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931.
R. Brout 《Zeitschrift für Physik B Condensed Matter》1987,68(2-3):339-341
It is shown how in the functional integral approach, time arises as a natural parametrization for the way matter adiabatically follows gravitational configurations where the latter are treated in the semi-classical approximation. In the presence of horizons this time becomes complex and if the motion is periodic behind the horizon such functional integrals become partition functions. So the functional integral approach naturally associates the very concept of time and horizon thermal radiation.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday 相似文献
932.
N. K. Hansen P. Pattison J. R. Schneider 《Zeitschrift für Physik B Condensed Matter》1987,66(3):305-315
A method of reconstructing the electron momentum density (p), and its Fourier transform,B(t), from a series of directional Compton profiles is described. It is based on a double Fourier inversion technique and an expansion in lattice harmonic functions. The effect of random errors has been analysed, and the implications for the data collection discussed. We have used the reconstruction technique to obtain (p) andB(t) for silicon from six directional Compton profiles measured with 412 KeV gamma-radiation. The experimental result is in good agreement with earlier measurements and with available solid state theories. A recent Wannier function calculation for silicon using orthogonalised bond orbitals provides a useful tool for identifying the physical origins of the observed anisotropies. A comparison between the information presented in position and momentum space shows that the ease of interpretation depends upon the degree to which the various interactions give rise to localised features in each representation. 相似文献
933.
Dependent on temperature and coverage, numerous spectral density functionsW(f) of the field-emission flicker noise of potassium adsorbed on the tungsten (112) plane were determined. The analysis in terms of the Timm and van der Ziel model gives surface diffusion energies between 0.55 and 0.83 eV for (average) coverages from 0.3 to 1.0 and diffusion coefficients between 2×10–10 and 3×10–9 cm2/s at 400 K. The results are compared with those obtained previously for the tungsten (111) region. Some conclusions as to the mechanism of diffusion and the manifestation of phase transitions between commensurate and incommensurate adlayer structures are discussed.On leave from Wrocaw University 相似文献
934.
Silica aerogels form mutually self-similar fractal structures for a broad range of densities and preparation conditions. This allows to scale dynamical results obtained on longitudinal acoustic waves up to the onset of the phonon to fracton crossover. An effective value of the fracton dimension
is found, and various possible interpretations of that value are discussed.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday 相似文献
935.
A. Mandelis W. Lo R. E. Wagner 《Applied Physics A: Materials Science & Processing》1987,43(2):123-130
The electrical and dielectric properties of mercuric iodide were studied at room temperature under various intensities and colours of light in the frequency range 1 Hz–10 kHz. In the high-frequency region (>40 Hz), the real part of the dielectric constant () is almost constant with frequency (f), colour and intensity of light. At lower frequencies, varies nearly as 1/f and monotonically increases with intensity (I) of the yellow (or green) light, whereas it is almost constant with red light intensity. This behaviour is discussed in the view of the different polarization contributions. The imaginary part of the dielectric constant () was found to vary as 1/f over the frequency range studied. This behaviour was observed whether the crystal was in dark or illuminated implying that the roomtemperature ac dark- or photo-conductivity () is independent of frequency. The observed variation of with intensity of yellow (or green) light was found to follow anI
1/2 dependence and a weaker dependence for the red light. the red light. The conductivity behaviour is discussed in the view of the current theories. 相似文献
936.
W. Borchers R. Neugart E. W. Otten H. T. Duong G. Ulm K. Wendt ISOLDE Collaboration 《Hyperfine Interactions》1987,34(1-4):25-29
The hyperfine structure (hfs) and isotope shift (IS) in the isotopic chain of the radioactive element radon have been studied for the first time. The measurements were carried out by collinear fast-beam laser spectroscopy at the mass separator facility ISOLDE at CERN. The IS between 16 isotopes in the mass range 202A222 and the hfs of 7 odd-A isotopes were determined in the transitions 7s [3/2]2-7p [5/2]3 (745 nm) of Rn I. The nuclear spins and moments, as well as the observed inversion of the odd-even staggering for218–222Rn, can be associated with the effects of octupole instability around N=134.This work was supported by the Bundesministerium für Forschung und Technologie and the Deutsche Forschungsgemeinschaft. 相似文献
937.
Since the polarization structure of reactions in the collinear directions is greatly simplified, since reactions at very high energies tend to be predominantly close to collinear, and since the one-particle exchange mechanisms are more pronounced in the forward direction, tests of one-particle-exchange (OPE) mechanisms are formulated for collinear reactions. The number of amplitudes are derived for a reaction with arbitrary spins, and examples for the practically occurring cases are given. The results are applied to the reaction 1/2+1/21+1 and in particular ton+pd+ (or to its inverse). A detailed procedure is outlined for a step-by-step testing of the various OPE processes in this reaction through a series of polarization experiments. In particular, the tests can separate out theJ=0 andJ=1/2 OPE processes. 相似文献
938.
G. R. Sudhakaran J. C. Sarker R. L. Bhattacharjee L. H. Johnston 《International Journal of Infrared and Millimeter Waves》1987,8(12):1531-1540
Submillimeter laser-Stark spectra have been observed for the isotopic species of methyl fluoride,13CH3F, using the 337 m line of the HCN laser. We have identified the multiplet transitions as JK=18K17K in the ground vibrational state. Ten distinct families with K=8, 9, 10, 11, 12, 13, 14, 15, 16 and 17 have been observed. Zero-field frequencies for all the transitions are given and in most cases with better accuracy than predicted from the previous constants. 相似文献
939.
A. Parrish R. L. de Zafra J. W. Barrett P. Solomon B. Connor 《International Journal of Infrared and Millimeter Waves》1987,8(5):431-440
Atmospheric opacity values in the zenith direction are given for a wavelength of 1.1 mm (278 GHz) at the summit of Mauna Kea in the Hawaiian Islands. A total of 75 days is covered during the period 1983–1986. Observations were made on a quasi-continuous basis, with opacity measured every 20 minutes around the clock for significant periods of time. A conversion from opacity at =1.1 mm to the equivalent preciptable water vapor column is given from the measurements of Zammit and Ade, from which opacities at other wavelengths may be derived. The data presented here supplement those in an earlier paper covering 34 days in the fall of 1982. 相似文献
940.
We study the two-dimensional first passage problem in which bonds have zero and unit passage times with probabilityp and 1–p, respectively. We prove that as the zero-time bonds approach the percolation thresholdp
c, the first passage time exhibits the same critical behavior as the correlation function of the underlying percolation problem. In particular, if the correlation length obeys(p) ¦p–p
c¦–v, then the first passage time constant satisfies(p)¦p–p
c¦v. At pc, where it has been asserted that the first passage time from 0 tox scales as ¦x¦ to a power with 0<<1, we show that the passage times grow like log ¦x¦, i.e., the fluid spreads exponentially rapidly. 相似文献