Volume 62, Number 12, 2017
Editorial Material
Editorial Material on the Introduction of Article Number for Romanian Journal of Physics Aureliu Sandulescu Romanian Journal of Physics 62,
001 (2017)
Theoretical, Mathematical, and Computational Physics
SpatiallyFlat RobertsonWalker Models with Combined and Stiff Matter Sources and the Corresponding Thermodynamics MarinaAura Dariescu, DenisaAndreea Mihu, Ciprian Dariescu Romanian Journal of Physics 62,
101 (2017)
In the present paper, we are considering a spatiallyflat FriedmannRobertsonWalker cosmological model, fueled with stiff matter and dust, treated as noninteracting ideal fluid sources. By solving the corresponding Friedmann equation with a nonzero cosmological constant, we are deriving the scale function and the fundamental cosmological parameters. Within a thermodynamic approach, the general form of the Equation of State is obtained, together with the explicit dependence of the energy density and pressure on temperature.
HigherOrder Rogue Wave Dynamics for a Derivative Nonlinear Schrödinger Equation Yongshuai Zhang, Lijuan Guo, Amin Chabchoub, Jingsong He Romanian Journal of Physics 62,
102 (2017)
The mixed ChenLeeLiu derivative nonlinear Schrödinger (CLLNLS) equation can be considered as the simplest model to approximate the dynamics of weakly nonlinear and dispersive waves, taking into account the selfsteepening effect (SSE). The latter effect arises as a higherorder correction of the nonlinear Schrödinger (NLS) equation, which is known to describe the dynamics of pulses in nonlinear fiber optics, and constitutes a fundamental part of the generalized NLS equation. Similar effects are described within the framework of the modified NLS equation, also referred to as the Dysthe equation, in hydrodynamics. In this work, we derive fundamental and higherorder solutions of the CLLNLS equation by applying the Darboux transformation. Exact expressions of nonvanishing solitons at boundaries, breathers, and a hierarchy of rogue wave solutions are presented. In addition, we discuss the localization properties of such rogue waves, by characterizing their length and width. In particular, we describe how the localization properties of firstorder NLS rogue waves can be modified by taking into account the SSE, presented in the CLLNLS equation. This is illustrated by use of an analytical and a graphical method. The results may motivate similar analytical studies, extending the family of the reported rogue wave solutions as well as possible experiments in several nonlinear dispersive media, confirming these theoretical results.
Numerical Resolution of Coupled TwoDimensional Burgers’ Equation Ion Aurel Cristescu Romanian Journal of Physics 62,
103 (2017)
The purpose of this study is to investigate a combination between the homotopy analysis method and finite differences for the numerical resolution of coupled twodimensional Burgers’ equation. The performance of the proposed technique is successfully verified. The application shows very good agreement of the two convergence regions for absolute and relative errors. This fact is important in case the exact solution is unknown.
A Numerical Approach to Solve LaneEmden Type Equations by the Fractional Order of Rational Bernoulli Functions K. Parand, H. Yousefi, M. Delkhosh Romanian Journal of Physics 62,
104 (2017)
In this paper, a numerical method based on the hybrid of the quasilinearization method (QLM) and the collocation method is suggested for solving wellknown nonlinear LaneEmdentype equations as singular initial value problems, which model many phenomena in mathematical physics and astrophysics. First, by using the QLM method, the nonlinear ordinary differential equation is converted into a sequence of linear differential equations, and then the linear equations by the fractional order of rational Bernoulli collocation (FRBC) method on the semiinfinite interval $[0, \infty)$ are solved. This method reduces the solution of these problems to the solution of a system of algebraic equations. Computational results of several problems are presented to demonstrate the viability and powerfulness of the method. Further, the fractional order of rational Bernoulli functions has also been used for the first time. The first zeros of standard LaneEmden equation and the approximations of $y(x)$ for LaneEmdentype equations are given with unprecedented accuracy.
A Pseudospectral Method for Solving the TimeFractional Generalized HirotaSatsuma Coupled Kortewegde Vries System M.A. Saker, S.S. EzzEldien, A.H. Bhrawy Romanian Journal of Physics 62,
105 (2017)
In this paper, a new spacetime spectral algorithm is constructed to solve the generalized HirotaSatsuma coupled Kortewegde Vries (GHSCKdV) system of timefractional order. The present algorithm consists of applying the collocationspectral method in conjunction with the operational matrix of fractional derivative for the double Jacobi polynomials, which will be employed as a basis function for the spectral solution. The main characteristic behind this approach is that such problems will reduce to those of solving algebraic systems of equations that greatly simplifying the problem. For ensuring the accuracy and efficiency of the presented algorithm, we apply it to find the approximate solutions of two specific problems, namely, a homogeneous form of the GHSCKdV system and a inhomogeneous GHSCKdV system.
Atomic, Molecular, and Optical Physics
Macroscopic Quantum SelfTrapping of Two Component BoseEinstein Condensates with Two and ThreeBody Interactions F. Li, Z. Li, L. Xu Romanian Journal of Physics 62,
201 (2017)
The macroscopic quantum selftrapping (MQST) of twocomponent BoseEinstein condensates (BECs) with two and threebody interactions is studied. For the undamped case, a high modulating frequency causes a monotonic increase in the number of localized atoms in one well. Decreasing the modulating frequency changes this monotonic increasing trend and lead to an oscillating appearance of MQST in the two wells. But a weak damping changes this oscillating behavior and keep the MQST in one well after a transient process. The parametric resonance is also observed in the timeevolution of the population imbalance.
Effect of ElectronElectron Correlation on the Nonsequential Ionization Process in a Linearly Polarized Laser Field V.M. Petrović, T.B. Miladinović Romanian Journal of Physics 62,
202 (2017)
Analytic expression for the nonsequential transition rate in a linearly polarized laser field has been found, based on the adiabatic LandauDykhne approach. The formula involves electronelectron correlation through the mechanism of collective tunneling. The formula fails for a “knee” structure, but improves agreement with experimental results in the range of higher laser field intensities. A brief discussion on the dependence of the nonsequential transition rate on the laser pulse shape and wavelength was made.
Handling Shocks and Rogue Waves in Optical Fibers Jingsong He, Shuwei Xu, Kappuswamy Porsezian, Patrice Tchofo Dinda, Dumitru Mihalache, Boris A. Malomed, Edwin Ding Romanian Journal of Physics 62,
203 (2017)
In standard optical fibers, combined effects of dispersion and nonlinearity can generate critical effects of localization of energy, which are potentially harmful for the transmission of data. Using the nonlinear Schrödinger equation as the universal transmission model, we establish the existence of ultrashort light pulses, in the form of breathers on top of the continuouswave (CW) background, and of structural discontinuities (SDCs), in the form of jumps of the breathers’ phase and group velocities (i.e., the SDC is a variety of an optical shock). We produce exact analytical solutions, which demonstrate that, passing the SDC point, the breathers are converted into rogue waves (RWs), which is a potentially penalizing nonlinear effect in optical telecommunications. On the other hand, numerical simulations demonstrate that the modulational instability of the underlying CW effectively replaces the abrupt transition by a smooth one, and makes the breathers and RWs strongly unstable close to the SDC point. This dynamical scenario, which may be effectively controlled by a frequency shift of the optical signal from the CW background, opens a way to mitigate the strong nonlinear effects. On the other hand, we also consider possibilities to stabilize the RWs, for their possible use in other settings.
Nuclear Physics
The PygmyDipole Contribution to Polarizability: Isospin and MassDependence V. Baran, A.I. Nicolin, D.G. David, M. Colonna, R. Zus Romanian Journal of Physics 62,
301 (2017)
Based on the dipole response of neutronrich nuclear systems obtained within a transport model which relies on two coupled Vlasov equations for protons and neutrons, respectively, we determine the contribution to polarizability of the pygmy dipole mode. We employ two different density parameterizations of the symmetry energy and investigate the effect of isospin and mass on the pygmy contribution to polarizability.
Degeneracies with the $QQ$ Interaction in a Single$j$ Shell Larry Zamick, Alberto Escuderos Romanian Journal of Physics 62,
302 (2017)
Previously [1] it was shown that for a configuration of two protons and two neutrons in the $g_{9/2}$ shell, there is a certain degeneracy that occurs when the quadrupole–quadrupole ($QQ$) interaction is used to obtain wave functions. We here show three other examples of such degenerate $T = 0$, $T = 2$ pairs. More importantly, we note a peculiarity of the $T = 0$ partner in the original example $(g_{9/2}$ , $J = 4$, $T = 0)$. Also we point out that degeneracies can be confusing and steps can be taken to remove them.
Physics of Elementary Particles and Fields
Study of the $\Lambda$ Resonances in the $\Lambda_{b}\to \Lambda^{*}(\to p^{+}K^{})\gamma$ Decay Using Helicity Formalism L.E. Giubega, A.I. Jipa, A.C. Ene Romanian Journal of Physics 62,
401 (2017)
Starting from the $\Lambda^{0}_{b} \to p^+ K^− \gamma$ decay, we study the $\Lambda^{0}_{b} \to \Lambda^* (p^+ K^−) \gamma$ decay, with the intermediary resonances being treated in the helicity formalism. A specific algorithm is presented which transforms a sample of events generated for the $S$wave decay $\Lambda^{0}_{b} \to p^+ K^− \gamma$ by adding twelve intermediary resonances $\Lambda^{*} \to p^+ K^−$ . This information is introduced using weights depending on the mass hypothesis and spin configuration of each resonance. The method allows fast Monte Carlo (MC) sample generation for efficiency and systematic uncertainties determination in future LHCb measurements involving $b$hadron radiative decays. MC samples are produced for headon protonproton collisions at 8 TeV using PYTHIA 8.1 in the default and a LHCb specific configuration. The kinematics of the $\Lambda_{b}^{0}$ decay in the presence of a complex resonance structure is investigated.
Condensed and Soft Matter Physics
Ferrimagnetic Ordering of Ca_{2}(Fe,Ni)MoO_{6} Perovskites E. Burzo, I. BalaszMuresan Romanian Journal of Physics 62,
601 (2017)
The Ca_{2}Fe_{1x}Ni_{x}MoO_{6} perovskites with $x \le 0.2$ crystallize in a monoclinic P2_{1}/ntype structure. The lattice parameters increase parallelly with the nickel content. The perovskites are ferrimagnetically ordered, the saturation magnetization decreasing as result of nickel substitution. The reciprocal susceptibilities show nonlinear temperature dependences. Assuming a two sublattices model, the distribution of ions, their valence states as well as the exchange interactions parameters between and inside magnetic sublattices were determined. These values are discussed in correlation with perovskite compositions.
Mott Type Electrical Conductivity in ZnS_{x}Se_{1x} Thin Films M. Popa, I. Tiginyanu, V. Ursaki Romanian Journal of Physics 62,
602 (2017)
Thin ZnS_{x}Se_{1x} films on glass substrates have been obtained by thermal evaporation. Electrodes from In or other materials have been deposited on thin films, and the temperature dependence of electrical conductivity was investigated during a series of successive cycles of heating and cooling performed at a rate of 6 K/min in a temperature interval from 300 K to 500 K. The measurements demonstrated that the energy of thermal activation at low temperatures (∆E_{2} = 0.13–0.43 eV) is much lower as compared to that measured at high temperatures (∆E_{1} = 0.43–1.89 eV). It was found that in both ranges of low and high temperatures the thermal activation energy increases with increasing the sulfur content in thin films. It was demonstrated that at low temperatures the dominant mechanism of electrical conduction is of Motttype.
Environmental and Earth Physics
New Correlation for the Mixing of Wastewater Sludge A. Barbulescu, A.E. Sterpu, L. Barbes, C.I. Koncsag Romanian Journal of Physics 62,
801 (2017)
Treatment the sewage sludge is a major problem in preserving a clean environment. In this study we develop a model that allows the prediction of the net power consumption at the stirring of sludge proceeding from wastewater treatment. Its novelty consists in describing the mixing power not only as a function of Reynolds number and some geometrical dimensions ratios but also as a function on the fluid’s consistency, expressed as the dry matter fraction in the sludge.
Experimental Results of Laboratory Simulation of Extremely Low Frequency Magnetic Field Pretreatment of Barley Seeds Influence M. Răcuciu, H. Oloşutean, M. Perju Romanian Journal of Physics 62,
802 (2017)
11days old plantlets developed from barley seeds exposed to homogenous 50 Hz magnetic field (1 ÷ 5 mT) for 22 hours, showed decreased level of chlorophyll a while the content of chlorophyll b was significantly increased with enhanced magnetic energy doses. The nucleic acids levels were increased in comparison to the control.
Application of Light Stable Isotope Ratios and Elemental Profile in the Organic Vegetables Characterization I. Feher, D.A. Magdas, A. Dehelean, G. Cristea, C. Voica Romanian Journal of Physics 62,
803 (2017)
This work proposed marker associations for the differentiation of some organic vegetable types (salads, tomatoes, potatoes, cabbages, garlic and leek) from vegetables obtained through conventional agricultural practices. For this purpose, a number of 30 organic and 15 conventional vegetables samples were analyzed from isotopic and elemental point of view. Thus, the best differentiation markers, for these two categories, were found for each vegetable type. Another aim of this study was the differentiation of vegetables grown in greenhouses from those produced in field. For this purpose, the best differentiation elements prove to be: δ^{13}C, Ni, Mo, Cd and Pb.
Applied and Interdisciplinary Physics
Techniques to Determine the Provenance of Limestone Used in Neolithic Architecture of Malta Lino Bianco Romanian Journal of Physics 62,
901 (2017)
The scope of this paper is to put a case for lithological mapping of the limestone used in the Neolithic architecture of Malta to establish, through a comparative analysis, the provenance of the building fabric utilised in the erection of such monumental buildings. In this study, rock samples from the same lithology were assessed through destructive and nondestructive physicomechanical, textural, chemical and mineralogical analytical techniques, to determine the principal characteristics of the limestone.
Application of XRay Fluorescence Elemental Analysis for Mural Painting Restoration of “Oteteleşanu“ Church in Măgurele (painted by Gh. Tăttărescu) Daniela CristeaStan, B. Constantinescu, Catalina Chiojdeanu, Corina Anca Simion Romanian Journal of Physics 62,
902 (2017)
Pigments used in 1853 by famous Romanian painter Gh. Tattarescu for oil mural painting and iconsiconostasis of Church St. Constantine and Helena located in Măgurele, Ilfov County analyzed using a portable XRay Fluorescence spectrometer are discussed. The chemical element predominant in all spectra for the red areas is mercury suggesting the pigment is cinnabar (HgS  mercury sulfide). In pink areas we detected Hg together with Pb, which means cinnabar was mixed with lead white – (PbCO_{3})_{2}$\cdot$Pb(OH)_{2}. Yellow pigment was made from a mixture of chromeyellow (PbCrO_{4}) and ochre (Fe based yellow ochre – Fe_{2}O_{3}$\cdot$H_{2}O, – hydrated iron oxide). In a blue area (an ironbased pigment – very probably Prussian blue – Fe_{7}(CN)_{18}$\cdot$H_{2}O) we detected the presence of zinc suggesting a late repainting with zinc white (ZnO) on the original lead white layer.
