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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Popov M. A.
Заглавие : Tree growth parameter in the Eden model on face-centered hypercubic lattices
Место публикации : Theor. Math. Phys. - 2005. - Vol. 144, Is. 3. - P.1361-1371. - ISSN 0040-5779, DOI 10.1007/s11232-005-0165-z
Примечания : Cited References: 19
Предметные рубрики: BRANCHED POLYMERS
HIGH-TEMPERATURES
EXPANSION
CLUSTERS
SYSTEMS
TIME
Ключевые слова (''Своб.индексиров.''): eden model--number of lattice trees--monte carlo method--growth parameter--singular points of generating function--large-dimension expansion--face-centered hypercubic lattice--eden model--face-centered hypercubic lattice--growth parameter--large-dimension expansion--monte carlo method--number of lattice trees--singular points of generating function
Аннотация: In the Eden model, we investigate how the tree growth parameter depends on the space dimension d for face-centered hypercubic lattices. We find the first three terms of the 1/d-expansion for this parameter directly from the generating function without calculating the number of trees because the growth parameter is the reciprocal coordinate of the singular point of the tree generating function. The same growth parameter was calculated by computer experiment where the ratios between the numbers of trees without intersections and trees without restrictions in the dimensions 3, 4, 6, 8, and 10 were estimated by the Monte Carlo method on face-centered cubic lattices. The results of the two methods agree well. Comparing with the previously performed computer experiment for simple hypercubic lattices, we observe that the values of the singular exponents for the tree generating functions are close for two different types of lattices.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Popov M. A.
Заглавие : The coordinate of a singular point of the time correlation functions for a heteronuclear spin system of a crystal
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2005. - Vol. 100, Is. 4. - P775-783. - ISSN 1063-7761, DOI 10.1134/1.1926438
Примечания : Cited References: 24
Предметные рубрики: FLUCTUATION SPECTRUM
CROSS-RELAXATION
NMR ABSORPTION
SHAPE
WINGS
LINE
Ключевые слова (''Своб.индексиров.''): correlation methods--crystal lattices--crystallography--functions--integral equations--lithium compounds--nuclear magnetic resonance--quantum theory--random processes--autocorrelation functions (acf)--dipole-dipole interactions (ddi)--heteronuclear spin systems--self-consistent fluctuating field (scff)--crystals
Аннотация: The singularities of the time autocorrelation functions (ACFs) for a heteronuclear spin system of a crystal are investigated. Exact expressions are obtained for ten moments of the spectra of ACFs in the approximation of a self-consistent fluctuating field (SCFF) with arbitrary axial symmetry. These expressions are applied to determine the coordinate of the lowest singular point of these functions on the imaginary-time axis for a spin system with a dipole-dipole interaction (DDI). The leading corrections to this coordinate due to the correlation of local fields in real crystals are calculated. These corrections are determined by lattice sums with triangles of four bonds and pairs of four bonds. Numerical values of the coordinate are obtained for a LiF crystal in a magnetic field directed along three crystallographic axes. An increase in the coordinate of the singular point, which follows from the theory and leads to a faster falloff of the wings of the ACF spectra, qualitatively agrees with experiment. © 2005 Pleiades Publishing, Inc.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E.
Заглавие : Singular points of time-dependent correlation functions of spin systems on large-dimensional lattices at high temperatures
Место публикации : Theor. Math. Phys.: PLENUM PUBL CORP, 2000. - Vol. 123, Is. 1. - P511-523. - ISSN 0040-5779, DOI 10.1007/BF02551058
Примечания : Cited References: 21
Предметные рубрики: BRANCHED POLYMERS
HEISENBERG MAGNET
EXPANSION
MODELS
Аннотация: Time-dependent autocorrelation functions are investigated for the Heisenberg model with spins 1/2 on d-dimensional simple cubic lattices of large dimensions d at infinite temperature. The autocorrelation function on the imaginary time axis is interpreted as the generating function of bond trees constructed with double bonds. These trees provide the leading terms with respect to lid for the time-expansion coefficients of the autocorrelation function. The correction terms from branch intersections to the generating function in the Bethe approximation are derived for these trees. A procedure is suggested for finding the correction to the coordinate of the singular point of the generating function (i.e., to the reciprocal of the branch growth-rate parameter) from the above correction terms without calculating the number of trees. The leading correction terms of order 1/sigma(2) (where sigma = 2d - 1) are found for the coordinates of the singular points of the autocorrelation function in question and for the generating function of the trees constructed with single bonds in the Eden model.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Second moment of multiple-quantum NMR and a time-dependent growth of the number of multispin correlations in solids
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 103, Is. 6. - P904-916. - ISSN 1063-7761, DOI 10.1134/S1063776106120089
Примечания : Cited References: 39
Предметные рубрики: NUCLEAR-MAGNETIC-RESONANCE
LINE-SHAPE
SPIN SYSTEMS
DYNAMICS
SPECTRA
COHERENCES
STATE
BEHAVIOR
CRYSTAL
MODEL
Ключевые слова (''Своб.индексиров.''): correlation methods--mathematical models--nuclear magnetic resonance spectroscopy--spectrum analysis--time series analysis--four-spin time correlation--multispin correlations--second moment--time power series--quantum theory
Аннотация: The time evolution of multispin correlations (the growth of the number of correlated spins as a function of time) can be observed directly using the multiple-quantum nuclear magnetic resonance spectroscopy of solids. A quantity related to this number, namely, the second moment n(2)(t) of the intensity distribution of coherences of different orders in the multiple-quantum spectrum can be calculated using the theory proposed in this work. An approach to the calculation of the four-spin time correlation function through which this moment is expressed is developed. The main sequences of contributions in the expansion of this function into a time power series are summed using the approximation of a large number of neighbors both for systems with a secular dipole-dipole interaction and for systems with a nonsecular effective interaction. An exponential dependence of n(2)(t) is obtained. The value of n(2)(t) is additionally calculated using an expansion in terms of orthogonal operators for three model examples corresponding to different limiting realizations of spin systems. It is shown that the results of the microscopic theory at least qualitatively agree with both the results obtained for model examples and experimental results obtained recently for adamantane.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Shauro V. P.
Заглавие : On time-optimal NMR control of states of qutrits represented by quadrupole nuclei with the spin I=1
Разночтения заглавия :авие SCOPUS: On time-optimal NMR control of states of qutrits represented by quadrupole nuclei with the spin i = 1
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 113, Is. 2. - P181-191. - ISSN 1063-7761, DOI 10.1134/S1063776111060094
Примечания : Cited References: 48. - This work was supported by the Russian Foundation for Basic Research (project no. 09-07-00138) and the Dynasty Foundation.
Предметные рубрики: QUANTUM COMPUTATION
MAGNETIC-RESONANCE
ALGORITHMS
ELEMENTS
PULSES
DESIGN
QUDITS
GATES
Ключевые слова (''Своб.индексиров.''): logical operators--nuclear spins--numerical optimizations--optimality--physical parameters--quadrupole nuclei--qutrits--radio frequencies--rf pulse--three level systems--time dependence--time-optimal--computer control systems--computer simulation--fourier transforms--optimization--quantum computers--resonance--nuclear quadrupole resonance
Аннотация: Elementary logical operators (selective rotation, Fourier transform, controllable phase shift, and SUM gate) are considered for a quantum computer based on three-level systems (qutrits) represented by nuclear spins I = 1 under nuclear magnetic resonance conditions. The computer simulation of the realization of these operators by means of simple and composite selective radiofrequency (RF) pulses and optimized RF pulses is performed. The time dependence of the amplitude of last pulses is found by numerical optimization at different durations. Two variants are proposed for realization of a two-qutrit SUM gate by using one-qutrit or two-qutrit optimized RF pulses. The calculated time dependences of realization errors were used to study the time optimality of different methods for obtaining gates, proposed earlier and in this paper. The advantages and disadvantages of each of the methods are evaluated for different values of physical parameters.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Popov M. A.
Заглавие : On the radius of convergence of series in powers of time for spin correlation functions of the Heisenberg magnet at high temperature
Место публикации : Theor. Math. Phys.: PLENUM PUBL CORP, 1997. - Vol. 112, Is. 3. - P1182-1191. - ISSN 0040-5779, DOI 10.1007/BF02583049
Примечания : Cited References: 22
Предметные рубрики: AUTO-CORRELATION FUNCTION
INFINITE-TEMPERATURE
PARAMAGNET
DYNAMICS
MODEL
Аннотация: The convergence of series in powers of time for spin autocorrelation functions of the Heisenberg magnet are investigated at infinite temperatures on lattices of different dimensions d. The calculation data available at the present time for the coefficients of these series are used to estimate the corresponding radii of convergence, whose growth with decreasing d is revealed and explained in a self-consistent approximation. To this end, a simplified nonlinear equation corresponding to this approximation is suggested and solved for the autocorrelation function of a system with an arbitrary number Z of nearest neighbors. The coefficients of the expansion in powers of time for the solution are represented in the form of trees on the Bethe lattice with the coordination number Z. A computer simulation method is applied to calculate the expansion coefficients for trees embedded in square, triangular, and simple cubic lattices under the condition that the intersection of tree branches is forbidden. It is found that the excluded volume effect that manifests itself in a decrease in these coefficients and in an increase in the coordinate and exponent of the singularity of the autocorrelation function on the imaginary time axis is intensified with decreasing lattice dimensions.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Kucherov M. M.
Заглавие : On the effect of an inhomogeneous magnetic field on high-frequency asymptotic behaviors of correlation functions of spin lattices
Место публикации : JETP Letters. - 2018. - Vol. 107, Is. 9. - P.553-557. - ISSN 0021-3640, DOI 10.1134/S002136401809014X. - ISSN 1090-6487(eISSN)
Примечания : Cited References: 39
Предметные рубрики: HEISENBERG PARAMAGNET
SYSTEMS
TIME
RELAXATION
DYNAMICS
SPECTRA
Аннотация: Singular points of spin autocorrelation functions on the imaginary time axis, which determine the arguments of exponential high-frequency asymptotic behaviors, have been analyzed. It has been shown that randomly distributed inhomogeneous magnetic fields expand the wings of spectra of autocorrelation functions and, thereby, intensify the heating of a system subjected to variable magnetic fields, which are used to create effective Hamiltonians or at the saturation of inhomogeneously broadened EPR lines.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : On the effect of an inhomogeneous magnetic field and many-body localization on the increase in the second moment of multiple-quantum NMR with time
Место публикации : JETP Letters. - 2017. - Vol. 105, Is. 8. - P.514-518. - ISSN 00213640 (ISSN), DOI 10.1134/S0021364017080148
Примечания : Cited References: 27
Аннотация: A change in the time dependence of the second moment of the distribution of intensities of coherences with various orders in the spectrum of multiple-quantum NMR in a solid at the inclusion of an inhomogeneous magnetic field in the effective interaction is studied. Both the secular dipole–dipole and nonspecular twoquantum interactions are considered as nucleus–nucleus interactions, which correspond to traditional experimental realizations. It is shown that, with an increase in the magnitude of the inhomogeneous field, an exponential increase in the second moment of multiple-quantum NMR with time changes to a power-law increase. The results obtained in this work indicate that this second moment, which determines the average number of dynamically correlated spins, can be used as a convenient characteristic for studying a transition to a many-body localized state. © 2017, Pleiades Publishing, Inc.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Popov M. A.
Заглавие : On the coordinate of a singular point of time correlation functions for the system of nuclear magnetic moments of a crystal
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2003. - Vol. 97, Is. 1. - P78-84. - ISSN 1063-7761, DOI 10.1134/1.1600799
Примечания : Cited References: 22
Предметные рубрики: DIPOLAR FLUCTUATION SPECTRUM
FREE-INDUCTION DECAY
CROSS-RELAXATION
DOUBLE-RESONANCE
SPIN SYSTEMS
NMR-SPECTRA
LINE SHAPE
IRREVERSIBILITY
ABSORPTION
CAF2
Ключевые слова (''Своб.индексиров.''): absorption spectroscopy--barium compounds--crystallography--lattice constants--magnetic fields--nuclear magnetic resonance--absorption spectrum--dipole-dipole interaction--magnetic field directions--nuclear magnetic moments--magnetic moments
Аннотация: The hypothesis concerning the existence of singular points on the imaginary time axis for a correlation function of a system with the dipole-dipole interaction of nuclear spins of a crystal is verified. Within the framework of the self-consistent fluctuating field theory taking into account the principal corrections related to the correlation of local fields, a result for this coordinate is obtained in terms of the ratios of lattice sums. Experimental values of this coordinate are calculated from the wings of the nuclear magnetic resonance absorption spectrum of a BaF2 crystal for the magnetic field directions along the three crystallographic axes. Good agreement of the theoretical and experimental results justifies this hypothesis. (C) 2003 MAIK "Nauka / Interperiodica".
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Popov M. A.
Заглавие : On the coordinate of a singular point of the time correlation function for a spin system on a simple hypercubic lattice at high temperatures
Место публикации : Theor. Math. Phys. - 2002. - Vol. 131, Is. 3. - P.862-872. - ISSN 0040-5779, DOI 10.1023/A:1015935809388
Примечания : Cited References: 19
Предметные рубрики: NUCLEAR-DOUBLE-RESONANCE
HEISENBERG MAGNET
DEPENDENCE
MODEL
Ключевые слова (''Своб.индексиров.''): spin dynamics--correlation functions--power series in time--frequency moments--singular points--generated functions--lattice trees--multidimensional expansion--correlation functions--frequency moments--generated functions--lattice trees--multidimensional expansion--power series in time--singular points--spin dynamics
Аннотация: Using the d(-1) expansion method (d is the space dimension), we estimate the coordinate of the time-dependent autocorrelation function singular point on the imaginary time axis for the spin 1/2 Heisenberg model on a simple hypercubic lattice at high temperatures. We represent the coefficients of the time expansion (the spectral moments) for the autocorrelation function as the sums of the weighted lattice figures in which the trees constructed from the double bonds give the leading contributions with respect to d(-1) and the same trees with the built-in squares from six bonds or diagrams with the fourfold bonds give the contribution of the next-to-leading order. We find the corrections to the coordinate of the autocorrelation function singular point that are due to the latter contributions.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Kucherov M. M.
Заглавие : On the concentration dependence of wings of spectra of spin correlation functions of diluted heisenberg paramagnets
Место публикации : JETP Letters. - 2016. - Vol. 103, Is. 11. - P.687-691. - ISSN 0021-3640, DOI 10.1134/S0021364016110138. - ISSN 1090-6487(eISSN)
Примечания : Cited References:26
Предметные рубрики: HIGH-TEMPERATURES
AUTOCORRELATION FUNCTION
SINGULAR POINT
SYSTEMS
TIME
COORDINATE
LATTICE
Аннотация: Singular points of the autocorrelation function on the imaginary time axis that is averaged over the location of spins in the magnetically dilute spin lattice with isotropic spin-spin interaction at a high temperature have been studied. For the autocorrelation function in the approximation of the self-consistent fluctuating local field, nonlinear integral equations have been proposed which reflect the separation of the inhomogeneous spin systems into close spins and other spins. The coordinates of the nearest singular points have been determined in terms of the radius of convergence of the expansion in powers of time, the coefficients of which have been calculated from recurrence equations. It has been shown that the coordinates of singular points and, consequently, the wings of the autocorrelation function spectrum at strong magnetic dilution are determined by the modulation of the local field by the nearest pairs of spins leading to its logarithmic concentration dependence.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Modeling multiparticle coherences in solid-state nuclear spin systems using infinite-range interaction
Место публикации : Theor. Math. Phys. - 2004. - Vol. 141, Is. 3. - P.1737-1749. - ISSN 0040-5779, DOI 10.1023/B:TAMP.0000049765.41265.dd
Примечания : Cited References: 24
Предметные рубрики: MULTIPLE-QUANTUM DYNAMICS
NMR-SPECTRA
TEMPERATURE DYNAMICS
SHAPE
VAN
Ключевые слова (''Своб.индексиров.''): multipulse method--dipole-dipole interaction--multispin coherence--time correlation function--rotating reference frame--dipole-dipole interaction--multipulse method--multispin coherence--rotating reference frame--time correlation function
Аннотация: Using the exactly solvable model known in statistical physics as the infinite-range interaction model (the van der Waals model), we obtain expressions for the hierarchy of multispin multiquantum time correlation functions for a solid-state paramagnetic nuclear spin system with magnetic dipole-dipole interaction between nuclei. These functions are observed experimentally using contemporary multiquantum NMR spectroscopy methods. We write the complete set of orthogonal multispin operators explicitly and find the time dependence for amplitudes of multiparticle time correlation functions. The proposed model describes the behavior of multiparticle correlation functions well, at least for not very large numbers n of expansion harmonics. The theoretical results agree well with the experimental data obtained for hexamethylbenzol.
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13.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Effect of intramolecular interaction on time growth of second moment of multiple quantum NMR in solids
Место публикации : INTERNATIONAL CONFERENCE ON RESONANCES IN CONDENSED MATTER: ALTSHULER100. Ser. Journal of Physics Conference Series: IOP PUBLISHING LTD, 2011. - Vol. 324: International Conference on Resonances in Condensed Matter (JUN 21-25, 2011, Kazan, RUSSIA). - Ст.12010. - ISBN 1742-6588, DOI 10.1088/1742-6596/324/1/012010
Примечания : Cited References: 12
Предметные рубрики: COHERENCES
DYNAMICS
Ключевые слова (''Своб.индексиров.''): dipole dipole interactions--double-quantum--intramolecular interactions--multiple quantum nmr--nuclear spin system--quantum spectrum--rate increase--second moments--solids containing methyl groups--time dependence--functional groups--quantum optics--solids--spin dynamics--hamiltonians
Аннотация: The time dependence of the NMR multiple quantum spectrum in solids containing methyl groups is investigated. We studied both of types of the nuclear spin systems: namely linking by secular part of the mutual dipole-dipole interaction and linking by effective double quantum Hamiltonian. It is revealed for the first type of systems the rate with the time of the growing up of the second moment when intramolecular interaction is present becomes less in compare with situation when a strong intramolecular interaction is absent. On the contrary for the second type of Hamiltonian the above rate increases.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Shauro V. P.
Заглавие : Effect of a phase factor on the minimum time of a quantum gate
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2014. - Vol. 118, Is. 1. - P.18-26. - ISSN 1063-7761, DOI 10.1134/S106377611401021X. - ISSN 1090-6509
Примечания : Cited References: 42
Предметные рубрики: ALGORITHMS
Аннотация: A relationship between the phase factor of a quantum gate, the layout of energy levels of its effective Hamiltonian, and the implementation time of the gate is demonstrated. By an example of the direct and inverse quantum Fourier transforms (QFT) gates for a qutrit represented by a quadrupole nucleus with spin I = 1, as well as for a system of two qubits (I = 1/2), effective Hamiltonians and minimum implementation times corresponding to different global phases are obtained. Implementation schemes are proposed for these Hamiltonians by the nuclear magnetic resonance (NMR) technique with the use of sequences of radio-frequency (RF) pulses separated by intervals of free evolution. Analytic results for the minimum times of gates are in agreement with the results obtained by numerical optimization methods. The phase considered is divided into dynamic and geometric parts.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Decay of Multispin Multiple-Quantum Coherent States in the NMR of a Solid and the Stabilization of Their Intensity Profile with Time
Разночтения заглавия :авие SCOPUS: Decay of multispin multiple-quantum coherent states in the NMR of a solid and the stabilization of their intensity profile with time
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 113, Is. 6. - P1006-1014. - ISSN 1063-7761, DOI 10.1134/S1063776111140111
Примечания : Cited References: 27
Ключевые слова (''Своб.индексиров.''): cluster sizes--coherent state--decay rate--effective size--experimental data--intensity profiles--coherent light--decay (organic)--stabilization
Аннотация: Variations, experimentally observed in [14], in the intensity profiles of multiple-quantum (MQ) coherences in the presence of two special types of perturbations are explained on the basis of the theory, earlier developed by the authors, of the growth of the effective size of correlated clusters (the number of correlated spins) and the relaxation of MQ coherent states [23]. The intensity and the character of perturbation were controlled by the experimenters. It is shown that the observed stabilization of profiles with time is not associated with the stabilization of the cluster size. Quite the contrary, a cluster of correlated spins monotonically grows, while the observed variations in the intensity profile and its stabilization with time are attributed to the dependence of the decay rate of an MQ coherence on its order (its position in the MQ spectrum). The results of the theory are in good agreement with the experimental data.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Kucherov M. M.
Заглавие : Concentration dependence of the wings of a dipole-broadened magnetic resonance line in magnetically diluted lattices
Место публикации : J. Exp. Theor. Phys.: Maik Nauka-Interperiodica Publishing, 2017. - Vol. 124, Is. 1. - P.151-158. - ISSN 10637761 (ISSN), DOI 10.1134/S106377611615005X
Примечания : Cited References: 34
Ключевые слова (''Своб.индексиров.''): drug interactions--magnetic fields--magnetic resonance--magnetism--nonlinear equations--optical systems--autocorrelation functions--concentration dependence--high-frequency asymptotics--local field approximations--magnetic resonance line--modulation frequencies--strong static magnetic fields--time autocorrelation functions--autocorrelation
Аннотация: The singularities of the time autocorrelation functions (ACFs) of magnetically diluted spin systems with dipole–dipole interaction (DDI), which determine the high-frequency asymptotics of autocorrelation functions and the wings of a magnetic resonance line, are studied. Using the self-consistent fluctuating local field approximation, nonlinear equations are derived for autocorrelation functions averaged over the independent random arrangement of spins (magnetic atoms) in a diamagnetic lattice with different spin concentrations. The equations take into account the specificity of the dipole–dipole interaction. First, due to its axial symmetry in a strong static magnetic field, the autocorrelation functions of longitudinal and transverse spin components are described by different equations. Second, the long-range type of the dipole–dipole interaction is taken into account by separating contributions into the local field from distant and near spins. The recurrent equations are obtained for the expansion coefficients of autocorrelation functions in power series in time. From them, the numerical value of the coordinate of the nearest singularity of the autocorrelation function is found on the imaginary time axis, which is equal to the radius of convergence of these expansions. It is shown that in the strong dilution case, the logarithmic concentration dependence of the coordinate of the singularity is observed, which is caused by the presence of a cluster of near spins whose fraction is small but contribution to the modulation frequency is large. As an example a silicon crystal with different 29Si concentrations in magnetic fields directed along three crystallographic axes is considered. © 2017, Pleiades Publishing, Inc.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Popov M. A.
Заглавие : A Monte Carlo study of the dependence of the growth parameter for trees on the lattice dimension in the Eden model
Место публикации : Theor. Math. Phys. - 2001. - Vol. 126, Is. 2. - P.270-279. - ISSN 0040-5779, DOI 10.1023/A:1005260114182
Примечания : Cited References: 17
Предметные рубрики: DIFFUSION-LIMITED AGGREGATION
BRANCHED POLYMERS
HIGH-TEMPERATURES
EXPANSION
TIME
Аннотация: We use the Monte Carlo method to compute the number of trees with n edges in the Eden model on d-dimensional simple cubic lattices for d = 2, 3, 4, 6, 8, 10. We compare these numbers with the exact data derived by the enumeration method up to n = 12 on the square lattice and up to n = 10 on the cubic lattice. We find that for d greater than or equal to 3, the computed values of the growth parameter for trees agree with the values that we derived earlier by the expansion in inverse powers of 2d - 1.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shi, Xin, Wu, Yong, Wang, Jian Guo, Kimberg V., Zhang, Song Bin
Заглавие : X-ray transient absorption spectroscopy by an ultrashort x-ray-laser pulse in a continuous-wave IR field
Место публикации : Phys. Rev. A. - 2020. - Vol. 101, Is. 2. - Ст.023401. - ISSN 2469-9926, DOI 10.1103/PhysRevA.101.023401. - ISSN 2469-9934(eISSN)
Примечания : Cited References: 56. - Grants from the National Basic Research Program of China (Grant No. 2017YFA0403200), National Natural Science Foundation of China (Grants No. 11604197, No. 11934004, and No. 11974230), the Science Challenge Program of China (Grants No. TZ2018005 and No. TZ2016005), and the Organization Department of CCCPC are acknowledged. V.K. acknowledges financial support from Swedish Research Council within the State Contract of the Ministry of Education and Science of the Russian Federation for Siberian Federal University for Scientific Research in 2017-2019 (Project No. 3.2662.2017)
Предметные рубрики: MOLECULAR NITROGEN
TIME
DYNAMICS
PHASE
SPECTRA
DECAY
Аннотация: X-ray transient absorption spectra (XTAS) of molecules are theoretically investigated in a femtosecond x-ray pump and continuous-wave (cw) infrared (IR)-control scenario. The scheme is exemplified by a CO molecule resonantly pumped into carbon and oxygen core-excited 1s→π∗ states by a weak femtosecond x-ray pulse, while dynamic Stark shifts are induced by the cw IR-control radiation. As a result, significant shoulder structures appear in XTAS showing strong dependence on the phase of IR radiation relative to the envelope of the x-ray pulse. Due to a significant difference in the frequencies of the two pulses, the present XTAS scheme provides much clear interpretation of the dynamic Stark effects as compared to the attosecond UV transient absorption scenario. Within the suggested two-level model, where the total spectrum is decomposed as incoherent superposition of contributions from different vibrational excitations weighted by the Franck-Condon Factors, all spectral structures can be well identified and interpreted in a good agreement with the full-scale molecular simulations. Well-characterized XTAS in the proposed IR-control scheme can be applied for fine phase synchronization between IR and x-ray pulses, highly demanded in modern experiments on x-ray free-electron lasers.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : Anomalies in the characteristics of electronic structure upon a quantum phase transition to a state with two order parameters and the breaking of time-reversal symmetry
Место публикации : Bull. Russ. Acad. Sci. Phys.: Allerton Press, 2016. - Vol. 80, Is. 6. - P.616-619. - ISSN 10628738 (ISSN), DOI 10.3103/S106287381606040X
Примечания : Cited References: 9
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--electronic structure--phase transitions--temperature distribution--antiferromagnetic order parameter--density of state--landau expansion--periodic anderson model--quantum phase transitions--temperature dependence--time reversal symmetries--two order parameters--quantum theory
Аннотация: Based on the periodic Anderson model, microscopic expressions for the Ginzburg–Landau expansion coefficients in a phase with superconducting and antiferromagnetic order parameters are obtained. Temperature dependences of the order parameters near the temperature of the transition to this phase are established. The emergence of anomalous properties upon the quantum phase transition to the phase with two order parameters is investigated. This transition is accompanied by drastic reconstruction of the density of states, reflected by the interplay between superconductivity and antiferromagnetism. © 2016, Allerton Press, Inc.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Tomilin F. N., Rogova A. V., Burakova L. P., Tchaikovskaya O. N., Avramov P. V., Fedorov D. G., Vysotski E. S.
Заглавие : Unusual shift in the visible absorption spectrum of an active ctenophore photoprotein elucidated by time-dependent density functional theory
Коллективы : RFBRRussian Foundation for Basic Research (RFBR) [20-04-00085]; NSFCNational Natural Science Foundation of China (NSFC) [19-54-53004]; Russian Ministry of Science and EducationMinistry of Education and Science, Russian Federation [0721-2020-0033]
Место публикации : Photochem. Photobiol. Sci. - 2021. - Vol. 20, Is. 4. - P.559-570. - ISSN 1474-905X, DOI 10.1007/s43630-021-00039-5. - ISSN 1474-9092(eISSN)
Примечания : Cited References: 61. - The ab initio quantum chemical calculations were funded by RFBR and NSFC as the research project No. 19-54-53004 and RFBR research project No. 20-04-00085. The development of structural atomistic model of berovin without calcium ions generated by the I-TASSER server was funded by project 0721-2020-0033 of the Russian Ministry of Science and Education
Аннотация: Active hydromedusan and ctenophore Ca2+-regulated photoproteins form complexes consisting of apoprotein and strongly non-covalently bound 2-hydroperoxycoelenterazine (an oxygenated intermediate of coelenterazine). Whereas the absorption maximum of hydromedusan photoproteins is at 460–470 nm, ctenophore photoproteins absorb at 437 nm. Finding out a physical reason for this blue shift is the main objective of this work, and, to achieve it, the whole structure of the protein–substrate complex was optimized using a linear scaling quantum–mechanical method. Electronic excitations pertinent to the spectra of the 2-hydroperoxy adduct of coelenterazine were simulated with time-dependent density functional theory. The dihedral angle of 60° of the 6-(p-hydroxy)-phenyl group relative to the imidazopyrazinone core of 2-hydroperoxycoelenterazine molecule was found to be the key factor determining the absorption of ctenophore photoproteins at 437 nm. The residues relevant to binding of the substrate and its adopting the particular rotation were also identified.
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