A striking and puzzling phenomenon 1s that neutrinos appear nearly massless in contrast to all other leptons and quarks. The left-handed neutrinos may combine with their chiral partners (if theyâ€¦ (More)

We reconsider the possibility that inflation was driven by a sneutrino the scalar supersymmetric partner of a heavy singlet neutrino in the minimal seesaw model of neutrino masses. We show that thisâ€¦ (More)

We consider supersymmetric theories where the gravitino is the lightest superparticle (LSP). Assuming that the long-lived next-to-lightest superparticle (NSP) is a charged slepton, we investigate twoâ€¦ (More)

We make a detailed analysis on the nucleon decay in the minimal super-symmetric SU(5) grand unified model. We find that a requirement of the unification of three gauge coupling constants leads to aâ€¦ (More)

We examine the lepton-flavor violation caused by a Yukawa coupling matrix y Î½,ij for right-handed neutrinos in the supersymmetric standard model. We stress that decay rates for Ï„ â†’ ÂµÎ³ and Âµ â†’ eÎ³ mayâ€¦ (More)

We point out that supergravity effects enable the inflaton to decay into all matter fields, including the visible and the supersymmetry breaking sectors, once the inflaton acquires a non-vanishingâ€¦ (More)

Thermal leptogenesis requires the reheating temperature T R > âˆ¼ 3 Ã— 10 9 GeV, which contradicts a recently obtained constraint on the reheating temperature, T R < âˆ¼ 10 6 GeV, for the gravitino massâ€¦ (More)

We derive a constraint on the cosmic density of string moduli fields in gauge-mediated supersymmetry-breaking theories is obtained by requiring that photons emitted from the unstable moduli fieldsâ€¦ (More)

We consider dilaton stabilization with R invariance, which insures a vanishing cosmological constant at the scale of stabilization. We construct a few models which accommodate weak gauge couplingsâ€¦ (More)

We argue that moduli in the adjoint representation of the standard-model gauge group are a natural feature of superstring models, and that they can account for the apparent discrepancy between theâ€¦ (More)