123621838
No massless scalar adjoints for N=1, D=4 heterotic strings in the free fermionic formulation
Abstract Using the free fermionic formulation of four-dimensional heterotic superstrings with N =1 spacetime supersymmetry, we prove that the massless spectrum does not contain that transform as the adjoint representation of the gauge group. Some implications for model building are also discussed. We also show that no higher dimensional massless representations occur except possibly when the gauge group has an SU(9) or SO(16) factor. We discuss these two cases and their connection to the possible appearance of an E 8 factor.
121122277
Fermion masses and phenomenology in SO(10) or SU(5) superstring compactifications
Abstract Symmetry breaking patterns and phenomenology of the SO(10) and SU(5) compactifications of the E 8 ×E 8 ′ heterotic superstring recently proposed by Witten are examined with regard to the fermion mass matrix. Under some circumstances there exist constraints due to the presence of relatively light charged leptons.
123523374
Nonstandard fermion mass matrices and nucleon decay
We discuss how nonstandard fermion mass matrices (with hierarchical eigenvalues) lead to mixing effects in nucleon decay which can enhance the branching ratios of naively unexpected decay modes, and could suppress the rates for N..-->..e/sup +/+ nonstrange hadron(s).
120861006
PECCEI-QUINN SYMMETRIES WITHOUT DOMAINS
In general, the unbroken discrete subgroup of a Peccei-Quinn symmetry gives rise to a domain problem: the formation of unacceptable domain walls in the course of the evolution of the early universe. In this paper, we construct an SU(5) model in which the unbroken discrete subgroup of a Peccei-Quinn symmetry is a trivial Z/sub 1/. That means that there is no domain problem for this model. It is pointed out that in models with more than one global U(1) symmetry it is easy to achieve a solution to the domain problem.
85558805
Cosmological constraints on heavy weakly interacting fermions
Abstract The masses and lifetimes of very heavy weakly interacting fermions which appear in many grand unified gauge models are constrained by the requirement that their decays in the hot big bang early universe should not generate excessive entropy which would dilute n B / n γ below its observed value.
120357004
Neutral lepton mass matrix
Spinor particles are characterized by their transformation properties under the Lorentz group. (AIP)
118943918
Real-Time Detection of Gravitational Microlensing
Real-time detection of microlensing has moved from proof of concept in 1994 (Udalski et al. 1994a, Alcock et al.1994) to a steady stream of events this year. Global dissemination of these events by the MACHO and OGLE collaborations has made possible intensive photometric and spectroscopic follow up from widely dispersed sites confirming the microlensing hypothesis (Benetti 1995). Improved photometry and increased temporal resolution from follow up observations greatly increases the possibility of detecting deviations from the standard point-source, point-lens, inertial motion microlensing model. These deviations are crucial in understanding individual lensing systems by breaking the degeneracy between lens mass, position and velocity. We report here on GMAN (Global Microlensing Alert Network), the coordinated follow up of MACHO alerts.
118498735
Dust ejection from planetary bodies by temperature gradients: Laboratory experiments
Abstract Laboratory experiments show that dusty bodies in a gaseous environment eject dust particles if they are illuminated. We find that even more intense dust eruptions occur when the light source is turned off. We attribute this to a compression of gas by thermal creep in response to the changing temperature gradients in the top dust layers. The effect is studied at a light flux of 13 kW/m 2 and 1 mbar ambient pressure. The effect is applicable to protoplanetary disks and Mars. In the inner part of protoplanetary disks, planetesimals can be eroded especially at the terminator of a rotating body. This leads to the production of dust which can then be transported towards the disk edge or the outer disk regions. The generated dust might constitute a significant fraction of the warm dust observed in extrasolar protoplanetary disks. We estimate erosion rates of about 1 kg s −1 for 100 m parent bodies. The dust might also contribute to subsequent planetary growth in different locations or on existing protoplanets which are large enough not to be susceptible to particle loss by light induced ejection. Due to the ejections, planetesimals and smaller bodies will be accelerated or decelerated and drift outward or inward, respectively. The effect might also explain the entrainment of dust in dust devils on Mars, especially at high altitudes where gas drag alone might not be sufficient.