bluuebunny/crossref_metadata_2025_split huggingface dataset:
Asymptotic expansions of the oblate spheroidal eigenvalues and wave functions for large parameter c
Authors: Do-Nhat Tam 
Published: April 2011

The asymptotic expansion of the oblate spheroidal eigenfunctions can be expanded in terms of the Laguerre functions of the first and second kinds, from which their asymptotic eigenvalue can be expressed in an inverse power series of c, where the parameter c is proportional to the operating frequency. Analytical expressions of the eigenvalue coefficients, as well as those of the expansion coefficients of the eigenfunctions, are derived and verified with numerical results. PACS Nos.: 02.30Gp, 03.65ge
Photon-added one-photon and two-photon nonlinear coherent states
Authors: Wang Xiaoguang 
Published: April 2011

From the photon-added one-photon nonlinear coherent states a†m|α, 〉, we introduce a new type of nonlinear coherent states with negative values of m. The nonlinear coherent states corresponding to the positive and negative values of m are shown to be the result of nonunitarily deforming the number states |m〉 and |0〉, respectively. As an example, we study the sub-Poissonian statistics and squeezing effects of the photon-added geometric states with negative values of m in detail. Finally, we investigate the photon-added two-photon nonlinear coherent states and find that they are still the two-photon nonlinear coherent states with certain nonlinear functions. PACS Nos.: 42.50Dv, 03.65Fd
Cavity ring-down spectroscopy of transient O2-O2 dimers
Authors: Tiedje H F , DeMille S , MacArthur L , Brooks R L 
Published: April 2011

Cavity ring-down spectroscopy has been used to obtain the spectra of transient (O2)2 at 577 and 629 nm, at room temperature and pressures ranging from about 0.25 to 10.0 atm. A selection of these spectra are displayed showing the overlapping monomer and dimer features. Pressure-dependent cross sections have been obtained and Rayleigh extinction has been observed. The derived band parameters are compared to recent results from others. PACS Nos.: 33.20kf, 33.70Fd
Thermal radiation and buoyancy effects on MHD free convective heat generating flow over an accelerating permeable surface with temperature-dependent viscosity
Authors: Seddeek M A 
Published: April 2011

The paper presents a study of the flow of a viscous incompressible fluid over an accelerating permeable surface with temperature-dependent viscosity, taking into account the effect of thermal radiation and thermal buoyancy in the presence of a magnetic field. The fluid viscosity is assumed to vary as an inverse linear function of temperature. The governing equations for laminar free convection of fluid are changed to dimensionless ordinary differential equations by similarity transformation. They are solved by a shooting method. The effects of various parameters on the velocity and temperature profiles as well as the skin friction coefficient and wall heat transfer are presented graphically and in tabulated form. PACS Nos.: 47.65ta, 52.30q
Morphology changes of Hg1-xCdxTe target in the PLD process
Authors: Virt I S , Kuzma M , Rudyi I O , Frugynskyi M S , Kurilo I V , Lopatynskyj I Ye 
Published: April 2011

The surfaces of Hg1-xCdxTe samples used as targets in laser epitaxy were investigated by electron microscope methods. The samples were modified by two lasers: the YAG:Nd3+ and the excimer XeCl with pulse lengths of 40 and 25 ns, respectively, at different laser powers. The electrophysical properties of the samples were studied before and after irradiation. The morphological and structural properties of the surface investigated depend strongly on the type of laser pulse and on its energy. This provides two mechanisms for laser ablation of this material. PACS Nos.: 70, 72.27JV
Convective heat transfer, by the presence of radiation, in an electrically conducting fluid at a stretching surface
Authors: AboEldahab E M 
Published: April 2011

The problem of free-convection heat transfer due to the simultaneous action of buoyancy, radiation, and transverse magnetic field is investigated near an isothermal sheet. The sheet is linearly stretched in the presence of heat generation or absorption. The resulting coupled nonlinear differential equations are solved numerically. A parametric study is performed to illustrate the influence of the radiation parameter, magnetic parameter, heat generation or absorption parameter, and Prandtl number on the profiles of the velocity and temperature functions. Numerical data for the skin friction and the heat flux functions have been tabulated for various parametric conditions. PACS No.: 44.25+f
Seasonal and diurnal variations of geomagnetic activity and their role in Space Weather forecast
Authors: Lyatsky W , Hamza A M 
Published: April 2011

A possible test for different models explaining the seasonal variation in geomagnetic activity is the diurnal variation. We computed diurnal variations both in the occurrence of large AE (auroral electrojet) indices and in the AO index. (AO is the auroral electrojet index that provides a measure of the equivalent zonal current.) Both methods show a similar diurnal variation in geomagnetic activity with a deep minimum around (37) UT (universal time) in winter and a shallower minimum near 59 UT in equinoctial months. The observed UT variation is consistent with the results of other scientists, but it is different from that expected from the RussellMcPherron mechanism proposed to explain the seasonal variation. It is suggested that the possible cause for the diurnal and seasonal variations may be variations in nightside ionospheric conductivity. Recent experimental results show an important role for ionospheric conductivity in particle acceleration and geomagnetic disturbance generation. They also show that low ionospheric conductivity is favorable to the generation of auroral and geomagnetic activity. The conductivity in conjugate nightside auroral zones (where substorm generation takes place) is minimum at equinoxes, when both auroral zones are in darkness. The low ionospheric conductivity at equinoxes may be a possible cause for the seasonal variation in the geomagnetic activity with maxima in equinoctial months. The diurnal variation in geomagnetic activity can be produced by the UT variation in the nightside ionospheric conductivity, which in winter and at equinoxes has a maximum around 45 UT that may lead to a minimum in geomagnetic activity at this time. We calculated the correlation patterns for the AE index versus solar-wind parameters inside and outside the (27) UT sector related to the minimum in geomagnetic activity. The correlation patterns appear different in these two sectors indeed, which is well consistent with the UT variation in geomagnetic activity. It also shows that it is possible to improve significantly the reliability of the Space Weather forecast by taking into account the dependence of geomagnetic activity not only on solar-wind parameters but also on UT and season. Our test shows that a simple account for the dependence of geomagnetic activity on UT can improve the reliability of the Space Weather forecast by at least 50% in the 27 UT sector in winter and equinoctial months. PACS No.: 91.25Le
The growth of vapour bubbles in superheated water between two finite boundaries
Authors: Mohammadein S A , El-Rab RA Gab 
Published: April 2011

The paper analyses the behaviour of vapour-bubble growth between finite boundaries. The Plesset and Zwick theory is modified by assumptions that are different than those studied before. The growth problem is solved analytically in terms of initial bubble velocity and initial void fraction. The results are compared with those obtained from previous theories and experiment. Good agreement is obtained for certain values of the initial void fraction and the initial bubble velocity. PACS No.: 47.50Dz
The front-form Hamiltonian and BRST formulations of the Harada-gauged FloreaniniJackiw action
Authors: Kulshreshtha Usha 
Published: April 2011

The Hamiltonian and BRST formulations of the Harada-gauged FloreaniniJackiw action, which describes a chiral Schwinger model in terms of chiral bosonization, are investigated in the light-front frame. PACS No.: 11.15-q
On an application of a generalization of the discrete Fourier transform to short time series
Authors: Grindlay J 
Published: April 2011

A generalization of the discrete Fourier transform (DFT) is discussed. This generalization or GDFT provides a smooth interpolation between the points of the DFT. The GDFT of a sinusoidal function in a finite time window is (a) described in detail and (b) shown to coincide (aside from a simple scaling constant) with the corresponding Fourier transform, provided that certain conditions are satisfied by the sinusoidal parameters. The sinusoidal GDFT is proposed as a tool to investigate, (independently of any Fourier transform connection) the sinusoidal nature of time series. The method is applied successfully to the case of a specific trajectory of the Hénon and Heiles model. PACS Nos.: 02.30, 05.45
Electromagnetic (self-) interactions in relativistic Schrödinger theory
Authors: Mattes M , Rupp S , Sorg M 
Published: April 2011

The Relativistic Schrödinger Theory (RST) is applied to a system of N particles with electromagnetic interactions. The gauge group is U(1) × U(1)... × U(1). By exploiting the mathematical structure of fibre bundles, the energy-momentum content of the gauge field can be defined in such a way that no infinite self-energy of point charges can arise. However, the picture of classical point particles becomes insufficient in any case in view of the exchange and overlap effects occurring in RST. The presence of overlap currents seems to be necessary to remedy certain pathological features of the classical point-particle theories. PACS Nos.: 03.65Pm, 03.65Ge, 03.65Ta
Breit-Pauli energy levels and transition rates for the carbonlike sequence
Authors: Tachiev G , Fischer C Froese 
Published: April 2011

BreitPauli results for energy levels, lifetimes, and some transition data are reported for all levels up to 2s22p3d 1PJo of the C-like spectrum for 7 [Formula: see text] Z [Formula: see text] 15. For all but the lowest members of the sequence, these include all the states of the 2s22p2, 2s2p3, 2p4, 2s22p3s, 2s22p3p, and 2s22p3d configurations. For carbon, only the states for the 2s22p2, 2s2p3, and 2s22p3s configurations are included. A simultaneous optimization scheme was applied so that a radial basis could be determined for a set of terms that mix in the BreitPauli approximation. All results have been posted at a Web site. In this paper, lifetimes are reported and, in addition, results for N II, O III, and Si IX are critically evaluated. Energy levels are compared with experiment and adjusted transition rates, along with uncertainty estimates are presented. Selected results are compared with other theory and experiment. PACS Nos.: 31.25Jf, 32.30Jc, 32.70Cs
Interpretation of the spectrum of Pb(II). Theoretical transition probabilities and lifetimes
Authors: Colón C , Alonso-Medina A 
Published: April 2011

Radiative transition probabilities for 190 lines arising from the ns 2S1/2, np 2P1/2,3/2, nd 2D3/2,5/2, nf 2F5/2,7/2, and 6p2 (4P1/2,3/2,5/2, 2D3/2,5/2, 2P1/2,3/2, and 2S1/2) levels of Pb(II) have been calculated. Lifetimes of the above mentioned levels have been determined from the present transition probabilities. These values were obtained in intermediate coupling (IC) and using ab initio relativistic Hartree-Fock calculations. For the IC calculations, we use the standard method of least-square fitting of experimental energy levels by means of computer codes from Cowan. The results of calculations for radiative transition probabilities and excited states lifetimes are presented and compared with the experimental results present in the literature and with other theoretical values. There is generally good agreement between our values and the experimental data available. Analysis of the interaction shows that the level 4P5/2 of the 6s6p2 configuration presents a large contribution to the 2D5/2 level of the 6s26d configuration. This result explains the good agreement between our result and the experimental values obtained to the observed as the 6s6p2 4P5/2  6s 25f2F7/2 dipole-forbidden transition. PACS Nos.: 32.70^*, 32.70Fw, 32.70Cs
Energy transfer between the 2S and 2D states in alkalis: experiments and theory
Authors: Ekers A , Glodz M , Grushevsky V , Klavins J , Szonert J 
Published: April 2011

Collisional energy transfer (ET) between the 2S and 2D states of alkali atoms is reviewed. Recent experimental results on the ET in homonuclear collisions in Na, K, and Rb vapours upon cw (continuous wave) and pulsed laser excitation, as well as theoretical calculations of the respective cross sections are discussed. The mechanisms of these processes are considered in an attempt to clarify the role of the dipoledipole interaction. PACS No.: 34.50Fa
Thermoluminescence recorded in a hyperbolic heating profile
Authors: Bhattacharya M 
Published: April 2011

Thermoluminescence (TL) glow curves corresponding to a hyperbolic heating profile are computed, for the first time, by solving a system of coupled differential equations using the fourth-order RungeKutta method taking into account the presence of thermally disconnected traps. The variations of the peak temperature and the symmetry factor with the change of the fractional-filling ratio have been studied, not only for the TL peaks obtained as a result of the solution of the coupled differential equations but also for TL peaks obeying RandallWilkins and GarlickGibson equations in a hyperbolic heating program. Finally, the validity of the plateau test has also been considered. PACS No.: 78.60Kn
Polarization dependence of optical harmonic generation from solid targets at high intensities: Role of Faraday rotation
Authors: Wu S , Zhan R -J , Chen J 
Published: April 2011

In this letter, we show that the Faraday rotation effect of the strong spontaneous magnetic field generated by the focus of a short-pulse, high-power laser interacting with a solid target may blur out the distinction between the s and p polarization of the incident laser. This in effect leads to the result that the harmonic yield ratio between p and s polarization is not as large as a PIC (particle-in-cell) simulation predicted. An approximate calculation of the harmonic yield ratio versus the magnetic field is carried out and the result is in relatively good agreement with the observations by Norreys et al. PACS Nos.: 42.90, 78.90
Measurement of radiative lifetimes in Nd II
Authors: Pinciuc C M , Rivest R C , Izawa M R , Holt R A , Rosner S D , Scholl T J 
Published: April 2011

We have measured radiative lifetimes of 35 levels of Nd II using the collinear beam-laser method. The levels studied had term energies up to ~30 000 cm1 and lifetimes of 10 to 100 ns. Experimental accuracy was in the range 1.514%. These measurements are a first step to providing new and updated oscillator strengths needed for abundance determinations from stellar spectra. PACS No.: 32.70Cs
Ground state of an Ising-type spin-1/2 chain with competing interactions
Authors: Tonegawa T , Matsumoto H , Hikihara T , Kaburagi M 
Published: April 2011

The ground state of an Ising-type spin-1/2 chain with ferromagnetic bond-alternating nearest-neighbor and anti-ferromagnetic uniform next-nearest-neighbor interactions is studied by using the exact-diagonalization method and the density-matrix renormalization-group method. The Hamiltonian describing the system is expressed as H =  Σi h2i1,2i  J1 Σi h2i,2i+1 + J2 Σi hi,i+2 with hi,i' = γ(Six Si'x + Siy Si'y) + Siz Si'z, where J1 [Formula: see text] 0, J2 [Formula: see text] 0, and 1 > γ [Formula: see text] 0. Special attention is paid to the ground-state phase diagram on the J1 versus J2 plane for a given value of γ. The phase diagram is composed of the ferromagnetic, intermediate, and up-up-down-down phases, the intermediate phase being characterized by its magnetization, which takes finite but unsaturated values. The phase diagram obtained for γ = 0.5 shows that the region of the intermediate phase for a given value of J1 is widest when J1 = 1.0 and becomes narrower rather rapidly as J1 decreases or increases from 1.0. The J2-dependence of the ground-state magnetization for γ = 0.5 and J1 = 0.85 is also discussed. PACS Nos.: 75.10Jm, 75.40Mg
Is there a phase transition in the isotropic Heisenberg anti-ferromagnet on the triangular lattice?
Authors: Stephan W , Southern B W 
Published: April 2011

The phase diagram of the classical anisotropic (XXZ) Heisenberg model on the two-dimensional triangular lattice is investigated using Monte Carlo methods. In the easy-axis limit, two finite-temperature vortex-unbinding transitions have been observed. In the easy-plane limit, there also appear to be two distinct finite-temperature phase transitions that are very close in temperature. The upper transition corresponds to an Ising-like chirality ordering and the lower temperature transition corresponds to a KosterlitzThouless vortex-unbinding transition. These phase-transition lines all meet at the Heisenberg point and provide strong evidence that the isotropic model undergoes a novel finite-temperature phase transition. PACS Nos.: 75.10Hk, 75.40Mg
Alteration of the stacked 2π/3 magnetic structure in the triangular lattice anti-ferromagnet LiCrS2
Authors: Lafond A , Henggeler W , Mutka H , Ouladdiaf B 
Published: April 2011

LiCrS2 has magnetic Cr ions with spin S = 3/2 on a triangular lattice. Other researchers (J. Solid State Chem. 3, 590, 1971) concluded that this compound has an anti-ferromagnetic order with a stacked 2π/3 structure below a transition temperature of the order of TN = 50 K. We have re-examined this system with neutron scattering methods on powder samples, paying attention to the temperature dependence of the magnetic scattering. The overall characteristics of the magnetic ordering are in agreement with the earlier study but we have observed significant modifications of the stacked 2π/3 structure well below the critical temperature. The main new features observed on cooling from T = 25 K down to T = 1.5 K are (i) the gradual decrease from 2.5 µB to 2.3 µB of the ordered moment attributed to the 2π/3 structure, (ii) the appearance of new correlations corresponding to a multiplication of the magnetic unit cell, and (iii) the growth of a diffuse elastic scattering component that can be ascribed to a frozen disorder. These observation are not explained in the framework of the standard theoretical treatments concerning the stacked triangular anti-ferromagnet with Heisenberg or slightly anisotropic interactions. PACS Nos.: 75.10Nr, 75.25+z, 75.40Gb
Conventional and unconventional orderings in the jarosites
Authors: Wills A S 
Published: April 2011

The jarosites make up the most studied family of Kagome anti-ferromagnets. The flexibility of the structure to substitution of the A and B ions allows a wide range of compositions to be synthesized with the general formula AB3(SO4)2(OH)6 (A = Na+, K+, Ag+, Rb+, H3O+, NH4+, 1/2Ba2+, and 1/2Pb2+; B = Fe3+, Cr3+, and V3+). Additional chemical tuning of the exchange between layers is also possible by substitution of the (SO4)2 groups by (SeO4)2 or (CrO4)2. Thus, a variety of S = 5/2, 3/2, and 1 systems can be engineered to allow study of the effects of frustration in both the classical and more quantum limits. Within this family both conventional long-ranged magnetic order and more exotic unconventional orderings have been found. This article reviews the different types of magnetic orderings that occur and examines some of the parameters that are their cause. PACS Nos.: 75.25+z, 75.30Et, 75.30Gw, 75.50Ee, 75.50Lk
Triangular-lattice Heisenberg anti-ferromagnets: A Schwinger-boson study
Authors: Manuel L O , Ceccatto H A 
Published: April 2011

We study, within the Schwinger-boson approach, the ground-state structure of two Heisenberg anti-ferromagnets on the triangular lattice: the J1  J2 model, which includes a next-nearest-neighbor coupling J2, and the spatially-anisotropic J1  J'1 model, in which the nearest-neighbor coupling takes a different value J'1 along one of the bond directions. For both models, the inclusion of one-loop corrections to saddle-point results leads to the prediction of nonmagnetic phases for particular values of the parameters J1/J2 and J'1/J1. In the case of the J1  J2 model we shed light on the existence of such a disordered quantum state, a question which is controversial in the literature. For the J1  J'1 model our results nicely agree with series-expansions predictions. PACS No.: 75.10Jm
Effective Hamiltonians and dilution effects in Kagome and related anti-ferromagnets
Authors: Henley C L 
Published: April 2011

What is the zero-temperature ordering pattern of a Heisenberg anti-ferromagnet with large spin length S (and possibly small dilution), on the Kagome lattice, or others built from corner-sharing triangles and tetrahedra? First, I summarize the uses of effective Hamiltonians to resolve the large ground-state degeneracy, leading to long-range order of the usual kind. Secondly, I discuss the effects of dilution, in particular that the classical ground states become nonfrustrated, in that every simplex of spins is optimally satisfied. Of three explanations for this, the most satisfactory is the MoessnerChalker constraint enumeration. Quantum zero-point energy may compete with classical exchange energy in a diluted system, creating frustration and enabling a spin-glass state. I suggest that the regime of over 97% occupation is qualitatively different from the more strongly diluted regime. PACS Nos.: 75.10N, 75.50Ee, 75.40, 75.25+z
Origin of spin-ice behavior in Ising pyrochlore magnets with long-range dipole interactions: an insight from mean-field theory
Authors: Gingras M JP , den Hertog B C 
Published: April 2011

Recent experiments suggest that the Ising pyrochlore magnets Ho2Ti2O7 and Dy2Ti2O7 display qualitative properties of the ferromagnetic nearest-neighbor spin-ice model proposed by Harris et al. Phys. Rev. Lett. 79, 2554 (1997). The manifestation of spin-ice behavior in these systems despite the energetic constraints introduced by the strength and the long-range nature of dipoledipole interactions, remains difficult to understand. We report here results from a mean-field analysis that shed some light on the origin of spin-ice behavior in (111) Ising pyrochlores. Specifically, we find that there exist a large frustrating effect of the dipolar interactions beyond the nearest neighbor, and that the degeneracy established by effective ferromagnetic nearest-neighbor interactions is only very weakly lifted by the long-range interactions. Such behavior only appears beyond a cut-off distance corresponding to O(102) nearest neighbor. Our mean-field analysis shows that truncation of dipolar interactions leads to spurious ordering phenomena that change with the truncation cut-off distance. PACS Nos.: 75.10-b, 75.10Hk, 75.20-g, 75.30-m
Quantum tetrahedral mean-field theory of the pyrochlore lattice
Authors: García-Adeva A J , Huber D L 
Published: April 2011

A quantum mean-field theory of the pyrochlore lattice is presented. The starting point is not the individual magnetic ions, as in the usual Curie-Weiss mean-field theory, but a set of interacting corner-sharing tetrahedra. We check the consistency of the model against magnetic susceptibility data and find a good agreement between the theoretical predictions and the experimental data. Implications of the model and future extensions are also discussed. PACS Nos.: 75.10Jm, 75.30Cr, 75.40Cx