Vector constants of the motion and orbits in the Coulomb/Kepler problem

The equation for the conic sections describing the possible orbits in a potential $V \sim r^{-1}$ is obtained by means of a vector constant of the motion differing from the traditional Laplace-Runge-Lenz vector.Comment: 5 pages, no figure

Supersymmetric dark matter in the light of LEP

The negative outcome of searches for supersymmetry performed at LEP have been used to derive indirect constraints on the parameters of the most plausible models for cold dark matter based on supersymmetric extensions of the Standard Model. The main results are summarized.Comment: 3 pages, 1 figure, to be published in the proceedings of the XIII Italian meeting on Physics at LEP, LEPTRE, Rome, April 200

Standard Grand Unification from Superstrings

Recent developments about the construction of standard $SO(10)$ and $SU(5)$ grand unified theories from 4-dimensional superstrings are presented. Explicit techniques involving higher level affine Lie algebras, for obtaining such stringGUTs from symmetric orbifolds are discussed. Special emphasis is put on the different constraints and selection rules for model building in this string framework, trying to disentangle those which are generic from those depending on the orbifold construction proposed. Some phenomenological implications from such constraints are briefly discussed.Comment: 7 pages, Latex, no figures. Talk at Susy 95. Paris, May 199

Getting out of the car: an institutional/evolutionary approach to sustainable transport policies

Orthodox economics sees transport as a market which can be made more sustainable by improving its self-regulating capacity. To date this static approach has not been able to limit the growing demand for transport and its increasing environmental impact. Better results might be obtained by using evolutionary and institutional economics. Starting from these theories, a sustainable transport policy should be based on three fundamental considerations. First, transport is not a market, but a sum of systems affected by path-dependence and lock-in phenomena. Second, transport is not sustainable because it is locked in environmentally sub-optimal systems. Third, structural changes in technologies and organisations, institutions, and values are needed to establish more sustainable transport systems. We give an example of the use of an institutional/evolutionary approach to sustainable transport policies in the transition from the system of mass motorisation to the new urban mobility system