Evolution of Cosmological Perturbations in the Long Wavelength Limit

The relation between the long wavelength limit of solutions to the cosmological perturbation equations and the perturbations of solutions to the exactly homogeneous background equations is investigated for scalar perturbations on spatially flat cosmological models. It is shown that a homogeneous perturbation coincides with the long wavelength limit of some inhomogeneous perturbation only when the former satisfies an additional condition corresponding to the momentum constraint if the matter consists only of scalar fields. In contrast, no such constraint appears if the fundamental variables describing the matter contain a vector field as in the case of a fluid. Further, as a byproduct of this general analysis, it is shown that there exist two universal exact solutions to the perturbation equations in the long wavelength limit, which are expressed only in terms of the background quantities. They represent adiabatic growing and decaying modes, and correspond to the well-known exact solutions for perfect fluid systems and scalar field systems.Comment: 16 pages, no figure, submitted to PR

Homogeneity of Stellar Populations in Early-Type Galaxies with Different X-ray Properties

We have found the stellar populations of early-type galaxies are homogeneous with no significant difference in color or Mg2 index, despite the dichotomy between X-ray extended early-type galaxies and X-ray compact ones. Since the X-ray properties reflect the potential gravitational structure and hence the process of galaxy formation, the homogeneity of the stellar populations implies that the formation of stars in early-type galaxies predat es the epoch when the dichotomy of the potential structure was established.Comment: 6 pages, 5 figures, accepted for publication in Ap

Perturbative analysis of wave interactions in nonlinear systems

This work proposes a new way for handling obstacles to asymptotic integrability in perturbed nonlinear PDEs within the method of Normal Forms - NF - for the case of multi-wave solutions. Instead of including the whole obstacle in the NF, only its resonant part is included, and the remainder is assigned to the homological equation. This leaves the NF intergable and its solutons retain the character of the solutions of the unperturbed equation. We exploit the freedom in the expansion to construct canonical obstacles which are confined to te interaction region of the waves. Fo soliton solutions, e.g., in the KdV equation, the interaction region is a finite domain around the origin; the canonical obstacles then do not generate secular terms in the homological equation. When the interaction region is infifnite, or semi-infinite, e.g., in wave-front solutions of the Burgers equation, the obstacles may contain resonant terms. The obstacles generate waves of a new type, which cannot be written as functionals of the solutions of the NF. When an obstacle contributes a resonant term to the NF, this leads to a non-standard update of th wave velocity.Comment: 13 pages, including 6 figure

New X-ray Clusters in the EMSS II: Optical Properties

We present optical images for 9 new clusters of galaxies we have found in a reanalysis of the Einstein IPC images comprising the Extended Medium Sensitivity Survey (EMSS). Based on the presence of a red sequence of galaxies in a color-magnitude (CM) diagram, a redshift is estimated for each cluster. Galaxy overdensities (cluster richnesses) are measured in each field using the B_gc statistic which allows their plausible identification with the X-ray emission. The nature of our X-ray detection algorithm suggests that most of these clusters have low X-ray surface brightness (LSB) compared to the previously known EMSS clusters. We compare the optical and X-ray observations of these clusters with the well-studied Canadian Network for Observational Cosmology (CNOC) subsample of the EMSS, and conclude that the new clusters exhibit a similar range of optical richnesses, X-ray luminosities, and, somewhat surprisingly, galaxy populations as the predominantly rich, relaxed EMSS/CNOC clusters.Comment: Accepted to ApJ, 17 pages, 14 figures, uses emulateapj5.st

An Integrable Shallow Water Equation with Linear and Nonlinear Dispersion

We study a class of 1+1 quadratically nonlinear water wave equations that combines the linear dispersion of the Korteweg-deVries (KdV) equation with the nonlinear/nonlocal dispersion of the Camassa-Holm (CH) equation, yet still preserves integrability via the inverse scattering transform (IST) method. This IST-integrable class of equations contains both the KdV equation and the CH equation as limiting cases. It arises as the compatibility condition for a second order isospectral eigenvalue problem and a first order equation for the evolution of its eigenfunctions. This integrable equation is shown to be a shallow water wave equation derived by asymptotic expansion at one order higher approximation than KdV. We compare its traveling wave solutions to KdV solitons.Comment: 4 pages, no figure

Evolution of Cosmological Perturbations in the Universe dominated by Multiple Scalar Fields

By efforts of several authors, it is recently established that the dynamical behavior of the cosmological perturbation on superhorizon scales is well approximated in terms of that in the long wavelength limit, and the latter can be constructed from the evolution of corresponding exactly homogeneous universe. Using these facts, we investigate the evolution of the cosmological perturbation on superhorizon scales in the universe dominated by oscillating multiple scalar fields which are generally interacting with each other, and the ratio of whose masses is incommensurable. Since the scalar fields oscillate rapidly around the local minimum of the potential, we use the action angle variables. We found that this problem can be formulated as the canonical perturbation theory in which the perturbed part appearing as the result of the expansion of the universe and the interaction of the scalar fields is bounded by the negative power ot time. We show that by constructing the canonical transformations properly, the transformed hamiltonian becomes simple enough to be solved. As the result of the invetigation using the long wavelength limit and the canonical perturbation theory, under the sufficiently general conditions, we prove that for the adiabatic growing mode the Bardeen parameter stays constant and that for all the other modes the Bardeen parameter decays. From the viewpoint of the ergodic theory, it is discussed that as for the Bardeen parameter, the sigularities appear probabilistically. This analysis serves the understanding of the evolution of the cosmological perturbations on superhorizon scales during reheating.Comment: 31 Pages; Latex, No figure

Effects of Ram-Pressure from Intracluster Medium on the Star Formation Rate of Disk Galaxies in Clusters of Galaxies

Using a simple model of molecular cloud evolution, we have quantitatively estimated the change of star formation rate (SFR) of a disk galaxy falling radially into the potential well of a cluster of galaxies. The SFR is affected by the ram-pressure from the intracluster medium (ICM). As the galaxy approaches the cluster center, the SFR increases to twice the initial value, at most, in a cluster with high gas density and deep potential well, or with a central pressure of $\sim 10^{-2} cm^{-3} keV$ because the ram-pressure compresses the molecular gas of the galaxy. However, this increase does not affect the color of the galaxy significantly. Further into the central region of the cluster ($\lesssim 1$ Mpc from the center), the SFR of the disk component drops rapidly due to the effect of ram-pressure stripping. This makes the color of the galaxy redder and makes the disk dark. These effects may explain the observed color, morphology distribution and evolution of galaxies in high-redshift clusters. By contrast, in a cluster with low gas density and shallow potential well, or the central pressure of $\sim 10^{-3} cm^{-3} keV$, the SFR of a radially infalling galaxy changes less significantly, because neither ram-pressure compression nor stripping is effective. Therefore, the color of galaxies in poor clusters is as blue as that of field galaxies, if other environmental effects such as galaxy-galaxy interaction are not effective. The predictions of the model are compared with observations.Comment: 19 pages, 9 figures, to appear in Ap

KP line solitons and Tamari lattices

The KP-II equation possesses a class of line soliton solutions which can be qualitatively described via a tropical approximation as a chain of rooted binary trees, except at "critical" events where a transition to a different rooted binary tree takes place. We prove that these correspond to maximal chains in Tamari lattices (which are poset structures on associahedra). We further derive results that allow to compute details of the evolution, including the critical events. Moreover, we present some insights into the structure of the more general line soliton solutions. All this yields a characterization of possible evolutions of line soliton patterns on a shallow fluid surface (provided that the KP-II approximation applies).Comment: 49 pages, 36 figures, second version: section 4 expande

Results from the EPL monkey-pod flight experiments conducted aboard the NASA/Ames CV-990, May 1976

The participation of the Environmental Physiology Laboratory (EPL) in the general purpose laboratory concept verification test 3 is documented. The EPL Monkey-Pod Experiment was designed to incorporate a 10-12 kg, pig tailed monkey, Macaca nemestrina, into the pod and measure the physiological responses of the animal continously. Four major elements comprise the EPL Monkey-Pod Experiment System: (1) a fiberglass pod containing the instrumented monkey plus feeder and watering devices, (2) an inner console containing the SKYLAB mass spectrometer with its associated valving and electronic controls, sensing, control and monitoring units for lower body negative pressure, feeder activity, waterer activity, temperatures, and gas metabolism calibration, (3) an umbilical complex comprising gas flow lines and electrical cabling between the inner and outer console and (4) an outer console in principle representing the experiment support to be provided from general space craft sources

Results from the EPL monkey-pod experiment conducted as part of the 1974 NASA-Ames CVT/GPL 3

For abstract, see vol. 2