New Minimal Extension of MSSM

We construct a new minimal extension of the Minimal Supersymmetric Standard Model (MSSM) by promoting the $\mu$-parameter to a singlet superfield. The resulting renormalizable superpotential is enforced by a $\mathcal{Z}_5$ $R$-symmetry which is imposed on the non-renormalizable operators as well. The proposed model provides a natural solution to the $\mu$-problem and is free from phenomenological and cosmological problems.Comment: 5 page

Quasi-Fixed Points and Charge and Colour Breaking in Low Scale Models

We show that the current LEP2 lower bound upon the minimal supersymmetric standard model (MSSM) lightest Higgs mass rules out quasi-fixed scenarios for string scales between 10^6 and 10^{11} GeV unless the heaviest stop mass is more than 2 TeV. We consider the implications of the low string scale for charge and colour breaking (CCB) bounds in the MSSM, and demonstrate that CCB bounds from F and D-flat directions are significantly weakened. For scales less than 10^{10} GeV these bounds become merely that degenerate scalar mass squared values are positive at the string scale.Comment: 17 pages, 4 figures. Replacement has added discussion on errors due to alpha_s(MZ) errors, as well as deviations from the quasi-fixed point. Text has been clarifie

On the "initial" Angular Momentum of Galaxies

Spherical density profiles and specific angular momentum profiles of Dark Matter halos found in cosmological N-body simulations have been measured extensively. The distribution of the total angular momentum of dark matter halos is also used routinely in semi-analytic modeling of the formation of disk galaxies. However, it is unclear whether the initial (i.e. at the time the halo is assembled) angular momentum distributions of baryons is related to the dark matter at all. Theoretical models for ellipticities in weak lensing studies often rely on an assumed correlation of the angular momentum vectors of dark matter and gas in galaxies. Both of these assumptions are shown to be in reasonable agreement with high resolution cosmological smoothed particle hydrodynamical simulations that follow the dark matter as long as only adiabatic gas physics are included. However, we argue that in more realistic models of galaxy formation one expects pressure forces to play a significant role at turn--around. Consequently the torquing force on DM and baryons will be uncorrelated and their respective angular momenta are not expected to align. An SPH simulation with ad-hoc feedback is presented that illustrates these effects. Massive low redshift elliptical galaxies may be a notable exception where "light may trace mass".Comment: 4 latex pages (uses sprocl.sty), 1 eps figure. To appear in the proceedings of "The Shapes of Galaxies and Their Halos", Yale, May 200

Status of two studies on active control of aeroelastic response

The application of active control technology to the suppression of flutter has been successfully demonstrated during two recent studies in the Langley transonic dynamics tunnel. The first study involved the implementation of an aerodynamic-energy criterion, using both leading- and trailing-edge controls, to suppress flutter of a simplified delta-wing model. Use of this technique has resulted in an increase in the flutter dynamic pressure of approximately 12 percent for this model at a Mach number of 0.9 Analytical methods used to predict the open- and closed-loop behavior of the model are also discussed. The second study, was conducted to establish the effect of active flutter suppression on a model of the Boeing B-52 Control Configured Vehicle (CCV). Some preliminary results of this study indicate significant improvements in the damping associated with the critical flutter mode

Experimental Flow Models for SSME Flowfield Characterization

Full scale flow models with extensive instrumentation were designed and manufactured to provide data necessary for flow field characterization in rocket engines of the Space Shuttle Main Engine (SSME) type. These models include accurate flow path geometries from the pre-burner outlet through the throat of the main combustion chamber. The turbines are simulated with static models designed to provide the correct pressure drop and swirl for specific power levels. The correct turbopump-hot gas manifold interfaces were designed into the flow models to permit parametric/integration studies for new turbine designs. These experimental flow models provide a vehicle for understanding the fluid dynamics associated with specific engine issues and also fill the more general need for establishing a more detailed fluid dynamic base to support development and verification of advanced math models