39,782 research outputs found

### The Supernova Legacy Survey 3-year sample: Type Ia supernovae photometric distances and cosmological constraints

Aims. We present photometric properties and distance measurements of 252 high redshift Type Ia supernovae (0.15 < z < 1.1)
discovered during the first three years of the Supernova Legacy Survey (SNLS). These events were detected and their multi-colour
light curves measured using the MegaPrime/MegaCam instrument at the Canada-France-Hawaii Telescope (CFHT), by repeatedly
imaging four one-square degree fields in four bands. Follow-up spectroscopy was performed at the VLT, Gemini and Keck telescopes
to confirm the nature of the supernovae and to measure their redshifts.
Methods. Systematic uncertainties arising from light curve modeling are studied, making use of two techniques to derive the peak
magnitude, shape and colour of the supernovae, and taking advantage of a precise calibration of the SNLS fields.
Results. A flat ΛCDM cosmological fit to 231 SNLS high redshift type Ia supernovae alone gives Ω_M = 0.211 ± 0.034(stat) ±
0.069(sys). The dominant systematic uncertainty comes from uncertainties in the photometric calibration. Systematic uncertainties
from light curve fitters come next with a total contribution of ± 0.026 on Ω_M. No clear evidence is found for a possible evolution of
the slope (β) of the colour-luminosity relation with redshift

### Growth of covariant perturbations in the contracting phase of a bouncing universe

In this paper we examine the validity of the linear perturbation theory near
a bounce in the covariant analysis. Some linearity parameters are defined to
set up conditions for a linear theory. Linear evolution of density perturbation
and gravitational waves have been computed previously. We have calculated the
vector and scalar induced parts of the shear tensor. For radiationlike and
dustlike single fluid dominated collapsing Friedmann-Lemaitre-Robertson-Walker
background it is shown that the linearity conditions are not satisfied near a
bounce.Comment: 9 pages, final versio

### The K Band Luminosity Functions of Galaxies in High Redshift Clusters

K band luminosity functions (LFs) of three, massive, high redshift clusters
of galaxies are presented. The evolution of K*, the characteristic magnitude of
the LF, is consistent with purely passive evolution, and a redshift of forma
tion z = 1.5-2.Comment: 3 pages, to appear in Proceedings of IAU Colloquium 195 - Outskirts
of Galaxy Clusters: intense life in the suburb

### Direction Judgement Errors in Perspective Displays

Spatial information transfer characteristics of perspective situation displays were investigated by having eight subjects judge the directions of displayed targets relative to a fixed position in the center of computer generated perspective scenes. Their errors in judging azimuth angles varied sinusoidally with the azimuth of the targets. Errors alternated between clockwise and counterclock wise from one direction quadrant to the next. As the perspective geometry was varied between telephoto lens and wide angle lens views, the direction of error gradually reversed in all quadrants. The results can be explained by systematic differences between the three-dimensional stimulus angles and the perspective projections of those angles onto the display screen

### Threat perception while viewing single intruder conflicts on a cockpit display of traffic information

Subjective estimates of the threat posed by a single intruder aircraft were determined by showing pilots photographs of a cockpit display of traffic information. The time the intruder was away from the point of minimum separation was found to be the major determinant of the perception of threat. When asked to choose a maneuver to reduce the conflict, pilots selected maneuvers with a bias toward those that would have kept the intruders in sight had they been visible out the cockpit window

### The Large Deviation Principle for Coarse-Grained Processes

The large deviation principle is proved for a class of $L^2$-valued processes
that arise from the coarse-graining of a random field. Coarse-grained processes
of this kind form the basis of the analysis of local mean-field models in
statistical mechanics by exploiting the long-range nature of the interaction
function defining such models. In particular, the large deviation principle is
used in a companion paper to derive the variational principles that
characterize equilibrium macrostates in statistical models of two-dimensional
and quasi-geostrophic turbulence. Such macrostates correspond to large-scale,
long-lived flow structures, the description of which is the goal of the
statistical equilibrium theory of turbulence. The large deviation bounds for
the coarse-grained process under consideration are shown to hold with respect
to the strong $L^2$ topology, while the associated rate function is proved to
have compact level sets with respect to the weak topology. This compactness
property is nevertheless sufficient to establish the existence of equilibrium
macrostates for both the microcanonical and canonical ensembles.Comment: 19 page

### Large Deviation Principles and Complete Equivalence and Nonequivalence Results for Pure and Mixed Ensembles

We consider a general class of statistical mechanical models of coherent
structures in turbulence, which includes models of two-dimensional fluid
motion, quasi-geostrophic flows, and dispersive waves. First, large deviation
principles are proved for the canonical ensemble and the microcanonical
ensemble. For each ensemble the set of equilibrium macrostates is defined as
the set on which the corresponding rate function attains its minimum of 0. We
then present complete equivalence and nonequivalence results at the level of
equilibrium macrostates for the two ensembles.Comment: 57 page

### Analysis of phase transitions in the mean-field Blume-Emery-Griffiths model

In this paper we give a complete analysis of the phase transitions in the
mean-field Blume-Emery-Griffiths lattice-spin model with respect to the
canonical ensemble, showing both a second-order, continuous phase transition
and a first-order, discontinuous phase transition for appropriate values of the
thermodynamic parameters that define the model. These phase transitions are
analyzed both in terms of the empirical measure and the spin per site by
studying bifurcation phenomena of the corresponding sets of canonical
equilibrium macrostates, which are defined via large deviation principles.
Analogous phase transitions with respect to the microcanonical ensemble are
also studied via a combination of rigorous analysis and numerical calculations.
Finally, probabilistic limit theorems for appropriately scaled values of the
total spin are proved with respect to the canonical ensemble. These limit
theorems include both central-limit-type theorems when the thermodynamic
parameters are not equal to critical values and non-central-limit-type theorems
when these parameters equal critical values.Comment: 33 pages, revtex

### The Mass Assembly Histories of Galaxies of Various Morphologies in the GOODS Fields

We present an analysis of the growth of stellar mass with cosmic time
partitioned according to galaxy morphology. Using a well-defined catalog of
2150 galaxies based, in part, on archival data in the GOODS fields, we assign
morphological types in three broad classes (Ellipticals, Spirals,
Peculiar/Irregulars) to a limit of z_AB=22.5 and make the resulting catalog
publicly available. We combine redshift information, optical photometry from
the GOODS catalog and deep K-band imaging to assign stellar masses. We find
little evolution in the form of the galaxy stellar mass function from z~1 to
z=0, especially at the high mass end where our results are most robust.
Although the population of massive galaxies is relatively well established at
z~1, its morphological mix continues to change, with an increasing proportion
of early-type galaxies at later times. By constructing type-dependent stellar
mass functions, we show that in each of three redshift intervals, E/S0's
dominate the higher mass population, while spirals are favored at lower masses.
This transition occurs at a stellar mass of 2--3 times 10^{10} Msun at z~0.3
(similar to local studies) but there is evidence that the relevant mass scale
moves to higher mass at earlier epochs. Such evolution may represent the
morphological extension of the ``downsizing'' phenomenon, in which the most
massive galaxies stop forming stars first, with lower mass galaxies becoming
quiescent later. We infer that more massive galaxies evolve into spheroidal
systems at earlier times, and that this morphological transformation may only
be completed 1--2 Gyr after the galaxies emerge from their active star forming
phase. We discuss several lines of evidence suggesting that merging may play a
key role in generating this pattern of evolution.Comment: 24 pages, 1 table, 8 figures, accepted for publication in Ap

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