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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Polukhin D. S.
Заглавие : Effects of cross correlations between inhomogeneities of the parameters of an isotropic medium on the spectrum and damping of elastic waves
Место публикации : J. Exp. Theor. Phys. - NEW YORK: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 110, Is. 2. - С. 345-359. - FEB. - ISSN 1063-7761, DOI 10.1134/S1063776110020184
Примечания : Cited Reference Count: 17. - Гранты: This study was supported in part by the Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools (grant no. 3818.2008.3) and the Presidium of the Russian Academy of Sciences (program no. 27.1) and performed within the framework of the Federal Target Program (State Contract no. 02.740.11.0220).Финансирующая организация: Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools [3818.2008.3]; Presidium of the Russian Academy of Sciences [27.1]; Federal Target Program [02.740.11.0220]
Ключевые слова (''Своб.индексиров.''): cross correlations--dispersion law--elastic force--inhomogeneities--isotropic medium--negative cross-correlation--physical nature--two parameter--wave spectra--damping--dispersions--elastic waves--hamiltonians--dispersion (waves)
Аннотация: The dispersion and damping laws have been investigated for elastic waves in an isotropic medium with one- and three-dimensional inhomogeneities of the density p(x) of the material and the elastic force constants mu(x) and lambda(x) with allowance for the cross correlations between these inhomogeneities. It has been demonstrated that the positive cross correlations between mu(x) and lambda(x), as well as the negative cross correlations between p(x) and mu(x) or p(x) and lambda(x), lead to an enhancement of the modification of the dispersion law and an increase in the damping of waves. The positive cross correlations between p(x) and mu(x) or p(x) and lambda(x), as well as the negative cross correlations between mu(x) and lambda(x), result in the opposite effects: a weakening of the modification of the dispersion law and a decrease in the damping. An analysis of the results obtained in this paper and in our recent work [15] has made it possible to formulate the general regularity of the effects of cross correlations, irrespective of the physical nature of the waves: the effects of cross correlations between inhomogeneities of any two parameters of the material on the wave spectrum depend on whether both parameters related by the cross correlations belong to the same part of the Hamiltonian (i.e., if they both belong to either the kinetic part or the potential part of the Hamiltonian) or they belong to different parts of the Hamiltonian. The positive cross correlations lead to a greater modification of the dispersion law and to an increase in the damping of waves in the former case and to a decrease in these characteristics in the latter case. Correspondingly, the negative cross correlations in each of these cases result in the opposite effects. This regularity has been explained qualitatively.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Polukhin D. S.
Заглавие : Crossing resonance of stochastically interacting wave fields
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2013. - Vol. 116, Is. 2. - P.206-222. - ISSN 1063-7761, DOI 10.1134/S1063776113020118
Примечания : Cited References: 42. - We are grateful to V. V. Val'kov and A. F. Sadreev for useful discussions. This work was supported by the Presidium of the Russian Academy of Sciences (Program no. 24.29), the Dynasty Foundation (Program for Support of Young Scientists), the Federal Target Program (state contract no. 14.B37.21.0730), and the Special Program for Siberian Federal University of the Ministry of Education and Science of the Russian Federation.
Предметные рубрики: CRYSTALS
SYSTEMS
ALLOYS
MEDIA
Аннотация: The dynamic susceptibilities (Green's functions) of the system of two interacting wave fields of different physical natures with a stochastically inhomogeneous coupling parameter between them with zero mean value have been examined. The well-known self-consistent approximation taking into account all diagrams with noncrossing correlation/interaction lines has been generalized to the case of stochastically interacting wave fields. The analysis has been performed for spin and elastic waves. The results obtained taking into account the processes of multiple scattering of waves from inhomogeneities are significantly different from those obtained for this situation earlier in the Bourret approximation [R.C. Bourret, Nuovo Cimento 26, 1 (1962)]. Instead of frequencies degeneracy removal in the wave spectrum and the splitting of resonance peaks of dynamic susceptibilities, a wide single-mode resonance peak should be observed at the crossing point of the unperturbed dispersion curves. The fine structure appears at vertices of these wide peaks in the form of a narrow resonance on the Green's-function curve of one field and a narrow antiresonance on the vertex of the Green's-function curve of the other field.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Polukhin D. S.
Заглавие : Crossing resonance of wave fields in a medium with an inhomogeneous coupling parameter
Место публикации : J. Exp. Theor. Phys. - 2013. - Vol. 117, Is. 5. - P.846-861. - ISSN 1063-7761, DOI 10.1134/S1063776113130049
Аннотация: The dynamic susceptibilities (Green's functions) of the system of two coupled wave fields of different physical natures in a medium with an arbitrary relation between the mean value É and rms fluctuation ΔÉ of the coupling parameter have been examined. The self-consistent approximation involving all diagrams with noncrossing correlation lines has been developed for the case where the initial Green's function of the homogeneous medium describes the system of coupled wave fields. The analysis has been performed for spin and elastic waves. Expressions have been obtained for the diagonal elements G mm and G uu of the matrix Green's function, which describe spin and elastic waves in the case of magnetic and elastic excitations, and for the off-diagonal elements G mu and G um, which describe these waves in the case of cross excitation. Change in the forms of these elements has been numerically studied for the case of one-dimensional inhomogeneities with an increase in ΔÉ and with a decrease in É under the condition that the sum of the squares of these quantities is conserved: two peaks in the frequency dependences of imaginary parts of G mm and G uu are broadened and then joined into one broad peak; a fine structure appears in the form of narrow resonance at the vertex of the Green's function of one wave field and narrow antiresonance at the vertex of the Green's function of the other field; peaks of the fine structure are broadened and then disappear with an increase in the correlation wavenumber of the inhomogeneities of the coupling parameter; and the amplitudes of the off-diagonal elements vanish in the limit É → 0.
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4.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Ignatchenko V. A., Polukhin D. S.
Заглавие : Crossing resonance of wave fields in media with the inhomogeneouscoupling parameter
Коллективы : Euro-Asian Symposium "Trends in MAGnetism": Nanomagnetism
Место публикации : V Euro-Asian simposium "Trend in MAGnetism": Nanomagnetism: abstracts. - Vladivostok: FEFU, 2013. - С. 102. - ISBN 978-5-7444-3124-2
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Polukhin D. S.
Заглавие : Development of a self-consistent approximation
Место публикации : J. Phys. A: IOP Publishing, 2016. - Vol. 49, Is. 9. - Ст.095004. - ISSN 17518113 (ISSN), DOI 10.1088/1751-8113/49/9/095004
Примечания : Cited References: 43
Предметные рубрики: SUPERCONDUCTING CRITICAL-TEMPERATURE
LATTICE-VIBRATIONS
VERTEX FUNCTION
ELECTRON
Ключевые слова (''Своб.индексиров.''): self-consistent approximation--green's functions--vertex corrections--inhomogeneities--correlations--dynamic susceptibility
Аннотация: A self-consistent approximation of a higher level than the standard self-consistent approximation, known in various fields of physics as the Migdal, Kraichnan or Born self-consistent approximation, is derived taking into account both the first and second terms of the series for the vertex function. In contrast to the standard approximation, the new self-consistent approximation is described by a system of two coupled nonlinear integral equations for the self-energy and the vertex function. In addition to all the diagrams with non-intersecting lines of correlation/interaction taken into account by the standard self-consistent approximation, the new approach takes into account in each term of the Green's function expansion a significant number of diagrams with intersections of these lines. Because of this, the shape, linewidth, and amplitude of the resonance peaks of the dynamic susceptibility calculated in this approximation are much closer to the exact values of these characteristics. The advantage of the new self-consistent approach is demonstrated by the example of calculation of the dynamic susceptibility of waves in an inhomogeneous medium. © 2016 IOP Publishing Ltd.
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6.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Ignatchenko V. A., Polukhin D. S.
Заглавие : Development of the magnetoelastic resonance theory in ingomogeneous media
Коллективы : Moscow International Symposium on Magnetism, Московский государственный университет им. М.В. Ломоносова, Российский фонд фундаментальных исследований
Место публикации : Moscow Int. Symp. on Magnet. (MISM-2017): 1-7 July 2017 : book of abstracts. - 2017. - Ст.2PO-K-20. - P.223
Примечания : Cited References: 3
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Polukhin D. S.
Заглавие : Development of the self-consistent approximation and its application to the problem of magnetoelastic resonance in an inhomogeneous medium
Коллективы : Siberian Branch of the Russian Academy of Sciences [0356-2015-0411]
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2017. - Vol. 125, Is. 1. - P.91-103. - ISSN 1063-7761, DOI 10.1134/S1063776117060115. - ISSN 1090-6509(eISSN)
Примечания : Cited References:27. - This work was supported in part by the Complex Program II.2P (0356-2015-0411) of the Siberian Branch of the Russian Academy of Sciences.
Предметные рубрики: SUPERCONDUCTING CRITICAL-TEMPERATURE
COUPLING PARAMETER
MIGDALS
Аннотация: Our previously proposed approximation involving both the first and second terms of the expansion of the vertex function is generalized to the system of two interacting wavefields of different physical nature. A system of self-consistent equations for the matrix Green’s function and matrix vertex function is derived. On the basis of this matrix generalization of the new self-consistent approximation, a theory of magnetoelastic resonance is developed for a ferromagnetic model, where the magnetoelastic coupling parameter ε(x) is inhomogeneous. Equations for magnetoelastic resonance are analyzed for one-dimensional inhomogeneities of the coupling parameter. The diagonal and off-diagonal elements of the matrix Green’s function of the system of coupled spin and elastic waves are calculated with the change in the ratio between the average value ε and rms fluctuation Δε of the coupling parameter between waves from the homogeneous case (ε ≠ 0, Δε = 0) to the extremely randomized case (ε = 0, Δε ≠ 0) at various correlation wavenumbers of inhomogeneities kc. For the limiting case of infinite correlation radius (kc = 0), in addition to approximate expressions, exact analytical expressions corresponding to the summation of all diagrams of elements of the matrix Green’s function are obtained. The results calculated for an arbitrary kc value in the new self-consistent approximation are compared to the results obtained in the standard self-consistent approximation, where only the first term of the expansion of the vertex function is taken into account. It is shown that the new approximation corrects disadvantages of the Green’s functions calculated in the standard approximation such as the dome shape of resonances and bends on the sides of resonance peaks. The appearance of a fine structure of the spectrum in the form of a narrow resonance on the Green’s function of spin waves and a narrow antiresonance on the Green’s function of elastic waves, which was previously predicted in the standard self-consistent approximation, is confirmed. With an increase in the parameter kc, the Green’s functions calculated in the standard and new approximations approach each other and almost coincide with each other at kc/k ≥ 0.5. At the same time, the results of this work indicate that the new self-consistent approximation has a certain advantage for studying the problems of stochastic radiophysics in media with long-wavelength inhomogeneities (small kc values), because it describes both the shape and width of peaks much better than the standard approximation.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Polukhin D. S.
Заглавие : Effect of cross correlations between inhomogeneities on the spectrum and damping of spin and elastic waves
Коллективы :
Место публикации : Low Temp. Phys. - 2010. - Vol. 36, Is. 8-9. - P.741-746. - ISSN 1063-777X, DOI 10.1063/1.3490860; \b Физика низких температур
Примечания : Cited References: 13. - This work was partially supported by Program No. 27 of the Presidium of the Russian Academy of Sciences, State contract No. 02.740.11.0220 as part of the Federal targeted program and the State program "Development of the scientific potential of higher education," project No. 2.1.1/3498.
Предметные рубрики: FERROMAGNET
Аннотация: This is a study of the dispersion relations and damping of spin waves in ferromagnets with inhomogeneities in their exchange and magnetic anisotropy parameters and of elastic waves in isotropic media with inhomogeneities in the density of matter and in the elastic force constants, with cross correlations between these inhomogeneities taken into account. A general behavior is found which is independent of the physical nature of the waves: the kind of effect cross correlations between inhomogeneities in any two parameters of a material will have on the wave spectrum depends on whether both parameters belong to the same (i.e., both belong to the kinetic part or both belong to the potential part) or to different parts of the hamiltonian. In the former case, positive cross correlations lead to a substantial modification of the dispersion relation and to increased wave damping, and in the latter case, to a smaller modification of these characteristics. On the other hand, negative cross correlations lead to the opposite effects in both cases. This behavior is explained qualitatively. (c) 2010 American Institute of Physics. [doi:10.1063/1.3490860]
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Polukhin D. S.
Заглавие : Effects of cross correlations between exchange and magnetic-anisotropy inhomogeneities on the spectrum and damping of spin waves
Коллективы : Russian Federation for the Support of Leading Scientific Schools [3818.2008.3]
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2009. - Vol. 51, Is. 5. - P940-948. - ISSN 1063-7834, DOI 10.1134/S1063783409050096
Примечания : Cited References: 9. - This study was supported in part by the Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools (project no. 3818.2008.3).
Аннотация: Effects of cross correlations between inhomogeneities of the exchange and magnetic-anisotropy parameters on the spectrum and damping of spin waves in a ferromagnet are investigated. One- and three-dimensional inhomogeneities are considered. It is demonstrated that the positive cross correlations lead to an increase in the modification of the dispersion law and the damping of spin waves. The negative cross correlations result in the opposite effects: a decrease in the modification of the dispersion law and a decrease in the damping of spin waves. A comparison of the specific features revealed in this work and the results of targeted experimental investigations of modifications of the dispersion laws and damping in inhomogeneous magnets would make it possible to determine the contribution of the cross correlations to the formation of the stochastically inhomogeneous ground state in amorphous magnetic alloys.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Polukhin D. S.
Заглавие : Effects of cross correlations between inhomogeneities of the parameters of an isotropic medium on the spectrum and damping of elastic waves
Коллективы :
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 110, Is. 2. - P345-359. - ISSN 1063-7761, DOI 10.1134/S1063776110020184
Примечания : Cited References: 17. - This study was supported in part by the Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools (grant no. 3818.2008.3) and the Presidium of the Russian Academy of Sciences (program no. 27.1) and performed within the framework of the Federal Target Program (State Contract no. 02.740.11.0220).
Ключевые слова (''Своб.индексиров.''): cross correlations--dispersion law--elastic force--inhomogeneities--isotropic medium--negative cross-correlation--physical nature--two parameter--wave spectra--damping--dispersions--elastic waves--hamiltonians--dispersion (waves)
Аннотация: The dispersion and damping laws have been investigated for elastic waves in an isotropic medium with one- and three-dimensional inhomogeneities of the density p(x) of the material and the elastic force constants mu(x) and lambda(x) with allowance for the cross correlations between these inhomogeneities. It has been demonstrated that the positive cross correlations between mu(x) and lambda(x), as well as the negative cross correlations between p(x) and mu(x) or p(x) and lambda(x), lead to an enhancement of the modification of the dispersion law and an increase in the damping of waves. The positive cross correlations between p(x) and mu(x) or p(x) and lambda(x), as well as the negative cross correlations between mu(x) and lambda(x), result in the opposite effects: a weakening of the modification of the dispersion law and a decrease in the damping. An analysis of the results obtained in this paper and in our recent work [15] has made it possible to formulate the general regularity of the effects of cross correlations, irrespective of the physical nature of the waves: the effects of cross correlations between inhomogeneities of any two parameters of the material on the wave spectrum depend on whether both parameters related by the cross correlations belong to the same part of the Hamiltonian (i.e., if they both belong to either the kinetic part or the potential part of the Hamiltonian) or they belong to different parts of the Hamiltonian. The positive cross correlations lead to a greater modification of the dispersion law and to an increase in the damping of waves in the former case and to a decrease in these characteristics in the latter case. Correspondingly, the negative cross correlations in each of these cases result in the opposite effects. This regularity has been explained qualitatively.
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