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E. V. Zemlyanaya

Publications and source records attributed to E. V. Zemlyanaya.

At least 37 records · Page 2Linked to original sources
arXiv2010

Numerical investigation of the second harmonic effects in the LJJ

We study the long Josephson junction (LJJ) model which takes into account the second harmonic of the Fourier expansion of Josephson current. The sign of second harmonic is important for many physical applications. The influence of the sign and value of the second harmonic on the magnetic flux distributions is investigated. At each step of numerical continuation in parameters of the model, the corresponding nonlinear boundary problem is solved on the basis of the continuous analog of Newton's method with the 4th order Numerov discretization scheme. New solutions which do not exist in the traditional model have been found. The influence of the second harmonic on stability of magnetic flux distributions for main solutions is investigated.

cond-mat.supr-con↗
arXiv2010

Numerical study of magnetic flux in the LJJ model with double sine-Gordon equation

The decrease of the barrier transparency in superconductor-insulator-superconductor (SIS) Josephson junctions leads to the deviations of the current-phase relation from the sinusoidal form. The sign of second harmonics is important for many applications, in particular in junctions with a more complex structure like SNINS or SFIFS, where N is a normal metal and F is a weak metallic ferromagnet. In our work we study the static magnetic flux distributions in long Josephson junctions taking into account the higher harmonics in the Fourier-decomposition of the Josephson current. Stability analysis is based on numerical solution of a spectral Sturm-Liouville problem formulated for each distribution. In this approach the nullification of the minimal eigenvalue of this problem indicates a bifurcation point in one of parameters. At each step of numerical continuation in parameters of the model, the corresponding nonlinear boundary problem is solved on the basis of the continuous analog of Newton's method. The solutions which do not exist in the traditional model have been found. The influence of second harmonic on stability of magnetic flux distributions for main solutions is investigated.

cond-mat.supr-con↗
arXiv2009

Calculations of $^{8}$He+p Elastic Cross Sections Using Microscopic Optical Potential

An approach to calculate microscopic optical potential (OP) with the real part obtained by a folding procedure and with the imaginary part inherent in the high-energy approximation (HEA) is applied to study the $^8$He+p elastic scattering data at energies of tens of MeV/nucleon (MeV/N). The neutron and proton density distributions obtained in different models for $^{8}$He are utilized in the calculations of the differential cross sections. The role of the spin-orbit potential is studied. Comparison of the calculations with the available experimental data on the elastic scattering differential cross sections at beam energies of 15.7, 26.25, 32, 66 and 73 MeV/N is performed. The problem of the ambiguities of the depths of each component of the optical potential is considered by means of the imposed physical criterion related to the known behavior of the volume integrals as functions of the incident energy. It is shown also that the role of the surface absorption is rather important, in particular for the lowest incident energies (e.g., 15.7 and 26.25 MeV/nucleon).

nucl-th↗
arXiv2009

Calculations of the K$^{+}$-Nucleus Microscopic Optical Potential and of the Corresponding Differential Elastic Cross Sections

Calculations are made of the $K^{+}+^{12}$C, $^{40}$Ca differential elastic scattering cross sections at the beam momenta 0.635, 0.715, and 0.8 GeV/c. To this end the microscopic optical potential derived in the high-energy approximation was used where existing data on the kaon-nucleon amplitude and on the point-like density distributions of target-nuclei were utilized. The effect of different methods of relativization was studied and shown to play an important role. A good agreement with the experimental data on differential elastic cross sections was obtained.

nucl-th↗
arXiv2007

Calculations of $^{6}$He+p elastic scattering cross sections using folding approach and high-energy approximation for the optical potential

Calculations of microscopic optical potentials (OP's) (their real and imaginary parts) are performed to analyze the $^6$He+p elastic scattering data at a few tens of MeV/nucleon (MeV/N). The OP's and the cross sections are calculated using three model densities of $^6$He. Effects of the regularization of the NN forces and their dependence on nuclear density are investigated. Also, the role of the spin-orbit terms and of the non-linearity in the calculations of the OP's, as well as effects of their renormalization are studied. The sensitivity of the cross sections to the nuclear densities was tested and one of them that gives a better agreement with the data was chosen.

nucl-th↗
arXiv2007

Microscopic Approach in Inelastic Heavy-Ions Scattering with Excitation of Nuclear Collective States

In the density distribution of a deformed target-nucleus, the spherical $λ= 0$ and the deformed $λ= 2$ parts were considered. On this basis, the corresponding potential parts $U_0$ and $U^{(2)}_{int}$ of a double -folding microscopic nucleus-nucleus optical potential are obtained. Then, for these potentials and by using the coupled-channel technique (ECIS), the elastic and inelastic amplitudes are calculated for $^{17}O$ heavy ion scattering on $2^{+}$ collective excited state of various target nuclei. Besides, the same cross-sections are calculated in the frame of an adiabatic approach of the eikonal approximation, where the inelastic amplitude is the linear function of $U^{(2)}_{int}$. Both the obtained results are compared with the experimental data, and also discuss their efficiency in predicting the deformation parameters of nuclei.

nucl-th↗
arXiv2006

Interactions of Parametrically Driven Dark Solitons. I: Néel-Néel and Bloch-Bloch interactions

We study interactions between the dark solitons of the parametrically driven nonlinear Schrödinger equation, Eq.(\ref{NLS}). When the driving strength, $h$, is below $\sqrt{γ^2 +1/9}$, two well-separated Néel walls may repel or attract. They repel if their initial separation $2z(0)$ is larger than the distance $2z_u$ between the constituents in the unstable stationary complex of two walls. They attract and annihilate if $2z(0)$ is smaller than $2z_u$. Two Néel walls with $h$ lying between $\sqrt{γ^2 + 1/9}$ and a threshold driving strength $h_{sn}$ attract for $2z(0)<2z_u$ and evolve into a stable stationary bound state for $2z(0)>2z_u$. Finally, the Néel walls with $h$ greater than $h_{sn}$ attract and annihilate -- irrespective of their initial separation. Two Bloch walls of opposite chiralities attract, while Bloch walls of like chiralities repel -- except near the critical driving strength, where the difference between the like-handed and oppositely-handed walls becomes negligible. In this limit, similarly-handed walls at large separations repel while those placed at shorter distances may start moving in the same direction or transmute into an oppositely-handed pair and attract. The collision of two Bloch walls or two nondissipative Néel walls typically produces a quiescent or moving breather.

nlin.PS↗
arXiv2006

Microscopic Model Analysis of the $^{6}$He,$^{6}$Li+$^{28}$Si Total Reaction Cross Sections at the Energy Range 5-50 a Mev

The existing and some preliminary experimental data on the total cross sections of the $^{4,6}$He, $^{6,7}$Li +$^{28}$Si reactions at energies E=5-50 A MeV are demonstrated. The data on $^{6}$Li,$^{6}$He+$^{28}$Si are analyzed in the framework of the microscopic optical potential with real and imaginary parts obtained with a help of the double-folding procedure and by using the current models of densities of the projectile nuclei. Besides, the microscopic double-folding Coulomb potential is calculated and its effect on cross sections is compared with that when one applies the traditional Coulomb potential of the uniform charge distribution. The semi-microscopic potentials are constructed from both the renormalized microscopic potentials and their derivatives to take into account collective motion effect and to improve an agreement with experimental data.

nucl-th↗
arXiv2005

Excitation of Nuclear Collective States by Heavy Ions within the Model of Semi-Microscopic Optical Potential

The (semi-)microscopic double-folding nucleus-nucleus optical potentials are suggested for consideration of inelastic scattering with excitation of collective nuclear states by using the adiabatic approach and the elastic scattering amplitude in the high-energy approximation. The analytical expression for inelastic scattering amplitude is obtained keeping the first order terms in the deformation parameter of a potential. Calculations of inelastic cross sections for the $^{17}$O heavy ions scattered on different nuclei at about hundred Mev/nucleon are made, and the acceptable qualitative agreement with the experimental data is obtained without introducing free parameters. The prospect of the method for further applications is discussed.

nucl-th↗
arXiv2005

Charge and matter distributions and form factors of light, medium and heavy neutron-rich nuclei

Results of charge form factors calculations for several unstable neutron-rich isotopes of light, medium and heavy nuclei (He, Li, Ni, Kr, Sn) are presented and compared to those of stable isotopes in the same isotopic chain. For the lighter isotopes (He and Li) the proton and neutron densities are obtained within a microscopic large-scale shell-model, while for heavier ones Ni, Kr and Sn the densities are calculated in deformed self-consistent mean-field Skyrme HF+BCS method. We also compare proton densities to matter densities together with their rms radii and diffuseness parameter values. Whenever possible comparison of form factors, densities and rms radii with available experimental data is also performed. Calculations of form factors are carried out both in plane wave Born approximation (PWBA) and in distorted wave Born approximation (DWBA). These form factors are suggested as predictions for the future experiments on the electron-radioactive beam colliders where the effect of the neutron halo or skin on the proton distributions in exotic nuclei is planned to be studied and thereby the various theoretical models of exotic nuclei will be tested.

nucl-th↗
arXiv2005

High-Energy Approach for Heavy-Ion Scattering with Excitations of Nuclear Collective States

A phenomenological optical potential is generalized to include the Coulomb and nuclear interactions caused by the dynamical deformation of its surface. In the high-energy approach analytical expressions for elastic and inelastic scattering amplitudes are obtained where all the orders in the deformation parameters are included. The multistep effect of the 2$^+$ rotational state excitation on elastic scattering is analyzed. Calculations of inelastic cross sections for the $^{17}$O ions scattered on different nuclei at about hundred Mev/nucleon are compared with experimental data, and important role of the Coulomb excitation is established.

nucl-th↗
arXiv2005

What can we learn about the lipid vesicle structure from the small-angle neutron scattering experiment? (Investigation DMPC vesicle structure by small angle neutron scattering)

Small angle neutron scattering (SANS) on the unilamellar vesicle populations (diameter 500 and 1000 angstrom) was used to characterize lipid vesicles from dimyristoylphosphatidylcholine (DMPC) at three phases (gel, ripple, and liquid). Parameters of vesicle populations and internal structure of the DMPC bilayer were characterized on the basis of the Separated Form Factor (SFF) model. Parameters of the internal bilayer structure (thickness of the membrane and the hydrophobic core, hydration, and surface area of lipid molecule) were determined on the basis of the Hydrophobic-Hydrophilic (HH) approximation of neutron scattering length density across the bilayer r(x) and of the Step Function (SF) approximation of r(x). It was demonstrated in frame of HH approximation that DMPC membrane thickness in liquid phase (T=30 degrees) depends on the membrane curvature. The dependence of the DMPC membrane thickness on temperature was restored from the SANS experiment.

physics.bio-ph↗
arXiv2004

Model for Restoration of Heavy-Ion Potentials at Intermediate Energies

Three types of microscopic nucleus-nucleus optical potentials are constructed using three patterns for their real and imaginary parts. Two of these patterns are the real $V^H$ and imaginary $W^H$ parts of the potential which reproduces the high-energy amplitude of scattering in the microscopic Glauber-Sitenko theory. Another template $V^{DF}$ is calculated within the standard double-folding model with the exchange term included. For either of the three tested potentials, the contribution of real and imaginary patterns is adjusted by introducing two fitted factors. An acceptable agreement with the experimental data on elastic differential cross-sections was obtained for scattering the $^{16, 17}$O heavy-ions at about hundred Mev/nucleon on different target-nuclei. The relativization effect is also studied and found that, to somewhat, it improves the agreement with experimental data.

nucl-th↗
arXiv2004

Structure of Unilamellar Dimyristoylphosphatidylcholine Vesicle. Small-Angle Neutron Scattering Study

On the basis of the separated form-factor model, a code for fitting the small-angle neutron scattering spectra of the polydispersed vesicle population has been developed. Vesicle and membrane bilayer parameters are analyzed for various hierarchical models of the neutron scattering length density across the membrane. It is shown that hydration of vesicle can be described by a linear distribution function of water molecules. For the first time, the average radius and polydispersity of the vesicle population, thickness of the membrane bilayer, thickness of hydrophobic and hydrophilic parts of bilayer, and water distribution function have been calculated from the SANS experiment, without additional methods such as dynamic light scattering or freeze-fracture electron microscopy. The results, obtained at two different spectrometers, are discussed. The appropriate conditions of the SANS experiment on vesicles are formulated as a necessity to collect the SANS curve in the region of scattering vectors from qmin=0.0033 1/angstrom to qmax=0.56 1/angstrom.

physics.chem-ph↗
arXiv2004

Sans Study of the Unilamellar DMPC Vesicles. the Fluctuation Model of Lipid Bilayer

On the basis of the separated form-factors model, parameters of the polydispersed unilamellar DMPC vesicle population are analyzed. The neutron scattering length density across the membrane is simulated on the basis of fluctuated model of lipid bilayer. The hydration of vesicle is described by sigmoid distribution function of the water molecules. The results of fitting of the experimental data obtained at the small angle spectrometer SANS-I, PSI (Switzerland) are: average vesicle radius 272 angstrom, polydispersity of the radius 27%, membrane thickness 50.6 angstrom, thickness of hydrocarbon chain region 21.4 angstrom, number of water molecules located per lipid molecule 13, and DMPC surface area 59. The calculated water distribution function across the bilayer directly explains why lipid membrane is easy penetrated by water molecules.

physics.bio-ph↗
arXiv2004

Nodal two-dimensional solitons in nonlinear parametric resonance

The parametrically driven damped nonlinear Schrödinger equation serves as an amplitude equation for a variety of resonantly forced oscillatory systems on the plane. In this note, we consider its nodal soliton solutions. We show that although the nodal solitons are stable against radially-symmetric perturbations for sufficiently large damping coefficients, they are always unstable to azimuthal perturbations. The corresponding break-up scenarios are studied using direct numerical simulations. Typically, the nodal solutions break into symmetric "necklaces" of stable nodeless solitons.

nlin.PS↗
arXiv2004

Restoration of Heavy-Ion Potentials at Intermediate Energies

The microscopic nucleus-nucleus optical potential is constructed basing on two patterns for real and imaginary parts, each calculated in the framework of microscopic models and multiplied by two normalizing factors, the free parameters, fitted to experimental data. The first supplementary model yields the real and imaginary templates for our potential, and itself reproduces the scattering amplitude of the microscopic Glauber-Sitenko theory. The other pattern, for real part only, is the standard double-folding model with the exchange term included. As a result, we obtain an acceptable agreement with elastic differential cross-sections.

nucl-th↗