Entropies of a Toroidal Black Hole Due to Scalar and Dirac Fields

Using the thin film brick-wall model, the entropies of a toroidal black hole due to scalar and Dirac fields are investigated. The entropy due to the scalar field is one fourth of the horizon area, and that due to the Dirac field is seven eighth of the area. These results are similar to that in black holes with horizon topology S ². The cutoff in toroidal black hole is chosen as the same as one in black holes with horizon topology S ², which seems to mean that the thin film brick-wall model is universal.     

Three-body structure of low-lying <Superscript>18</Superscript>Ne states

We investigate to what extent ¹⁸Ne can be descibed as a three-body system made of an inert ¹⁶O core and two protons. We compare to experimental data and occasionally to shell model results. We obtain three-body wave functions with the hyperspherical adiabatic expansion method. We study the spectrum of ¹⁸Ne , the structure of the different states and the predominant transition strengths. Two 0⁺, two 2⁺, and one 4⁺ bound states are found where they are all known experimentally. Also one 3⁺ close to threshold is found and several negative-parity states, 1^-, 3^-, 0^-, 2^-, most of them bound with respect to the ¹⁶O excited 3^- state. The structures are extracted as partial-wave components, as spatial sizes of matter and charge, and as probability distributions. Electromagnetic decay rates are calculated for these states. The dominating decay mode for the bound states is E2 and occasionally also M1 .     

Mean-field like renormalization group study of random two-component magnetic systems

Using a mean-field like renormalization group approach, we investigate three classes of disordered systems. The first one is characterized by bond disorder, the bonds being Heisenberg or Ising like. The last two are characterized by site disorder with Heisenberg-or Ising-like ions. Among the three interactions J^II, J^?? and J^I⊥, the last one is either zero or not. Phase diagrams and effective correlation length exponent are determined as a function of the concentration of disorder. Factors influencing the behaviour of these models are discussed.     

The R.I. Pimenov unified gravitation and electromagnetism field theory as semi-Riemannian geometry

More than forty years ago R.I. Pimenov introduced a new geometry—semi-Riemannian one—as a set of geometrical objects consistent with a fibering pr: M _n → M _m . He suggested the heuristic principle according to which the physically different quantities (meter, second, Coulomb, etc.) are geometrically modelled as space coordinates that are not superposed by automorphisms. As there is only one type of coordinates in Riemannian geometry and only three types of coordinates in pseudo-Riemannian one, a multiple-fibered semi-Riemannian geometry is the most appropriate one for the treatment of more than three different physical quantities as unified geometrical field theory. Semi-Euclidean geometry ³ R ₅⁴ with 1-dimensional fiber x ⁵ and 4-dimensional Minkowski space-time as a base is naturally interpreted as classical electrodynamics. Semi-Riemannian geometry ³ V ₅⁴ with the general relativity pseudo-Riemannian space-time ³ V ₄, and 1-dimensional fiber x ⁵, responsible for the electromagnetism, provides the unified field theory of gravitation and electromagnetism. Unlike Kaluza-Klein theories, where the fifth coordinate appears in nondegenerate Riemannian or pseudo-Riemannian geometry, the theory based on semi-Riemannian geometry is free from defects of the former. In particular, scalar field does not arise. The text was submitted by the author in English.     

类锂“洞原子”2s2s2p2P0和2s2p2p2D三激发共振系列的能量、精细结构和寿命

采用多通道鞍点和鞍点复数转动方法，计算了类锂离子(Z=3—10)2s2s2p²P⁰和2s2p2p²D三激发共振态系列的能量、精细结构和寿命.Auger宽度由耦合主要的通道得到，相对论效应计算到一级微扰，质量极化效应计算到无穷级. 关键词：     

Configuration interaction of Er3+ with a charge transfer configuration in the elpasolite compound Cs2NaErCl6

The discrepancies of the crystal-field analysis in Cs₂NaErCl₆ are lowered by letting the 4f¹¹ configuration interact with a charge transfer configuration enclosing a p electron. 75 levels with a total degeneracy equal to 130 were fitted with a mean deviation of 10.5 cm^?1, compared with 21.4 cm^?1 in the standard model. It is found that: (i) the p electrons involved in the process originate most probably from the six Cl^? ligands; (ii) 14% of the 3p⁶ orbitals are projected onto the central ion coordinate system as an unique orbital with p angular character; (iii) this projected orbital can be coupled with 4fⁿ configurations and handled by tensorial methods; and (iv) the most probable mechanism responsible for the improvement of the crystal-field analysis is a 4f¹¹ 3p⁶-4f¹²3p⁵ interaction. The first configuration represents Er³⁺ surrounded by six Cl^? ligands, whereas in the second one, the rare-earth ion and the ligands have gained and lost one electron respectively. The crystal-field analysis enables the estimation of the location of the charge transfer band.     

Isotopically engineered Si and Ge for spintronics and quantum computation

Si, Ge as well as SiGe structures are the promising materials for spintronics and quantum computation due to the fact that in both crystals only one isotope (²⁹Si and ⁷³Ge) has nuclear spin. As a result, isotope engineering of Si and Ge permits to control the density of nuclear spins and vary the spin coherence time, a crucial parameter in spintronics. In the first part we discuss the NMR study of nuclear spin decoherence in Ge single crystals with different abundance of the ⁷³Ge isotope. It was observed that the slow component of the dephasing process is elongated with depletion of Ge crystal with isotope ⁷³Ge. The second part is devoted to the development of the Kane's model of nuclear spin-based quantum computer, which uses the nuclear spin of ³¹P impurity atoms in a ²⁸Si matrix as quantum bits (qubits). We discuss a new method of placing ³¹P atoms in a ²⁸Si based on neutron-transmutation-doping of isotopically engineered Si and Ge. In the proposed structure, interqubit coupling is due to indirect hyperfine interaction of ³¹P nuclear spins with electrons localized in a ²⁸Si quasi-one-dimensional nanowire, which allows one to control the coupling between distant qubits.     

Zeeman relaxation of N2 + (2Σ+) in collisions with 3He and 4He

We compare the cross sections for the transitions changing the projection of the total angular momentum of N₂ ⁺(²Σ) in collisions with ³He and ⁴He at very low collision energy. The fundamental states of the two nuclear spin isomers of N₂ ⁺ are considered as well as the two fine structure levels of the first excited para level N=2. It is shown that the two fundamental states of the two nuclear spin isomers behave differently. For the fundamental para level N=0 of N₂ ⁺, the projection changing cross section is always negligible compared to the elastic one for both He isotopes. For the fundamental ortho level N=1 of N₂ ⁺, the spin-rotation interaction couples the different spin levels directly so the spin relaxation becomes a first order process. The associated resonances increase the projection changing cross section which remains smaller but becomes comparable with the elastic one. This is in contrast with the excited rotational levels of N₂ ⁺, which for the rotational deactivation and elastic channels are found to be equal around the resonances for the collisions involving ³He. These two channels are always larger than the projection changing one. We also find that, for transitions involving the fundamental rotational state, the domain of validity of the threshold laws discussed by Krems and Dalgarno [Phys. Rev. A 67, 050704 (2003)] for a potential decreasing faster than 1/r2 is shortened, due to the long range charge induced dipole potential. This effect is illustrated for the collisions of ³He with the fundamental para state of N₂ ⁺.     

High sensitivity torsion magnetometers for oligatomic films

For thin film studies in magnetic surface and size effects, magnetometers of extreme sensitivity are required, capable to detect a small part of one monolayer. They may be realized as torsion magnetometers using the torque on an anisotropic film in a homogeneous field. A complete analysis of the method is given for ferromagnetic films, both saturated and unsaturated, and for paramagnetic (superparamagnetic) films. Two existing instruments are described, both working in a contact gas, from 4 to 600 K. The first one works in the oscillation mode, using the period of oscillation of the oscillating film as a measure of the magnetic directional moment; this instrument is capable to detect 2·10⁻¹⁸ Wb·m (2·10⁻⁹ G·cm³). The second one works preferentially in the static mode, as a loop tracer, in which the magnetic torque is compensated by a quadrant electrometer; this second instrument detects 6·10⁻¹⁸ Wb·m in the static mode; with a reduced sensitivity (2·10⁻¹⁶ Wb·m), it works also in the oscillation mode. The relative merits of both instruments are discussed.     

Pressure broadening measurement of submillimeter-wave lines of O3

The pressure broadening coefficients and their temperature dependences for two submillimeter-wave transitions of ozone, one being monitored with Odin and the other to be monitored with JEM/SMILES and EOS-MLS, have been determined by using a BWO based submillimeter-wave spectrometer. The measurements have also been extended to one of the symmetric isotopic species, ¹⁶O¹⁸O¹⁶O. The isotopic species is observed in natural abundance and as a consequence the temperature dependence is not determined due to weak signal intensity. The pressure broadening parameters are determined with better than 1% accuracy, while the temperature dependence exponents are obtained within 1.5-3% accuracy for the normal species transitions.     

Negatively charged excitons and the optical properties of modulation-doped quantum wells

Optical and magneto-optical properties are studied for II-VI semiconductor multiple quantum wells (MQWs) doped with donors in the barriers to give electron concentrations of 2 10¹⁰ to 6 10¹¹ cm^-2 in the well layers. Following on from the recent identification of negatively charged excitons X^- (two electrons bound to one hole) in CdTe/Cd_1-xZn_xTe MQWs, this paper presents more specifically the circular polarisation of the luminescence associated with X^- and with the normal exciton X (one electron and one hole) in this type of structure. Very similar magneto-optical properties are observed for modulation doped Zn_0.9Cd_0.1Se/ZnSe MQWs, and X^- is identified in these wells with a binding energy as large as 7 meV for the second electron at 50Å, well-width.     

The reaction 26Mg(3He,n)28Si at 23 and 45 MeV

Angular distributions of neutron groups from the ²⁶Mg(³He, n)²⁸Si reaction have been measured at bombarding energies of 23.1 and 45.5 MeV. The experimental results are compared with DWBA and coupled-channel calculations. The zero-range DWBA calculation using shell-model two-nucleon spectroscopic amplitudes explains rather well most of the experimental data of the lowest four states in ²⁸Si, but it is necessary to take two-step processes into account to reproduce all of them satisfactorily. A strong neutron group observed at about 6.9 MeV in residual excitation is described as one composed of unresolved four groups, of which three are attributed to positive-parity states in ²⁸Si predicted in this energy region by the shell-model calculation and one to the 6.88 MeV 3⁻ state in ²⁸Si.     

The calculated spectra of the azanaphthalenes

A modified INDO (intermediate neglect of differential overlap) method is used to calculate the electronic spectra of naphthalene and some mono-, di-, and tetraazanaphthalenes. The technique is capable of reproducing the better classified bands of this series within a rms error of 1000 cm⁻¹.The four lowest π-π^* bands of naphthalene are well represented; a fifth band reported at 52,600 cm⁻¹, and generally assigned ¹B_2u(π-π^*), may be ¹B_3g(π-π^*) borrowing intensity. The lowest excited singlet state calculated for quinoline is n → π^*, estimated nearly degenerate with the lowest π-π^*, while that for isoquinoline is calculated π-π^*; experimental evidence supports the π-π^* assignment in both cases, but the corresponding absorption in quinoline appears complex. Of the diazanaphthalenes examined (with two nitrogens in one benzenoid ring) all are calculated to have one n-π^* transition before the first π-π^* except phthalazine, in which two n-π^* transitions are calculated to be the lowest lying. This is in accord with experimental evidence to date, although the nature of the observation in phthalazine is reinterpreted as one ¹B₂(n-π). 1,4,5,8-tetrazanaphthalene is predicted to have a group theoretically forbidden n-π^* excited state as low as 21,000 cm⁻¹, and should prove interesting experimentally. Even though n-π^* excited states are often calculated to be the lowest lying, none of these compounds are predicted to have an “n” orbital as homo.Further interpretations of the spectra of the azanaphthalenes are made in view of the calculations. Theoretical limitations of the method employed for this study are discussed.     

The Triton from the Reid93 Potential in the UPA

The unitary pole approximation (UPA) provides an effective means to construct a rank one separable potential for calculations in which one requires a simple representation of the deuteron and/or triton ground-state wave function. By construction the deuteron wave function and the ¹S₀ anti-bound state wave function of the original potential are reproduced. We report results for the corresponding triton ground state. We choose to utilize the realistic Reid93 potential for this purpose. The Reid93 potential, generated by the Nijmegen group, is a Reid-like, partial-wave local potential that produces a χ² representation of the nucleon–nucleon (NN) scattering data that is as precise as an NN partial-wave analysis. Results for properties of ²H and ³H from the UPA are compared with those for the original potential. To further illustrate the precision of the method, results for properties of the deuteron and triton from the UPA are also compared with those for the original Reid68 potential.     

Vacuum spacetimes with two-parameter spacelike isometry groups and compact invariant hypersurfaces: Topologies and boundary conditions

Spacetimes with closed spacelike hypersurfaces and spacelike two-parameter isometry groups are investigated to determine their possible global structures. It is shown that the two spacelike Killing vectors always commute with each other. Connected group-invariant spacelike hypersurfaces must be homeomorphic to S¹ ? S¹ ? S¹ (three-torus), S¹ ? S² (three-handle), S³ (three-sphere), or to a manifold which is covered by one of these. The spacetime metric and Einstein equations are simplified in the absence of nongravitational sources and used to establish the impossibility of topology change as well as other limitations on global structure. Regularity conditions for spacetimes of this type are derived and shown to be compatible with Einstein's equations.     

Detection of a new SRS‐promoting phonon mode and cross‐cascaded χ(3)‐nonlinear lasing in single crystals of calcite (trigonal CaCO3)

For calcite (CaCO₃), one of the pioneer crystals in nonlinear optics, new results of stimulated Raman scattering (SRS) spectroscopy are presented. Among them are the discovery of a new SRS‐promoting vibration mode with ω_SRS2 ≈︁ 282 cm^‐1 and its participation, together with the main SRS mode ω_SRS1 ≈︁ 1086.5 cm^‐1, in cross‐cascaded (χ⁽³⁾ ↔ χ⁽³⁾) nonlinear‐lasing generation, as well as the observation of efficient self‐upconversion via cascaded parametric four‐wave processes of one‐micron Stokes and anti‐Stokes χ⁽³⁾‐lasing into the UV‐region of third harmonic generation. The investigations show that calcite is able to generate a χ⁽³⁾‐lasing comb of more than two octaves bandwidth. The article also gives a brief review on the discovery and study of the SRS‐effect in natural crystals (minerals), which have expanded our ability to study the photon‐phonon nonlinear‐laser interactions in crystalline materials. A short summary of information about χ⁽³⁾‐lasing properties of the triangular planar structure units in SRS‐active crystals is included.     

On the use of Skyrme forces in self-consistent RPA calculations

Self-consistent random-phase (RPA) calculations including the continuum are presented using Skyrme forces. The density-dependent interpretation of the interaction is favoured as it does not violate the spin stability. A possible density dependence of the momentum-dependent S- and P-interaction is taken into account, which allows one to vary the incompressibility K and the effective mass $\text{m}{}^1\text{/m}$ independently. It is shown by analytic relations that these two quantities are the only degrees of freedom left in the parameterization of this Skyrme force,if the ground-state properties shall be reproduced, except for a still open degree of freedom in the spin exchange parameterization. The Landau parameters are discussed as a function of these degrees of freedom in order to find the best possible particle-hole interaction. Continuum calculations of the 1^?, 2 ⁺ and 3^? states in ¹⁶O are presented and compared with-discretized continuum calculations. It is found that the existing Skyrme forces do not show enough attraction and in addition cause relatively large isospin impurities, in ¹⁶O as well as in ²⁰⁸Pb. The influence of large configuration spaces is discussed. A systematic search for an interaction with a stronger particle-hole interaction is presented which seems to favour interactions with a high effective mass, but a low compression modulus.     

The unimolecular decomposition of the fluoroethylene radical anions formed by electron attachment

Dissociative electron attachement by monofluoroethylene, cis-1,2-difluoroethylene, trans-1,2-difluoroethylene, 1,1-difluoroethylene, and trifluoroethylene shows three distinct and separated resonances in the energy range 0–17 eV. The resonance of low energy is interpreted as a²Π shape resonance and the second resonance as a Feshbach type resonance. Apart from the well known dissociation channel associated with the formation of F (which is generally not the dominant one in the present compounds), a variety of negative ions are generated from the ²Π resonance (CCH₂⁻, CCHF⁻, CCF₂⁻, C₂⁻, FHF⁻). The fragments observed clearly reflect the parent ions from which they are generated.     

Role of helium in a He-Xe plasma

The populations of the 5p⁵6s and 5p⁵6p levels of Xe are reported as functions of current and partial pressure of He for the positive column of a glow discharge at medium pressures. The populations of the first ones (especially the metastable 5p⁵6s³P₂ one) decrease as the He pressure is raised, whereas those of the upper 5p⁵6p levels increase. An explanation is proposed for the observed changes in the level populations.We are indebted to Professor A. N. Tekuchev for direction and comments, and to Z. P. Gasko for help with the measurements.