The first part of this report gives a very quick sketch of how string theory concepts originated and evolved during its first 25 years (1968-93). The second part presents a somewhat more detailed discussion of the highlights of the past decade. The final part discusses some of the major problems that remain to be solved.

We study a two 3-branes system embedded in a 5-dimensional spacetime with the fifth dimension compactified on a $$S^{1}/Z_{2}$$S1/Z2 orbifold. Assuming isotropic and homogeneous branes, we show that… Expand

At the Planck scale I combine a finite subgroup of SO(3,1) operating in 4-dimensional discrete spacetime with a finite subgroup of the Standard Model gauge group SU(2)L x U(1)Y x SU(3)C acting in… Expand

This review analyzes the geometry, dynamics and perturbations of simple brane-world models for cosmology and astrophysics, mainly focusing on warped 5-dimensional brane -worlds based on the Randall-Sundrum models.Expand

I assume that both spacetime and the internal symmetry space of the Standard Model (SM) of leptons and quarks are discrete. If lepton and quark states represent specific finite binary rotational… Expand

A recent survey amongst leading oil companies, contractors, manufacturers and independent geophysicists investigated issues in regard to views and first-hand knowledge of various new land exploration… Expand