Beam collimation light deflection and time delay in the Kerr spacetime

By using an alternative method valid in weak and strong gravitational fields, we study beam collimation, light bending and time delays in the equatorial Kerr spacetime. Three applications are carried out. First, it is shown that the interaction spin-orbit could collimate a beam only if the particle or photon moves in a opposite direction to the compact object's spin. Secondly, the deflection angles of light rays grazing a quasar, a pulsar (PSR 1937+214), and a rotating black hole are computed and compared with approximate solutions. Finally, we calculate the photon's time delay traveling from SN1987A to Earth. The result of this undertaking is compared with a similar calculation using the PPN formalism.     

Gravitational radiation from an orbiting pulsar

We describe an experiment which establishes, with a high degree of confidence, the existence of gravitational radiation as predicted by general relativity. The experiment involves observations of binary pulsar PSR 1913 + 16, measurements of which now reveal a rate of change of orbital period within about 15% of that predicted by the general relativistic quadrupole formula. We show that the gravitation theories of Rosen, Ni, and Lightman-Lee predict an orbital periodincrease, regardless of the relative masses of the pulsar and its (assumed compact) companion. The Brans-Dicke theory predicts a much more rapid period decrease than does general relativity, unless the masses and internal structures of the two bodies are very similar. Thus, in the absence of additionalad hoc assumptions, general relativity is the only well-studied theory of gravity consistent with our data.     

Development of the SRAO 1024-Channel Digital Auto-Correlator

We developed a 1024-channel digital auto-correlation spectrometer for the Seoul Radio Astronomy Observatory (hereafter the SRAO-1KACS). The SRAO-1KACS has two main modules: the IF-to-baseband converter (IFBC) module and the 1024-channel auto-correlator (1KACR) module. The input frequency range of the IFBC module is from 1.5 to 1.55 GHz with a dynamic range of –4 +3 dBm. The 1KACR module performs calculations of auto-correlation coefficients by the accumulation and modulo-2-counting method in 3-level configuration. The system is controlled by a Linux-based personal computer. The SRAO-1KACS provides 3 different observational modes: 50, 25, and 12.5 MHz bandwidth modes. The channel losses are 20%, 12%, and 8% for each bandwidth mode, respectively. Various tests were executed including lab tests and astronomical tests. Lab tests were performed for a 1.5625MHz sinusoidal wave input and for a white noise source. We also executed astronomical tests in 12CO J=1–0 emission line at 115.2712 GHz, which showed that SRAO-1KACS can be used at astronomical observatories.     

A new bundle completion for parallelizable space-times

The Schmidt [9]b-boundaryM, for completing a space-timeM, has several desirable features. It is uniquely determined by the space-time metric in an elegant geometrical manner. The completed space-time is¯M=M M, where¯M= ⁺ M/O ⁺ and ⁺ M is the Cauchy completion (with respect to a toplogical metric induced by the Levi-Cività connection) of a component of the orthonormal frame bundle having structure groupO ⁺. ThenM consists of the endpoints of incomplete curves inM that have finite horizontal lifts in ⁺ M, and ifM= we say thatM isb-complete. It turns out thatM isb-complete if and only ifO ⁺ M is complete. This criterion for space-time completeness is stronger than geodesic completeness and Beem [1] has shown that this remains so even for the restricted class of globally hyperbolic space-times. Clarice [3] has shown that for such space-times the curvature becomes unbounded as theb-boundary is approached.Now ifM, then ⁺ M may contain degenerate fibers; thus the quotient topology for¯M is non-Hausdorff and precludes a manifold structure. Precisely this has been demonstrated by Bosshard [2] for Friedmann space-time, casting doubt on the physical significance of the completion. The only neighborhood of the Friedmann singularity is the whole of¯M, and in the closed model initial and final singularities are identified inM. Similarly, Johnson [7] showed that the completion of Schwarzschild space-time is non-Hausdorff because of degenerate ibers in¯O ⁺ M.Here we introduce a modification of the Schmidt procedure that appears to be useful in avoiding fiber degeneracy and in promoting a Hausdorff completion. The modification is to introduce an explicit vertical component into the metric forO ⁺ M by reference to a standard section, that is, to a parallelizationpMO ⁺ M We prove some general properties of thisp-completion and examine the particular case of a Friedmann space-time where there is a fairly natural choice of parallelization.     

Microprobe photoluminescence measurement on heteroepitaxial GaAs on Si grown by metalorganic chemical vapor deposition

Microprobe photoluminescence (PL) measurements at 77 K were used to study the effect of the GaAs layer thickness on optical quality and variations in strain in GaAs/Si containing microcracks. PL peak intensities increase with the increase in thickness of GaAs layers and the peak intensity for the 5.5 m GaAs layer was a factor of 20 higher than those for the 1–2 m GaAs layers. Spatial nonuniformities in strain in the vicinity of two microcracks reveal that stress was almost released at the intersection of two microcracks and is maximum half way between two microcracks.On leave from Semiconductor Materials Lab., Korea Institute of Science and Technology (KIST)     

Elimination of variables in simple laser equations

The usual way of obtaining rate equations (RE) and a single equation for the field amplitude (EFA) from the semiclassical laser equations (Lorenz-Haken model) is reexamined by undertaking a systematic elimination procedure developed in synergetics. The RE and EFA are justified in the case 1 (, ) and case 2 (, ), respectively. We show that, because the eliminated variable happens to contain a considerable contribution from an unstable mode, the usual elimination technique in the case 3 (, ) leads to an inconsistency. As important by-products we obtain the RE and EFA for arbitrary cavity relaxation constant (). Some remarks are given on the direct elimination technique in the non-diagonal representation in the study of instabilities.     

EPR Spectra of Cr3+ Ions in Sr3Ga2Ge4O14:Cr Single Crystals

The results of investigations of chromiumdoped Sr₃Ga₂Ge₄O₁₄ single crystals by the EPRspectroscopy method are presented. It is shown that activating chromium ions form Cr³⁺ Ga³⁺ (Ge⁴⁺) substitution centers in the 1aoctahedral positions of the lattice of Sr₃Ga₂Ge₄O₁₄. Depending on the combination of occupation of the 3ftetrahedral positions of the first cationic coordination sphere by Ga³⁺ and Ge⁴⁺ ions, Cr³⁺ centers of two types are formed. Their individual magnetic spectra are characterized by axial and rhombic symmetry. The magnetic multiplicity of the axialsymmetry spectrum is equal to unity. There exist rhombicsymmetry centers of two types differing in the orientation of the principal magnetic axes and the value of the spinHamiltonian parameter E. The magnetic multiplicity of the individual magnetic spectra of rhombic centers of each type is equal to three. The detected EPR spectra of Cr³⁺ ions have been described by the spin Hamiltonian of rhombic symmetry. Its parameters and their spread have been determined.     

The operator method for perturbations in the theory of infrared molecular spectra

The application of contact transformations of Hamiltonians with a degenerate zeroth approximation to an approximate separation of variables is studied. Unitary transformations are formed that interrelate various effective Hamiltonians by the method of contact transformations of Van Vleck, Jorgensen, Pedersen, Primas, ENRST and Soliverez with an accuracy up to 0(⁵). The relation between the contact transformations and the perturbation theory of Rayleigh-Schrödinger is studied, and it is shown that the intermediate denominators in effective Hamiltonians vanish in a nondegenerate case. A generalized variant is constructed of contact transformations and of transformation yielding an even effective Hamiltonian from which the results of the above methods in particular cases follow.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, No. 7, pp. 82–90, July, 1977.The authors would like to thank V. N. Bryukhanov and P. I. Gaev for useful discussions.     

Investigation of output parameters of a 4.3-μm longitudinal-discharge CO2 laser

A simple hot-cell-free 4.3-m CO₂ laser with longitudinal d.c. discharge is described and the results of its parametrization are presented. It is shown that for effective operation of the 4.3-m (10° 1-10°0 band) CO₂ laser, use of active mixtures containing 4 to 5% of carbon dioxide with 20% nitrogen is needed. The laser is mechanically Q-switched producing peak powers in excess of 60 W with a pulse duration of 300 ns FWHM. The 4.3-m laser is easily tunable and operates on the P and R branches of the 10°1-10°0 band of CO₂. The peculiarities of spectral performances are discussed.     

Luminescence of Tm3+ Ions in Yttrium Oxide

The concentration and temperature dependences of the blue luminescence intensity of the Tm³⁺ ion in yttrium oxide under UV and IR excitation have been measured. We made a proposal that the main role in the formation of these dependences is played by the interionic cross relaxation of excited states of Tm³⁺; the presence of admixed secondary rareearth ions can strongly influence the shape of the temperature dependence of the antiStokes luminescence intensity, displacing the position of its maximum. It is shown that the quenching action of admixtures under Stokes and antiStokes excitation shows up differently because of the differences in the mechanisms of population of the luminescent level.     

Post-Newtonian gravitational radiation from binary stars

A method is presented for evaluating post-Newtonian orbital corrections to the orbital-period decrease of a relativistic binary, by using previous results on the gravitational-radiation luminosity of a bounded source and the binary's relative motion. The method is based on an energy-balance equation, whose validity to post-Newtonian accuracy is not proved here, but, in view of recent theoretical results on the classical energy-balance equation, seems to be quite reasonable, and, in view of the available observational data, is practically correct. In the case of the binary pulsar PSR 1913 + 16 the proposed relative orbital correction amounts to 10^–6 of the current observational uncertainty, thus greatly favoring the predictions of the classical quadrupole formula.     

Bunching phenomena during electron injection into the betatron

Under favourable conditions electrons injected into the betatron give rise to high-frequency oscillations. An experimental investigation of the properties of the oscillations is presented, in which new experimental material is added to an earlier paper [1] and the hypothesis regarding the nature of the oscillations is corrected.The oscillations are due to azimuthal bunching of the injected or captured electrons. The bunching is caused by a regenerative amplification of space-charge density fluctuations. The amplification is produced by the negative mass instability mechanism theoretically investigated by Nielsen, Sessler and Symon [2] and Kolomenskij and Lebedev [3].Bunching of the injected electrons is the primary cause of the capture of electrons injected into a static or slowly varying magnetic field. Bunching of the captured electrons represents a limitation in the magnitude of the capturable charge.

---

, I.

, , . , [1] . . . , [2] [3]. , . .

     

Residence sites of fluorine in crystalline silicon and highly oriented pyrolytic graphite

Measurements of the electric field gradient (efg) at F impurity sites in crystalline silicon and highly oriented pyrolytic graphite (HOPG) have been compared with cluster model calculations using both Hartree-Fock (HF) and density functional theory (DFT) formalisms. The technique of time-differential perturbed angular distributions of -ravs was employed to derive the efg parameters following implantation of¹⁹F via the¹⁹F(p, p)¹⁹F^* reaction. For the case of HOPG the DFT method gave closer agreement with the experimental values of ¦V _zz¦=3.24(14)×10²²V/m² and=0.16(3), yieldingV _zz=–3.09×10²²V/m²and=0.13 for¹⁹F at a site between the layers with point group symmetry C_2h and inter-layer spacingd=3.70 Å. For¹⁹F implantation in silicon three sites were found corresponding to quadrupole frequencies 23.2(3) MHz, 35.2(3) MHz and 37.1(5) MHz. Both HF and DFT calculations are consistent with the assignment of interstitial antibonding and bond centre sites for the 23.2 and 35.2 MHz, respectively. In the former case, the F atom is located 1.81 Å along a <111> direction from a silicon atom; in the latter situation the Si-Si bond length is found to expand by 1.02 Å from its normal lattice value. It is speculated that the third interaction, which occurs at only the 10% level, possibly arises from sites associated with a defect or other impurity. To achieve a reduction in cluster size, the completion of dangling bonds with atoms other than hydrogen was investigated. The results were found to be comparable.     

On the electroluminescence of ZnS at low voltages

The possibility of explaining non-zero electroluminescence brightness below the minimum ionization voltage by the influence of thermal velocities of electrons is pointed out; the derived voltage dependence of electroluminescence brightness agrees with the measurements in [1].

---

ZnS

; [1].

     

Layering transition in SOS model with external magnetic field

For the SOS model defined by the Hamiltonian , where _x , _x ,{1,2,...},h>0,x ^d ,d2 it is shown that in the low-temperature region an infinite sequence of first-order phase transitions takes place whenh»0 and the temperature is fixed.     

Study of noise characteristics of baw and SAW quartz resonators

The low-frequency noise of bulk- and surface-acoustic-wave (BAW and SAW) resonators at frequencies of from 100 to 600 MHz is studied. It is shown that both SAW and BAW resonators have parameter (resonant-frequency) fluctuations with 1/f power spectra with considerable intensity spreads: approximately 20 dB for SAW and more than 30 dB for BAW resonators. The phase-noise floor of 100-MHz oscillators with BAW resonators is –150 dB/Hz for a 1-kHz offset frequency. The phase-noise level of oscillators with SAW resonators at 400–600 MHz is higher by 5–10 dB (scaled to a 100-MHz carrier frequency).Presented at All-Union Coordinating Conference Low-Frequency Noise in Semiconductor Devices (Chernogolovka, Moscow Region, June, 1991).Ural Polytechnic Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 36, No. 12, pp. 1143–1152, December, 1993.     

Nuclear quadrupole interaction of199mHg-ferrocenethiol complexes

We determined the^199mHg nuclear quadrupole interaction (NQI) by time differential perturbed angular correlation in the following ferrocenethiol complexes with mercury: ferrocenethiol (v _Q =1253(4) MHz, =0); 1,1-ferrocenedithiol (47%v _Q =1555(8) MHz, =0.13(2); 25%v _Q =726(19) MHz, =0.81(2); rest unspecific); 2-ferrocenyl-ethanethiol (v _Q =1306(6) MHz, =0.17(1)); and a 1, 1-bis (2-mercapto-propylthio)ferrocene oligomer (v _Q =1411(5), =0). All NQIs are rather large with small asymmetry parameters, indicating essentially linear S-Hg-S bonds. The only exception is the minority fraction in 1,2-ferrocenedithiol which suggests the formation of a 1,3-dithia-2-mercura[3]ferrocenophane.     

Influence of the charge of surface states on the characteristics of mis transistors made of p-type indium antimonide

An experimental investigation was made of metal-insulator-semiconductor transistors with thick insulator and long channel and made of single-crystal p-type InSb (78° K). An empirical relation was obtained for the output drain conductance in the case of carrier degeneracy in the n-type channel. The parameters of the InSb surface after etching were determined.Translated from Izvestiya Uchebnykh Zavedenii, Fizika, No. 4, pp. 84–88, April, 1980.     

Low-Frequency Pulsations of Coronal Magnetic Loops

We analyze low-frequency intensity fluctuations of the microwave emission from solar flares at frequencies 22 and 37 GHz. The three microwave bursts of durations of about 1 h, observed at the Metsähovi Radio Observatory (Finland) with the time resolution of 0.1 and 0.05 s, are studied. To obtain spectral-temporal characteristics of the low-frequency fluctuations, we apply the Wigner-Ville method, i.e., the time-lag Fourier transform of the local autocorrelation function of an analytical signal. As a result, we obtain for the first time the dynamical spectra of the low-frequency fluctuations, which are identified as MHD eigenoscillations of coronal magnetic loops. The features of the dynamical spectra testify that several types of low-frequency pulsations are excited in coronal magnetic loops during solar flares: 1) Fast and slow magnetosonic oscillations with periods of 1-1.5 s and 200-280 s, respectively. Fast magnetosonic oscillations appear as pulse trains of duration 100-200 s and have the positive frequency drift d/ dt 0.125 Hz/min and the frequency splitting 0.05 Hz; 2) The eigenoscillations of a coronal magnetic loop as an equivalent electric circuit. The period of these oscillations is about 1 s during the initial stage of a microwave burst and increases gradually up to 4 s during the decay stage of the radio emission; and 3) Intensity modulation of the microwave radiation by a periodic pulse sequence with a period of about 1 s at the burst onset and about 2 s at its end. The parameters of the dynamical spectra and identification of the MHD pulsations allow us to obtain information on the loop parameters, such as the ratio of the loop radius to its length (r/L 0.1), the ratio of the gas pressure to the magnetic-field pressure inside the loop ( 3· 10^-3), the ratio of plasma densities outside and inside the loop, and the electric current in the coronal loop (I 1.5 · 10¹² A).     

A dynamical phase transition in a caricature of a spin glass

This paper studies the rate of convergence to equilibrium of Glauber dynamics (Gibbs Sampler) for a system ofN Ising spins with random energy (at inverse temperature >0). For each of the 2 ^N spin configurations the energy is drawn independently from the values 0 and-logN with probabilities 1-N ^–7, resp.N ^– (>0), and is kept fixed during the evolution. The main result is an estimate of the coupling time of two Glauber dynamics starting from different configurations and coupled via the same updating noise. AsN the system exhibits two dynamical phase transitions: (1) at =1 the coupling time changes from polynomial (>1) to stretched exponential (<1) inN; (2) if <1, then at = the almost coupling time [i.e., the first time that the two dynamics are within distanceo(N)] changes from polynomial (<) to stretched exponential (>) inN. The techniques used to control the randomness in the coupling are static and dynamic large-deviation estimates and stochastic domination arguments.