Can Conformally Coupled Modified Gravity Solve The Hubble Tension?

The discrepancy between early-Universe inferences and direct measurements of the Hubble constant, known as the Hubble tension, recently became a pressing subject in high precision cosmology. As a result, a large variety of theoretical models have been proposed to relieve this tension. In this work we analyze a conformally-coupled modified gravity (CCMG) model of an evolving gravitational constant due to the coupling of a scalar field to the Ricci scalar, which becomes active around matter-radiation equality, as required for solutions to the Hubble tension based on increasing the sound horizon at recombination. The model is theoretically advantageous as it has only one free parameter in addition to the baseline $\Lambda$CDM ones. Inspired by similar recent analyses of so-called early-dark-energy models, we constrain the CCMG model using a combination of early and late-Universe cosmological datasets. In addition to the Planck 2018 cosmic microwave background (CMB) anisotropies and weak lensing measurements, baryon acoustic oscillations and the Supernova H0 for the Equation of State datasets, we also use large-scale structure (LSS) datasets such as the Dark Energy Survey year 1 and the full-shape power spectrum likelihood from the Baryon Oscillation Spectroscopic Survey, including its recent analysis using effective field theory, to check the effect of the CCMG model on the (milder) S8 tension between the CMB and LSS. We find that the CCMG model can slightly relax the Hubble tension, with $H_0 = 69.6 \pm 1.6$ km/s/Mpc at 95% CL, while barely affecting the S8 tension. However, current data does not exhibit strong preference for CCMG over the standard cosmological model. Lastly, we show that the planned CMB-S4 experiment will have the sensitivity required to distinguish between the CCMG model and the more general class of models involving an evolving gravitational constant.Comment: 14 pages, 4 figures, 9 table

Charge transport across metal/molecular (alkyl) monolayer-Si junctions is dominated by the LUMO level

We compare the charge transport characteristics of heavy doped p- and n-Si-alkyl chain/Hg junctions. Photoelectron spectroscopy (UPS, IPES and XPS) results for the molecule-Si band alignment at equilibrium show the Fermi level to LUMO energy difference to be much smaller than the corresponding Fermi level to HOMO one. This result supports the conclusion we reach, based on negative differential resistance in an analogous semiconductor-inorganic insulator/metal junction, that for both p- and n-type junctions the energy difference between the Fermi level and LUMO, i.e., electron tunneling, controls charge transport. The Fermi level-LUMO energy difference, experimentally determined by IPES, agrees with the non-resonant tunneling barrier height deduced from the exponential length-attenuation of the current

A Package for OpenCL Based Heterogeneous Computing on Clusters with Many GPU Devices

Abstract—Heterogeneous systems provide new opportunities to increase the performance of parallel applications on clusters with CPU and GPU architectures. Currently, applications that utilize GPU devices run their device-executable code on local devices in their respective hosting-nodes. This paper presents a package for running OpenMP, C++ and unmodified OpenCL applications on clusters with many GPU devices. This Many GPUs Package (MGP) includes an implementation of the OpenCL specifications and extensions of the OpenMP API that allow applications on one hosting-node to transparently utilize cluster-wide devices (CPUs and/or GPUs). MGP provides means for reducing the complexity of programming and running parallel applications on clusters, including scheduling based on task dependencies and buffer management. The paper presents MGP and the performance of its internals

Constraining Primordial Magnetic Fields with Line-Intensity Mapping

Primordial magnetic fields (PMFs) offer a compelling explanation for the origin of observed magnetic fields, especially on extragalactic scales. Such PMFs give rise to excess of power in small scale matter perturbations that could strongly influence structure formation. We study the impact of the magnetically enhanced matter power spectrum on the signal that will be observed by line-intensity mapping (LIM) surveys targeting carbon monoxide (CO) emission from star-forming galaxies at high redshifts. Specifically, the voxel intensity distribution of intensity maps provides access to small-scale information, which makes it highly sensitive to signatures of PMFs on matter overdensities. We present forecasts for future LIM CO surveys, finding that they can constrain PMF amplitudes as small as $\sigma_{B,0}\sim0.04-1\,{\rm nG}$, depending on the magnetic spectral index and the targeted redshifts.Comment: 9 pages, 3 figures, 2 table

Effect of Molecule–Surface Reaction Mechanism on the Electronic Characteristics and Photovoltaic Performance of Molecularly Modified Si

We report on the passivation properties of molecularly modified, oxide-free Si(111) surfaces. The reaction of 1-alcohol with the H-passivated Si(111) surface can follow two possible paths, nucleophilic substitution (S_N) and radical chain reaction (RCR), depending on adsorption conditions. Moderate heating leads to the S_N reaction, whereas with UV irradiation RCR dominates, with S_N as a secondary path. We show that the site-sensitive S_N reaction leads to better electrical passivation, as indicated by smaller surface band bending and a longer lifetime of minority carriers. However, the surface-insensitive RCR reaction leads to more dense monolayers and, therefore, to much better chemical stability, with lasting protection of the Si surface against oxidation. Thus, our study reveals an inherent dissonance between electrical and chemical passivation. Alkoxy monolayers, formed under UV irradiation, benefit, though, from both chemical and electronic passivation because under these conditions both S_N and RCR occur. This is reflected in longer minority carrier lifetimes, lower reverse currents in the dark, and improved photovoltaic performance, over what is obtained if only one of the mechanisms operates. <i>These results show how chemical kinetics and reaction paths impact electronic properties at the device level</i>. It further suggests an approach for effective passivation of other semiconductors

A multi-site pilot randomized clinical trial of the Treatment and Education Approach for Childhood-onset Lupus (TEACH) program: study design and COVID-19 adaptations

Abstract Background Childhood-onset Systemic Lupus Erythematosus (cSLE) is an autoimmune disease associated with fatigue, mood symptoms, and pain. Fortunately, these symptoms are potentially modifiable with psychological intervention such as cognitive-behavioral therapy (CBT). The Treatment and Education Approach for Childhood-onset Lupus (TEACH) program is a CBT intervention developed to target these symptoms for adolescents and young adults with cSLE. This pilot randomized controlled trial (RCT) aims to determine the feasibility and effect of TEACH for youth with cSLE. Adjustments to the study protocol following the COVID-19 pandemic are also described. Methods This two-arm multisite RCT will explore the feasibility (primary outcome) and effect (secondary outcome) of a remotely delivered TEACH protocol. Participants will be randomized to a six-week remotely delivered TEACH program plus medical treatment as usual (TAU) or TAU alone. We will include patients ages 12–22 years presenting to rheumatology clinics from six sites. Validated measures of fatigue, depressive symptoms, and pain will be obtained at baseline and approximately eight and 20 weeks later. Protocol adjustments were also made due to the COVID-19 pandemic, in collaboration with the investigative team, which included patients and caregivers. Conclusions Findings from this multi-site RCT aim to document the feasibility of TEACH and provide an estimate of effect of a remotely delivered TEACH protocol on fatigue, depression, and pain symptoms in youth with cSLE as compared to standard medical treatment alone. This findings may positively impact clinical care for patients with cSLE. Clinical trials.gov registration: NCT04335643