Simulations of dual morphology in spiral galaxies

Gas and stars in spiral galaxies are modelled with the DUAL code, using hydrodynamic and N-body techniques. The simulations reveal morphological differences mirroring the dual morphologies seen in B and K' band observations of many spiral galaxies. In particular, the gaseous images are more flocculent with lower pitch angles than the stellar images, and the stellar arm-interarm contrast correlates with the degree of morphological decoupling.Comment: 4 pages, 4 figures, to appear in Disk of Galaxies: Kinematics, Dynamics and Perturbations, ASP Conf. Series, 200

New optical and radio frequency angular tropospheric refraction models for deep space applications

The development of angular tropospheric refraction models for optical and radio frequency usage is presented. The models are compact analytic functions, finite over the entire domain of elevation angle, and accurate over large ranges of pressure, temperature, and relative humidity. Additionally, FORTRAN subroutines for each of the models are included

On the Creation of the Universe out of Nothing

We explain how the Universe was created with no expenditure of energy or initial mass.Comment: To be presented at IWARA 2009 (4th International Workshop on Astronomy and Relativistic Astrophysics), to be held in Brazil, October 200

Relaxation and Zeno effect in qubit measurements

We consider a qubit interacting with its environment and continuously monitored by a detector represented by a point contact. Bloch-type equations describing the entire system of the qubit, the environment and the detector are derived. Using these equations we evaluate the detector current and its noise spectrum in terms of the decoherence and relaxation rates of the qubit. Simple expressions are obtained that show how these quantities can be accurately measured. We demonstrate that due to interaction with the environment, the measurement can never localize a qubit even for infinite decoherence rate.Comment: some clarifications added, to appear in Phys. Rev. Let

Dispersion management using betatron resonances in an ultracold-atom storage ring

Specific velocities of particles circulating in a storage ring can lead to betatron resonances at which static perturbations of the particles' orbit yield large transverse (betatron) oscillations. We have observed betatron resonances in an ultracold-atom storage ring by direct observation of betatron motion. These resonances caused a near-elimination of the longitudinal dispersion of atomic beams propagating at resonant velocities, an effect which can improve the performance of atom interferometric devices. Both the resonant velocities and the strength of the resonances were varied by deliberate modifications to the storage ring.Comment: 4 pages, 5 figures. Also available at http://physics.berkeley.edu/research/ultracol

Corporate Social Performance and Economic Cycles

Do firms respond to changes in economic growth by altering their corporate social responsibility programs? If they do respond, are their responses simply neglect of areas associated with corporate social performance (CSP) or do they also cut back on positive programs such as profit sharing, public/private housing programs, or charitable contributions? In this paper we argue that because CSP-related actions and programs tend to be discretionary, they are likely to receive less attention during tough economic times, a result of cost-cutting efforts. However, the various CSP performance areas vary in terms of their resource requirements and their influence on financial performance (short- and long-term), which suggests that firms may respond differently depending on area. Consequently, in addition to examining CSP concerns separately from positive actions and programs (CSP strengths), we also examine the influence of economic growth across the five areas of diversity, employee relations, the environment, product quality/safety, and the community. Based on data from 837 firms over fifteen years, our results suggest that firms neglect some areas associated with CSP during economic downturns, resulting in increased concerns about community and employee relations, product safety/quality, and the environment. However, this relationship does not apply to positive actions and programs. Instead, firms tend to increase their positive CSP programs in areas such as diversity, employee relations, and the environment during periods of slow economic growth and reduce them when the economy picks up. We offer potential explanations for our findings and discuss their importance to research on CSP

Dynamical Stability and Quantum Chaos of Ions in a Linear Trap

The realization of a paradigm chaotic system, namely the harmonically driven oscillator, in the quantum domain using cold trapped ions driven by lasers is theoretically investigated. The simplest characteristics of regular and chaotic dynamics are calculated. The possibilities of experimental realization are discussed.Comment: 24 pages, 17 figures, submitted to Phys. Rev

Sub Shot-Noise Phase Sensitivity with a Bose-Einstein Condensate Mach-Zehnder Interferometer

Bose Einstein Condensates, with their coherence properties, have attracted wide interest for their possible application to ultra precise interferometry and ultra weak force sensors. Since condensates, unlike photons, are interacting, they may permit the realization of specific quantum states needed as input of an interferometer to approach the Heisenberg limit, the supposed lower bound to precision phase measurements. To this end, we study the sensitivity to external weak perturbations of a representative matter-wave Mach-Zehnder interferometer whose input are two Bose-Einstein condensates created by splitting a single condensate in two parts. The interferometric phase sensitivity depends on the specific quantum state created with the two condensates, and, therefore, on the time scale of the splitting process. We identify three different regimes, characterized by a phase sensitivity $\Delta \theta$ scaling with the total number of condensate particles $N$ as i) the standard quantum limit $\Delta \theta \sim 1/N^{1/2}$, ii) the sub shot-noise $\Delta \theta \sim 1/N^{3/4}$ and the iii) the Heisenberg limit $\Delta \theta \sim 1/N$. However, in a realistic dynamical BEC splitting, the 1/N limit requires a long adiabaticity time scale, which is hardly reachable experimentally. On the other hand, the sub shot-noise sensitivity $\Delta \theta \sim 1/N^{3/4}$ can be reached in a realistic experimental setting. We also show that the $1/N^{3/4}$ scaling is a rigorous upper bound in the limit $N \to \infty$, while keeping constant all different parameters of the bosonic Mach-Zehnder interferometer.Comment: 4 figure