Topological invariants for spin-orbit coupled superconductor nanowires

We show that a spin-orbit coupled semiconductor nanowire with Zeeman splitting and s-wave superconductivity is in symmetry class BDI (not D as is commonly thought) of the topological classification of band Hamiltonians. The class BDI allows for an integer Z topological invariant equal to the number of Majorana fermion (MF) modes at each end of the quantum wire protected by the chirality symmetry (reality of the Hamiltonian). Thus it is possible for this system (and all other d=1 models related to it by symmetry) to have an arbitrary integer number, not just 0 or 1 as is commonly assumed, of MFs localized at each end of the wire. The integer counting the number of MFs at each end reduces to 0 or 1, and the class BDI reduces to D, in the presence of terms in the Hamiltonian that break the chirality symmetry.Comment: 4+ pages, no figure

JT9D jet engine performance deterioration

The analytical techniques utilized to examine the effects of flight loads and engine operating conditions on performance deterioration are presented. The role of gyroscopic, gravitational, and aerodynamic loads are shown along with the effect of variations in engine build clearances. These analytical results are compared to engine test data along with the correlation between analytically predicted and measured clearances and rub patterns. Conclusions are drawn and important issues are discussed

Disentangling Dark Matter Dynamics with Directional Detection

Inelastic dark matter reconciles the DAMA anomaly with other null direct detection experiments and points to a non-minimal structure in the dark matter sector. In addition to the dominant inelastic interaction, dark matter scattering may have a subdominant elastic component. If these elastic interactions are suppressed at low momentum transfer, they will have similar nuclear recoil spectra to inelastic scattering events. While upcoming direct detection experiments will see strong signals from such models, they may not be able to unambiguously determine the presence of the subdominant elastic scattering from the recoil spectra alone. We show that directional detection experiments can separate elastic and inelastic scattering events and discover the underlying dynamics of dark matter models.Comment: 7 pages, 5 figures, references and figures update

Phenomenology of Electroweak Symmetry Breaking from Theory Space

Recently, a new class of realistic models for electroweak symmetry breaking have been constructed, without supersymmetry. These theories have naturally light Higgs bosons and perturbative new physics at the TeV scale. We describe these models in detail, and show that electroweak symmetry breaking can be triggered by a large top quark Yukawa coupling. A rich spectrum of particles is predicted, with a pair of light Higgs doublets accompanied by new light weak triplet and singlet scalars. The lightest of these new scalars is charged under a geometric discrete symmetry and is therefore stable, providing a new candidate for WIMP dark matter. At TeV energies, a plethora of new heavy scalars, gauge bosons and fermions are revealed, with distinctive quantum numbers and decay modes.Comment: 22 pages, latex, 6 figures. Numerical results corrected, clarifications added, conclusions unchange

High Resolution Rapid Response observations of compact radio sources with the Ceduna Hobart Interferometer (CHI)

Context. Frequent, simultaneous observations across the electromagnetic spectrum are essential to the study of a range of astrophysical phenomena including Active Galactic Nuclei. A key tool of such studies is the ability to observe an object when it flares i.e. exhibits a rapid and significant increase in its flux density. Aims. We describe the specific observational procedures and the calibration techniques that have been developed and tested to create a single baseline radio interferometer that can rapidly observe a flaring object. This is the only facility that is dedicated to rapid high resolution radio observations of an object south of -30 degrees declination. An immediate application is to provide rapid contemporaneous radio coverage of AGN flaring at {\gamma}-ray frequencies detected by the Fermi Gamma-ray Space Telescope. Methods. A single baseline interferometer was formed with radio telescopes in Hobart, Tasmania and Ceduna, South Australia. A software correlator was set up at the University of Tasmania to correlate these data. Results. Measurements of the flux densities of flaring objects can be made using our observing strategy within half an hour of a triggering event. These observations can be calibrated with amplitude errors better than 15%. Lower limits to the brightness temperatures of the sources can also be calculated using CHI.Comment: 6 pages, 6 figures, 1 table. Accepted for publication in A&

An integrated approach to rotorcraft human factors research

As the potential of civil and military helicopters has increased, more complex and demanding missions in increasingly hostile environments have been required. Users, designers, and manufacturers have an urgent need for information about human behavior and function to create systems that take advantage of human capabilities, without overloading them. Because there is a large gap between what is known about human behavior and the information needed to predict pilot workload and performance in the complex missions projected for pilots of advanced helicopters, Army and NASA scientists are actively engaged in Human Factors Research at Ames. The research ranges from laboratory experiments to computational modeling, simulation evaluation, and inflight testing. Information obtained in highly controlled but simpler environments generates predictions which can be tested in more realistic situations. These results are used, in turn, to refine theoretical models, provide the focus for subsequent research, and ensure operational relevance, while maintaining predictive advantages. The advantages and disadvantages of each type of research are described along with examples of experimental results

Infrared photometry, bolometric luminosities, and effective temperatures for giant stars in 26 globular clusters

Infrared observations of 307 giant stars in 26 globular clusters are presented. The effects of H_2O absorption on the infrared colors are examined. The color-color correlations and color-magnitude diagrams, derived using an internally consistent set of distance moduli and reddenings, identify specific clusters with problematical reddenings or low quality optical data. The mean behavior of the color-color relationships is, in all cases, in good agreement with our earlier work

Globular cluster giant branches and the metallicity scale

Using the data base of Frogel, Persson, and Cohen and our earlier work, we derive characteristic parameters that describe the systematic behavior of the giants in each of 33 globular clusters. The globular cluster giant branches form a strictly homologous sequence in the H-R diagram, and their ordering correlates well with the metallicity scale published by Zinn. Nevertheless, when the giant branch parameters are used to define a metallicity ranking scheme, it appears that the Zinn abundance scale systematically underestimates the metallicity of clusters with exceptionally blue horizontal branches. The observed luminosities of the brightest giant in each cluster agree with the theoretical core helium flash luminosity; the small dispersion of these luminosities implies that at a given metallicity the intrinsic scatter in the absolute magnitude of horizontal-branch stars is less than 0.1 mag. The mean CO index increases as metallicity increases; analysis of the residuals from the mean relationships both of CO and of horizontal-branch type against metallicity imply that the CO abundance is unrelated to the second parameter problem. All metal-rich clusters with an adequate sample of stars show a spread in CO within each cluster comparable to that seen in 47 Tuc. Metal-poor clusters which exhibit a large star to star spread in CO are NGC 362, 2808, and 6656. The integrated light measurements of (V - K)_0 and CO published by Aaronson and colleagues correlate with the cluster parameters determined from measurements of individual stars in a manner that can be predicted from stellar evolutionary calculations for old populations. The integrated light of such old systems, at least from V to K, is therefore well understood

Photometric studies of composite stellar systems. IV - Infrared photometry of globular clusters in M31 and a comparison with early-type galaxies

The results of an infrared photometric investigation of 40 globular clusters in and around M31 are presented. The (V - K)_0 colors of the M31 globulars are tightly correlated with other broadband colors and with reddening-free metallicity parameters derived from optical spectrophotometry by Searle. Over a range of ˜1.2 mag in (V - K)_0, the scatter is consistent with observational error. Thus the 0.3-2.2 μm energy distributions are uniquely predicted by the metallicity and vice versa. A comparison of the (V - K)0 colors with those of galactic globulars allows an independent derivation of the metallicities of individual M31 globulars. The broad-band infrared data are compared with predictions from integrated light models based on the Ciardullo and Demarque isochrones. The agreement is quite good for models with an initial mass function of slope ≲ the Salpeter value independent of metallicity, thus ruling out the possibility that a late-type dwarf component is making a significant contribution to the infrared light. CO and H_2O indices measured for eight and seven of the clusters, respectively, give the same result. Early-type galaxies are seen to have much redder broad-band colors and stronger CO and H_2O indices than the most metal-rich M31 or galactic globular observed. Compared to the reddest globular clusters, at a given (U - V)_0 early-type galaxies are on average 0.3 mag redder in (V - K)_0. Although the stellar synthesis models reproduce cluster broad-band colors reasonably well, they do not reproduce the U - V/ V - K distribution of early-type galaxies. We propose that the early-type galaxies contain a population of cool luminous stars present neither in the clusters nor in the stellar synthesis models. One candidate for this population is a giant branch of stars considerably more metal rich than the Sun. More interesting is the possibility that there is a contribution to the integrated infrared light from asymptotic giant-branch stars above the first red giant tip. Such stars could be of intermediate age. The luminosity functions for the M31 and the galactic globulars are examined with the aid of models to investigate the possibility that metal-enhanced star formation or variations in the initial mass function can be detected in integrated light. Two appendices present new infrared data for a faint dE galaxy in the Virgo cluster, and a recalibration of the integrated light models presented by Aaron son et al.