Physics of SNeIa and Cosmology

We give an overview of the current understanding of Type Ia supernovae relevant for their use as cosmological distance indicators. We present the physical basis to understand their homogeneity of the observed light curves and spectra and the observed correlations. This provides a robust method to determine the Hubble constant, 67 +- 8 (2 sigma) km/Mpc/sec, independently from primary distance indicators. We discuss the uncertainties and tests which include SNe Ia based distance determinations prior to delta-Ceph. measurements for the host galaxies. Based on detailed models, we study the small variations from homogeneities and their observable consequences. In combination with future data, this underlines the suitability and promises the refinements needed to determine accurate relative distances within 2 to 3 % and to use SNe Ia for high precision cosmology.Comment: to be published in "Stellar Candles", eds. Gieren et al. Lecture Notes in Physics (http://link.springer.de/series/lnpp

Single stage experimental evaluation of slotted rotor and stator blading. Part I - Analysis and design

Analysis and design of slotted rotor and stator blading for application to compressors in advanced airbreathing propulsion system

Strong Gravitational Lensing and Dark Energy Complementarity

In the search for the nature of dark energy most cosmological probes measure simple functions of the expansion rate. While powerful, these all involve roughly the same dependence on the dark energy equation of state parameters, with anticorrelation between its present value w_0 and time variation w_a. Quantities that have instead positive correlation and so a sensitivity direction largely orthogonal to, e.g., distance probes offer the hope of achieving tight constraints through complementarity. Such quantities are found in strong gravitational lensing observations of image separations and time delays. While degeneracy between cosmological parameters prevents full complementarity, strong lensing measurements to 1% accuracy can improve equation of state characterization by 15-50%. Next generation surveys should provide data on roughly 10^5 lens systems, though systematic errors will remain challenging.Comment: 7 pages, 5 figure

The time evolution of cosmological redshift as a test of dark energy

The variation of the expansion rate of the Universe with time produces an evolution in the cosmological redshift of distant sources (for example quasar Lyman-$\alpha$ absorption lines), that might be directly observed by future ultra stable, high-resolution spectrographs (such as CODEX) coupled to extremely large telescopes (such as European Southern Observatory's Extremely Large Telescope, ELT). This would open a new window to explore the physical mechanism responsible for the current acceleration of the Universe. We investigate the evolution of cosmological redshift from a variety of dark energy models, and compare it with simulated data. We perform a Fisher matrix analysis and discuss the prospects for constraining the parameters of these models and for discriminating among competing candidates. We find that, because of parameter degeneracies, and of the inherent technical difficulties involved in this kind of observations, the uncertainties on parameter reconstruction can be rather large unless strong external priors are assumed. However, the method could be a valuable complementary cosmological tool, and give important insights on the dynamics of dark energy, not obtainable using other probes.Comment: 9 pages, 2 figures. Matching published versio

The Effect of Repetitive Feedings on the Acceptability of Selected Metabolic Diets

Effect of repetitive feeding over extended periods of time on acceptability of selected metabolic diet

Competition between Pressure and Gravity Confinement in Lyman-Alpha Forest Observations

A break in the distribution function of Ly$\alpha$ clouds (at a typical redshift of $2.5$) has been reported by Petitjean et al. (1993). This feature is what would be expected from a transition between pressure confinement and gravity confinement (as predicted in Charlton, Salpeter, and Hogan (1993)). The column density at which the feature occurs has been used to determine the external confining pressure, $\sim 10 {\rm cm}^{-3} {\rm K}$, which could be due to a hot, intergalactic medium. For models that provide a good fit to the data, the contribution of the gas in clouds to $\Omega$ is small. The specific shape of the distribution function at the transition (predicted by models to have a non-monotonic slope) can serve as a diagnostic of the distribution of dark matter around Ly$\alpha$ forest clouds, and the present data already eliminate certain models.Comment: 10 pages plain TeX, 2 figures available upon request, submitted to ApJ Letters, PSU-jc-

Parametric resonance for antineutrino conversions using LSND best-fit results with a 3+1 flavor scheme

An analytical solution to a parametric resonance effect for antineutrinos in a 3+1 flavor (active+sterile) scheme using multiple non-adiabatic density shifts is presented. We derive the conditions for a full flavor conversion for antineutrino oscillations $\bar{\nu}_\alpha \to \bar{\nu}_s$ $(\alpha=e,\mu,\tau)$ under the assumption that LSND best-fits for the mixing parameters are valid in a short-baseline accelerator experiment. We show that the parametric resonance effect can be exploited to increase the effective antineutrino oscillation length by a factor of 10-40, thus sustaining a high oscillation probability for a much longer period of time than in the vacuum scenario. We propose a realistic experimental setup that could probe for this effect which leaves a signature in terms of a specific oscillation probability profile. Moreover, since the parametric resonance effect is valid in any 2 or 1+1 flavor approximation, our results could be suggestive for future short-baseline accelerator neutrino detection experiments.Comment: 6 pages, 4 figure

Surface-micromachined Ta–Si–N beams for use in micromechanics

Realization and characterization of free-standing surface-microstructures based on Ta-Si-N films are presented. Due to their significant physical and chemical properties, such ternary films are promising candidates for application in microelectromechanical devices

Exploring the Expanding Universe and Dark Energy using the Statefinder Diagnostic

The coming few years are likely to witness a dramatic increase in high quality Sn data as current surveys add more high redshift supernovae to their inventory and as newer and deeper supernova experiments become operational. Given the current variety in dark energy models and the expected improvement in observational data, an accurate and versatile diagnostic of dark energy is the need of the hour. This paper examines the Statefinder diagnostic in the light of the proposed SNAP satellite which is expected to observe about 2000 supernovae per year. We show that the Statefinder is versatile enough to differentiate between dark energy models as varied as the cosmological constant on the one hand, and quintessence, the Chaplygin gas and braneworld models, on the other. Using SNAP data, the Statefinder can distinguish a cosmological constant ($w=-1$) from quintessence models with $w \geq -0.9$ and Chaplygin gas models with $\kappa \leq 15$ at the $3\sigma$ level if the value of \om is known exactly. The Statefinder gives reasonable results even when the value of \om is known to only $\sim 20$ accuracy. In this case, marginalizing over \om and assuming a fiducial LCDM model allows us to rule out quintessence with $w \geq -0.85$ and the Chaplygin gas with $\kappa \leq 7$ (both at $3\sigma$). These constraints can be made even tighter if we use the Statefinders in conjunction with the deceleration parameter. The Statefinder is very sensitive to the total pressure exerted by all forms of matter and radiation in the universe. It can therefore differentiate between dark energy models at moderately high redshifts of z \lleq 10.Comment: 21 pages, 17 figures. Minor typos corrected to agree with version published in MNRAS. Results unchange

Evaluation of trends in derived snowfall and rainfall across Eurasia and linkages with discharge to the Arctic Ocean

To more fully understand the role of precipitation in observed increases in freshwater discharge to the Arctic Ocean, data from a new archive of bias-adjusted precipitation records for the former USSR (TD9813), along with the CRU and Willmott-Matsuura data sets, were examined for the period 1936–1999. Across the six largest Eurasian river basins, snowfall derived from TD9813 exhibits a strongly significant increase until the late 1950s and a moderately significant decrease thereafter. A strongly significant decline in derived rainfall is also noted. Spatially, snowfall increases are found primarily across north-central Eurasia, an area where the rainfall decreases are most prominent. Although no significant change is determined in Eurasian-basin snowfall over the entire 64 year period, we note that interpolation from early, uneven station networks causes an overestimation of spatial precipitation, and that the local snowfall trends determined from gridded TD9813 data are likely underestimated. Yet, numerous uncertainties in historical Arctic climate data and the sparse, irregular nature of Arctic station networks preclude a confident assessment of precipitation-discharge linkages during the period of reported discharge trends