A metric containing a parameterb is presented. It represents two distinct families of space-times, the Taub-nut family and the deSitter family, according asb=1 andb=4 respectively.

The metric of the deSitter family of space-times contains a further parameterm. Whenm=0, the space-time is the usual homogeneous and isotropic deSitter space-time. But ifm≠0, the metric represents a space-time which is homogeneous but not isotropic satisfyingR_ik=Λg_ik. In this space-time, the 4-velocity of an observer at rest will have non-zero twist. The metric withb=4,m≠0 is interpreted as a metric representing a “rotating deSitter space-time”.

Belavin, Zamlodochikov and Polyakov have recently proposed a class of conformally invariant field theories in two dimension with exactly determined rational critical indices. We establish a tentative identification of a subset of these theories in terms of the O(n) model and theq-state Potts model in 2-dimensions for appropriaten andq.

The influence of pionic corrections to the masses of heavier hadrons is investigated in the cloudy bag model. After determining the bag parameters from ordinary baryons and mesons the heavier hadron mass spectrum is calculated. A sizable amount of pionic correction is observed which has improved the masses favourably.

It is shown that the most recent measurements of differential cross-section at small momentum transfers, integrated and total cross-sections, and the slope of np elastic scattering from 100 to 400 GeV/c are successfully fitted by using the simple Regge pole model proposed by the authors several years ago.

We have performed a computer-aided analysis of position behaviour in atomic hydrogen. Effect of electric, magnetic and temperature fields on the diffusion and annihilation of positrons has been studied. Electric field is varied over a wide range of 0–200 V cm⁻¹ amagat⁻¹, magnetic field over 0–30 kG while the temperature range considered is 300–10,000°K. The position decay rate decreases with electric and temperature fields but increases with magnetic fields. However, the effect of these fields is reversed on the diffusion coefficient.

The semiempirical molecular orbital method known as symmetrically orthogonalised intermediate neglect of differential overlap (sindo) has been employed to determine the geometry, bonding, binding energy, ionisation potential, dipole moment and net charges of diketene and cyclobutane-1,3-dione molecules. Results obtained have been compared with available experimental data.

Einstein A-coefficients for the electric-dipole transitions between the rotational levels up to 785 cm⁻¹ in the ground vibrational state of D₂O are calculated. The A-values are used to compute the mean-radiative life-times of the levels.

A method is described for the efficiency calibration of Si(Li) and HpGe detectors in the 5–60 keV energy region. The method utilizes theK x-ray lines from⁵⁴Mn,⁶⁵Zn,⁷⁵Se,⁸⁵Sr,⁸⁸Y,¹⁰⁹Cd,¹³⁷Cs,¹⁴¹Ce and¹⁵⁹Dy in addition to⁵⁷Co and²⁴¹Am radioactive sources to have sufficient number of data points. Since the emission intensities are required at variousK x-ray energies from the decay of these sources, this paper reports theK x-ray emission intensities per 100 disintegrations for these nuclei using the latest adopted data for gamma ray intensities, electron capture and internal conversion coefficients, fluorescence yield values and the relative intensities of the fourK x-ray lines.

The emission spectrum of diatomic magnesium chloride molecule has been reinvestigated in the region 5030-4380 Å (B²Σ⁺ —A²Π transition) at a higher dispersion. The vibrational assignments of the bands are confirmed by observing the vibrational isotope shifts due to isotopes of magnesium and chlorine. Precise values of the vibrational constants are determined for theB²Σ⁺ state.

The dispersion relation for ion sound waves generated in a perpendicular shock is derived and the energy density of ion-sound turbulence is obtained using quasilinear theory. The result is compared with the lower hybrid turbulence generated under similar conditions. It is shown that ion-sound turbulence is a better candidate for the generation of type-I radio bursts in the solar corona.

The theoretical optimization of the design parametersN_A,N_D andW_P has been done for efficient operation of Au-p-n Si solar cell including thermionic field emission, dependence of lifetime and mobility on impurity concentrations, dependence of absorption coefficient on wavelength, variation of barrier height and hence the optimum thickness ofp region with illumination. The optimized design parametersN_D=5×10²⁰ m⁻³,N_A=3×10²⁴ m⁻³ andW_P=11.8 nm yield efficiencyη=17.1% (AM0) andη=19.6% (AM1). These are reduced to 14.9% and 17.1% respectively if the metal layer series resistance and transmittance with ZnS antireflection coating are included. A practical value ofW_P=97.0 nm gives an efficiency of 12.2% (AM1).

It is shown that starting from a Fourier transform relation one can derive, in a surprisingly simple manner, all the well-known results of lattice summation, that have been obtained so far by a complicated use of the Ewald theta transformation. We show that the Ewald transformation follows directly from the Fourier transform relation.

The origin of the elastic inconsistency ofdaf, mas andgtf models for non-cubic solids and the failure of their force constants to comply with all the rotational invariance conditions are analysed by resolving the atomic displacements of face-centred tetragonal indium along three mutually perpendicular directions. It is shown that a lattice dynamical model suffers from these deficiencies as a consequence of its neglect of three-body interactions as well as the mixed neighbour interactions associated with the angular forces, while thecgw model which incorporates both these interactions is elastically consistent and its potential energy rotationally invariant. The degree of equivalence that exists among the force constants ofdaf, mas, gtf andcgw models, the distortions introduced by the elastic inconsistency into the phonon dispersion curves of fct indium as well as the consequences of imposing the rotational invariance conditions on the force constants of a lattice dynamical model are discussed.

Based on the assumption that in the groundbcs state the net gain in energy is equivalent to the repulsive electron-ion and electron-electron Darwin interactions, an expression forT_c has been obtained which depends on only a few atomic parameters. The theory provides a criterion for the occurrence of superconductivity and yields satisfactory values ofT_c for metals and alloys, and ternary chalcogenides and borides. It explains the difference inT_c in the crystalline and amorphous states as well as the pressure dependence ofT_c. The possibility of occurrence of high temperature superconductivity has been explored.