Special Geometry and Twisted Moduli in Orbifold Theories with Continuous Wilson Lines

Target space duality symmetries, which acts on K\"ahler and continuous Wilson line moduli, of a ${\bf Z}_N$ ($N\not=2$) 2-dimensional subspace of the moduli space of orbifold compactification are modified to include twisted moduli. These spaces described by the cosets $SU(n,1)\over SU(n)\times U(1)$ are $special$ K\"ahler, a fact which is exploited in deriving the extension of tree level duality transformation to include higher orders of the twisted moduli. Also, restrictions on these higher order terms are derived.Comment: 13 page

Strings And Dyonic Plasmas

Recently Olesen has shown the existence of dual string solutions to the equations of ideal Magnetohydrodynamics that describe the long wavelength properties of electrically charged plasmas. Here, we extend these solutions to include the case of plasmas consisting of point like dyons, which carry both electric and magnetic charge. Such strings are dyonic in that they consist of both magnetic and electric flux. We contrast some physical features of dyonic plasmas with those of the purely electric or magnetic type, particularly in relation to the validity of the ideal approximation.Comment: 11 pages, LaTeX, no figure

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

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

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

Black Holes and Flop Transitions in M-Theory on Calabi-Yau Threefolds

We present fivedimensional extreme black hole solutions of M-theory compactified on Calabi-Yau threefolds and study these solutions in the context of flop transitions in the extended Kahler cone. In particular we consider a specific model and present black hole solutions, breaking half of N=2 supersymmetry, in two regions of the extended Kahler cone, which are connected by a flop transition. The conditions necessary to match both solutions at the flop transition are analysed. Finally we also discuss the conditions to obtain massless black holes at the flop transition.Comment: 19 pp, LaTe

General Static N=2 Black Holes

We find general static BPS black hole solutions for general N=2, d=4 supergravity theories with an arbitrary number of vector multiplets. These solutions are completely specified by the K\"ahler potential of the underlying special K\"ahler geometry and a set of constrained harmonic functions.Comment: Latex, 7 pages, typos corrected, version to appear in MPL

Geant4 Predictions of Energy Spectra in Typical Space Radiation Environment

Accurate knowledge of energy spectra inside spacecraft is important for protecting astronauts as well as sensitive electronics from the harmful effects of space radiation. Such knowledge allows one to confidently map the radiation environment inside the vehicle. The purpose of this talk is to present preliminary calculations for energy spectra inside a spherical shell shielding and behind a slab in typical space radiation environment using the 3D Monte-Carlo transport code Geant4. We have simulated proton and iron isotropic sources and beams impinging on Aluminum and Gallium arsenide (GaAs) targets at energies of 0.2, 0.6, 1, and 10 GeV/u. If time permits, other radiation sources and beams (_, C, O) and targets (C, Si, Ge, water) will be presented. The results are compared to ground-based measurements where available