83 research outputs found
MPTbreeze: A fast renormalized perturbative scheme
We put forward and test a simple description of multi-point propagators (MP),
which serve as building-blocks to calculate the nonlinear matter power
spectrum. On large scales these propagators reduce to the well-known kernels in
standard perturbation theory, while at smaller scales they are suppresed due to
nonlinear couplings. Through extensive testing with numerical simulations we
find that this decay is characterized by the same damping scale for both two
and three-point propagators. In turn this transition can be well modeled with
resummation results that exponentiate one-loop computations. For the first
time, we measure the four components of the non-linear (two-point) propagator
using dedicated simulations started from two independent random Gaussian fields
for positions and velocities, verifying in detail the fundamentals of
propagator resummation.
We use these results to develop an implementation of the MP-expansion for the
nonlinear power spectrum that only requires seconds to evaluate at BAO scales.
To test it we construct six suites of large numerical simulations with
different cosmologies. From these and
LasDamas runs we show that the nonlinear power spectrum can be described at
the ~ 2% level at BAO scales for redshifts in the range [0-2.5]. We make a
public release of the MPTbreeze code with the hope that it can be useful to the
community.Comment: 16 pages, 10 figures. Accepted for publication in MNRAS (minor
comments included to match accepted version). Public code available at
http://maia.ice.cat/crocce/mptbreeze
Multi-Point Propagators in Cosmological Gravitational Instability
We introduce the concept of multi-point propagators between linear cosmic
fields and their nonlinear counterparts in the context of cosmological
perturbation theory. Such functions express how a non-linearly evolved Fourier
mode depends on the full ensemble of modes in the initial density field. We
identify and resum the dominant diagrams in the large- limit, showing
explicitly that multi-point propagators decay into the nonlinear regime at the
same rate as the two-point propagator. These analytic results generalize the
large- limit behavior of the two-point propagator to arbitrary order. We
measure the three-point propagator as a function of triangle shape in numerical
simulations and confirm the results of our high- resummation. We show that
any point spectrum can be reconstructed from multi-point propagators, which
leads to a physical connection between nonlinear corrections to the power
spectrum at small scales and higher-order correlations at large scales. As a
first application of these results, we calculate the reduced bispectrum at
one-loop in renormalized perturbation theory and show that we can predict the
decrease in its dependence on triangle shape at redshift zero, when standard
perturbation theory is least successful.Comment: 21 pages, 14 figures. Minor changes to match published version (Fig
11 changed, added reference
Model for resonant photon creation in a cavity with time dependent conductivity
In an electromagnetic cavity, photons can be created from the vacuum state by
changing the cavity's properties with time. Using a simple model based on a
massless scalar field, we analyze resonant photon creation induced by the
time-dependent conductivity of a thin semiconductor film contained in the
cavity. This time dependence may be achieved by irradiating periodically the
film with short laser pulses. This setup offers several experimental advantages
over the case of moving mirrors.Comment: 9 pages, 1 figure. Minor changes. Version to appear in Phys. Rev.
Clustering with general photo-z uncertainties: application to Baryon Acoustic Oscillations
This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record Monthly Notices of the Royal Astronomical Society 511.3 (2022): 3965–3982 is available online at: https://academic.oup.com/mnras/article-abstract/511/3/3965/6526328#no-access-messagePhotometric data can be analysed using the 3D correlation function ξp to extract cosmological information via e.g. measurement of the Baryon Acoustic Oscillations (BAO). Previous studies modeled ξp assuming a Gaussian photo-z approximation. In this work we improve the modeling by incorporating realistic photo-z distribution. We show that the position of the BAO scale in ξp is determined by the photo-z distribution and the Jacobian of the transformation. The latter diverges at the transverse scale of the separation s⊥, and it explains why ξp traces the underlying correlation function at s⊥, rather than s, when the photo-z uncertainty σz/(1+ z) ≳ 0.02. We also obtain the Gaussian covariance for ξp. Due to photo-z mixing, the covariance of ξp shows strong off-diagonal elements. The high correlation of the data causes some issues to the data fitting. None the less, we find that either it can be solved by suppressing the largest eigenvalues of the covariance or it is not directly related to the BAO. We test our BAO fitting pipeline using a set of mock catalogs. The data set is dedicated for Dark Energy Survey Year 3 (DES Y3) BAO analyses and includes realistic photo-z distributions. The theory template is in good agreement with mock measurement. Based on the DES Y3 mocks, ξp statistic is forecast to constrain the BAO shift parameter α to be 1.001 ± 0.023, which is well consistent with the corresponding constraint derived from the angular correlation function measurements. Thus, ξp offers a competitive alternative for the photometric data analyse
Measuring Redshift-Space Distortions using Photometric Surveys
We outline how redshift-space distortions (RSD) can be measured from the
angular correlation function w({\theta}), of galaxies selected from photometric
surveys. The natural degeneracy between RSD and galaxy bias can be minimized by
comparing results from bins with top-hat galaxy selection in redshift, and bins
based on the radial position of galaxy pair centres. This comparison can also
be used to test the accuracy of the photometric redshifts. The presence of RSD
will be clearly detectable with the next generation of photometric redshift
surveys. We show that the Dark Energy Survey (DES) will be able to measure
f(z){\sigma}_8(z) to a 1{\sigma} accuracy of (17 {\times} b)%, using galaxies
drawn from a single narrow redshift slice centered at z = 1. Here b is the
linear bias, and f is the logarithmic rate of change of the linear growth rate
with respect to the scale factor. Extending to measurements of w({\theta}) for
a series of bins of width 0.02(1 + z) over 0.5 < z < 1.4 will measure {\gamma}
to a 1{\sigma} accuracy of 25%, given the model f = {\Omega}_m(z)^{\gamma}, and
assuming a linear bias model that evolves such that b = 0.5 + z (and fixing
other cosmological parameters). The accuracy of our analytic predictions is
confirmed using mock catalogs drawn from simulations conducted by the MICE
collaboration.Comment: Accepted by MNRAS, revisions include fixing of typos and
clarification of the tex
Hertz potentials approach to the dynamical Casimir effect in cylindrical cavities of arbitrary section
We study the creation of photons in resonant cylindrical cavities with time
dependent length. The physical degrees of freedom of the electromagnetic field
are described using Hertz potentials. We describe the general formalism for
cavities with arbitrary section. Then we compute explicitly the number of TE
and TM motion-induced photons for cylindrical cavities with rectangular and
circular sections. We also discuss the creation of TEM photons in non-simply
connected cylindrical cavities.Comment: 13 pages, 3 figures, revtex
Accurate dark matter halo elongation from weak-lensing stacking analysis
Halo shape estimates that describe their anisotropic mass distribution are
valuable parameters that provide useful information on their assembly process
and evolution. Measurements of the mean shape estimates for a sample of
cluster-size halos, can be used to test halo formation scenarios as well as
improving the modelling of potential biases in constraining cosmological
parameters using these systems. In this work we test the recovery of halo
cluster shapes and masses applying weak lensing stacking techniques, using
lensing shear and a new dark matter halo catalogues, derived from the
light-cone output of the cosmological simulation MICE-GC. We perform this study
by combining the lensing signals obtained for several samples of halos selected
according to their mass and redshift, considering the main directions of the
dark-matter distributions. In the analysis we test the impact of several
potential introduced systematics, such as the adopted modelling, the
contribution of the neighbouring mass distribution, miscentering and
misalignment effects. Our results show that, when some considerations regarding
the halo relaxation state are taken into account, the lensing semi-axis ratio
estimates are in agreement within a with the mean shapes of the projected
dark-matter particle distribution of the stacked halos. The presented
methodology provides a useful tool to derive reliable shapes of galaxy clusters
and to contrast them with those expected from numerical simulations.
Furthermore, our proposed modelling, that takes into account the contribution
of neighbouring halos, allows to constraint the elongation of the surrounding
mass distribution.Comment: 15 pages, 8 figures, submitted to MNRA
Simulating the Universe with MICE: The abundance of massive clusters
We introduce a new set of large N-body runs, the MICE simulations, that
provide a unique combination of very large cosmological volumes with good mass
resolution. They follow the gravitational evolution of ~ 8.5 billion particles
(2048^3) in volumes covering up to 450 (Gpc/h)^3. Our main goal is to
accurately model and calibrate basic cosmological probes that will be used by
upcoming astronomical surveys. Here we take advantage of the very large volumes
of MICE to make a robust sampling of the high-mass tail of the halo mass
function (MF). We discuss and avoid possible systematic effects in our study,
and do a detailed analysis of different error estimators. We find that
available fits to the local abundance of halos (Warren et al. (2006)) match
well the abundance in MICE up to M ~ 10^{14}\Msun, but significantly deviate
for larger masses, underestimating the mass function by 10% (30%) at M = 3.16 x
10^{14}\Msun (10^{15}\Msun). Similarly, the widely used Sheth & Tormen (1999)
fit, if extrapolated to high redshift assuming universality, leads to an
underestimation of the cluster abundance by 30%, 20% and 15% at z=0, 0.5, 1 for
M ~ [7 - 2.5 - 0.8] x 10^{14}\Msun respectively ().
We provide a re-calibration of the halo MF valid over 5 orders of magnitude in
mass, 10^{10} < M/(\Msun) < 10^{15}, that accurately describes its redshift
evolution up to z=1. We explore the impact of this re-calibration on the
determination of dark-energy, and conclude that using available fits may
systematically bias the estimate of w by as much as 50% for medium-depth (z <=
1) surveys. MICE halo catalogues are publicly available at
http://www.ice.cat/miceComment: 16 pages, 11 figures. Data publicly available at
http://www.ice.cat/mice. New version adds discussion on halo definition (SO
vs FoF) and minor modifications. Accepted for publication in MNRA
Cosmology from large-scale structure::Constraining ΛCDM with BOSS
We reanalyse the anisotropic galaxy clustering measurement from the Baryon Oscillation Spectroscopic Survey (BOSS), demonstrating that using the full shape information provides cosmological constraints that are comparable to other low-redshift probes. We find , and h = 0.704 ± 0.024 for flat ΛCDM cosmologies using uninformative priors on Ωch2, 100θMC, ln1010As, and ns, and a prior on Ωbh2 that is much wider than current constraints. We quantify the agreement between the Planck 2018 constraints from the cosmic microwave background and BOSS, finding the two data sets to be consistent within a flat ΛCDM cosmology using the Bayes factor as well as the prior-insensitive suspiciousness statistic. Combining two low-redshift probes, we jointly analyse the clustering of BOSS galaxies with weak lensing measurements from the Kilo-Degree Survey (KV450). The combination of BOSS and KV450 improves the measurement by up to 45%, constraining σ8 = 0.702 ± 0.029 and . Over the full 5D parameter space, the odds in favour of a single cosmology describing galaxy clustering, lensing, and the cosmic microwave background are 7 ± 2. The suspiciousness statistic signals a 2.1 ± 0.3σ tension between the combined low-redshift probes and measurements from the cosmic microwave background
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