Статті та доповіді ФМФІТ

Постійне посилання зібрання

https://dspace.onu.edu.ua/handle/123456789/1928

Переглянути

Перегляд Статті та доповіді ФМФІТ за Автор "Adamyan, Vadym M."

Зараз показуємо 1 - 3 з 3
  • Ескіз
    Документ
    Bending sound in graphene: Origin and manifestation
    (2016-11-11) Adamyan, Vadym M.; Bondarev, Viktor N.; Zavalniuk, V. V.; Адамян, Вадим Мовсесович
    It is proved that the acoustic-type dispersion of bending mode in graphene is generated by the fluctuation interaction between in-plane and out-of-plane terms in the free energy arising with account of non-linear components in the graphene strain tensor. In doing so we use an original adiabatic approximation based on the alleged (confirmed a posteriori) significant difference of sound speeds for in-plane and bending modes. The explicit expression for the bending sound speed depending only on the graphene mass density, in-plane elastic constants and temperature is deduced as well as the characteristics of the microscopic corrugations of graphene. The obtained results are in good quantitative agreement with the data of real experiments and computer simulations.
  • Ескіз
    Документ
    Dirac–Krein Systems on Star Graphs
    (2016-08-26) Adamyan, Vadym M.; Langer, H.; Tretter, C.; Winklmeier, M.; Адамян, Вадим Мовсесович
    We study the spectrum of a self-adjoint Dirac–Krein operator with potential on a compact star graph G with a finite number n of edges. This operator is defined by a Dirac–Krein differential expression with summable matrix potentials on each edge, by self-adjoint boundary conditions at the outer vertices, and by a self-adjoint matching condition at the common central vertex of G. Special attention is paid to Robin matching conditions with parameter τ ∈ R∪{∞}. Choosing the decoupled operator with Dirichlet condition at the central vertex as a reference operator, we derive Krein’s resolvent formula, introduce corresponding Weyl–Titchmarsh functions, study the multiplicities, dependence on τ , and interlacing properties of the eigenvalues, and prove a trace formula. Moreover, we show that, asymptotically for R → ∞, the difference of the number of eigenvalues in the intervals [0,R) and [−R, 0) deviates from some integer κ0, which we call dislocation index, at most by n+2.
  • Ескіз
    Документ
    Surface waveguide States and Nanocatalyst Activity.
    (2016) Adamyan, Vadym M.; Popov, I. Yu; Bliniva, I. V.; Адамян, Вадим Мовсесович
    Spectral problem for Schrodinger operator of half-crystal with surface impurities is considered. We use zero-range potentials model based on the theory of self-adjoint extensions of symmetric operators. The impurities are one-periodic chains of point-like potentials. The impurity leads to appearance of additional bands. The corresponding states are concentrated near the chain, i.e. it looks like a waveguide state. Hence, the electron density near the nanoparticle surface increases. This results in increasing of the catalytic activity of the nanoparticle.