Impact of survey geometry and super-sample covariance on future photometric galaxy surveys

Photometric galaxy surveys probe the late-time Universe where the density field is highly non-Gaussian. A consequence is the emergence of the super-sample covariance (SSC), a non-Gaussian covariance term that is sensitive to fluctuations on scales larger than the survey window. In this work, we study the impact of the survey geometry on the SSC and, subsequently, on cosmological parameter inference. We devise a fast SSC approximation that accounts for the survey geometry and compare its performance to the common approximation of rescaling the results by the fraction of the sky covered by the survey, fSKY, dubbed ‘full-sky approximation’. To gauge the impact of our new SSC recipe, that we call ‘partial-sky’, we perform Fisher forecasts on the parameters of the (w0, wa)-CDM model in a 3 × 2 point analysis, varying the survey area, the geometry of the mask, and the galaxy distribution inside our redshift bins. The differences in the marginalised forecast errors –with the full-sky approximation performing poorly for small survey areas but excellently for stage-IV-like areas– are found to be absorbed by the marginalisation on galaxy bias nuisance parameters. For large survey areas, the unmarginalised errors are underestimated by about 10% for all probes considered. This is a hint that, even for stage-IV-like surveys, the partial-sky method introduced in this work will be necessary if tight priors are applied on these nuisance parameters. We make the partial-sky method public with a new release of the public code PySSC

The Copernican principle in light of the latest cosmological data

We pursue a program to confront observations with inhomogeneous extensions of the FLRW metric. The main idea is to test the Copernican principle (CP) rather than assuming it a priori. We consider the CDM model endowed with a spherical LTB inhomogeneity around us, that is, we assume isotropy and test the hypothesis of homogeneity. We confront the LTB model with the latest available data from cosmic microwave background, BAO, type Ia supernovae, local H0, cosmic chronometers, Compton y-distortion, and kinetic Sunyaev-Zeldovich effect. We find that these data can constrain tightly this extra inhomogeneity, almost to the cosmic variance level: on scales 100 Mpc structures can have a small non-Copernican effective contrast of just δL 0.01. Furtheore, the constraints on the standard CDM parameters are not weakened after marginalizing over the parameters that model the local structure, to which we assign ignorance priors. In other words, dropping the CP assumption does not imply worse constraints on the cosmological parameters. This positive result confis that the present and future data can be meaningfully analyzed within the framework of inhomogeneous cosmology. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society

Radial artery ultrasound predicts the success of transradial coronary angiography

Background: The transradial approach has become the preferred vascular access during conventional coronary angiography (CCA). Hereby, we evaluated the impact of pre-procedural radial artery diameter (RAD), the cross-sectional area (CSA), and the perimeter on vascular complications (VACs). Methods: We conducted a single-center prospective analysis of 513 patients who underwent CCA. Radial artery ultrasonography was performed before and after CCA to measure the RAD, CSA, and perimeter. Results: The average RAD, CSA, and perimeter were 2.60 ± 0.48 mm, 6.2 ± 3.0 mm2, and 8.9 ± 1.7 mm, respectively. Vascular complications were reported in 56 (11%) patients. The RAD, CSA, and perimeter were significantly smaller in patients in whom procedure-related VACs were observed than in those with no complications: 2.3 ± 0.5 vs. 2.70 ± 0.54 mm (p = 0.0001), 4.9 ± 2.1 vs. 6.4 ± 3 mm2 (p = 0.001), and 7.6 ± 2.1 vs. 9.2 ± 1.6 mm (p = 0.0001), respectively. Univariate logistic regression showed that RAD, CSA and perimeter can independently predict VACs (OR 0.833, 95% CI 0.777–0.894, p < 0.0001; OR 0.647, 95% CI 0.541–0.773, p < 0.0001; OR 0.545, 95% CI 0.446–0.665, p < 0.0001, respectively). Conclusions: Ultrasonographic study of the radial artery before CCA can provide valuable information regarding vascular access.  

Numerical modelling of Tb3+ doped selenide-chalcogenide multimode fibre based spontaneous emission sources

A model is developed of a terbium (III) ion doped selenide chalcogenide glass fibre source that provides spontaneous emission within the mid-infrared (MIR) wavelength range. Three numerical algorithms are used to calculate the solution and compare their properties

Double quantum dot with integrated charge sensor based on Ge/Si heterostructure nanowires

Coupled electron spins in semiconductor double quantum dots hold promise as the basis for solid-state qubits. To date, most experiments have used III-V materials, in which coherence is limited by hyperfine interactions. Ge/Si heterostructure nanowires seem ideally suited to overcome this limitation: the predominance of spin-zero nuclei suppresses the hyperfine interaction and chemical synthesis creates a clean and defect-free system with highly controllable properties. Here we present a top gate-defined double quantum dot based on Ge/Si heterostructure nanowires with fully tunable coupling between the dots and to the leads. We also demonstrate a novel approach to charge sensing in a one-dimensional nanostructure by capacitively coupling the double dot to a single dot on an adjacent nanowire. The double quantum dot and integrated charge sensor serve as an essential building block required to form a solid-state spin qubit free of nuclear spin.Comment: Related work at http://marcuslab.harvard.edu and http://cmliris.harvard.ed

Broadband, mid-infrared emission from Pr3+ doped GeAsGaSe chalcogenide fiber, optically clad

We present a study of mid-infrared photoluminescence in the wavelength range 3.5–5.5lm emitted from Pr3+: GeAsGaSe core/GeAsGaSe cladding chalcogenide fiber. The Pr3+doped fiber optic preform is fabricated using extrusion and is successfully drawn to low optical loss, step-index fiber. Broadband mid-infrared photoluminescence is observed from the fiber, both under 1.55microns or 1.94 microns wavelength excitation. Absorption, and emission, spectra of bulk glass and fiber are presented. Luminescent lifetimesare measured for the fiber and the Judd–Ofelt parameters are calculated. The radiative transition rates calculated from Judd–Ofelt theory are compared with experimental lifetimes. The observed strong broad-band emission suggests that this type of fiber is a good candidate for further development to realize both fiber lasers and amplified spontaneous emission fiber sources in the mid-infrared region