155 research outputs found
Phase Separation of Rigid-Rod Suspensions in Shear Flow
We analyze the behavior of a suspension of rigid rod-like particles in shear
flow using a modified version of the Doi model, and construct diagrams for
phase coexistence under conditions of constant imposed stress and constant
imposed strain rate, among paranematic, flow-aligning nematic, and log-rolling
nematic states. We calculate the effective constitutive relations that would be
measured through the regime of phase separation into shear bands. We calculate
phase coexistence by examining the stability of interfacial steady states and
find a wide range of possible ``phase'' behaviors.Comment: 23 pages 19 figures, revised version to be published in Physical
Review
Improving Cosmological Constraints from Galaxy Cluster Number Counts with CMB-cluster-lensing Data: Results from the SPT-SZ Survey and Forecasts for the Future
We show the improvement to cosmological constraints from galaxy cluster surveys with the addition of cosmic microwave background (CMB)-cluster lensing data. We explore the cosmological implications of adding mass information from the 3.1 sigma detection of gravitational lensing of the CMB by galaxy clusters to the Sunyaev-Zel'dovich (SZ) selected galaxy cluster sample from the 2500 deg(2) SPT-SZ survey and targeted optical and X-ray follow-up data. In the ACDM model, the combination of the cluster sample with the Planck power spectrum measurements prefers sigma(8) (Omega(m)/0.3)(0.5) = 0.831 +/- 0.020. Adding the cluster data reduces the uncertainty on this quantity by a factor of 1.4, which is unchanged whether the 3.1 sigma CMB-cluster lensing measurement is included or not. We then forecast the impact of CMB-cluster lensing measurements with future cluster catalogs. Adding CMB-cluster lensing measurements to the SZ cluster catalog of the ongoing SPT-3G survey is expected to improve the expected constraint on the dark energy equation of state w by a factor of 1.3 to sigma(w) = 0.19. We find the largest improvements from CMB-cluster lensing measurements to be for sigma(8), where adding CMB-cluster lensing data to the cluster number counts reduces the expected uncertainty on sigma(8) by respective factors of 2.4 and 3.6 for SPT-3G and CMB-S4
Optimal CMB Lensing Reconstruction and Parameter Estimation with SPTpol Data
We perform the first simultaneous Bayesian parameter inference and optimal
reconstruction of the gravitational lensing of the cosmic microwave background
(CMB), using 100 deg of polarization observations from the SPTpol receiver
on the South Pole Telescope. These data reach noise levels as low as 5.8
K-arcmin in polarization, which are low enough that the typically used
quadratic estimator (QE) technique for analyzing CMB lensing is significantly
sub-optimal. Conversely, the Bayesian procedure extracts all lensing
information from the data and is optimal at any noise level. We infer the
amplitude of the gravitational lensing potential to be
using the Bayesian pipeline, consistent with
our QE pipeline result, but with 17\% smaller error bars. The Bayesian analysis
also provides a simple way to account for systematic uncertainties, performing
a similar job as frequentist "bias hardening," and reducing the systematic
uncertainty on due to polarization calibration from almost half of the
statistical error to effectively zero. Finally, we jointly constrain
along with , the amplitude of lensing-like effects on the CMB power
spectra, demonstrating that the Bayesian method can be used to easily infer
parameters both from an optimal lensing reconstruction and from the delensed
CMB, while exactly accounting for the correlation between the two. These
results demonstrate the feasibility of the Bayesian approach on real data, and
pave the way for future analysis of deep CMB polarization measurements with
SPT-3G, Simons Observatory, and CMB-S4, where improvements relative to the QE
can reach 1.5 times tighter constraints on and 7 times lower effective
lensing reconstruction noise.Comment: 27 pages, 14 figures, accompanying software package available at
https://cosmicmar.com/CMBLensing.j
Measurements of B-mode Polarization of the Cosmic Microwave Background from 500 Square Degrees of SPTpol Data
We report a B-mode power spectrum measurement from the cosmic microwave
background (CMB) polarization anisotropy observations made using the SPTpol
instrument on the South Pole Telescope. This work uses 500 deg of SPTpol
data, a five-fold increase over the last SPTpol B-mode release. As a result,
the bandpower uncertainties have been reduced by more than a factor of two, and
the measurement extends to lower multipoles: . Data from both
95 and 150 GHz are used, allowing for three cross-spectra: 95 GHz x 95 GHz, 95
GHz x 150 GHz, and 150 GHz x 150 GHz. B-mode power is detected at very high
significance; we find , corresponding to a
detection of power. An upper limit is set on the tensor-to-scalar
ratio, at 95% confidence (the expected constraint on
given the measurement uncertainties is 0.22). We find the measured B-mode power
is consistent with the Planck best-fit CDM model predictions. Scaling
the predicted lensing B-mode power in this model by a factor Alens, the data
prefer Alens = . These data are currently the most precise
measurements of B-mode power at .Comment: 16 pages, 4 figures, Submitted to PR
Measurements of B-mode polarization of the cosmic microwave background from 500 square degrees of SPTpol data
We report a B-mode power spectrum measurement from the cosmic microwave background (CMB) polarization anisotropy observations made using the SPTpol instrument on the South Pole Telescope. This work uses 500 deg² of SPTpol data, a five-fold increase over the last SPTpol B-mode release. As a result, the bandpower uncertainties have been reduced by more than a factor of two, and the measurement extends to lower multipoles: 52 < ℓ < 2301. Data from both 95 and 150 GHz are used, allowing for three cross-spectra: 95 GHz × 95
GHz, 95 GHz × 150 GHz, and 150 GHz × 150 GHz. B-mode power is detected at very high significance; we find P(BB < 0) = 5.8 × 10⁻⁷¹, corresponding to a 18.1σ detection of power. With a prior on the galactic dust from Planck, WMAP and BICEP2/Keck observations, the SPTpol B-mode data can be used to set an upper limit on the tensor-to-scalar ratio, r < 0.44 at 95% confidence (the expected 1σ constraint on r given the measurement uncertainties is 0.22). We find the measured B-mode power is consistent with the Planck best-fit
Λ CDM model predictions. Scaling the predicted lensing B-mode power in this model by a factor A_(lens), the data prefer A_(lens) = 1.17 ± 0.13. These data are currently the most precise measurements of B-mode power at ℓ > 320
Constraints on cosmological parameters from the 500 deg2 SPTPOL lensing power spectrum
We present cosmological constraints based on the cosmic microwave background (CMB) lensing potential power spectrum measurement from the recent 500 deg2 SPTpol survey, the most precise CMB lensing measurement from the ground to date. We fit a flat ΛCDM model to the reconstructed lensing power spectrum alone and in addition with other data sets: baryon acoustic oscillations (BAO), as well as primary CMB spectra from Planck and SPTpol. The cosmological constraints based on SPTpol and Planck lensing band powers are in good agreement when analyzed alone and in combination with Planck full-sky primary CMB data. With weak priors on the baryon density and other parameters, the SPTpol CMB lensing data alone provide a 4% constraint on . Jointly fitting with BAO data, we find , , and , up to away from the central values preferred by Planck lensing + BAO. However, we recover good agreement between SPTpol and Planck when restricting the analysis to similar scales. We also consider single-parameter extensions to the flat ΛCDM model. The SPTpol lensing spectrum constrains the spatial curvature to be and the sum of the neutrino masses to be eV at 95% C.L. (with Planck primary CMB and BAO data), in good agreement with the Planck lensing results. With the differences in the signal-to-noise ratio of the lensing modes and the angular scales covered in the lensing spectra, this analysis represents an important independent check on the full-sky Planck lensing measurement
An Improved Measurement of the Secondary Cosmic Microwave Background Anisotropies from the SPT-SZ + SPTpol Surveys
We report new measurements of millimeter-wave power spectra in the angular
multipole range (angular scales ). By adding 95 and 150\,GHz data from the low-noise
500 deg SPTpol survey to the SPT-SZ three-frequency 2540 deg survey, we
substantially reduce the uncertainties in these bands. These power spectra
include contributions from the primary cosmic microwave background, cosmic
infrared background, radio galaxies, and thermal and kinematic
Sunyaev-Zel'dovich (SZ) effects. The data favor a thermal SZ (tSZ) power at
143\,GHz of and a kinematic
SZ (kSZ) power of . This is
the first measurement of kSZ power at . We study the
implications of the measured kSZ power for the epoch of reionization, finding
the duration of reionization to be ( at 95% confidence), when combined with our previously published
tSZ bispectrum measurement.Comment: Submitted to ApJ, 16 pages. (revised portions of the introduction and
description of bandpower estimation
Searching for Anisotropic Cosmic Birefringence with Polarization Data from SPTpol
We present a search for anisotropic cosmic birefringence in 500 deg of
southern sky observed at 150 GHz with the SPTpol camera on the South Pole
Telescope. We reconstruct a map of cosmic polarization rotation anisotropies
using higher-order correlations between the observed cosmic microwave
background (CMB) and fields. We then measure the angular power spectrum
of this map, which is found to be consistent with zero. The non-detection is
translated into an upper limit on the amplitude of the scale-invariant cosmic
rotation power spectrum,
rad (0.033 deg, 95% C.L.). This upper limit can be used to place
constraints on the strength of primordial magnetic fields, (95% C.L.), and on the coupling constant of the Chern-Simons
electromagnetic term (95% C.L.), where
is the inflationary Hubble scale. For the first time, we also
cross-correlate the CMB temperature fluctuations with the reconstructed
rotation angle map, a signal expected to be non-vanishing in certain
theoretical scenarios, and find no detectable signal. We perform a suite of
systematics and consistency checks and find no evidence for contamination.Comment: 17 pages, 7 figures - new subsection on non-Gaussian foregrounds,
conclusions unchanged - updated to match published version on PR
A measurement of the CMB temperature power spectrum and constraints on cosmology from the SPT-3G 2018 TT/TE/EE Data Set
We present a sample-variance-limited measurement of the temperature power spectrum () of the cosmic microwave background (CMB) using observations of a field made by SPT-3G in 2018. We report multifrequency power spectrum measurements at 95, 150, and 220GHz covering the angular multipole range . We combine this measurement with the published polarization power spectrum measurements from the 2018 observing season and update their associated covariance matrix to complete the SPT-3G 2018 data set. This is the first analysis to present cosmological constraints from SPT , , and power spectrum measurements jointly. We blind the cosmological results and subject the data set to a series of consistency tests at the power spectrum and parameter level. We find excellent agreement between frequencies and spectrum types and our results are robust to the modeling of astrophysical foregrounds. We report results for CDM and a series of extensions, drawing on the following parameters: the amplitude of the gravitational lensing effect on primary power spectra , the effective number of neutrino species , the primordial helium abundance , and the baryon clumping factor due to primordial magnetic fields . We find that the SPT-3G 2018 data are well fit by CDM with a probability-to-exceed of . For CDM, we constrain the expansion rate today to and the combined structure growth parameter to . The SPT-based results are effectively independent of Planck, and the cosmological parameter constraints from either data set are within of each other. (abridged)..
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