1,361,527 research outputs found
Tkachenko polarons in vortex lattices
No full textWe analyze the properties of impurities immersed in a vortex lattice formed by ultracold bosons in the mean field quantum Hall regime. In addition to the effects of a periodic lattice potential, the impurity is dressed by collective modes with parabolic dispersion (Tkachenko modes). We derive the effective polaron model, which contains a marginal impurity-phonon interaction. The polaron spectral function exhibits a Lorentzian broadening for arbitrarily small wave vectors even at zero temperature, in contrast with the result for optical or acoustic phonons. The anomalous damping of Tkachenko polarons could be detected experimentally using momentum-resolved spectroscopy.FAPESP/CEPIDCNPq - CAPES/INCTCNPq (309234/2011-5
Electrical reorientation of liquid crystal molecules inside cylindrical pores for photonic device applications
No full textThe role of collective motion in examples of coarsening and self-assembly
No full textThe simplest prescription for building a patterned structure from its constituents is to add particles, one at a time, to an appropriate template. However, self-organizing molecular and colloidal systems in nature can evolve in much more hierarchical ways. Specifically, constituents (or clusters of constituents) may aggregate to form clusters (or clusters of clusters) that serve as building blocks for later stages of assembly. Here we evaluate the character and consequences of such collective motion in a set of prototypical assembly processes. We do so using computer simulations in which a system's capacity for hierarchical dynamics can be controlled systematically. By explicitly allowing or suppressing collective motion, we quantify its effects. We find that coarsening within a two dimensional attractive lattice gas (and an analogous off-lattice model in three dimensions) is naturally dominated by collective motion over a broad range of temperatures and densities. Under such circumstances, cluster mobility inhibits the development of uniform coexisting phases, especially when macroscopic segregation is strongly favored by thermodynamics. By contrast, the assembly of model viral capsids is not frustrated but is instead facilitated by collective moves, which promote the orderly binding of intermediates consisting of several monomers
Tkachenko modes of the square vortex lattice in a two-component Bose-Einstein condensate
No full textWe study Tkachenko modes of the square vortex lattice of a two-component Bose-Einstein condensate (BEC) in the mean-field quantum Hall regime, considering the coupling of these modes with density excitations. We derive the hydrodynamic equations and obtain the dispersion relations of the excitation modes. We find that there are two types of excitations, gapped inertial modes and gapless Tkachenko modes. These modes have two branches which we call acoustic and optical modes in analogy with phonons. The former has quadratic while the latter has linear wave-number dependence in both inertial and Tkachenko modes. Acoustic Tkachenko mode is found to be anisotropic while the other three modes are isotropic. The anisotropy of the acoustic Tkachenko mode reflects the four-fold symmetry of the square lattice
Tkachenko modes and structural phase transitions of the vortex lattice of a two-component Bose-Einstein condensate
No full textWe consider a rapidly rotating two-component Bose-Einstein condensate (BEC) containing a vortex lattice. We calculate the dispersion relation for small oscillations of vortex positions (Tkachenko modes) in the mean-field quantum Hall regime, taking into account the coupling of these modes with density excitations. Using an analytic form for the density of the vortex lattice, we numerically calculate the elastic constants for different lattice geometries. We also apply this method to calculate the elastic constant for the single-component triangular lattice. For a two-component BEC, there are two kinds of Tkachenko modes, which we call acoustic and optical in analogy with phonons. For all lattice types, acoustic Tkachenko mode frequencies have quadratic wave-number dependence at long wavelengths, while the optical Tkachenko modes have linear dependence. For triangular lattices the dispersion of the Tkachenko modes are isotropic, while for other lattice types the dispersion relations show directional dependence consistent with the symmetry of the lattice. Depending on the intercomponent interaction there are five distinct lattice types, and four structural phase transitions between them. Two of these transitions are second order and are accompanied by the softening of an acoustic Tkachenko mode. The remaining two transitions are first order and while one of them is accompanied by the softening of an optical mode, the other does not have any dramatic effect on the Tkachenko spectrum. We also find an instability of the vortex lattice when the intercomponent repulsion becomes stronger than the repulsion within components
Coulomb oscillations of the ballistic conductance in a quasi-one-dimensional quantum dot
No full textDevelopment of technology for production of bakery products a long shelf life flour from different types
No full textTkachenko N. Development of technology for production of bakery products a long shelf life flour from different types / N. Tkachenko, V. Dobrovolsky ; sci. supervisor I. Solonytska // Збірник наукових праць молодих учених, аспірантів та студентів / Одес. нац. акад. харч. технологій; гол. ред. Б.В. Єгоров, заст. гол. ред. Л.В. Капрельянц, Н.М. Поварова, відп. ред. Г.М. Станкевич. – Одеса: ОНАХТ, 2016. – с. 55–56 : – Бібліогр.: 4 назв
Tkachenko Ivan Hurovych
No full textУ статті відображено життєвий шлях Ткаченка Івана Гуровича, відомого українського педагога, дослідника, фахівця у галузі трудового виховання. Автором статті з’ясовано, шо науковий внесок вченого в розвиток української педагогічної науки є досить вагомим. Визначено, що науково-педагогічна спадщина вченого багатогранна, цікава і може бути предметом спеціального наукового дослідження.The article deals with the way of life of Tkachenko Ivan Hurovych, a famous Ukrainian educator, researcher, specialist in labor education. The scientific contribution of scientist to the development of Ukrainian pedagogical science is quite significant. It is identify that the scientific and pedagogical heritage of the scientist is multifaceted, interesting and can be the subject of special scientific research
Noncommutative Field Theory of the Tkachenko Mode: Symmetries and Decay Rate
No full textWe construct an effective field theory describing the collective Tkachenko
oscillation mode of a vortex lattice in a two-dimensional rotating
Bose-Einstein condensate in the long-wavelength regime. The theory has the form
of a noncommutative field theory of a Nambu-Goldstone boson, which exhibits a
noncommutative version of dipole symmetry. From the effective field theory, we
show that, at zero temperature, the decay width of the Tkachenko mode
scales with its energy as in the low-energy limit. We also
discuss the width of the Tkachenko mode at a small temperature.Comment: 6+8 pages. Accepted version to Physical Review Research Letters
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