Weak Gravitational Lensing from Regular Bardeen Black Holes

In this article we study weak gravitational lensing of regular Bardeen black hole which has scalar charge g and mass m. We investigate the angular position and magnification of non-relativistic images in two cases depending on the presence or absence of photon sphere. Defining dimensionless charge parameter \(q=\frac {g}{2m}\) we seek to disappear photon sphere in the case of \(|q|>{24\sqrt 5}/{125}\) for which the space time metric encounters strongly with naked singularities. We specify the basic parameters of lensing in terms of scalar charge by using the perturbative method and found that the parity of images is different in two cases: (a) The strongly naked singularities is present in the space time. (b) singularity of space time is weak or is eliminated (the black hole lens).     

Gamma-X-ray coincidence Mössbauer emission spectroscopy on57Co/CoO

The time integral Mössbauer emission spectrum of a⁵⁷Co/Co_1–x O source (x 10^–5) at RT consists of two single Lorentzian lines of an Fe²⁺ (76%) charge state and an Fe³⁺ (24%) aliovalent charge state. The spectrum measured by -X-ray coincidence spectrpscopy shows the same fraction of the aliovalent charge state, contrary to the expectation derived from the competing acceptor model as successfully applied by Tejada and Parak [1], who could explain the dependence of the formation of aliovalent charge states after the nuclear transformation on the stoichiometric parameterx. The consequences of this unexpected behaviour for the competing acceptor model are discussed.     

Development of a miniature STM holder for study of electronic conductance of metal nanowires in UHV-TEM

A new miniature scanning tunneling microscope (STM) holder was developed in order to simultaneously investigate electronic conductance and structure of nanowires in an ultra high-vacuum electron microscope (UHV-TEM). A thin gold wire held between the STM tip and substrate stage of the specimen holder was stretched to form a suspended gold nanowire. The new TEM-STM system allowed us to measure electronic conductance at intervals of 20 ms, and to record high-resolution TEM images on videotape at 30 fps. Suspended gold nanowires formed from [1 1 0] oriented electrodes were well-elongated. In contrast, [1 0 0] and [1 1 1] electrodes produced nanowires with short necks. Electronic conductance was found to change as nanowire structure changed, with conductance quantization in units of 2e²/h, where e is the electron charge and h is Planck’s constant, only being exhibited for well-elongated nanowires.     

Positron lifetime and 2D-ACAR studies of divacancies in Si

We have measured positron lifetime and Two Dimensional Angular Correlation of Annihilation Radiation (2D-ACAR) distributions of Floating-Zone grown (FZ) Si specimens containing divacancies (V₂) with the definite charge states, V ₂ ⁰ , V ₂ ^–1 or V ₂ ^–2 from room temperature to about 10 K. These charge states are accomplished by an appropriate combination of dopant species, their concentration and irradiation doses of 15 MeV electrons. with reference to the currently accepted ionization level of divacancies. The positron lifetime of the negatively charged divacancy increases with temperature, while that of the neutral divacancy shows little change with temperature. The positron trapping rate, obtained from lifetime and 2D-ACAR measurements, increases markedly with decreasing temperature. This is found not only for the negative divacancies but also for the neutral divacancy. We need a model which explains this temperature dependence. The 2D-ACAR distribution from positrons trapped at divacancies shows nearly the same distribution for the different charge states, which differs considerably from the case of As vacancies in GaAs studied by Ambigapathy et al. We have observed a small but definite anisotropy in the distribution of trapped positrons in V ₂ ^– using a specimen containing oriented divacancies.Paper presented at the 132nd WE-Heraeus-Seminar on Positron Studies of Semiconductor Defects, Halle, Germany, 29 August to 2 September 1994     

Magnetic charge,black holes,and cosmic censorship

The possibility of converting a Reissner-Nordström black hole into a naked singularity by means of test particle accretion is considered. The dually charged Reissner-Nordström metric describes a black hole only when M² > Q³ + P². The test particle equations of motion are shown to allow test particles with arbitrarily large magnetic charge/mass ratios to fall radially into electrically charged black holes. To determine the nature of the final state (black hole or naked singularity) an exact solution of Einstein's equations representing a spherical shell of magnetically charged dust falling into an electrically charged black hole is studied. Naked singularities are never formed so long as the weak energy condition is obeyed by the infalling matter. The differences between the spherical shell model and an infalling point test particle are examined and discussed.     

Kerr–Newman Solution as a Dirac Particle

For m ² < a ² + q ², with m, a, and q respectively the source mass, angular momentum per unit mass, and electric charge, the Kerr–Newman (KN) solution of Einstein's equation reduces to a naked singularity of circular shape, enclosing a disk across which the metric components fail to be smooth. By considering the Hawking and Ellis extended interpretation of the KN spacetime, it is shown that, similarly to the electron-positron system, this solution presents four inequivalent classical states. Making use of Wheeler's idea of charge without charge, the topological structure of the extended KN spatial section is found to be highly non-trivial, leading thus to the existence of gravitational states with half-integral angular momentum. This property is corroborated by the fact that, under a rotation of the space coordinates, those inequivalent states transform into themselves only after a 4 rotation. As a consequence, it becomes possible to naturally represent them in a Lorentz spinor basis. The state vector representing the whole KN solution is then constructed, and its evolution is shown to be governed by the Dirac equation. The KN solution can thus be consistently interpreted as a model for the electron-positron system, in which the concepts of mass, charge and spin become connected with the spacetime geometry. Some phenomenological consequences of the model are explored.     

Trajectory of neutron–neutron–C excited three-body state

The trajectory of the first excited Efimov state is investigated by using a renormalized zero-range three-body model for a system with two bound and one virtual two-body subsystems. The approach is applied to n–n–¹⁸C, where the n–n$n\text{–}n$ virtual energy and the three-body ground state are kept fixed. It is shown that such three-body excited state goes from a bound to a virtual state when the n–¹⁸C binding energy is increased. Results obtained for the n–¹⁹C elastic cross-section at low energies also show dominance of an S-matrix pole corresponding to a bound or virtual Efimov state. It is also presented a brief discussion of these findings in the context of ultracold atom physics with tunable scattering lengths.     

Hall coefficient in solution for a simple dynamical model

A model Liouville equation is proposed for a system composed of an ion moving in a solvent fluid. Using this model, explicit results are obtained for the Ohmic conductivityL and the Hall conductivityh. These results are then used to calculate the Hall coefficientR = ehL^–2, which is a measure of the effect of non-Brownian motion, for several charge carriers of interest. Our results are in agreement with earlier findings based on a stochastic model which predictR > 1 for H⁺(aq). Our results also indicate thatR 1 for charge carriers such as Na⁺, Cl^–, and K⁺ which have a mass greater than that of a solvent molecule (here taken as 18 amu).This research was supported in part by grants from the National Science Foundation and by the Research Foundation of the State University of New York.     

Unconventional spin-charge phase separation in a model 2D cuprate

In this work, we address a challenging problem of a competition of charge and spin orders for high-T _c cuprates within a simplified 2D spin-pseudospin model which takes into account both conventional Heisenberg Cu²⁺?Cu²⁺ antiferromagnetic spin exchange coupling (J) and the on-site (U) and intersite (V) charge correlations in the CuO₂ planes with the on-site Hilbert space reduced to only three effective charge states (nominally Cu^1+;2+;3+). We performed classical Monte Carlo calculations for large square lattices implying the mobile doped charges and focusing on a case of a small intersite repulsion V ? J. The on-site attraction (U < 0) does suppress the antiferromagnetic ordering and gives rise to a checkerboard charge order with the doped charge distributed randomly over a system in the whole temperature range. However, under the on-site repulsion (U > 0) the homogeneous ground state antiferromagnetic solutions of the doped system found in a mean-field approximation are shown to be unstable with respect to a phase separation with the charge and spin subsystems behaving like immiscible quantum liquids. Puzzlingly, with lowering the temperature one can observe two sequential phase transitions: first, an antiferromagnetic ordering in the spin subsystem diluted by randomly distributed charges, then, a charge condensation in the charge droplets. The effects are illustrated by the Monte Carlo calculations of the specific heat and longitudinal magnetic susceptibility.     

Charging of inorganic glasses during irradiation and the energetics of their structure

Conclusions The energetics of the glass structure glasses characterizing the magnitude of the cation-oxygen bond constitutes the key factor which determines the quantity of charge stored. In the successive replacement of cation-modifiers, most charge is stored in those glasses in which the lowest concentration of hole color centers is produced. In the event of a percentage change in the content of the cation-modifier in the glass structure, most charge is stored in those glasses that lie closest to the metaphosphate line.A law of charge storage in phosphate glasses has been established. The kinetics of charge storage is more complex: a rapid increase in the quantity of charge stored is observed in the first stage of storage, whereas in the second stage the quantity of charge stored is observed to decrease slowly at large doses. Analysis of the curves indicates two processes occurring in the glasses during irradiation.The mechanism of neutralization of electrically active centers consists in a neutral P₂O₇ complex being formed from the charged radicals PO ₃ ^– and PO ₄ .Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 60–65, July, 1977.     

A dependence of inclusive pion double charge exchange

The A dependence of the forward cross section for inclusive pion double charge exchange on nine target nuclei from ⁶Li to ²⁰⁹Bi at T₀ = 0.59 GeV, as well as the cross section for ⁶Li, ⁷Li, and ¹²C nuclei at T₀ = 0.59, 0.75, and 1.1 GeV, was measured with the 3-m magnetic spectrometer of the Institute of Theoretical and Experimental Physics (ITEP, Moscow). The resulting A dependence is well described within the model involving two sequential single charge exchanges and taking into account the renormalization of the amplitude for pion single charge exchange in a nucleus. A relatively weak energy dependence of the cross section for the ⁶Li, ⁷Li, and ¹²C nuclei agrees with the analogous dependence obtained previously for the ¹⁶O nucleus, but it contradicts the predicted sharp decrease in the cross section within the model involving two sequential single charge exchanges. This result provides an additional piece of evidence that the contribution from the mechanism of inelastic Glauber rescattering is significant at T₀ ? 0.6 GeV.     

Parity-violating electron scattering – an experimental overview

We discuss the current status and future plans of world-wide efforts of parity-violating asymmetry measurements in the scattering of longitudinally polarized electrons off unpolarized fixed targets. One thrust is the measurements of nucleon neutral weak form factors at intermediate four-momentum transfer (0.1 < Q ² < 1) (GeV/c)² which provides information about the role of virtual strange quarks on the charge and current distributions inside nucleons. A new topic is the elastic neutral weak amplitude at very low Q ² from scattering off a heavy spinless nucleus, which is sensitive to the presence of a neutron skin. Finally, we discuss the neutral current elastic amplitude at very low Q ² off protons and electrons and in the DIS regime off deuterium, which allows precision measurements of the weak mixing angle at low energy and is thus sensitive to new physics at the TeV scale. The physics implications of recent results, potential measurements from experiments under construction as well as new ideas at future facilities are discussed.     

Study of dielectric and ac impedance properties of Ti doped Mn ferrites

We have reported dielectric and ac impedance properties of Ti doped Mn_1+xFe_2−2xO₄ (0x0.5) ferrites prepared by solid-state reaction method, using dielectric and impedance spectroscopy in the frequency range of 42 Hz–5 MHz, between the temperatures (300K–473K). The dielectric constant and dielectric loss (tan δ) decreases with increasing frequency but these parameters increase with increasing temperature. The dielectric loss tangent curves exhibit dielectric relaxation peaks at high frequencies (3.6 kHz–5 MHz), which are attributed to the coincidence of the frequency of charge hopping between the localized charge states and the external field. The dielectric properties have been explained on the basis of space charge polarization according to Maxwell–Wagner’s two-layer model and the hopping of charge between Fe²⁺ and Fe³⁺ as well as between Mn³⁺ and Mn²⁺ ions at B-sites. The complex impedance analysis has been used to separate grain and grain boundary in studied samples. Two semicircles corresponding to grain and grain boundary have been observed at low temperature, while only one semicircle has been seen at high temperatures. The resistance of grain and grain boundary both increase with Ti⁴⁺ doping.     

Extraction of the neutron charge form factor G<Superscript>n</Superscript><Subscript>E</Subscript>(Q<Superscript>2</Superscript>) from the charge form factor of deuteron G<Superscript>d</Superscript><Subscript>C</Subscript>(Q<Superscript>2</Superscript>)

We extract the neutron charge form factor G ⁿ _E(Q ²) from the charge form factor of deuteron G ^d _C(Q ²) obtained from T ₂₀(Q ²) data at 0≤Q ²≤ 1.717 (GeV/c)². The extraction is based on the relativistic impulse approximation in the instant form of the relativistic Hamiltonian dynamics. Our results (12 new points) are compatible with existing values of the neutron charge form factor of other authors. We propose a fit for the whole set (36 points) taking into account the data for the slope of the form factor at Q ² = 0. Received: 26 July 2002 / Accepted: 18 September 2002 / Published online: 4 February 2003 RID="a" ID="a"e-mail: krutov@ssu.samara.ru RID="b" ID="b"e-mail: troitsky@theory.sinp.msu.ru Communicated by V.V. Anisovich     

Quasiclassical calculation of the fermi level and of the forbidden energy band narrowing in crystal semiconductors with heavy doping

In an effective-mass approximation it is shown that in a heavily doped slightly compensated crystal the narrowing of the band ΔE_g>0 on complete ionization of the impurity is equal to the sum of the exchange interaction ΔE_g ^(exc) of the majority charge carriers and of the energy of the correlation interaction ΔE_g ^(cor) of a nonequilibrium minority charge carrier with a screening cloud of majority ones. When the mean-square fluctuation of the potential energy of an electron (hole) is much higher than the thermal energy, the approximation ΔE_g/E_B=1.3(Na_B ³/v)^0.58+2.7(Na_B ³/v)^0.23 is obtained, where v is the number of equivalent energy minima (valleys) at different values of the quasimomentum of the majority charge carriers, are the Bohr energy and radius; ε is the dielectric permittivity of the crystal lattice; m is the effective mass of the state density in one valley; N is the concentration of the doping impurity. The values of ΔE_g and of the high-energy edge of the interband radiating recombination calculated by the model suggested agree with the data on low-temperature photoluminescence of n-Si, p-Si, p-GaAs, and p-GaSb for 3·10⁻³<Na_B ³<2. Belarusian State University, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 367–373, May–June, 1997.     

Properties of MOS-structures based on anode-oxidized CdSnAs2

The properties of metal (Al, Au)-anodic oxide-CdSnAs₂ monocrystal structures are studied. It is established that MOS-structures using undoped CdSnAs₂ crystals show a high positive fixed charge in the anodic oxide (N_S 5·10¹² cm^–2) and high surface state density on the oxide-CdSnAs₂ boundary surface (N_SS 2·10¹³ cm^–2·eV^–1). In MOS-structures using diffusion-doped (copper) crystals the sign of the fixed charge is negative (N_S 10¹¹ cm^–2, N_SS 2·10¹² cm^–2·eV^–1). The latter structures show a definite photosensitivity and photomemory. The possibility of effective control of the fixed charge value within the oxide by illumination is shown. The surface state distribution over energy, time constant, and capture section is determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 90–93, September, 1982.     

Excitation of the giant monopole resonance and coulomb excitation of the giant dipole resonance in hadron inelastic scattering from208Pb

It is shown that the charge varianceσ _z ² observed in the low energy fission is consistent with the quantum mechanical zero point motion of an isovector giant dipole resonance. Theσ _z ² is determined at the ‘exit point’, where the neck radius ≈2.4 fm.     

Mössbauer and optical spectrometry of selected schörl-dravite tourmalines

Spectrometric studies were carried out on samples of tourmaline (schörl-dravite series) from geological environments where first-phase-formed tourmaline underwent influence of geochemically different fluids. Samples are from a differentiated magmatic complex of Trento-Alto Adige, Italy, and from hydrothermal gold and silver deposits of the Humboldt Range, Nevada, USA. Chemical data were obtained from electron microprobes. The results of Mössbauer measurements suggest three to five doublets. Fe occurs in two valence states. The Z-site, usually fulfilled with Al³⁺ and Fe³⁺, is assigned only to Al³⁺ and Fe²⁺. This location was found in nearly all samples studied. In the Y-site Fe²⁺ and Fe³⁺ are obviously present. Isomer shifts with intermediate values can be assumed to be related to intervalence charge transfer (IVCT). Optical spectroscopy reveals absorption bands at 9 000 and 14000 cm^–1, which are assigned to a charge transfer between Fe²⁺ and Fe³⁺, the 23 000 cm^–1 absorption band is supposed to be due to Fe²⁺ Ti⁴⁺ charge transfer. The occupation of the Z-site only by Fe²⁺ and the coexistence of divalent and trivalent Fe in the Y-site could be explained by selective oxidation in Y-site through a late process.     

Charge compensation on the luminescence properties of ZnWO4:Tb phosphors via hydrothermal synthesis

A phosphor Tb³⁺-doped ZnWO₄ (ZWO:Tb) phosphors were prepared by a hydrothermal method. X-ray powder diffraction (XRD) analysis revealed that the as-obtained sample is pure ZnWO₄ phase. The excitation and emission spectra indicated that the phosphor could be well excited by ultraviolet light (272 nm) and emit blue light at about 491 nm and green light at about 545 nm. Significant energy transfer from WO₄²⁻ groups to Tb³⁺ ions has been observed. Two approaches to charge compensation are investigated: (a) 2Zn²⁺ = Tb³⁺ + M⁺, where M⁺ is a monovalent cation like Li⁺, Na⁺ and K⁺ acting as a charge compensator; (b) 3Zn²⁺ = 2Tb³⁺ + vacancy. Compared with two charge compensation patterns in the ZnWO₄:Tb³⁺, it has been found that ZnWO₄:Tb³⁺ phosphors used Li⁺ as charge compensation show greatly enhanced bluish-green emission under 272 nm excitation.