Gauge mediation of supersymmetry breaking is among the leading candidates for physics beyond the Standard Model (SM) and purportedly gives a very light gravitino. In a paper with H.S. Goh and N. Okada (hep-ph/0511301), we invoke the new paradigm of ”Supersymmetry without supersymmetry” (by H.S. Goh, M.A. Luty and myself, hep-th/0309103) in conjunction with the AdS-CFT correspondence to explicitly construct a viable natural alternative framework to the conventional picture. In this scenario, supersymmetry is posited to be an accidental symmetry of Nature and the SM fields are composite bound states that emerge from a conformal field theory. The resultant effective theory can, through sequestering and conformal dynamics, exhibit most of the properties of low energy supersymmetry breaking. However, the gravitino is very heavy and decouples from low-energy physics. Additionally, flavor changing neutral currents are at the very least only an order of magnitude below current experimental bounds and could be ruled out in future experiments. The neutralino lightest supersymmetric partner in this scenario is also a viable candidate of cold dark matter. H.S. Goh, N. Okada and I are undertaking further detailed phenomenological studies of this model.

Despite the wealth of evidence available, we have, as yet, been unable to conclusively determine the very stuff that holds our universe together. With further precision cosmological measurements expected in the next few years, there is a crucial need to develop a coherent framework to understand and explain the plethora of cosmological data we have. The dark energy question is perhaps the most profound. One possibility would be to invoke a cosmological constant that naively looks unnaturally small. An intriguing way around the naturalness problem would be to implement an accelerescence mechanism as proposed by Chacko, Hall and Nomura (astro-ph/0405596). Interestingly enough, this scenario dovetails very nicely with inflation as was shown in a paper with Q. Shafi, A. Sil and I(hep-ph/0502254). Another rather intriguing possibility is that there is a feedback mechanism through the coupling of the Ricci scalar to a scalar field that controls the evolution of the vacuum energy. In a soon-tobe- published paper by S.M. Barr, R.J. Scherrer and I, we explore a simple toy model that realizes this idea through an improvement of the earlier cosmon mechanism by S.M. Barr (PRD36:1691,1987).

In recent years, neutrino physics has proven to be one of the most exciting topics in particle physics by giving us a tantalizing glimpse of what lies beyond the Standard Model. Understanding how neutrinos fit into the grand scheme of things and trying to surmise the deeper underlying structure of Nature from the neutrino sector are some of the major challenges we face in particle physics today. To this end, grand unified theories (GUTs) provide a compelling framework for us to address these questions. R.N. Mohapatra, H.S. Goh and I have shown that b-\tau unification within a supersymmetric SO(10) GUT without additional symmetries can reproduce the large mixing angles and the observed hierarchy in the neutrino sector as well as satisfy the quark mass constraints (hep-ph/0303055). The model also predicts that the U_{e3} mixing angle is approximately 0.16 which can be tested by detectors within the next year. In a further paper, we investigated CP violation in this minimal model (hep-ph/0308197), and concluded that generically, without nonrenormalizable terms for the electron mass, there will have to be supersymmetric contributions to CP violation. In collaboration with S. Nasri, we have also completed the detailed analysis of proton decay lifetimes for this model (hep-ph/0311330).