Volume 30, Issue 4
April 1988, pages 1-340
pp 1- April 1988 Rapid Communications
Specific heat anomaly in the 90 K superconductor HoBa_{2}Cu_{3}O_{7−y}
B K Basu S M Pattalwar R N Dixit S Y Shete A K Rajarajan L C Gupta R Vijayaraghavan
We report here the results of our heat capacityC_{p} measurements on a monophasic material HoBa_{2}Cu_{3}O_{7−y}. ΔC_{p}/T_{c}, the jump inC_{p} at the superconducting transition temperature (=91 K) of the material is measured to be 31 mJ/mol-K^{2}.
pp 259-277 April 1988 Quantum Mechanics
The fundamental prescriptions of quantum theory have so far remained incomplete in that there is no satisfactory prescription for the joint probabilities of successive observations of arbitrary sequence of observables. The joint probability formula derived by Wigner is based on the collapse postulate due to Von Neuman and Lüders and is applicable only to observables with purely discrete spectra. Earlier attempts to generalize the collapse postulate to observables with continuous spectra have been unsatisfactory as they lead to only finitely additive (and notσ-additive) joint probabilities in general. In this paper a suitable generalisation of the Wigner joint probability formula is proposed, which is completely satisfactory in the sense that it leads toσ-additive joint probabilities for successive observations of arbitrary sequence of observables, consistent with all the other basic prescriptions of quantum theory. This general law for quantum mechanical joint probabilities is arrived at by a reformulation of earlier results on expectation values in successive measurements. The generalized Wigner joint probability formula is also shown to be a consequence of a general collapse postulate, which allows for changes in state due to measurement from normal states to non-normal states also. As an illustration of our results, the probability distribution of the outcomes of a momentum measurement which immediately succeeds a position measurement is computed, and this seems to shed an entirely new light on the uncertainty principle.
pp 279-292 April 1988 General Relativity
The trousers problem revisited
Corinne A Manogue Ed Copeland Tevian Dray
Anderson and DeWitt considered the quantization of a massless scalar field in a spacetime whose spacelike hypersurfaces change topology and concluded that the topology change gives rise to infinite particle and energy production. We show here that their calculations are insufficient and that their propagation rule is unphysical. However, our results using a more general propagation rule support their conclusion.
pp 293-297 April 1988 Particle Physics
Baryon masses in the SU(4) skyrme model
We consider the SU(4) Skyrme model with explicit chiral and flavour symmetry-breaking terms. Using the masses of the 15-plet pseudoscalar mesons as the input, we calculate the masses of the 20-plet baryons. The baryon masses predicted by this model agree with results based on quark model to about 15%. We find that the generalized Gell-Mann Okubo mass relation is very well satisfied.
pp 299-304 April 1988 Particle Physics
The superconformal anomaly in the 1 + 1 dimensional Wess-Zumino model
The superconformal trace anomaly is worked out to one-loop order in perturbation theory for the 1+1 dimensional Wess-Zumino model.
pp 305-307 April 1988 Nuclear Physics
A note on the mean-internucleon distance in the central region of heavy nuclei
The density distribution of nucleons in a heavy nucleus is used to show that the mean-internucleon distance in the central region of heavy nuclei is 1.99 fm.
pp 309-317 April 1988 Molecular Physics
On the non-BoltzmannA-X emission in Na_{2} following laser excitation of theB state
A Sharma G L Bhale M A N Razvi M N Dixit
A^{1}Σ_{u}^{+}-X^{1}Σ_{g}^{+} emission in Na_{2} is observed following excitation ofB^{1}π_{u} by various lines of an argon ion laser. The excitation energy ofB^{1}π_{u} is collisionally transferred to the (2)^{1}Σ_{g}^{+} which then radiatively populates theA^{1}Σ_{u}^{+} state. The Na vapour is contained in a stainless steel crossed heat pipe with Ar buffer gas and temperature around 600°C. For all laser lines except 4579 Å, the coarse features ofA-X emission are independent of the laser wavelength. However, at high resolution the finer differences between different laser line excitation are explained. Variousv′-v″ transitions in this emission are identified. Computer simulation is presented to help explain some features of this emission.
pp 319-329 April 1988 Condensed Matter Physics
Effects of lattice dispersion and elastic anisotropy on the thermal properties of bcc metals
Two new parameters which take into account the effects of elastic anisotropy and phonon dispersion on lattice specific heat in the case of sodium and potassium have been evaluated. A new graded mesh method which uses a 162-direction approximation in (1/16) part of the Brillouin Zone (BZ) has been considered to evaluate the two parameters.
pp 331-336 April 1988 Condensed Matter Physics
The temperature variation of the Debye-Waller factors of Cs^{+} and Cl^{−} ions in CsCl powder has been studied using X-ray powder diffraction. A continuous flow cryostat has been used to record the diffractograms and the integrated intensities of the Bragg peaks at different temperatures have been obtained. The integrated intensities of the odd and even reflections have been analysed following the structure of the CsCl compound and the Debye-Waller factors of the Cs^{+} and Cl^{−} ions have been estimated. The results have been verified by structure factor least squares refinement. Theoretical shell model lattice dynamical calculations have been done using a 7-parameter model in the harmonic approximation and the values compared with the present X-ray measurements.
pp 337-340 April 1988 Condensed Matter Physics
The temperature variation of the Debye-Waller factors of Cs^{+} and Br^{−} ions in CsBr powder has been studied using powder X-ray diffraction. The integrated intensities of the Bragg peaks at different temperatures have been obtained. These results have been verified by structure factor least squares refinement program. Theoretical shell model lattice dynamical calculations have been done using a 7-parameter model in the harmonic approximation and the values compared with the present X-ray measurements. The observed intensities have been corrected for first order thermal diffuse scattering.
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