Table of contents

It is shown that the invariant charge of quantum electrodynamics cannot change sign as a function of q². Asymptotically, the invariant charge is given by a non-linear equation that has no real and negative solutions. Contrary to the indications from low-order perturbation theory, therefore, the invariant charge is everywhere non-negative, and the vacuum does not become unstable.

The Weinberg-Salam theory is reformulated as a pure Yang-Mills theory in a six-dimensional space, the Higgs field being interpreted as gauge potentials in the additional dimensions. Viewed in this way, the condition that the Higgs field transforms as a U(1) representation of charge one is equivalent to requiring a value of 30 degrees for the Weinberg angle. A second consistent determination comes form the idea borrowed from monopole theory that the electromagnetic field is the direction of the Higgs field.

The ¹⁸O(t,p) reaction has been used to locate 0⁺ and 2⁺6p-2h levels at 4456 and 5304 keV, respectively, in ²⁰O. Excitation energies and (t,p) strengths are in good agreement with this identification. Results for all other levels observed below 5.4 MeV excitation are well accounted for in an (sd)⁴ model.

Excitation functions and angular distributions at backward angles have been measured for the reaction ²⁸Si(¹²C,¹⁶O)²⁴Mg as well as for elastic scattering of ¹⁶O from ²⁴Mg. At peaks of the strongly structured excitation curves P_J²(cos theta )-type angular distributions are observed. Peak positions and J values show some similarities for the reaction data and the ¹⁶O+²⁴Mg exit channel but disagree with recent data for the ¹²C+²⁸Si entrance channel. No convincing evidence for resonant molecular states is found.

From a phenomenological optical-model analysis of the ³²S(³He,³He)³²S scattering, discrete ambiguities were found in the radius of the ³He spin-orbit potential. In agreement with results for other nuclei, a small spin-orbit diffuseness a_s approximately=0.2 fm is required.

It is pointed out how, for ¹¹⁰Cd, the cluster-vibration coupling generates the 'g band' and the 'p band' and their approximate mixing, possibly providing a general clue to the semimicroscopic theory of band mixing.

The total E1 and M1 photo-absorption cross section in ¹¹⁷Sn and ¹¹⁹Sn is calculated within the quasiparticle-phonon nuclear model. It is shown that at an energy of about 8 MeV the cross section has a substructure caused by the E1 transitions 3s_1/2 to 2p_1/2, 3s_1/2 to 2p_3/2 and a peak of the giant M1 resonance in the region of 8 MeV. Thus the authors have explained the substructure observed by Winhold et al. (1970).

The effect of number conservation on nuclear deformation, energy spectra and B(E2) values is investigated in the variational projected BCS formalism. It is found that number conservation substantially improves the agreement between the calculated and experimental energy spectra in ^158,160Er.

The author discusses the possibilities of finding solutions for the static Yang-Mills theory in three spatial dimensions in the context of a general cylindrically symmetric ansatz. A 'dyon' solution is also presented.

A super-Thirring equation is proposed and studied. A solution of the renormalised Thirring model is constructed from two massless scalar superfields. The representations of the superconformal algebra for the scalar superfields as well as for the Thirring superfield are obtained. It is shown that the renormalised Thirring equation is convariant with respect to these representations.

In a U(1) model of a single axial vector field coupled to massless fermion the AAA triangle diagram is calculated using three different methods. The reasons for a unique result for the AAA vertex function are analysed.

The authors examine s-channel helicity conservation at the gamma V, gamma gamma and NN vertices and show that in each of these cases the phenomenon can be ascribed to the vanishing of the same spin-zero covariant coupling. The implications of this for the NN* vertex are considered.

The multipole E₁₊^(3/2) of photoproduction of pions on nucleons in the region of the first resonance has been calculated with the use of relativistic dispersion relations supplemented with the values of pion-nucleon scattering phase-shifts at moderate energies and with summary information on the dynamics in the region of higher energies. This approach, which has previously been applied successfully to the magnetic dipole amplitude M₁₊^(3/2) of photo- and electroproduction of pion on nucleons, is shown to work remarkably well in the case of E₁₊^(3/2) also.

The comparison of forward and backward Argand diagrams (instead of partial-wave Argand diagrams) provides a simple and powerful criterion to distinguish between true resonances and pseudoresonances. When applied to the elastic pi d amplitudes, it provides definitive evidence for a pseudoresonance near the Delta N threshold and an upper limit for the partial width of a possible dibaryon resonance.

By means of a model involving the Delta (1236), an improved set of imaginary components for the T=1 nucleon-nucleon phase-shifts is obtained. These phase-shifts are then used to calculate inelastic nucleon-nucleon cross sections below 720 MeV, including the spin-dependent inelastic cross sections Delta sigma _Tⁱ and Delta sigma _Lⁱ.

The results of a series of lowest-order constrained variational calculations for various nucleon fluids are presented. The calculations are based upon the Reid soft-core potential (1968) and allow in a self-consistent fashion for the explicit excitation of a nucleon into an N*(1234) state via a recent transition potential proposed by Green, Niskanen and Sainio (1978). For nuclear matter a binding energy of 16 MeV per nucleon is obtained at a saturation density 0.25 N fm^-3. The compressibility of nuclear matter is calculated to be 300 MeV. From a study of asymmetric matter a symmetry coefficient of 33 MeV is obtained. It is found that the inclusion of N*'s in beta-stable matter leads to a suppression of the proton abundance at high densities.

The behaviour of a droplet of nuclear matter under rapid rotation is analysed by means of an extended Thomas-Fermi method and by using appropriate trial functions for the density. The authors' description includes the mass as well as density redistribution of the rotating nucleus. Because of the finite compressibility of nuclear matter the central density of the nucleus is reduced while the surface thickness becomes anisotropic if the nucleus rotates rather fast. The consequences of this behaviour for the nuclear stability are discussed. The nuclear deformation at high angular momenta shows a great similarity to that of liquid drops.

By considering the variation in core size, the Lambda wavefunction, and accounting approximately for the centre-of-mass (CM) energy with mass number. The authors have analysed the Lambda binding energy of p-shell hypernuclei with charge-independent, central, spin- and state-dependent effective Lambda -nucleon potentials of gaussian form and Skyrme type within the shell-model framework. The fits to the data in the present analysis indicate that in earlier analyses (Lee et al. 1970, Gal et al. 1971, 1972) the roles of non-central and three-body forces have been over-emphasised, and so it is hard to place much reliance on the matrix elements of the Lambda -nucleon force. Alternatively one may say that the effect of the non-central and three-body forces can be simulated by the spin and state dependence of the interaction. The effective potentials so obtained are used to estimate the well depth of Lambda in nuclear matter and are found to give values in close agreement with the empirical estimates.

Analytic expressions are presented for the off-shell p-p T matrix for the Graz l=0 and l=1 separable potentials. Physical on-shell results are also obtained and used to compute the phase-shifts for the ¹S₀, ³P₀, ³P₁ and ³P₂ states. Improved fits to the experimental data are obtained. Analytic expressions are also presented for the effective range function and are used to compute the low-energy scattering parameters.

Angular distributions of ⁸Be from the reaction ¹²C(⁹Be,⁸Be)¹³C were measured at a ⁹Be energy of 20 MeV (lab). Transitions to the ground state and to the first excited state of ¹³C were resolved in the whole angular region while those for the second and third excited states were separated at forward angles only. The results were analysed with the aid of a DWBA method taking into account neutron transfer processes as well as alpha-particle transfer processes as the two leading direct reaction mechanisms. A contribution from the compound-nucleus mechanism was also included.

The mean lives of three excited states have been measured by bombarding an implanted ⁴He target with a ²⁸Si beam and observing the (particle coincident) gamma -ray line-shapes at 0 degrees . The results are: (in ²⁸Si) 1778 keV level, tau _m=697+or-39 fs; (in ³¹P) 1266 keV level, tau _m=761+or-47 fs, 2234 keV level, tau _m=391+or-25 fs. The last lifetime is of interest in attempts to calibrate the Doppler-shift attenuation method at low initial recoil velocities.

Mean lifetimes or lower limits on mean lifetimes have been obtained for seven levels of ⁸⁵Sr by the Doppler-shift attenuation method using the ⁸⁵Rb(p,n gamma )⁸⁵Sr reaction at E_p=3.8 MeV and a high-resolution Ge(Li) detector. The results are discussed in the light of single-hole and three-hole cluster configurations coupled to the quadrupole vibration of the corresponding even Sr core.

The sea-level hadron spectrum has been redetermined. From comparison with the primary spectrum it is shown that the effective p-air total cross section is rising faster than 1nE in the energy region 1-100 TeV. Comparison with calculations by Hillas shows that simulations using a scaling model and incorporating a rising cross section are in agreement with the experimental data if the inelasticity is constant in this energy region.