[en] The assumption is made that the total energy of the Universe vanishes; then it follows that f approximately t^-1 and M approximately t², as required by Dirac's Large Number Hypothesis. (Auth.)

[en] Dirac's cosmology, based on his large number hypothesis, took the gravitational coupling to be decreasing with time and matter to be created as the square of time. Since the effects predicted by Dirac's theory are very small, it is difficult to find a ''clean'' test for it. Here we show that the observed radiation from pulsars is inconsistent with Dirac's multiplicative creation model, in which the matter created is proportional to the density of matter already present. Of course, this discussion makes no comment on the ''additive creation'' model, or on the revised version of Dirac's theory. (author)

[en] An attempt is made to relate observational data to Dirac cosmology, with a view to identifying its predictions and testing the theory. Some familiar problems in cosmology are reviewed using the criteria, assuming Dirac's large numbers hypothesis, that there are two metric scales applicable in his theory: (i) the atomic or A scale in which conventional atomic and Maxwellian electromagnetic theory holds, (ii) the Einstein or E scale in which conventional Einsteinian gravitational theory holds. If Dirac's hypothesis is correct several important consequences for observational cosmology follow, featuring Hubble's constant, the age of the Universe, the cosmic mass density, the deceleration parameter and the evolutionary characteristics of the cosmic medium including the formation of galaxies. These are summarized in the various sections of the paper. (author)

[en] A modified ''large Number theory'' is considered, which leads to a gravitational constant, which is independent of time. (U.K.)

No abstract available

[en] Current views on Dirac's creative heritage and on his role in the formation and development of quantum physics and in shaping the physical picture of the world are discussed. Dirac's fundamental ideas in later life (1948 - 1984) and their current development are given considerable attention. (from the history of physics)

[en] Dirac has postulated that all large dimensionless numbers occurring in Nature must be inter-related. On this basis he suggested that the gravitational coupling decreases linearly with time (as measured by atomic clocks) while the number of nucleons in the observable Universe increases quadratically with time. It has already been demonstrated that one of the three possible modes for Dirac's theory to work, the ''multiplicative creation'' mode, is not compatible with the observations of pulsars. Here we demonstrate that the other mode of creation of matter also faces severe problems, and we suggest that the comparison of red shifted galaxies could provide a comparatively ''clean'' test of Dirac's theory. (author)

[en] Dirac's method for variations of a brane embedded in co-dimension one is demonstrated. The variation in the location of the brane invokes a rest frame formulation of the 'sandwiched' brane action. We first demonstrate the necessity of this method by re-deriving Snell's law. Second, we apply the method to a general N-dimensional brane embedded in co-dimension one bulk in the presence of gravity. We re-derive the brane equations: (i) the Israel junction condition, (ii) the energy/momentum conservation on the brane and (iii) a geodetic-type equation for the brane

[en] The Hubble-Sandage diagrams for the Dirac cosmology have been discussed in the case of the modified dependence of luminosity upon the gravitational parameter G and mass. It is shown that the observational data for galaxies and the brightest quasars can be explained by the Dirac cosmology with the reasonably chosen changes of the gravitational parameter and of mass with the time. 41 refs., 2 figs. (author)

[en] Dirac numercal principle and Brans-Dicke theory (BDT) is are considered. It is concluded that the numerical prinsiple, which initiated the development of scalar-tensor theories and ideas of gravity constant variation, is likely to be inconsistent with BDT cosmological solutions (without a trivial contradiction to data observed and exotic state of matter equations being not applyed)