A new geometrical gravitational theory

A geometrical gravitational theory based on the connection ={ } + ln + ln –g ln is developed. The field equations for the new theory are uniquely determined apart from one unknown dimensionless parameter ₂. The geometry on which our theory is based is an extension of the Weyl geometry, and by the extension the gravitational coupling constant and the gravitational mass are made to be dynamical and geometrical. The fundamental geometrical objects in the theory are a metricg and two gauge scalars and. Physically the gravitational potential corresponds tog in the same way as in general relativity, the gravitational coupling constant to ^–2, and the gravitational mass tou(, ), which is a coscalar of power –1 algebraically made of and. The theory satisfies the weak equivalence principle, but breaks the strong one generally. We shall find outu(, )= on the assumption that the strong one keeps holding good at least for bosons of low spins. Thus we have the simple correspondence between the geometrical objects and the gravitational objects. Since the theory satisfies the weak one, the inertial mass is also dynamical and geometrical in the same way as is the gravitational mass. Moreover, the cosmological term in the theory is a coscalar of power –4 algebraically made of andu(, ), so it is dynamical, too. Finally we give spherically symmetric exact solutions. The permissible range of the unknown parameter ₂ is experimentally determined by applying the solutions to the solar system.     

Electrical and optical properties of electron-irradiated ZnGeP2

Conclusions and summary The following conclusions are drawn from the reported study:The electrophysical properties of ZnGeP₂ crystals and their optical transparency in the range hG are attributable to the presence of a density-dominant (10¹⁷–10¹⁹ cm^–3) deep [E_v+(0.5–0.6) eV] growth defect associated predominantly with Zn vacancy clusters.Irradiation by high-energy electrons induces a shift of the Fermi level in the direction of E_G/2 and increases the resistivity of ZnGeP₂ to values of approximately 10¹² ·cm at 300 K. Irradiation with high-energy electrons is an effective technique for the optical bleaching of p-ZnGeP₂. The reversible modification of the optical absorption spectra of p-ZnGeP₂ in connection with irradiation and subsequent annealing indicates that the absorption step in the vicinity of h 0.6 eV is not attributable to light absorption by germanium inclusions, but to optical transition from the valence band to the growth-defect level E_v+(0.5–0.6) eV.Enhancement of the optical transmissivity of p-ZnGeP₂ in the range hG can be achieved in two wayss 1) as the result of a decrease in the density of centers with the level E_v+0.6 eV by variation of the growth conditions or subsequent annealing; 2) by shifting the Fermi level above the energy position E_v+0.6 eV through the irradiation-induced injection of compensating donor centers.The injection of radiation defects is an effective technique for controlling the electrical and optical parameters of the compound ZnGeP₂.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 122–130, August, 1986.     

On the yellow colouring of lithium fluoride crystals

The paper deals with the causes of the yellow colouring of LiF crystals. In accordance with some other writers the authors arrived at the conclusion that colouring is caused by impurities. Selective absorption in the infra-red region at 2·8 is independent of this colouring. Analytical data were supplemented by crystal growing experiments in which defined admixtures of heavy metals, such as Co, Mn, Fe, Cr, Ni, Pt, Cu, were added to the melt. It is shown that, of the admixtures used, the most intense colouring is produced by manganese. Experiments on the effect of Cu and Pt were not entirely conclusive. In vacuum colour-producing impurities evaporate quite easily from the melt until their concentration drops below the critical limit required for colouring; in air this happens only if the charge is left in the melted state for a longer period (in our case a 1 kg charge was kept at 100°C above melting point for 36 hours). Results are improved if a dried gas, for instance nitrogen, is bubbled through the meit. A colourless crystal can be obtained in this manner even without using a vacuum; the starting material, however, must be sufficiently pure. A new method was worked out for preparing the salt by direct precipitation of LiCl and HF. Heavy metals are removed from the lithium component by means of cupral and dithizone. The construction of the apparatus used for the crystal growing experients in vacuum differs from that described in the appropriate literature.

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LiF

LiF. , . 2,8 . . , , , Mn, Fe, Cr, Ni, Pt, Cu. , . , . Pt . , , , ( : 1 kg-36 100° ). , , , . , , . LiCl HF. . , .

     

Radiation defects in II-IV-V2 semiconductor compounds

Conclusion The survey presented gives the contenporary state of experimental studies of RD in group II-IV-V₂ semiconductors. The most important result of this work is the fact that the properties of irradiated triple semiconductors can be predicted on the basis of the corresponding studies of their binary electronic-nuclear group III–V analogs. The feasibility of controlling the properties of II-IV-V₂ compounds, such as electroconductivity, conductivity type, optical transmission, and piezoelectric characteristics, by way of irradiation with high energy particles is shown.The data presented in this survey show the necessity of further study of RD in triple semiconductors. The immediate tasks are: refinement and determination of the limiting electrical characteristics of a series of irradiated binaries (AlP, AlAs, AlSb, and nitrides) and triple (CdSiP₂, ZnSiP₂, MgSiP₂, and other compounds) semiconductors, low temperature irradiation, and the annealing of RD in II-IV-V₂ compounds. Further experimental research is required for optical and piezoelectric characteristics of irradiated materials and charge transfer mechanisms in highly imperfect samples. In the capacity of theoretical problems, one can mention calculations of the electronic structure of intrinsic defects intriple semiconductors and clarifying the genetic relationships between the levels of rD and the energy bands.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 84–97, August, 1986.     

Mössbauer study of mixed valent silicides Eu(Ir1−x Pd x )2Si2

The solid solutions Eu(Ir_1–x Pd _x )₂Si₂, which exist for 0x0.125 and 0.75x1. cristallize with the tetragonal ThCr₂Si₂-type structure. The variation of the europium valence with composition has been thoroughly studied at temperatures 4.2T293 K by¹⁵¹Eu Mössbauer resonance. For 0x0.125 the europium valence at room temperature decreases asx increases. For 0.75x1 the valence transition temperature Eu³⁺Eu²⁺ increases asx increases.     

Thes-f model with Coulomb repulsion: Thermodynamics of two atomic cluster. Spin 1/2

A cluster of two atoms described by thes-f model with Coulomb repulsion has been considered. The interaction between localized 4f electrons (S=1/2) is taken in the molecular field approximation. The thermodynamic quantities like magnetization, specific heat and correlation functions n , n , S ^z n , S ^z n , S ^z (n –n ), n n and S ⁺ a ⁺ a as functions of temperature are presented for different band fillingN=0, 0.5, 1, 1.5, 2. The dependence of Curie temperature onN is calculated. The phase diagram forN=1 (T=0K) shows the possibility of existence of two phases: paramagnetic and ferromagnetic.The Curie temperature and the specific heat as functions ofN exhibit similar trends as found in experiments on doped magnetic semiconductors.     

Atomic volume dependence of the153Eu isomer shift in ScxY1−x

Mössbauer studies of dilute¹⁵³Eu in Sm_0.05Sc _x Y_0.95–x (0x0.95) reveal large changes in the isomer shift as a function ofx. The strong dependence of the isomer shift on alloy composition, is interpreted in terms of changes in the charge density at the Eu nucleus ((0)), which result from changes in atomic volume. The isomer shift was found to depend linearly on V/V (V/V changes between 0 and –0.3). A value of (–17.5±2.0)a ₀ ^–3 was obtained for d(0)/d lnV.This research was supported by a grant from the United States—Israel Binational Science Foundation (BSF), Jerusalem, Israel.     

Emissivity of CO2-H2O mixtures at temperatures up to 1000° K

The emissivity in the 2.7 m range is examined with a spectrometer having 25 cm^–1 for 2.5, ,7.5 cm·atm,4 8cm·atm, 400T1000° K; 150P730 mm Hg. It is found that relation (1) is obeyed to within /0.1, though the calculated transmission is usually less than the measured value. It is shown that the relation is obeyed on account of the mutual position of the CO₂ and H₂O lines in the band, i.e., one gas may be considered as unselective relative to the other.     

Electrical properties of p-type ZnGeP2 irradiated by H+ ions

The properties of p-type ZnGeP₂ [p₀=(5–10)·10¹⁰ cm^–3, ₀=(2–5)·10^–7 (·cm)^–1], irradiated with H⁺ ions [E=5 MeV, T_irr=300 K, D=(1·10¹²–1.7·10¹⁶) cm^–2] are studied. An increase in the resistivity (to gr_max - 5·10¹¹ ·cm) and subsequent reduction in for large currents of H⁺ ions ( - 9·10⁸ ·cm for D - 1.7·10¹⁶ cm^–2), is observed in irradiated crystals. The resistivity of irradiated p-type ZnGeP₂ is found to be very sensitive to hydrostatic pressure [(4–5)·10^–5 bar^–1]. The annealing of radiation defects in the temperature interval (20–600) °C is examined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 91–93, October, 1991.     

State space as projective space. The case of massless particles

The fact that the space of states of a quantum mechanical system is a projective space (as opposed to a linear manifold) has many consequences. We develop some of these here. First, the space is nearly contractible, namely all the finite homotopy groups (except the second) vanish (i.e., it is the Eilenberg-MacLane space K(, 2)). Moreover, there is strictly speaking no superposition principle in quantum mechanics as one cannot add rays; instead, there is adecomposition principle by which a given ray has well-defined projections in other rays. When the evolution of a system is cyclic, any representativevector traces out an open curve, defining an element of the holonomy group, which is essentially the (geometrical) Berry phase. Finally, for the massless case of the representations of the Poincaré group (the so-called Wigner program), there could be in principle arbitrarily multivalued representations coming from the Lie algebra of the Euclidean plane group. In fact they are at most bivalued (as commonly admitted).Presented at the International Symposium on Space-Time Symmetries, University of Maryland, Baltimore, Maryland, May 1988.     

Valence change of europium in the Eu(Ir1−x Pd x )2Si2 silicides

Eu(Ir_1–x Pd _x )₂Si₂ solid solutions which exist only for 0x0.125 and 0.75x1 crystallize in the tetragonal ThCr₂Si₂-type structure. X-ray diffraction data, magnetic susceptibility and¹⁵¹Eu Mössbauer measurements suggest that these compounds can be characterized as homogeneous mixed valence systems. At room temperature and for 0x0.125, the europium valence decreases asx increases. For 0.75x1, a sharp continuous valence transition from Eu²⁺ to Eu³⁺ occurs near 48 K, 54 K and 78 K forx=0.75, 0.81 and 0.94 respectively. These valence changes are discussed in relation with the Eu–(Ir, Pd) interatomic distance.     

Mixed valencies: Structure of phase diagrams,lattice properties and the consequences of electron hole symmetry

Symmetry properties and phonon phenomena of mixed valence compounds are discussed within the framework of the periodic Anderson model which was extended to include the interaction of 4f electrons with longitudinal optical phonons. The temperature anomaly in the thermal expansion found in CeSn₃ (positive thermal expansion coefficient) and YbCuAl (negative) is correctly described. Within the model the anomaly is a consequence of the particle hole symmetry of the underlying Hamiltonian. Moreover, the theory gives the positive slope of the phase boundary in the pressure-temperature phase diagram (dP/dT>0), for example for Ce, and predicts a negative slope (dP/dT<0) for Yb compounds.Furthermore, the quite unusual low temperature features of the pressure-temperature phase diagram have been calculated. It is found that the lattice vibrational contribution renormalizes the two essential parameters of the periodic Anderson model. The hybridization energyV ₀ of 4f and 5d–6s states is changed to =V ₀–a–b ² whereas the energy of the 4f stateE ₀ with respect to the 5d band becomes =E ₀–a–b ²., being proportional to the lattice constant, is determined by minimizing the Gibbs free energy, while ² is proportional to the mean square displacement of the rare earth ions. The strong temperature dependence of and ² determines the behaviour of the phase boundary and for large enough coefficientsb andb the phase boundary terminates at two critical points. An argument is given why the unusual low temperature features are more expressed in dirty mixed valence compounds as Sm_1–x Gd _x S than in the pure compound SmS. Furthermore, the theory predicts a quite unusual behaviour of the plasma-like phonon mode in the mixed valence phase: It softens at the critical temperature and at an intermediate temperature.Work performed within the program of the Sonderforschungsbereich 125, Aachen-Jülich-Köln     

Wavevector scaling,surface critical behavior,and wetting in the 2-d, 3-state chiral clock model

The controversial 2-d, 3-state chiral Potts model is studied using transfer matrix finite size scaling. at =0, we find dq _N/dN ^–4/5, whereq is the wavevector, the chiral field, andN the strip width (N=4–10). The result is consistent with den Nijs's crossover exponent =1/6. With surface fields on the infinite free boundaries, exponents associated with bulk magnetizationy _H, surface magnetizationy _H, and surface susceptibility are computed vs. ; results are similar for or to the infinite direction. Preliminary results are given for the bulk specific heat critical amplitudes, to test the universality of amplitude ratios. The interface wetting line is located for 01/4 using simple transfer matrix calculations of surface tensions in the solid-on-solid approximation. Overhangs or bubbles seem relatively unimportant at all temperatures.     

Electronic structure of amorphous Nb1-x Si x films studied by X-ray emission and X-ray photoelectron spectroscopy

We present valence band spectra of the amorphous system Nb_1–x Si _x (0.2x0.8), of bcc-Nb and of a-Si obtained by X-ray photoelectron spectroscopy (XPS, Al K) and X-ray emission spectroscopy (XES, Si K-emission bands). The samples were prepared as thin films by sputtering. The origin of all prominent spectral features was identified and consistently correlated to Si 3s-, Si 3p-and Nb 4d-derived states. The Nb4d-Si3p coupling is stable in binding energy over a wide concentration range. There is strong experimental evidence that the short range order changes considerably within the concentration interval 0.4x0.7, whereas the partial density of states of the Si 3p-electrons is clearly altered in the small concentration range 0.50x0.57.     

Nelson's symmetry and the infinite volume behavior of the vacuum inP(φ)2

LetH _l be the Hamiltonian in aP()₂ theory with sharp space cutoff in the interval (–l/2,l/2). LetE _l =inf(H _l ), (l)=–E _l /l, and let _l be the vacuum forH _l . discuss properties of (l) and _l . In particular, asl, there are finite constants <0 and such that (l), ((l)–)l, and hence (l)=+/l+o(l ^–1). Moreover exp(–c ₁ l) _{l 1}exp(–c ₂ l) forc ₁,c ₂ positive constants, where _{l 1} is theL ¹(Q, d₀) norm of ₁ with respect to the Fock vacuum measure. We also present a new proof of recent estimates of Glimm and Jaffe on local perturbations ofH _l in the infinite volume limit.Research sponsored by AFOSR under Contract No. F44620-71-C-0108.On leave from Istituto di Fisica Teorica, Universitá di Napoli and Istituto Nazionale di Fisica Nucleare, Sezione di Napoli.A. Sloan Foundation Fellow.     

Bianchi V imperfect fluid cosmology

Bianchi V, spatially homogeneous imperfect fluid cosmological models which contain both viscosity and heat flow are investigated. The Einstein field equations are established in the case that the equations of state are given byp-(-1),=o ^m, and=o ⁿ (where, o, o,m andn are constants). The physical constraints on the solutions of the Einstein field equations, and, in particular, the thermodynamical laws and energy conditions that govern such solutions, are discussed in some detail. Simple power law solutions and solutions in which there is no heat conduction are studied first. Exact solutions are then investigated in more generality, and it is shown that there exist two first integrals of the field equations for certain values of the physical parameters, m andn. Finally, it is shown that in a special case of interest (in whichm =n = 1/2) the imperfect fluid Bianchi V field equations can be written as a plane-autonomous system, thus facilitating the qualitative analysis of these cosmological models.     

Influence of Hydrothermal Temperature on Structures and Photovoltaic Properties of SnO2 Nanoparticles

Two SnO₂ nanoparticles were synthesized by hydrothermal method at 170°C and 180°C, respectively. Transmission electron microscope observations reveal that the diameters of both the nanoparticles are around 6nm. At the same time, surface photovoltage spectroscopy measurements show that the nanoparticle synthesized at 180°C has more surface electronic states at 0.3eV below the conduction band than the one synthesized at 170°C. This means that the temperatures chosen in hydrothermal synthesis have significant influence on the surface electronic characteristics of resultant SnO² nanoparticles but the effect on their sizes is not obvious. However, after being calcined at 500°C for 2h, the diameter of the nanoparticle synthesized at 180°C increased to 23nm and that of the nanoparticle synthesized at 170°C increased to 32nm as calculated from X-ray diffraction pattern.     

Determination of the strain potential constant by means of the p-InSb photoconductivity spectra under uniaxial compression

The influence of uniaxial pressure (0 < P < 2600 kg/cm2) on the intrinsic photoconductivity (PC) spectrum of p-InSb at 93 and 15°K is investigated. At 77°K the carrier concentration and mobility in the specimens were, respectively, (1.4–3.2)·10¹⁴ cm^–3 and 7000 cm²/V. sec. It is established that the maximum in the PC(E_m) spectra under compression is shifted towards higher energies. In the low-compression range E_m/P=5·10^–6eV·cm²/kg, while E_m/P=1·10^–6eV·cm²/kg for P > 1000 kg/cm². It is shown that the shift of the maximum of the intrinsic PC spectra with pressure is due to the growC;th in the forbidden bandwidth (E_g), and the change in parameters characterizing carrier diffusion in the specimen bulk (the diffusion coefficient, lifetime, surface recombination velocity) plays no part. The change in E_m/P with pressure is explained by the influence of valence band splitting. The deformation potential constants of the valence band |b|=(1.7±0.3) eV and |d|=(4.4±0.8)eV are calculated on the basis of a comparison between experimentally obtained data and theoretical results.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 159–162, February, 1976.     

More inequalities for critical exponents

A variety of rigorous inequalities for critical exponents is proved. Most notable is the low-temperature Josephson inequalitydv +2 2–. Others are 1 1 +v, 1 1 , 1,d 1 + 1/ (for d),dv, ₃ + (for d), ₄ , and _{2m 2m+2} (form 2). The hypotheses vary; all inequalities are true for the spin-1/2 Ising model with nearest-neighbor ferromagnetic pair interactions.NSF Predoctoral Fellow (1976–1979). Research supported in part by NSF Grant PHY 78-23952.     

New cascade laser transitions in CH2F2 pumped with the 9R32 line of a cw CO2 laser

New cascade laser transitions of¹²CH₂F₂ at 172.50m, 208.83m, 220.44m, 223.99m and 250.61m are reported. A waveguide FIR laser was pumped with a quasi cw¹²C¹⁶O₂ laser operating on the 9R32 line. Together with the already known lines at 184.3m, 196.1m and 235.9m, the laser lines can be assigned to rotational transitions in the ₉ vibrational band of¹²CH₂F₂ and to refill transitions of the vibrational ground state ₀.