Dark Matter Constraints in Heterotic M-Theory with Five-Brane Dominance

The phenomenological implications of the M-theory limit in which supersymmetry is broken by the auxiliary fields of five-brane moduli is investigated. Assuming that the lightest neutralino provides the dark matter in the universe, constraints on the sparticle spectrum are obtained. Direct detection rates for dark matter are estimated.Comment: 10 pages, LaTeX file plus 8 EPS figure

Modular Symmetries, Threshold Corrections And Moduli For Z2×Z2Z_2 \times Z_2 Orbifolds

${\bf Z}_2\times {\bf Z}_2$ Coxeter orbifolds are constructed with the property that some twisted sectors have fixed planes for which the six-torus can not be decomposed into a direct sum ${\bf T}^2\bigoplus{\bf T}^4$ with the fixed plane lying in ${\bf T}^2$. The string loop threshold corrections to the gauge coupling constants are derived, and display symmetry groups for the $T$ and $U$ moduli that are subgroups of the full modular group $PSL(2,Z)$. The effective potential for duality invariant gaugino condensate in the presence of hidden sector matter is constructed and minimized for the values of the moduli. The effect of Wilson lines on the modular symmetries is also studied.Comment: QMW--TH--94/18, 12 page

Sparticle Spectrum and Dark Matter in M-Theory

The phenomenological implications of the eleven dimensional limit of $M$-theory (strongly coupled $E_8\times E_8$) are investigated. In particular we calculate the supersymmetric spectrum subject to constraints of correct electroweak symmetry breaking and the requirement that the lighest supersymmetric particle provides the dark matter of the universe. The $B$-soft term associated with the generation of a $\mu$ term in the superpotential is calculated and its phenomenology is discussed.Comment: LaTeX file 15 pages,1 figure adde

Duality Symmetries in Orbifold Models

We derive the duality symmetries relevant to moduli dependent gauge coupling constant threshold corrections, in Coxeter ${\bf Z_N}$ orbifolds. We consider those orbifolds for which the point group leaves fixed a 2-dimensional sublattice $\Lambda_2$, of the six dimensional torus lattice $\Lambda_6$, where $\Lambda_6$ cannot be decomposed as $\Lambda_2 \bigoplus{\Lambda_4}.$Comment: 13 pages, QMW--TH--93/21, SUSX--TH--93/1

Sparticle spectrum in M-theory with five-brane dominance

The phenomenological implications of the M-theory limit in which supersymmetry is broken by the F-terms of five-brane moduli is investigated. In particular we calculate the supersymmetric spectrum subject to constraints of correct electroweak symmetry breaking. We find interesting differences especially in the squark sector compared with $M$-theory scenarios with standard embedding and weakly-coupled Calabi-Yau compactifications in the large $T$-limit.Comment: 12 pages, LaTeX 4 figures (EPS), typos fixed reference adde

Anisotropic Solutions For Orbifold Moduli From Duality Invariant Gaugino Condensates

The values of the $T$ and $U$ moduli are studied for those ${\bf Z}_N$ Coxeter orbifolds with the property that some of the twisted sectors have fixed planes for which the six-torus ${\bf T}^6$ can not be decomposed into a direct sum ${\bf T}^2\bigoplus {\bf T}^4$ with the fixed plane lying in ${\bf T}^2$. Such moduli in general transform under a subgroup of the modular group $SL(2,Z).$ The moduli are determined by minimizing the effective potential derived from a duality invariant gaugino condensate.Comment: QMW--TH--94/11, SUSX--TH--94/11, 16 page

Modular Symmetries in ZNZ_N Orbifold Compactified String Theories with Wilson lines

Target space modular symmetries relevant to string loop threshold corrections are studied for $Z_N$ orbifold compactified string theories containing Wilson line background fields.Comment: SUSX--TH--93/17, QMW--TH--93/31, 12 page

Orientation and solvatochromism of dyes in liquid crystals.

The orientation and solvatochromism of some dye molecules in a liquid crystal have been investigated. Interactions with the host and the structure of the dye molecule affect the macroscopic alignment of dichroic dye molecules in a liquid crystal: It was observed that some dye molecules show a large bathochromic shift of their absorption maxima in the liquid crystal host relative to the situation in isotropic solvents. It is suggested that this is due to the occurrence of a much weaker reaction field in the anisotropic, rigid host. These dye molecules show little or no apparent order in the anisotropic host despite the observation of a reduction in the electro optic switching time when the dye is present. The highest degree of macroscopic alignment was observed for a merocyanine compound, which showed the smallest solvatochromic shift in the liquid crystal host. These results are discussed in terms of the steric, dipolar and hydrogen bond interactions between the guest and the host