A supercurrent superfield whose components include a conserved energy-momentum tensor and supersymmetry current as well as a (generally broken) R-symmetry current is constructed for a generic effective N=1 supersymmet-ric gauge theory. The general form of the R-symmetry breaking is isolated. Included within the various special cases considered is the identification of those models which exhibit...

We propose a model of cosmology and particle physics in which all relevant scales arise in a natural way from an intermediate string scale. We are led to assign the string scale to the intermediate scale M * ∼ 10 13 GeV by four independent pieces of physics: electroweak symmetry breaking; the µ parameter; the axion scale; and the neutrino mass scale. The model involves hybrid inflation with the...

The physics prospects of the high energy Photon Linear Collider are reviewed, emphasizing its potential to study the symmetry breaking sector, including Higgs searches and precision anomalous W couplings measurements.

The existence of a shadow world (or mirror universe) with matter and forces identical to that of the visible world but interacting with the latter only via gravity can be motivated by superstring theories as well as by recent attempts to understand the nature of a sterile neutrino needed if all known neutrino data are to be consistent with each other. A simple way to reconcile the constraints o...

This paper, part I of a two-part project, aims at answering the simple question 'what is spontaneous symmetry breaking?' by analyzing from a philosophical perspective a simple classical model. Related questions include: what does

We study flat directions and soft scalar masses using a Z3 orbifold model with SU(3)×SU(2)×U(1) gauge group and extra gauge symmetries including an anomalous U(1) symmetry. Soft scalar masses contain D-term contributions and particle mixing effects after symmetry breaking and they are parametrized by a few number of parameters. Some specific relations among scalar masses are obtained. e-mail: y...

Both inflationary and quintessence cosmologies require scalar fields which roll very slowly over cosmological time scales, and so typically demand extremely flat potentials. Sufficiently flat potentials are notoriously difficult to obtain from realistic theories of microscopic physics, and this poses a naturalness problem for both types of cosmologies. We propose a brane-world-based microscopic...

Recent progress in some selected areas of grand unification and physics beyond the standard model is reviewed. Topics include gauge coupling unification, SU(5), SO(10), symmetry breaking mechanisms, finite field theory: SU(3), leptonic color: SU(3), chiral color and quark-lepton nonuniversality: SU(3). **Talk at V-SILAFAE, Lima, Peru (July 2004).

We discuss the separation of isospin-symmetric and isospin-breaking contributions in the hadronic observables within the framework of QCD plus QED. Further, we briefly review some recent work on the low-energy hadron phenomenology, in which the isospin-breaking effect plays a prominent role.