed in terms of the confluent hypergeometric function. The Hankel transform of the coefficients of the corresponding Taylor series is computed on the basis of the Wronskian representation of the solution.

CDD factors in integrable models perturbed by the current-current operators

29 March in 11:30

M. Lashkevich, Y. Pugai

F. Smirnov and A. Zamolodchikov in the paper published in 2016 showed that a special class of irrelevant perturbations (current-current perturbations) in integrable models of quantum field theory leads to appearance of CDD factors in the scattering matrices, i.e. scalar factors corresponding to non-uniqueness of solution to the Yang-Baxter equation for S matrices. They considered the sine-Gordon model and analogous models that only contain odd-spin integrals of motion. We find CDD factors (in the first order in the perturbation theory) for the current-current perturbations on the example of models that contain even-spin integrals of motion as well, the complex sinh-Gordon model and the scaling Z_N symmetric Ising model. Thus we generalize the Smirnov-Zamolodchikov formula to the case of several particles with diagonal scattering. We also obtain the CDD factors for Lorentz non-invariant perturbations of this type. Technically we use the representation by free fields for form factors, developed by us earlier.

Sud’ba oskolkov obrazovaniya Luny: geofizicheskie sledstviya Gigantskogo stolknoveniya

29 March in 11:30

A.V. Byalko, M.I. Kuz’min (Institut geokhimii SO RAN)

Naibolee veroyatnyi stsenarii obrazovaniya Luny daetsya raschetami Gigantskogo stolknoveniya (GS) ProtoZemli s protoplanetoi, po masse, blizkoi Marsu [1, 2]. Iskhodya iz vozrasta zemnykh i lunnykh tsirkonov, GS proizoshlo 4.4—4.5 mlrd. let nazad, na 160—170 mln let pozzhe vzryva Sverkhnovoi, zadavshego izotopnyi sostav Solnechnoi sistemy (SS). Pri GS na beskonechnost’ ukhodyat gazy i silikatnye oskolki s obshchei massoi poryadka 55-70% massy Luny. Odnako beskonechnost’ ubegayushchikh chastits est’ beskonechnost’ v zemnoi sisteme otscheta, v SS eti oskolki vykhodyat na konechnye orbity s periodami kak men’she, tak i bol’she goda. Vazhneishaya osobennost’ ikh orbit v tom, chto vse oni prokhodyat cherez uzkuyu oblast’ zemnoi orbity, gde proiskhodilo GS. Tam formiruetsya gazopylevoi struinyi potok, s zatukhayushchei intensivnost’yu on sushchestvuet menee milliona let. Chislennymi resheniyami zadachi trekh tel rasschitany mnogochislennye traektorii oskolkov. Otseneny veroyatnosti ikh stolknovenii s Zemlei i Lunoi v zavisimosti ot vremeni posle GS, a takzhe popadaniya v treugol’nye tochki Lagranzha L4 i L5. Rassmotreny geofizicheskie sledstviya etikh stolknovenii.

1.Canup R.M. & Asphaug E. Origin of the Moon in a giant impact near the end of the Earth's formation, Nature, 412, 208–212 (2001).
2.Canup R.M. Simulations of a late lunar-forming impact, Icarus 168, 433–456 (2004).

Studies of the Liquid Crystal Surface Anchoring Potential using Grandjean-Cano Wedge

22 March in 11:30 (short)

V.A. Belyakov

We extend further the theoretical and experimental studies of the actual surface anchoring potential restoration by polarization microscope technique and using micro-images in a wedge-shaped cell with weak surface anchoring forces filled by a chiral nematic liquid crystal (in Grandjean-Cano Wedge). To realize the theoretically predicted options of observation of large director deviation angles from the easy axes the experimental studies of director distribution in Grandjean-Cano zones were performed for differing easy axes orientations at the wedge surfaces in white light. A weak surface anchoring at one wedge surface was obtained by a photo-alignment technique. A strong surface anchoring at the second wedge surface was obtained by a rubbing. There were observed for the first time jump-less walls (without jumps of the director orientation) between neighboring Grandjean-Cano zones and jumps in color in the Newton's rings (lines) at the positions of the walls between Grandjean-Cano zones. Qualitative explanations of the both phenomena are presented and an expression for the jump in color value in the Newton's rings (lines) at the positions of the walls between Grandjean-Cano zones is presented. Some experimentally found by the polarization microscope and by the micro-photo technique images demonstrate jump-less walls between the first Grandjean-Cano zones. To ensure optimal parameters of the further experiments on the actual surface anchoring potential restoration theoretical calculations of the director distribution in individual Grandjean-Cano zones were performed for various model surface anchoring potentials. It was found that especially promising for description of the experimentally found director distribution looks the modified D-potential. As a result of the present studies the ways to enlarge (compared to the previous studies) angular range of the actual surface anchoring potential restoration were proposed.
(The presentation is based at the following papers: V.A. Belyakov, D.V. Shmeliova, S.V. Semenov, On the way of reconstruction of the liquid crystal surface anchoring potential Journal of Molecular Liquids 267, 151–157 (2018), С. В. Семенов, В. А. Беляков, ПОВЕРХНОСТНОЕ СЦЕПЛЕНИЕ И РАСПРЕДЕЛЕНИЕ ДИРЕКТОРА В КЛИНЕ ГРАНЖАНА–КАНО, ЖЭТФ, 2018, том 153, вып. 5, стр. 838–844 ( 2018), V.A.Belyakov , D.V.Shmeliova, and S.V. Semenov, Studies of the Liquid Crystal Surface Anchoring Potential using Grandjean-Cano Wedge, LIQUID CRYSTALS (Published online: https://doi.org/10.1080/02678292.2018.1546412).

Obshchie osobennosti uglovykh diagramm provodimosti metallov v sil’nykh magnitnykh polyakh i slozhnost’ uglovykh diagrammakh magnitoprovodimosti v sil’nykh magnitnykh polyakh

22 March in 11:30

A.Ya. Maltsev

My rassmotrim samye obshchie osobennosti uglovykh diagramm provodimosti v normal’nykh metallakh so slozhnymi poverkhnostyami Fermi v prisutstvii sil’nykh magnitnykh polei. Opisanie takikh osobennostei budet osnovano na topologicheskom opisanii dinamicheskoi sistemy, voznikayushchei dlya evolyutsii elektronnykh sostoyanii na poverkhnosti Fermi v prisutstvii vneshnego magnitnogo polya. My rassmotrim uglovye diagrammy provodimosti dlya normal’nykh (monokristallicheskikh) metallov so slozhnymi poverkhnostyami Fermi v prisutstvii sil’nykh magnitnykh polei. Povedenie provodimosti v etom sluchae sil’no zavisit ot napravleniya magnitnogo polya i ustoichivye netrivial’nye rezhimy takogo povedeniya sootvetstvuyut pri etom spetsial’nym zonam ustoichivosti na uglovoi diagramme, otvechayushchim opredelennym (topologicheskim) svoistvam tenzora provodimosti. Kak my pokazhem, v obshchem sluchae mozhno razdelit’ takie diagrammy na dva obshchikh tipa, prostye (tip A) i slozhnye (tip B). Nas budut interesovat’ pri etom diagrammy vtorogo tipa, obladayushchie ryadom spetsificheskikh osobennostei (beskonechnoe chislo zon ustoichivosti, nalichie khaoticheskikh rezhimov i t.p.), kotorye my rassmotrim bolee podrobno. Po rezul’tatam rabot: ZhETF, t. 151, vyp. 5, 944-973 (2017); ZhETF, t. 152, vyp. 5(11), 1053-1064 (2017) , ZhETF, 154(6), 1183-1210 (2018)

Ergodic properties of dynamic systems on two-dimensional surfaces and electron transport phenomena in normal metals

22 March in 11:30 (short)

A.Ya. Maltsev, S.P. Novikov

V doklade obsuzhdaetsya svyaz’ spetsial’nykh kharakteristik dinamicheskikh sistem na poverkhnostyakh (indeksov Zoricha - Kontsevicha - Forni) s povedeniem provodimosti v metallakh v sil’nykh magnitnykh polyakh. Dannoe rassmotrenie yavlyaetsya vazhnym v sluchae vozniknoveniya naibolee slozhnykh (khaoticheskikh) elektronnykh traektorii na poverkhnosti Fermi, vozmozhnom dlya dostatochno slozhnykh poverkhnostei i spetsial’nykh napravlenii magnitnogo polya. Kak mozhno pokazat’, upomyanutye kharakteristiki imeyut neposredstvennoe otnoshenie k povedeniyu magnitoprovodimosti, takim obrazom, mozhno v printsipe govorit’ o vozmozhnosti ikh eksperimental’nogo opredeleniya v sootvetstvuyushchikh sluchayakh. Po rezul’tatam raboty: Trudy MIAN, tom 302, (2018) str. 296–315

SYK model with quadratic perturbations: the route to a non-Fermi-liquid

15 March in 11:30

A.V. Lunkin, K.S. Tikhonov, M.V. Feigel’man

Model’ SYK (Sachedev-Ye-Kitaev) opisyvaet sistemu sluchaino vzaimodeistvuyushchikh maioranovskikh fermionov bez kvadratichnykh chlenov v gamil’toniane. V predele bol’shogo chisla fermionov (N) i nizkikh temperaturakh (T « J, gde J - kharakternyi masshtab vzaimodeistviya) funktsiya Grina modeli, v sedlovom priblizhenii, imeet ne fermi-zhidkostnoe povedenie G(t) ~ t^(-1/2). Odnako, sedlovye uravneniya obladayut vysokoi simmetriei i dopuskayut zamenu t na proizvol’nuyu monotonnuyu funktsiyu f(t). Takoe reshenie imeet tol’ko SL(2,R) simmetriyu. Ponizhenie simmetrii ot polnoi gruppy reparametrizatsii do SL(2,R) privodit k sushchestovaniyu myagkoi mody, kotoraya stanovitsya sushchestvenna pri NT « J . Funktsiya Grina na samykh bol’shikh vremenakh menyaet svoyu asimptotiku na G(t) ~ t^(-3/2).
V nashei rabote my issleduem vliyanie kvadratichnogo vozmushcheniya na eto povedenie. Naivnoe rassmotrenie sedlovykh uravnenie pokazyvaet, chto na bol’shikh vremenakh fermi-zhidkostnoe povedenie dolzhno vosstanavlivat’sya. Odnako, voznikaet vopros: chto, proizoidyot esli eti vremena budut stol’ bol’shimi, chto nuzhno uchityvat’ fluktuatsii myagkoi mody? Rassmatrivaya vtoroi poryadok teorii vozmushcheniya my pokazyvaem, chto sushchestvuet nenulevoi interval amplitud vozmushchenii, kogda povedenie funktsii Grina ne menyaetsya, sokhranyaya asimptotiku G(t) ~ t^(-3/2). Eto pozvolyaet nadeyat’sya na ispol’zovanie modeli SYK dlya postroeniya kontroliruemoi teorii ne-fermizhidkostnogo povedeniya sil’no vzaimodeistvuyushchikh fermionov.

Boundary layer of elastic turbulence

15 March in 11:30 (short)

S. Belan, A. Chernykh, V. Lebedev

We consider the near-wall region in elastic turbulence of a dilute polymer solution in the limit of large Weissenberg number. As it was established experimentally, elastic turbulence possesses a boundary layer where the fluid velocity field can be approximated by a steady shear flow with relatively small fluctuations on the top of it. We examine analytically and numerically statistics of the polymer conformation in the boundary layer. An estimate for the ratio of the mean flow to the magnitude of flow fluctuations is obtained. This ratio is determined by the polymer concentration, the radius of gyration of polymers and their length in the fully extended state. The results of our asymptotic analysis reproduce the qualitative features of elastic turbulence at finite Weissenberg numbers.

XXXIV International Conference on Interaction of Intense Energy Fluxes with Matter, Elbrus-2019

15 March in 11:30 (short)

V.A. Khokhlov

Otchet ob uchastii v XXXIV Mezhdunarodnoi konferentsii po vzaimodeistviyu intensivnykh potokov energii s veshchestvom El’brus-2019

Physical processes during laser ablation into a liquid and during laser shock-wave pinning

15 March in 11:30 (short)

V.A. Khokhlov, N.A. Inogamov, V.V. Zhakhovsky,Yu.V. Petrov, S.I.Anisomov

The most important modern laser technologies include (1) the generation of colloid nanoparticles (NPs), laser ablation into a liquid (LAL—laser ablation in liquid) and (2) surface hardening of products by laser pinning (LSP—laser shock peening). Significantly, with laser pinning, the surface to be treated is washed with water. Therefore, the physics of processes during ablation into a liquid and during pinning is common. True, the accents are different. If the ablation in the liquid actually forget about the shock wave (SW) generated by the impact, and leaving the thickness of the target, in the problem with pinning, on the contrary, the main question is about the impact. In addition, the role of water in (1) and (2) is different. In (1) fluid contributes to the formation of NPs and adopts NPs, gently slowing them. Whereas in (2) water is needed to enhance the recoil and increase the amplitude of the hydrocarbon in the product. The complete picture, developed in the work, of course, should include both edges: and the formation of ejection into the liquid as a result of ablation—i.e. (1), observation of the SW wave from the nucleation stage to its attenuation in the product volume, i.e. (2).

Non-ergodic phase of the Quantum Random Energy Model

1 March in 11:30

L. Faoro, M. Feigel'man, L. Ioffe

Pokazano, chto fazovaya diagramma odnoi iz prosteishikh modelei kvantovogo spinovogo stekla – kvantovogo obobshcheniya modeli Derridy sluchainykh urovnei energii – obladaet neergodicheskoi delokalizovannoi fazoi s vremenem relaksatsii, eksponentsial’no dlinnym po chislu spinov n. Kak vremya relaksatsii, tak i ob’em Gil’bertova prostranstva, zanimaemyi mnogochastichnoi volnovoi funktsiei, yavlyayutsya stepennymi funktsiyami polnoi razmernosti Gil’bertova prostranstva N = 2^n. Oba eti pokazateli stepeni naideny v ramkakh priblizhennoi analiticheskoi teorii, poluchennye dlya nikh otvety neplokho soglasuyutsya s rezul’tatami pryamoi chislennoi diagonalizatsii. Poluchennye rezul’taty mogut byt’ polezny dlya fizicheskoi realizatsii kvantovogo simulyatora dlya resheniya zadach algoritmicheskoi optimizatsii tipa number partitioning.

Izuchenie sosushchestvovaniya faz v plenkakh smektikov v okrestnosti TKT dlya perekhoda geksatik - smektik A.

1 March in 11:30

V.V. Lebedev, E.S. Pikina , E.I. Kats

V rezul’tate teoreticheskogo analiza eksperimental’nykh dannykh po rasseyaniyu rentgenovkikh luchei na tonkikh svobodno podveshennykh plenkakh (SPP) zhidkogo kristalla 54COOBC vblizi fazovogo perekhoda smektik-A – geksatik ustanovleno, chto perekhod proiskhodit pervym rodom i vyyavlen temperaturnyi interval sosushchestvovaniya ukazannykh faz, kotoryi umen’shaetsya s umen’sheniem tolshchiny plenki. Eksperimental’nye dannye ob’yasnyayutsya blizost’yu sistemy k trikriticheskoi tochke (TKT). V ramkakh fenomenologicheskoi teorii fazovykh perekhodov Landau s vklyucheniem v rassmotrenie poverkhnostnykh effektov opredelena zavisimost’ shiriny dvukhfaznoi oblasti ot tolshchiny SPP v okrestnosti TKT. Analiticheskie raschety khorosho soglasuyutsya s rezul’tatami eksperimenta, i podtverzhdayut anomal’no glubokoe proniknovenie geksaticheskogo uporyadocheniya v SPP vblizi TKT. Zavisimost’ temperaturnogo intervala sosushchestvovaniya faz ot tolshchiny plenki svyazana s bol’shoi dlinoi korrelyatsii geksaticheskogo parametra poryadka. Poluchennye rezul’taty demonstriruyut unikal’nuyu vozmozhnost’ priblizheniya k trikriticheskoi tochke na linii fazovykh perekhodov smektik A - geksatik za schet izmeneniya tolshchiny plenki. Predlozhennyi podkhod mozhet byt’ primenen k shirokomu klassu sistem, obladayushchikh TKT.
Doklad osnovan na rabote: Evidence of a first-order smectic – hexatic transition and its proximity to tricritical point in smectic films., I.A. Zaluzhnyy, R.P. Kurta, N. Mukharamova, Y.Y. Kim, R.M. Khubbutdinov, D. Dzhigaev, V.V. Lebedev, E.S. Pikina, E.I. Kats, N.A. Clark, M. Sprung, B.I. Ostrovskii, I.A. Vartanyants, Phys. Rev. E, v. 98, p. 052703 (2018)

Laser technologies: science and applications

15 February in 11:30

N.A. Inogamov

In the first part of report the combined action of laser and plasmonic electromagnetic fields which dissipate in a metal film is considered. Fast dissipation of energy of light causes mechanical response moving a film. Motion and subsequent fast re-crystallization result in formation of surface micro-structures used for holographic purposes [1,2]. In the second part the physics of laser fragmentation of a liquid tin micro-droplet is analyzed. This is important for development of next generation of photo-lithography machines [3]. In the third part the indirect monitoring shot-to-shot shock waves strength reproducibility during the pump-probe experiments is studied [4]. The calibrated laser source is used after this checking for generation of shocks; goals for employing of these shocks are described in Albertazzi et al., Science Advances, 3(6), e1602705 (2017). [1] J. Phys.: Conf. Ser., 1092, 012051 (2018) [2] J. Phys.: Conf. Ser., 1092, 012052 (2018) [3] Phys. Rev. Applied 10, 064009 (2018) [4] J. Appl. Phys. 120, 035901 (2016)

Shock generation by laser and impact initiation of burning

15 February in 11:30

N.A. Inogamov

Generation of shocks by an ultrashort laser pulse is considered. Elastic-plastic response and polymorphic alpha-epsilon transition in iron are analyzed [1,2]. Initiation of initial stages of burning of high explosives by slow impact is studied [3]. Burning is caused by dissipative heating during plastic deformations.
[1] S.I. Ashitkov, V.V. Zhakhovsky, N.A. Inogamov, P.S. Komarov, M.B.Agranat, and G.I.Kanel, The behavior of iron under ultrafast shock loading driven by a femtosecond laser, AIP Conf. Proc. 1793, 100035 (2017) [2] V.V. Zhakhovsky, K.P. Migdal, N.A. Inogamov, S.I. Anisimov, MD simulation of steady shock-wave fronts with phase transition in single-crystal iron, AIP Conf. Proc. 1793, 070003 (2017) [3] D. Ilnitsky, N. Inogamov, V. Zhakhovsky, Response of explosive HMX to low-velocity impact: Modeling by the crystal plasticity finite element method, J. Phys.: Conf. Ser., 941, 012052 (2018)