scholarly journals improved Master for the LSS: fast and accurate analysis of the two-point power spectra and correlation functions

2021 ◽  
Vol 508 (2) ◽  
pp. 1632-1651
Author(s):  
Sukhdeep Singh

ABSTRACT We review the methodology for measurements of two-point functions of the cosmological observables, both power spectra and correlation functions. For pseudo-Cℓ estimators, we will argue that the window-weighted overdensity field can yield more optimal measurements as the window acts as an inverse noise weight, an effect that becomes more important for surveys with a variable selection function. We then discuss the impact of approximations made in the Master algorithm and suggest improvements, the iMaster algorithm, which uses the theoretical model to give unbiased results for arbitrarily complex windows provided that the model satisfies weak accuracy conditions. The methodology of iMaster algorithm is also generalized to the correlation functions to reconstruct the binned power spectra, for E/B mode separation, or to properly convolve the correlation functions to account for the scale cuts in the Fourier space model. We also show that the errors in the window estimation lead to both additive and multiplicative effects on the overdensity field. Accurate estimation of window power can be required up to scales of ∼2ℓmax or larger. Mis-estimation of the window power leads to biases in the measured power spectra, which scale as ${\delta C_\ell }\sim M^W_{\ell \ell ^{\prime }}\delta W_{\ell ^{\prime }}$, where the $M^W_{\ell \ell ^{\prime }}$ scales as ∼(2ℓ + 1)Cℓ leading to effects that can be important at high ℓ. While the notation in this paper is geared towards photometric galaxy surveys, the discussion is equally applicable to spectroscopic galaxy, intensity mapping, and Cosmic Microwave Background radiation (CMB) surveys.

2019 ◽  
Vol 485 (4) ◽  
pp. 5059-5072 ◽  
Author(s):  
Phoebe Upton Sanderbeck ◽  
Vid Iršič ◽  
Matthew McQuinn ◽  
Avery Meiksin

ABSTRACT Spatial fluctuations in ultraviolet backgrounds can subtly modulate the distribution of extragalactic sources, a potential signal and systematic for large-scale structure surveys. While this modulation has been shown to be significant for 3D Ly α forest surveys, its relevance for other large-scale structure probes has been hardly explored, despite being the only astrophysical process that likely can affect clustering measurements on the scales of ≳Mpc. We estimate that the background fluctuations, modulating the amount of H i, have a fractional effect of (0.03–0.3) × (k/[10−2 Mpc−1])−1 on the power spectrum of 21 cm intensity maps at z = 1–3. We find a smaller effect for H α and Ly α intensity mapping surveys of (0.001–0.1) × (k/[10−2 Mpc−1])−1 and even smaller effect for more traditional surveys that correlate the positions of individual H α or Ly α emitters. We also estimate the effect of backgrounds on low-redshift galaxy surveys in general based on a simple model in which background fluctuations modulate the rate halo gas cools, modulating star formation: We estimate a maximum fractional effect on the power of ∼0.01 (k/[10−2 Mpc−1])−1 at z = 1. We compare sizes of these imprints to cosmological parameter benchmarks for the next generation of redshift surveys: We find that ionizing backgrounds could result in a bias on the squeezed triangle non-Gaussianity parameter fNL that can be larger than unity for power spectrum measurements with a SPHEREx-like galaxy survey, and typical values of intensity bias. Marginalizing over a shape of the form k−1PL, where PL is the linear matter power spectrum, removes much of this bias at the cost of ${\approx } 40{{\ \rm per\ cent}}$ larger statistical errors.


Author(s):  
Sandhya Jagannathan ◽  
Ramkishor Sharma ◽  
T. R. Seshadri

Astrophysical magnetic fields decay primarily via two processes, namely ambipolar diffusion and turbulence. Constraints on the strength and the spectral index of nonhelical magnetic fields have been derived earlier in the literature through the effect of the above-mentioned processes on the cosmic microwave background (CMB) radiation. A helical component of the magnetic field is also produced in various models of magnetogenesis, which can explain larger coherence length magnetic field. In this study, we focus on studying the effects of post-recombination decay of maximally helical magnetic fields through ambipolar diffusion and decaying magnetic turbulence and the impact of this decay on CMB. We find that helical magnetic fields lead to changes in the evolution of baryon temperature and ionization fraction which in turn lead to modifications in the CMB temperature and polarization anisotropy. These modifications are different from those arising due to nonhelical magnetic fields with the changes dependent on the strength and the spectral index of the magnetic field power spectra.


2019 ◽  
Vol 489 (1) ◽  
pp. 153-167 ◽  
Author(s):  
Chris Blake

ABSTRACT Fluctuations in the large-scale structure of the Universe contain significant information about cosmological physics, but are modulated in survey data sets by various observational effects. Building on existing literature, we provide a general treatment of how fluctuation power spectra are modified by a position-dependent selection function, noise, weighting, smoothing, pixelization, and discretization. Our work has relevance for the spatial power spectrum analysis of galaxy surveys with spectroscopic or accurate photometric redshifts, and radio intensity-mapping surveys of the sky brightness temperature including generic noise, telescope beams, and pixelization. We consider the autopower spectrum of a field, the cross-power spectrum between two fields and the multipoles of these power spectra with respect to a curved sky, deriving the corresponding power spectrum models, estimators, errors, and optimal weights. We note that ‘FKP weights’ for individual tracers do not in general provide the optimal weights when measuring the cross-power spectrum. We validate our models using mock data sets drawn fromN-body simulations.1 Our treatment should be useful for modelling and studying cosmological fluctuation fields in observed and simulated data sets.


Author(s):  
Maria Cristina Fortuna ◽  
Henk Hoekstra ◽  
Benjamin Joachimi ◽  
Harry Johnston ◽  
Nora Elisa Chisari ◽  
...  

Abstract Intrinsic alignments (IAs) of galaxies are an important contaminant for cosmic shear studies, but the modelling is complicated by the dependence of the signal on the source galaxy sample. In this paper, we use the halo model formalism to capture this diversity and examine its implications for Stage-III and Stage-IV cosmic shear surveys. We account for the different IA signatures at large and small scales, as well for the different contributions from central/satellite and red/blue galaxies, and we use realistic mocks to account for the characteristics of the galaxy populations as a function of redshift. We inform our model using the most recent observational findings: we include a luminosity dependence at both large and small scales and a radial dependence of the signal within the halo. We predict the impact of the total IA signal on the lensing angular power spectra, including the current uncertainties from the IA best-fits to illustrate the range of possible impact on the lensing signal: the lack of constraints for fainter galaxies is the main source of uncertainty for our predictions of the IA signal. We investigate how well effective models with limited degrees of freedom can account for the complexity of the IA signal. Although these lead to negligible biases for Stage-III surveys, we find that, for Stage-IV surveys, it is essential to at least include an additional parameter to capture the redshift dependence.


2020 ◽  
Vol 30 (Supplement_5) ◽  
Author(s):  
C Quercioli ◽  
G A Carta ◽  
G Cevenini ◽  
G Messina ◽  
N Nante ◽  
...  

Abstract Background Careful scheduling of elective surgery Operating Rooms (ORs) is crucial for their efficient use, to avoid low/over utilization and staff overtime. Accurate estimation of procedures duration is essential to improve ORs scheduling. Therefore analysis of historical data about surgical times is fundamental to ORs management. We analyzed the effect, in a real setting, of an ORs scheduling model based on estimated optimum surgical time in improving ORs efficiency and decreasing the risk of overtime. Methods We studied all the 2014-2019 elective surgery sessions (3,758 sessions, 12,449 interventions) of a district general hospital in Siena's Province, Italy. The hospital had3 ORs open 5 days/week 08:00-14:00. Surgery specialties were general surgery, orthopedics, gynecology and urology. Based on a pilot study conducted in 2016, which estimated a 5 times greater risk of having an OR overtime for sessions with a surgical time (incision-suture)>200 minutes, from 2017 all the ORs were scheduled using a maximum surgical time of 200 minutes calculated summing the mean surgical times for intervention and surgeon (obtained from 2014-2016 data). We carried out multivariate logistic regression to calculate the probability of ORs overtime (of 15 and 30 minutes) for the periods 2014-2016 and 2017-2019adjusting for raw ORs utilization. Results The 2017-2019 risk of an OR overtime of 15 minutes decreased by 25% compared to the 2014-2016 period (OR = 0.75, 95%CI=0.618-0.902, p = 0.003); the risk of a OR overtime of 30 minutes decreased by 33% (OR = 0.67, 95%CI= 0.543-0.831, p < 0.001). Mean raw OR utilization increase from 62% to 66% (p < 0.001). Mean number of interventions per surgery sessions increased from 3.1 to 3.5 (p < 0.001). Conclusions This study has shown that an analysis of historical data and an estimate of the optimal surgical time per surgical session could be helpful to avoid both a low and excessive use of the ORs and therefore to increase the efficiency of the ORs. Key messages An accurate analysis of surgical procedures duration is crucial to optimize operating room utilization. A data-based approach can improve OR management efficiency without extra resources.


Author(s):  
Almudena Sanjurjo-de-No ◽  
Blanca Arenas-Ramírez ◽  
José Mira ◽  
Francisco Aparicio-Izquierdo

An accurate estimation of exposure is essential for road collision rate estimation, which is key when evaluating the impact of road safety measures. The quasi-induced exposure method was developed to estimate relative exposure for different driver groups based on its main hypothesis: the not-at-fault drivers involved in two-vehicle collisions are taken as a random sample of driver populations. Liability assignment is thus crucial in this method to identify not-at-fault drivers, but often no liability labels are given in collision records, so unsupervised analysis tools are required. To date, most researchers consider only driver and speed offences in liability assignment, but an open question is if more information could be added. To this end, in this paper, the visual clustering technique of self-organizing maps (SOM) has been applied to better understand the multivariate structure in the data, to find out the most important variables for driver liability, analyzing their influence, and to identify relevant liability patterns. The results show that alcohol/drug use could be influential on liability and further analysis is required for disability and sudden illness. More information has been used, given that a larger proportion of the data was considered. SOM thus appears as a promising tool for liability assessment.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ferenc Fekete ◽  
Katalin Mangó ◽  
Máté Déri ◽  
Evelyn Incze ◽  
Annamária Minus ◽  
...  

AbstractCYP2C9, one of the most abundant hepatic cytochrome P450 enzymes, is involved in metabolism of 15–20% of clinically important drugs (warfarin, sulfonylureas, phenytoin, non-steroid anti-inflammatory drugs). To avoid adverse events and/or impaired drug-response, CYP2C9 pharmacogenetic testing is recommended. The impact of CYP2C9 polymorphic alleles (CYP2C9*2, CYP2C9*3) and phenoconverting non-genetic factors on CYP2C9 function and expression was investigated in liver tissues from Caucasian subjects (N = 164). The presence of CYP2C9*3 allele was associated with CYP2C9 functional impairment, and CYP2C9*2 influenced tolbutamide 4′-hydroxylase activity only in subjects with two polymorphic alleles, whereas the contribution of CYP2C8*3 was not confirmed. In addition to CYP2C9 genetic polymorphisms, non-genetic factors (co-medication with CYP2C9-specific inhibitors/inducers and non-specific factors including amoxicillin + clavulanic acid therapy or chronic alcohol consumption) contributed to the prediction of hepatic CYP2C9 activity; however, a CYP2C9 genotype–phenotype mismatch still existed in 32.6% of the subjects. Substantial variability in CYP2C9 mRNA levels, irrespective of CYP2C9 genotype, was demonstrated; however, CYP2C9 induction and non-specific non-genetic factors potentially resulting in liver injury appeared to modify CYP2C9 expression. In conclusion, complex implementation of CYP2C9 genotype and non-genetic factors for the most accurate estimation of hepatic CYP2C9 activity may improve efficiency and safety of medication with CYP2C9 substrate drugs in clinical practice.


2019 ◽  
Vol 9 (15) ◽  
pp. 3083
Author(s):  
Kai-Jian Huang ◽  
Shui-Jie Qin ◽  
Zheng-Ping Zhang ◽  
Zhao Ding ◽  
Zhong-Chen Bai

We develop a theoretical approach to investigate the impact that nonlocal and finite-size effects have on the dielectric response of plasmonic nanostructures. Through simulations, comprehensive comparisons of the electron energy loss spectroscopy (EELS) and the optical performance are discussed for a gold spherical dimer system in terms of different dielectric models. Our study offers a paradigm of high efficiency compatible dielectric theoretical framework for accounting the metallic nanoparticles behavior combining local, nonlocal and size-dependent effects in broader energy and size ranges. The results of accurate analysis and simulation for these effects unveil the weight and the evolution of both surface and bulk plasmons vibrational mechanisms, which are important for further understanding the electrodynamics properties of structures at the nanoscale. Particularly, our method can be extended to other plasmonic nanostructures where quantum-size or strongly interacting effects are likely to play an important role.


2013 ◽  
Vol 28 (40) ◽  
pp. 1350188 ◽  
Author(s):  
JEREMIAH BIRRELL ◽  
CHENG-TAO YANG ◽  
PISIN CHEN ◽  
JOHANN RAFELSKI

We clarify in a quantitative way the impact that distinct chemical Tc and kinetic Tk freeze-out temperatures have on the reduction of the neutrino fugacity ϒν below equilibrium, i.e. ϒν<1, and the increase of the neutrino temperature Tν via partial reheating. We establish the connection between ϒν and Tk via the modified reheating relation Tν(ϒν)/Tγ, where Tγ is the temperature of the background radiation. Our results demonstrate that one must introduce the chemical nonequilibrium parameter, i.e. the fugacity, ϒν, as an additional standard cosmological model parameter in the evaluation of CMB fluctuations as its value allows measurement of Tk.


2016 ◽  
Vol 833 (2) ◽  
pp. 242 ◽  
Author(s):  
Adrian Liu ◽  
Yunfan Zhang ◽  
Aaron R. Parsons

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