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).
121480751
Fractional charges, monopoles, and peculiar photons
A grand unified model is proposed which incorporates a ''peculiar'' photon in addition to the familiar photon. The model is constructed to reconcile the possible observations of fractional charges and monopoles. One way to have the weak-mixing-angle prediction agree with the phenomenological value is to require the peculiar photon to couple more strongly than the regular photon.
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.
121161161
String model building in the free fermionic formulation
Abstract We consider the rules for string model building in the free fermionic formalism. Valid spin-structures on the string world-sheet correspond to automorphisms of the Lie algebra of the world-sheet supercharge. After reviewing and clarifying the model building rules we classify all such automorphisms. We then classify the mutually commuting sets of such automorphisms that are needed for model building. Finally we show how to construct all models with N = 4, N = 2, or N = 1 space-time supersymmetry. In four dimensional models, N = 1 space-time supersymmetry can only be achieved if the Lie algebra of the world-sheet supercharge is SU(2) 6 .
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.