Table of contents

It is shown that an order of magnitude gain in the statistical accuracy of optical linewidths measured by digital autocorrelation of photon- counting fluctuations may be achieved by heterodyne detection in the weak signal limit.

The MARS instrument at Durham has been used to study the charge ratio of near vertical cosmic ray muons in the momentum range 10-300 GeV/c. No significant structure is seen and there is no firm evidence to favour a significant deviation from the mean value of 1.284+or-0.004. Including the results from the Utah detector, which correspond to muon momenta in the range 1000-2000 GeV/c, there is the suggestion of near constancy from 10 GeV/c to 2000 GeV/c.

Using Komar's localized energy and spin conserved vectors associated with the Killing fields of a stationary axisymmetric universe, the author derives a covariant identity which describes in terms of variations of fields and matter functions a perfect fluid in general relativity, exhibiting in a clear and straightforward way a variety of known extremal theorems, or analogous ones, for energy or entropy.

The relativistically invariant field equations relevant to mechanics thermodynamics and electromagnetism are presented in a phenomenological continuum theory of magnetoelastic interactions in which the magnetic spin is accounted for.

The relationship between Mach's principle and the Brans-Dicke scalar- tensor theory of gravitation is discussed. A converse formulation is proposed. It is shown that the geometry of space-time determines the mass- energy content only up to a position dependent gauge transformation. This is interpreted as a scale change in the unit of mass which preserves the conservation laws. For arbitrary values of the scalar field coupling constant omega the theory is invariant only under a restricted group of gauge transformations. Complete invariance applies in the case omega =0. Furthermore it is shown that whenever the curvature scalar R vanishes the theory can be transformed into the usual form of Einstein's general relativity. Equivalence classes of solutions are defined which have the same geometry and lead to the same geodesic motion for test particles. Examples are constructed for the case of static spherical symmetry and for uniform cosmology which exhibit these properties. Some further consequences are discussed.

A one dimensional three body problem is treated by the path integral approach of Feynman. When expressed in suitable coordinates, it is possible to extract the symmetry from the path integral of the problem. The resulting propagator is evaluated in a closed analytical form.

The method of characteristics is used to analyse the system of five nonlinear partial differential equations describing ultrashort optical pulse propagation through a medium of two-level atoms. Contrary to previous suggestions it is shown rigorously that the system is causal: no physical speeds exceed c. The method is well adapted to numerical integration. It can take full account of both back scattering and the effect of a surface to the dielectric. A number of new physical results obtained this way are briefly reported.

The general second rank SU(3) tensor formed from a single hermitian octet vector is expressed in terms of a base set constructed to have particularly simple properties. The relevance to chiral lagrangian theories of hadron physics is discussed, and other applications are suggested.

The multiple scattering model of Frautschi and Margolis, with secondary trajectories included, is applied to pion-nucleon elastic and charge- exchange scattering. It is possible to explain the Serpukhov high energy total cross section data, but not other data such as the phase of the forward amplitude and the elastic scattering polarization.

The authors study the exact form of the ABEST integral equation treating it as an equation for the irreducible kernel given the total pi pi cross section. The usual identification of the irreducible kernel with the elastic cross section is seen to be highly unlikely. The result depends violently on the off-mass-shell behaviour of the pi pi amplitude. In general the irreducible kernel is not even positive definite.

Monte Carlo simulations of hadron and electron-photon cascades in the large multiplate cloud chamber operating at Ootacamund have been carried out using some plausible interaction models. Some extreme assumptions about multiplicity and inelasticity have been incorporated in order to study their effect on the detailed features of the cascades. A new method for estimating the energies of the cascades of energy above about 200 GeV by measuring cascade widths at different depths in the absorber has been developed with calibrations provided by the simulations. The estimated energy is accurate to within 50%. The experimentally observed cascades due to pions and nucleons at energies below 200 GeV are similar and a comparison of the detailed profiles with the simulated cascades suggests that pions like nucleons are only partially inelastic at these energies. Hadron cascades in the TeV energy range show rather fast absorption after the cascade maxima.

A systematic investigation of the average neutron capture cross sections at 25 keV is undertaken to study the structure of giant resonances in the p wave neutron strength functions. As a part of this program and to fill in the gaps in the existing cross section data, radiative capture cross sections for the following isotopes have been measured. ⁷⁴Se, ⁷⁸Se, ⁸⁴Sr, ¹⁰⁹Ag, ¹²²Te, ¹⁵⁹Tb, ¹⁶⁹Tm, ¹⁷⁴Yb, ¹⁷⁶Yb, ¹⁷⁸Hf, ¹⁷⁹Hf and ¹⁹²Os. The activation method and absolute gamma counting technique have been employed. The new results are reported with a discussion of the p wave neutron capture in these nuclei.

A study of wave-wave interactions in plasmas is made using a lagrangian formulation developed by Low. Coupled mode equations are derived. The method offers distinct advantages over the conventional approach starting from the Vlasov- Maxwell equations. Two examples of the lagrangian method are considered: (i) the nonlinear interaction of transverse waves in a warm field-free plasma to produce plasma oscillations and (ii) the interaction of three- electromagnetic waves in a cold magnetized plasma. Its application to waves in warm magnetized plasmas and to explosive instabilities is considered in part II.

Precision measurements of the relative permittivity of the n alkanes from n pentane to n decane have been made over a range of pressures and temperatures. All the data for each alkane have been fitted by a polynomial to within better than 0.1%. Results are compared where possible with those of other workers.

By following the trajectories of protons in the galaxy the authors predict the detailed form of the anisotropy of ultrahigh energy cosmic rays of galactic origin for given magnetic fields and source distributions. Three specific magnetic field models based on interpretations of the observational data are used and they consider sources uniformly distributed throughout the galactic disc or spiral arms or concentrated at the galactic centre. Data on the arrival directions of extensive air showers are then compared with the predicted distributions for these models, and, assuming that metagalactic cosmic rays are isotropic, upper limits are given for the fraction of cosmic rays of galactic origin.