251 research outputs found
High Performance P3M N-body code: CUBEP3M
This paper presents CUBEP3M, a publicly-available high performance
cosmological N-body code and describes many utilities and extensions that have
been added to the standard package. These include a memory-light runtime SO
halo finder, a non-Gaussian initial conditions generator, and a system of
unique particle identification. CUBEP3M is fast, its accuracy is tuneable to
optimize speed or memory, and has been run on more than 27,000 cores, achieving
within a factor of two of ideal weak scaling even at this problem size. The
code can be run in an extra-lean mode where the peak memory imprint for large
runs is as low as 37 bytes per particles, which is almost two times leaner than
other widely used N-body codes. However, load imbalances can increase this
requirement by a factor of two, such that fast configurations with all the
utilities enabled and load imbalances factored in require between 70 and 120
bytes per particles. CUBEP3M is well designed to study large scales
cosmological systems, where imbalances are not too large and adaptive
time-stepping not essential. It has already been used for a broad number of
science applications that require either large samples of non-linear
realizations or very large dark matter N-body simulations, including
cosmological reionization, halo formation, baryonic acoustic oscillations, weak
lensing or non-Gaussian statistics. We discuss the structure, the accuracy,
known systematic effects and the scaling performance of the code and its
utilities, when applicable.Comment: 20 pages, 17 figures, added halo profiles, updated to match MNRAS
accepted versio
Painting with baryons: augmenting N-body simulations with gas using deep generative models
Running hydrodynamical simulations to produce mock data of large-scale structure and baryonic probes, such as the thermal Sunyaev-Zeldovich (tSZ) effect, at cosmological scales is computationally challenging. We propose to leverage the expressive power of deep generative models to find an effective description of the large-scale gas distribution and temperature. We train two deep generative models, a variational auto-encoder and a generative adversarial network, on pairs of matter density and pressure slices from the BAHAMAS hydrodynamical simulation. The trained models are able to successfully map matter density to the corresponding gas pressure. We then apply the trained models on 100 lines-of-sight from SLICS, a suite of N-body simulations optimised for weak lensing covariance estimation, to generate maps of the tSZ effect. The generated tSZ maps are found to be statistically consistent with those from BAHAMAS. We conclude by considering a specific observable, the angular cross-power spectrum between the weak lensing convergence and the tSZ effect and its variance, where we find excellent agreement between the predictions from BAHAMAS and SLICS, thus enabling the use of SLICS for tSZ covariance estimation
Magnetic moment of welded HTS samples: dependence on the current flowing through the welds
We present a method to calculate the magnetic moments of the high-temperature
superconducting (HTS) samples which consist of a few welded HTS parts. The
approach is generalized for the samples of various geometrical shapes and an
arbitrary number of welds. The obtained relations between the sample moment and
the density of critical current, which flows through the welds, allow to use
the magnetization loops for a quantitative characterization of the weld quality
in a wide range of temperatures and/or magnetic fields.Comment: RevTeX4, 4 pages, 2 figures. Submitted to Supercond. Sci. Techno
MGLENS: Modified gravity weak lensing simulations for emulation-based cosmological inference
We present MGLENS, a large series of modified gravity lensing simulations tailored for cosmic shear data analyses and forecasts in which cosmological and modified gravity parameters are varied simultaneously. Based on the FORGE and BRIDGE N-body simulation suites presented in companion papers, we construct 100 Ă 5000 deg2 of mock Stage-IV lensing data from two 4D Latin hypercubes that sample cosmological and gravitational parameters in f(R) and nDGP gravity, respectively. These are then used to validate our inference analysis pipeline based on the lensing power spectrum, exploiting our implementation of these modified gravity models within the COSMOSIS cosmological inference package. Sampling this new likelihood, we find that cosmic shear can achieve 95 per cent CL constraints on the modified gravity parameters of log10[fR0 ] 0.09, after marginalizing over intrinsic alignments of galaxies and including scales up to = 5000. We also investigate the impact of photometric uncertainty, scale cuts, and covariance matrices. We finally explore the consequences of analysing MGLENS data with the wrong gravity model, and report catastrophic biases for a number of possible scenarios. The Stage-IV MGLENS simulations,the FORGE and BRIDGE emulators and the COSMOSIS interface modules will be made publicly available upon journal acceptance
The Kinetic Sunyaev-Zel'dovich effect as a probe of the physics of cosmic reionization: the effect of self-regulated reionization
We calculate the angular power spectrum of the Cosmic Microwave Background
(CMB) temperature fluctuations induced by the kinetic Sunyaev-Zel'dovich (kSZ)
effect from the epoch of reionization (EOR). We use detailed N-body+radiative
transfer simulations to follow inhomogeneous reionization of the intergalactic
medium (IGM). For the first time we take into account the "self-regulation" of
reionization: star formation in low-mass dwarf galaxies (10^8 M_\sun \lesssim M
\lesssim 10^9 M_\sun) or minihalos (10^5 M_\sun \lesssim M \lesssim 10^8
M_\sun) is suppressed if these halos form in the regions that were already
ionized or Lyman-Werner dissociated. Some previous work suggested that the
amplitude of the kSZ power spectrum from the EOR can be described by a
two-parameter family: the epoch of half ionization and the duration of
reionization. However, we argue that this picture applies only to simple forms
of the reionization history which are roughly symmetric about the
half-ionization epoch. In self-regulated reionization, the universe begins to
be ionized early, maintains a low level of ionization for an extended period,
and then finishes reionization as soon as high-mass atomically-cooling halos
dominate. While inclusion of self-regulation affects the amplitude of the kSZ
power spectrum only modestly (\sim 10 %), it can change the duration of
reionization by a factor of more than two. We conclude that the simple
two-parameter family does not capture the effect of a physical, yet complex,
reionization history caused by self-regulation. When added to the
post-reionization kSZ contribution, our prediction for the total kSZ power
spectrum is below the current upper bound from the South Pole Telescope.
Therefore, the current upper bound on the kSZ effect from the EOR is consistent
with our understanding of the physics of reionization
CFHTLenS and RCSLenS cross-correlation with Planck lensing detected in fourier and configuration space
We measure the cross-correlation signature between the Planck cosmic microwave background (CMB) lensing map and the weak lensing observations from both the Red-sequence Cluster Lensing Survey and the CanadaâFranceâHawaii Telescope Lensing Survey. In addition to a Fourier analysis, we include the first configuration-space detection, based on the estimators ăÎșCMBÎșgală and ăÎșCMBÎłtă. Combining 747.2 deg2 from both surveys, we find a detection significance that exceeds 4.2Ï in both Fourier- and configuration-space analyses. Scaling the predictions by a free parameter A, we obtain APlanckCFHT=0.68±0.31 and APlanckRCS=1.31±0.33â . In preparation for the next generation of measurements similar to these, we quantify the impact of different analysis choices on these results. First, since none of these estimators probes the exact same dynamical range, we improve our detection by combining them. Secondly, we carry out a detailed investigation on the effect of apodization, zero-padding and mask multiplication, validated on a suite of high-resolution simulations, and find that the latter produces the largest systematic bias in the cosmological interpretation. Finally, we show that residual contamination from intrinsic alignment and the effect of photometric redshift error are both largely degenerate with the characteristic signal from massive neutrinos, however the signature of baryon feedback might be easier to distinguish. The three lensing data sets are publicly available
Are transnational tobacco companies' market access strategies linked to economic development models? A case study of South Korea.
Transnational tobacco companies (TTCs) have used varied strategies to access previously closed markets. Using TTCs' efforts to enter the South Korean market from the late 1980s as a case study, this article asks whether there are common patterns in these strategies that relate to the broader economic development models adopted by targeted countries. An analytical review of the existing literature on TTCs' efforts to access emerging markets was conducted to develop hypotheses relating TTCs' strategies to countries' economic development models. A case study of Korea was then undertaken based on analysis of internal tobacco industry documents. Findings were consistent with the hypothesis that TTCs' strategies in Korea were linked to Korea's export-oriented economic development model and its hostile attitude towards foreign investment. A fuller understanding of TTCs' strategies for expansion globally can be derived by locating them within the economic development models of specific countries or regions. Of foremost importance is the need for governments to carefully balance economic and public health policies when considering liberalisation
CFHTLenS and RCSLenS cross-correlation with Planck lensing detected in fourier and configuration space
We measure the cross-correlation signature between the Planck cosmic microwave background (CMB) lensing map and the weak lensing observations from both the Red-sequence Cluster Lensing Survey and the CanadaâFranceâHawaii Telescope Lensing Survey. In addition to a Fourier analysis, we include the first configuration-space detection, based on the estimators ăÎșCMBÎșgală and ăÎșCMBÎłtă. Combining 747.2 deg2 from both surveys, we find a detection significance that exceeds 4.2Ï in both Fourier- and configuration-space analyses. Scaling the predictions by a free parameter A, we obtain APlanckCFHT=0.68±0.31 and APlanckRCS=1.31±0.33â . In preparation for the next generation of measurements similar to these, we quantify the impact of different analysis choices on these results. First, since none of these estimators probes the exact same dynamical range, we improve our detection by combining them. Secondly, we carry out a detailed investigation on the effect of apodization, zero-padding and mask multiplication, validated on a suite of high-resolution simulations, and find that the latter produces the largest systematic bias in the cosmological interpretation. Finally, we show that residual contamination from intrinsic alignment and the effect of photometric redshift error are both largely degenerate with the characteristic signal from massive neutrinos, however the signature of baryon feedback might be easier to distinguish. The three lensing data sets are publicly available
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