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Photophoretic levitation is a propulsion mechanism in which lightweight objects can be lifted and controlled through their interactions with light. Since photophoretic forces on macroscopic objects are usually maximized at low pressures, they may be tested in vacuum chambers in close proximity to the chamber floor and walls. We report here experimental evidence that the terrain under levitating microflyers, including the chamber floor or the launchpad from which microflyers lift off, can greatly increase the photophoretic lift forces relative to their free-space (mid-air) values. To characterize this so-called "ground effect" during vacuum chamber tests, we introduced a new miniature launchpad composed of three J-shaped (candy-cane-like) wires that minimized a microflyer's extraneous interactions with underlying surfaces. We compared our new launchpads to previously used wire-mesh launchpads for simple levitating mylar-based disks with diameters of 2, 4, and 8 cm. Importantly, wire-mesh launchpads increased the photophoretic lift force by up to sixfold. A significant ground effect was also associated with the bottom of the vacuum chamber, particularly when the distance to the bottom surface was less than the diameter of the levitating disk. We provide guidelines to minimize the ground effect in vacuum chamber experiments, which are necessary to test photophoretic microflyers intended for high-altitude exploration and surveillance on Earth or on Mars., Comment: 7 pages, 7 figures, including the Supplemental Material

We define a new morphology metric called "patchiness" ($P$) that is sensitive to deviations from the average of a resolved distribution, does not require the galaxy center to be defined, and can be used on the spatially-resolved distribution of any galaxy property. While the patchiness metric has a broad range of applications, we demonstrate its utility by investigating the distribution of dust in the interstellar medium of 310 star-forming galaxies at spectroscopic redshifts $1.36

Translation Quality Estimation (QE) is the task of predicting the quality of machine translation (MT) output without any reference. This task has gained increasing attention as an important component in the practical applications of MT. In this paper, we first propose XLMRScore, which is a cross-lingual counterpart of BERTScore computed via the XLM-RoBERTa (XLMR) model. This metric can be used as a simple unsupervised QE method, nevertheless facing two issues: firstly, the untranslated tokens leading to unexpectedly high translation scores, and secondly, the issue of mismatching errors between source and hypothesis tokens when applying the greedy matching in XLMRScore. To mitigate these issues, we suggest replacing untranslated words with the unknown token and the cross-lingual alignment of the pre-trained model to represent aligned words closer to each other, respectively. We evaluate the proposed method on four low-resource language pairs of the WMT21 QE shared task, as well as a new English$\rightarrow$Persian (En-Fa) test dataset introduced in this paper. Experiments show that our method could get comparable results with the supervised baseline for two zero-shot scenarios, i.e., with less than 0.01 difference in Pearson correlation, while outperforming unsupervised rivals in all the low-resource language pairs for above 8%, on average., Comment: Submitted to Language Resources and Evaluation

The LUX-ZEPLIN experiment is a dark matter detector centered on a dual-phase xenon time projection chamber operating at the Sanford Underground Research Facility in Lead, South Dakota, USA. This Letter reports results from LUX-ZEPLIN's first search for weakly interacting massive particles (WIMPs) with an exposure of 60~live days using a fiducial mass of 5.5 t. A profile-likelihood ratio analysis shows the data to be consistent with a background-only hypothesis, setting new limits on spin-independent WIMP-nucleon, spin-dependent WIMP-neutron, and spin-dependent WIMP-proton cross sections for WIMP masses above 9 GeV/c$^2$. The most stringent limit is set for spin-independent scattering at 36 GeV/c$^2$, rejecting cross sections above 9.2$\times 10^{-48}$ cm$^2$ at the 90% confidence level., Comment: 9 pages, 8 figures. See https://doi.org/10.1103/PhysRevLett.131.041002 for a data release related to this paper

We analyze the completeness of the MOSDEF survey, in which z ~ 2 galaxies were selected for rest-optical spectroscopy from well-studied HST extragalactic legacy fields down to a fixed rest-optical magnitude limit (H_AB = 24.5). The subset of z ~ 2 MOSDEF galaxies with high signal-to-noise (S/N) emission-line detections analyzed in previous work represents a small minority (<10%) of possible z ~ 2 MOSDEF targets. It is therefore crucial to understand how representative this high S/N subsample is, while also more fully exploiting the MOSDEF spectroscopic sample. Using spectral-energy-distribution (SED) models and rest-optical spectral stacking, we compare the MOSDEF z ~ 2 high S/N subsample with the full MOSDEF sample of z ~ 2 star-forming galaxies with redshifts, the latter representing an increase in sample size of more than a factor of three. We find that both samples have similar emission-line properties, in particular in terms of the magnitude of the offset from the local star-forming sequence on the [N II] BPT diagram. There are small differences in median host galaxy properties, including the stellar mass (M_*), star-formation rate (SFR) and specific SFR (sSFR), and UVJ colors; however, these offsets are minor considering the wide spread of the distributions. Using SED modeling, we also demonstrate that the sample of z ~ 2 star-forming galaxies observed by the MOSDEF survey is representative of the parent catalog of available such targets. We conclude that previous MOSDEF results on the evolution of star-forming galaxy emission-line properties were unbiased relative to the parent z ~ 2 galaxy population., Comment: 18 pages, 10 figures, 3 tables

The erosion and transport of particles by an impinging turbulent jet in air is observed in various situations, such as the cleaning of a surface or during the landing of a spacecraft. The presence of inter-particle cohesive forces modifies the erosion threshold, beyond which grains are transported. The cohesion also influences the resulting formation and shape of the crater. In this paper, we characterize the role of the cohesive forces on the erosion of a flat granular bed by an impinging normal turbulent jet in air. We perform experiments using a cohesion-controlled granular material to finely tune the cohesion between particles while keeping the other properties constant. We investigate the effects of the cohesion on the erosion threshold and show that the results can be rationalized by a cohesive Shields number that accounts for the inter-particles cohesion force. Despite the complex nature of a turbulent jet, we can provide a scaling law to correlate the jet erosion threshold, based on the outlet velocity at the nozzle, to a local cohesive Shields number. The presence of cohesion between the grains also modifies the shape of the resulting crater, the transport of grains, and the local erosion process.

To understand the impact of active galactic nuclei (AGN) on their host galaxies and large scale environment it is crucial to determine their total radiative power across all wavelengths (i.e., bolometric luminosity). In this contribution we describe how quasar accretion disk spectral energy distribution (SED) templates, parameterized by the black hole (BH) mass, Eddington ratio, and spin can be used to estimate their total radiated luminosity. To estimate the bolometric luminosity of AGN, we integrate the accretion disk SEDs from 1$\mu$m to 10keV. Our approach self-consistently covers any gaps in observations and does not include reprocessed emission from the torus. The accretion disk SED, and consequently the bolometric correction inferred from it, strongly depend on the BH mass, the Eddington ratio, and spin. In particular, the bolometric correction in the visible bands (5100$\,\mathring{A}$ and 3000$\,\mathring{A}$) strongly depends on BH mass, and at X-ray strongly depends on the Eddington ratio. At wavelengths closer to the peak of the accretion disk SED the dependence becomes weaker. Additionally, maximally-rotating (spin = 1) quasars require a higher bolometric correction than their non-rotating (spin = 0) counterparts at all wavelengths. The SEDs and the bolometric correction presented in this work can determine the radiative power of any sample of radio-quiet to radio-loud Type 1 AGN with observations in the range from 1$\mu$m to 10$\,$keV provided the observations are corrected for extinction.

Deep neural networks have been extremely successful as highly accurate wave function ans\"atze for variational Monte Carlo calculations of molecular ground states. We present an extension of one such ansatz, FermiNet, to calculations of the ground states of periodic Hamiltonians, and study the homogeneous electron gas. FermiNet calculations of the ground-state energies of small electron gas systems are in excellent agreement with previous initiator full configuration interaction quantum Monte Carlo and diffusion Monte Carlo calculations. We investigate the spin-polarized homogeneous electron gas and demonstrate that the same neural network architecture is capable of accurately representing both the delocalized Fermi liquid state and the localized Wigner crystal state. The network is given no \emph{a priori} knowledge that a phase transition exists, but converges on the translationally invariant ground state at high density and spontaneously breaks the symmetry to produce the crystalline ground state at low density., Comment: 12 pages, 3 figures

Variational and diffusion quantum Monte Carlo methods are employed to investigate the zero-temperature phase diagram of the three-dimensional homogeneous electron gas at very low density. Fermi fluid and body-centered cubic Wigner crystal ground state energies are determined using Slater-Jastrow-backflow and Slater-Jastrow many-body wave functions at different densities and spin polarizations in finite simulation cells. Finite-size errors are removed using twist-averaged boundary conditions and extrapolation of the energy per particle to the thermodynamic limit of infinite system size. Unlike previous studies, our results show that the electron gas undergoes a first-order quantum phase transition directly from a paramagnetic fluid to a body-centered cubic crystal at density parameter $r_\text{s} = 86.6(7)$, with no region of stability for an itinerant ferromagnetic fluid. However there is a possible magnetic phase transition from an antiferromagnetic crystal to a ferromagnetic crystal at $r_\text{s}=93(3)$., Comment: accepted for publication