1,625 research outputs found
Impact of Weak Lensing Mass Calibration on eROSITA Galaxy Cluster Cosmological Studies -- a Forecast
We forecast the impact of weak lensing (WL) cluster mass calibration on the
cosmological constraints from the X-ray selected galaxy cluster counts in the
upcoming eROSITA survey. We employ a prototype cosmology pipeline to analyze
mock cluster catalogs. Each cluster is sampled from the mass function in a
fiducial cosmology and given an eROSITA count rate and redshift, where count
rates are modeled using the eROSITA effective area, a typical exposure time,
Poisson noise and the scatter and form of the observed X-ray luminosity-- and
temperature--mass--redshift relations. A subset of clusters have mock shear
profiles to mimic either those from DES and HSC or from the future Euclid and
LSST surveys. Using a count rate selection, we generate a baseline cluster
cosmology catalog that contains 13k clusters over 14,892~deg of
extragalactic sky. Low mass groups are excluded using raised count rate
thresholds at low redshift. Forecast parameter uncertainties for
, and are 0.023 (0.016; 0.014), 0.017 (0.012;
0.010), and 0.085 (0.074; 0.071), respectively, when adopting DES+HSC WL
(Euclid; LSST), while marginalizing over the sum of the neutrino masses. A
degeneracy between the distance--redshift relation and the parameters of the
observable--mass scaling relation limits the impact of the WL calibration on
the constraints, but with BAO measurements from DESI an improved
determination of to 0.043 becomes possible. With Planck CMB priors,
() can be determined to (), and the
summed neutrino mass limited to eV (at 95\%). If
systematics on the group mass scale can be controlled, the eROSITA group and
cluster sample with 43k objects and LSST WL could constrain
and to 0.007 and to 0.050.Comment: 28 pages, 13 figur
Statistical characterization of the forces on spheres in an upflow of air
The dynamics of a sphere fluidized in a nearly-levitating upflow of air were
previously found to be identical to those of a Brownian particle in a
two-dimensional harmonic trap, consistent with a Langevin equation [Ojha {\it
et al.}, Nature {\bf 427}, 521 (2004)]. The random forcing, the drag, and the
trapping potential represent different aspects of the interaction of the sphere
with the air flow. In this paper we vary the experimental conditions for a
single sphere, and report on how the force terms in the Langevin equation scale
with air flow speed, sphere radius, sphere density, and system size. We also
report on the effective interaction potential between two spheres in an upflow
of air.Comment: 7 pages, experimen
Diffusion in pores and its dependence on boundary conditions
We study the influence of the boundary conditions at the solid liquid
interface on diffusion in a confined fluid. Using an hydrodynamic approach, we
compute numerical estimates for the diffusion of a particle confined between
two planes. Partial slip is shown to significantly influence the diffusion
coefficient near a wall. Analytical expressions are derived in the low and high
confinement limits, and are in good agreement with numerical results. These
calculations indicate that diffusion of tagged particles could be used as a
sensitive probe of the solid-liquid boundary conditions.Comment: soumis \`a J.Phys. Cond. Matt. special issue on "Diffusion in
Liquids, Polymers, Biophysics and Chemical Dynamics
Possibility to study eta-mesic nuclei and photoproduction of slow eta-mesons at the GRAAL facility
A new experiment is proposed with the aim to study eta-mesic nuclei and
low-energy interactions of eta with nuclei. Two decay modes of eta produced by
a photon beam inside a nucleus will be observed, namely a collisional decay
\eta N \to \pi N inside the nucleus and the radiative decay \eta \to \gamma
\gamma outside. In addition, a collisional decay of stopped S_{11}(1535)
resonance inside the nucleus, S_{11}(1535) N \to N N, will be studied. The
experiment can be performed using the tagged photon beam at ESRF with the
end-point energy 1000 MeV and the GRAAL detector which includes a
high-resolution BGO calorimeter and a large acceptance lead-scintillator
time-of-flight wall. Some results of simulation and estimates of yields are
given.Comment: 20 pages, 19 figure
The Diffusion of Humans and Cultures in the Course of the Spread of Farming
The most profound change in the relationship between humans and their
environment was the introduction of agriculture and pastoralism. [....] For an
understanding of the expansion process, it appears appropriate to apply a
diffusive model. Broadly, these numerical modeling approaches can be catego-
rized in correlative, continuous and discrete. Common to all approaches is the
comparison to collections of radiocarbon data that show the apparent wave of
advance of the transition to farming. However, these data sets differ in entry
density and data quality. Often they disregard local and regional specifics and
research gaps, or dating uncertainties. Thus, most of these data bases may only
be used on a very general, broad scale. One of the pitfalls of using
irregularly spaced or irregularly documented radiocarbon data becomes evident
from the map generated by Fort (this volume, Chapter 16): while the general
east-west and south-north trends become evident, some areas appear as having
undergone anomalously early transitions to farming. This may be due to faulty
entries into the data base or regional problems with radiocarbon dating, if not
unnoticed or undocumented laboratory mistakes.Comment: 20 pages, 5 figures, submitted to Diffusive Spreading in Nature,
Technology and Society, edited by Armin Bunde, J\"urgen Caro, J\"org
K\"arger, Gero Vogl, Chapter 1
Equilibrium Configurations of Strongly Magnetized Neutron Stars with Realistic Equations of State
We investigate equilibrium sequences of magnetized rotating stars with four
kinds of realistic equations of state (EOSs) of SLy (Douchin et al.), FPS
(Pandharipande et al.), Shen (Shen et al.), and LS (Lattimer & Swesty).
Employing the Tomimura-Eriguchi scheme to construct the equilibrium
configurations. we study the basic physical properties of the sequences in the
framework of Newton gravity. In addition we newly take into account a general
relativistic effect to the magnetized rotating configurations. With these
computations, we find that the properties of the Newtonian magnetized stars,
e.g., structure of magnetic field, highly depends on the EOSs.
The toroidal magnetic fields concentrate rather near the surface for Shen and
LS EOSs than those for SLy and FPS EOSs. The poloidal fields are also affected
by the toroidal configurations. Paying attention to the stiffness of the EOSs,
we analyze this tendency in detail. In the general relativistic stars, we find
that the difference due to the EOSs becomes small because all the employed EOSs
become sufficiently stiff for the large maximum density, typically greater than
. The maximum baryon mass of the magnetized stars
with axis ratio increases about up to twenty percents for that of
spherical stars. We furthermore compute equilibrium sequences at finite
temperature, which should serve as an initial condition for the hydrodynamic
study of newly-born magnetars. Our results suggest that we may obtain
information about the EOSs from the observation of the masses of magnetars.Comment: submitted to MNRA
DADA: data assimilation for the detection and attribution of weather and climate-related events
A new nudging method for data assimilation, delayâcoordinate nudging, is presented. Delayâcoordinate nudging makes explicit use of present and past observations in the formulation of the forcing driving the model evolution at each time step. Numerical experiments with a lowâorder chaotic system show that the new method systematically outperforms standard nudging in different model and observational scenarios, also when using an unoptimized formulation of the delayânudging coefficients. A connection between the optimal delay and the dominant Lyapunov exponent of the dynamics is found based on heuristic arguments and is confirmed by the numerical results, providing a guideline for the practical implementation of the algorithm. Delayâcoordinate nudging preserves the easiness of implementation, the intuitive functioning and the reduced computational cost of the standard nudging, making it a potential alternative especially in the field of seasonalâtoâdecadal predictions with large Earth system models that limit the use of more sophisticated data assimilation procedures
The supersymmetric technique for random-matrix ensembles with zero eigenvalues
The supersymmetric technique is applied to computing the average spectral
density near zero energy in the large-N limit of the random-matrix ensembles
with zero eigenvalues: B, DIII-odd, and the chiral ensembles (classes AIII,
BDI, and CII). The supersymmetric calculations reproduce the existing results
obtained by other methods. The effect of zero eigenvalues may be interpreted as
reducing the symmetry of the zero-energy supersymmetric action by breaking a
certain abelian symmetry.Comment: 22 pages, introduction modified, one reference adde
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