A Preliminary Look at the Physics Reach of a Solar Neutrino TPC: Time-Independent Two Neutrino Oscillations

This paper will discuss the physics reach of a solar neutrino TPC containing many tons of He4 under high pressure. Particular attention is given to the LMA and SMA solutions, which are allowed by current data, and which are characterized by a lack of time-dependent phenomena (either summer-winter or day-night asymmetries). In this case, the physics of neutrino masses and mixing is all contained in the energy dependence of the electron neutrino survival probability, (or in its reciprocal, the electron neutrino disappearance probability).Comment: 19 pages, 12 figure

Comment on ``Solidification of a Supercooled Liquid in a Narrow Channel''

Comment on PRL v. 86, p. 5084 (2001) [cond-mat/0101016]. We point out that the authors' simulations are consistent with the known theory of steady-state solutions in this system

Precision Measurement of the 29Si, 33S, and 36Cl Binding Energies

The binding energies of 29Si, 33S, and 36Cl have been measured with a relative uncertainty $< 0.59 \times 10^{-6}$ using a flat-crystal spectrometer. The unique features of these measurements are 1) nearly perfect crystals whose lattice spacing is known in meters, 2) a highly precise angle scale that is derived from first principles, and 3) a gamma-ray measurement facility that is coupled to a high flux reactor with near-core source capability. The binding energy is obtained by measuring all gamma-rays in a cascade scheme connecting the capture and ground states. The measurements require the extension of precision flat-crystal diffraction techniques to the 5 to 6 MeV energy region, a significant precision measurement challenge. The binding energies determined from these gamma-ray measurements are consistent with recent highly accurate atomic mass measurements within a relative uncertainty of $4.3 \times 10^{-7}$. The gamma-ray measurement uncertainties are the dominant contributors to the uncertainty of this consistency test. The measured gamma-ray energies are in agreement with earlier precision gamma-ray measurements.Comment: 13 pages, 4 figure

Viscous fingering in liquid crystals: Anisotropy and morphological transitions

We show that a minimal model for viscous fingering with a nematic liquid crystal in which anisotropy is considered to enter through two different viscosities in two perpendicular directions can be mapped to a two-fold anisotropy in the surface tension. We numerically integrate the dynamics of the resulting problem with the phase-field approach to find and characterize a transition between tip-splitting and side-branching as a function of both anisotropy and dimensionless surface tension. This anisotropy dependence could explain the experimentally observed (reentrant) transition as temperature and applied pressure are varied. Our observations are also consistent with previous experimental evidence in viscous fingering within an etched cell and simulations of solidification.Comment: 12 pages, 3 figures. Submitted to PR

OH rotational lines as a diagnostic of the warm neutral gas in galaxies

We present Infrared Space Observatory (ISO) observations of several OH, CH and H2O rotational lines toward the bright infrared galaxies NGC253 and NGC1068. As found in the Galactic clouds in SgrB2 and Orion, the extragalactic far-IR OH lines change from absorption to emission depending on the physical conditions and distribution of gas and dust along the line of sight. As a result, most of the OH rotational lines that appear in absorption toward NGC253 are observed in emission toward NGC1068. We show that the far-IR spectrum of OH can be used as a powerful diagnostic to derive the physical conditions of extragalactic neutral gas. In particular, we find that a warm (Tk~150 K, n(H2)< 5 10^4 cm^-3) component of molecular gas with an OH abundance of 10^{-7} from the inner <15'' can qualitatively reproduce the OH lines toward NGC253. Similar temperatures but higher densities (5 10^5 cm^-3) are required to explain the OH emission in NGC1068.Comment: 5 pages, 4 figures, accepted in ApJ Part I (2004, October 6

Aggregation Patterns in Stressed Bacteria

We study the formation of spot patterns seen in a variety of bacterial species when the bacteria are subjected to oxidative stress due to hazardous byproducts of respiration. Our approach consists of coupling the cell density field to a chemoattractant concentration as well as to nutrient and waste fields. The latter serves as a triggering field for emission of chemoattractant. Important elements in the proposed model include the propagation of a front of motile bacteria radially outward form an initial site, a Turing instability of the uniformly dense state and a reduction of motility for cells sufficiently far behind the front. The wide variety of patterns seen in the experiments is explained as being due the variation of the details of the initiation of the chemoattractant emission as well as the transition to a non-motile phase.Comment: 4 pages, REVTeX with 4 postscript figures (uuencoded) Figures 1a and 1b are available from the authors; paper submitted to PRL

Continuum and CO/HCO+ Emission from the Disk Around the T Tauri Star LkCa 15

We present OVRO Millimeter Array lambda = 3.4 - 1.2 mm dust continuum and spectral line observations of the accretion disk encircling the T Tauri star LkCa 15. The 1.2 mm dust continuum emission is resolved, and gives a minimum diameter of 190 AU and an inclination angle of 57+/-5 degrees. There is a noticeable, but at present poorly constrained, decrease in the continuum spectral slope with frequency that may result from the coupled processes of grain growth and dust settling. Imaging of the fairly intense emission from the lowest rotational transitions of CO, 13CO and HCO+ reveals a rotating disk and emission extends to 750 AU and the characteristic radius of the disk is determined to be around 425 AU (HWHM) based on model fits to the CO velocity field. The disk mass derived from the CO isotopologues with ``typical'' dense cloud abundances is still nearly two orders of magnitude less than that inferred from the dust emission, which is probably due to extensive molecular depletion in the cold, dense disk midplane. N2H+ 1-0 emission has also been detected which, along with HCO+, sets a lower limit to the fractional ionization of 10^{-8} in the near-surface regions of protoplanetary disks. This first detection of N2H+ in circumstellar disks has also made possible a determination of the N2/CO ratio (~2) that is at least an order of magnitude larger than those in the envelopes of young stellar objects and dense clouds. The large N2/CO ratio indicates that our observations probe disk layers in which CO is depleted but some N2 remains in the gas phase. Such differential depletion can lead to large variations in the fractional ionization with height in the outer reaches of circumstellar disks, and may help to explain the relative nitrogen deficiency observed in comets.Comment: Submitted to ApJ, 28 pages, 7 figure

BEAMS: separating the wheat from the chaff in supernova analysis

We introduce Bayesian Estimation Applied to Multiple Species (BEAMS), an algorithm designed to deal with parameter estimation when using contaminated data. We present the algorithm and demonstrate how it works with the help of a Gaussian simulation. We then apply it to supernova data from the Sloan Digital Sky Survey (SDSS), showing how the resulting confidence contours of the cosmological parameters shrink significantly.Comment: 23 pages, 9 figures. Chapter 4 in "Astrostatistical Challenges for the New Astronomy" (Joseph M. Hilbe, ed., Springer, New York, forthcoming in 2012), the inaugural volume for the Springer Series in Astrostatistic

Detection of Far-Infrared Water Vapor, Hydroxyl, and Carbon Monoxide Emissions from the Supernova Remnant 3C 391

We report the detection of shock-excited far-infrared emission of H2O, OH, and CO from the supernova remnant 3C 391, using the ISO Long-Wavelength Spectrometer. This is the first detection of thermal H2O and OH emission from a supernova remnant. For two other remnants, W~28 and W~44, CO emission was detected but OH was only detected in absorption. The observed H2O and OH emission lines arise from levels within ~400 K of the ground state, consistent with collisional excitation in warm, dense gas created after the passage of the shock front through the dense clumps in the pre-shock cloud. The post-shock gas we observe has a density ~2x10^5 cm^{-3} and temperature 100-1000 K, and the relative abundances of CO:OH:H2O in the emitting region are 100:1:7 for a temperature of 200 K. The presence of a significant column of warm H2O suggests that the chemistry has been significantly changed by the shock. The existence of significant column densities of both OH and H2O, which is at odds with models for non-dissociative shocks into dense gas, could be due to photodissociation of H2O or a mix of fast and slow shocks through regions with different pre-shock density.Comment: AASTeX manuscript and 4 postscript figure

Microscopic Selection of Fluid Fingering Pattern

We study the issue of the selection of viscous fingering patterns in the limit of small surface tension. Through detailed simulations of anisotropic fingering, we demonstrate conclusively that no selection independent of the small-scale cutoff (macroscopic selection) occurs in this system. Rather, the small-scale cutoff completely controls the pattern, even on short time scales, in accord with the theory of microscopic solvability. We demonstrate that ordered patterns are dynamically selected only for not too small surface tensions. For extremely small surface tensions, the system exhibits chaotic behavior and no regular pattern is realized.Comment: 6 pages, 5 figure