Miracle-dz/UniFAR-FTUs huggingface dataset:
Probabilistic identification of high‐frequency radar backscatter from the ground and ionosphere based on spectral characteristics

We present an analysis of the spectral characteristics of 1‐hop HF radar ground scatter and ‐ and 1‐hop ionospheric scatter as measured by the Super Dual Auroral Radar Network. Our objective is to determine criteria that separate signals scattered from the ground and the ionosphere. We find that for both ground scatter and ionospheric scatter that the probability density function of backscatter Doppler velocity decreases exponentially with velocity, but with significantly different e‐folding velocities for the two types of backscatter. We use this observation to separate the total probability density of Doppler velocity and spectral width into two component distributions. This process yields the posterior probability that a signal of given Doppler velocity and spectral width is ground scatter. The resulting criterion for classification of a particular signal as ground scatter, v < 33.1 m/s + 0.139w − (0.00133 s/m)w2, significantly reduces the probability that a signal will be erroneously classified as ionospheric scatter, while only moderately increasing the probability that an ionospheric scatter signal will be erroneously classified as ground scatter. Finally, we validate the ground scatter probability function by demonstrating that the backscatter virtual height increases as expected with increasing probability of ground scatter.
Constraining Sterile Neutrinos from Precision Higgs Data

We use the LHC Higgs data to derive updated constraints on electroweak-scale sterile neutrinos that naturally occur in many low-scale seesaw extensions of the Standard Model to explain the neutrino masses. We also analyze the signal sensitivity for a new final state involving a single charged lepton and two jets with missing energy, which arises from the decay of sterile neutrinos produced through the Higgs and $W,Z$ boson mediated processes at the LHC. Future prospects of these sterile neutrino signals in precision Higgs measurements, as well as at a future 100 TeV collider, are also discussed.
The Mira-based Distance to the Galactic Center

Mira variables are useful distance indicators, due to their high luminosities and well-defined period–luminosity relation. We select 1863 Miras from SAAO and MACHO observations to examine their use as distance estimators in the Milky Way. We measure a distance to the Galactic center of R0 = 7.9 ± 0.3 kpc, which is in good agreement with other literature values. The uncertainty has two components of ∼0.2 kpc each: the first is from our analysis and predominantly due to interstellar extinction, the second is due to zero-point uncertainties extrinsic to our investigation, such as the distance to the Large Magellanic Cloud (LMC). In an attempt to improve existing period–luminosity calibrations, we use theoretical models of Miras to determine the dependence of the period–luminosity relation on age, metallicity, and helium abundance, under the assumption that Miras trace the bulk stellar population. We find that at a fixed period of , changes in the predicted Ks magnitudes can be approximated by + , and these coefficients are nearly independent of period. The expected overestimate in the Galactic center distance from using an LMC-calibrated relation is ∼0.3 kpc. This prediction is not validated by our analysis; a few possible reasons are discussed. We separately show that while the predicted color–color diagrams of solar-neighborhood Miras work well in the near-infrared; though, there are offsets from the model predictions in the optical and mid-infrared.
The R-Process Alliance: Spectroscopic Follow-up of Low-metallicity Star Candidates from the Best & Brightest Survey

We present results from an observing campaign to identify low-metallicity stars in the Best & Brightest Survey. From medium-resolution (R ∼ 1200–2000) spectroscopy of 857 candidates, we estimate the stellar atmospheric parameters ( , , and ), as well as carbon and α-element abundances. We find that 69% of the observed stars have ≤ −1.0, 39% have ≤ −2.0, and 2% have ≤ −3.0. There are also 133 carbon-enhanced metal-poor (CEMP) stars in this sample, with 97 CEMP Group I and 36 CEMP Group II stars identified in the A(C) versus [Fe/H] diagram. A subset of the confirmed low-metallicity stars were followed-up with high-resolution spectroscopy, as part of the R-process Alliance, with the goal of identifying new highly and moderately r-process-enhanced stars. Comparison between the stellar atmospheric parameters estimated in this work and from high-resolution spectroscopy exhibit good agreement, confirming our expectation that medium-resolution observing campaigns are an effective way of selecting interesting stars for further, more targeted, efforts.
Statistical predictions for the first black holes

The recent observations of supermassive black holes (SMBHs) at high redshift challenge our understanding of their formation and growth. There are different proposed pathways to form black hole (BH) seeds, such as the remnants of the first stars (chapter 4), gas-dynamical processes (chapter 5), direct collapse (chapter 6), or stellar collisions in dense nuclear clusters (chapter 7). In this chapter, we discuss the probability of forming supermassive black holes (SMBHs) via these channels and determine the expected number density of the BH seeds. We start with a brief discussion of the observational constraints on SMBHs at low and high redshift that theoretical models have to reproduce (a more detailed account is provided in chapter 12). We further present the most popular formation channels of SMBHs, discuss under which conditions they can reproduce the observations, and compare various estimates in the literature on the expected number density of SMBHs. To account for the density of quasars at $z>6$ requires very efficient gas accretion mechanisms or high BH seeds masses. The bottleneck to obtain sufficiently high number densities of seed BHs with masses $>10^5$M$_\odot$ is the interplay between radiative and chemical feedback, which constrains the conditions for primordial, isothermal gas collapse.
Collisionality and magnetic geometry effects on tokamak edge turbulent transport. I. A two-region model with application to blobs

A two-region model is proposed to study the effect of collisionality and magnetic geometry on electrostatic turbulence and on the propagation of filamentary coherent structures (blobs) in the edge and scrape-off layer. The model invokes coupled vorticity and continuity equations in two different spatial regions along the magnetic field, taking into account the effect of magnetic field fanning and shear, e.g., near magnetic X-points. A linear dispersion relation for unstable modes illustrates the physics of mode disconnection (ballooning) along the magnetic field and its dependence on collisionality and wave number (scale size). Employing an invariant scaling analysis, dimensionless parameters for the nonlinear model are developed and used to describe the regimes of the system. A blob correspondence rule is postulated to relate the linear mode growth rates and regimes to the convective velocity of blobs. Nonlinear numerical simulations of blob convection show good agreement with a blob dispersion relation .
Sensitivity analysis on imaging the calcaneus using microwaves

The bone quality is associated with changes in its dielectric properties (permittivity and conductivity). The feasibility of detecting changes in these properties was evaluated by using a tomographic array of 16 monopole antennas with z-polarized microwaves at 1.3 GHz. The direct electromagnetic problem was solved computationally with the finite–difference–time–domain (FDTD) method. Local and global sensitivity analyses were implemented for identifying the parameters that most affect the detection. Magnitude and phase of the transmission coefficient of the antennas were evaluated separately. It was observed that the direct problem is highly sensitive to the dielectric properties of the tissues surrounding the calcaneus and to those of the calcaneus itself. Global and local sensitivity methods have shown evidence for feasible detection of variations in dielectric properties of the bone supporting the simplification of considering only two homogeneous media (calcaneus and surrounding tissue).
GALAXY EVOLUTION AT HIGH REDSHIFT: OBSCURED STAR FORMATION, GRB RATES, COSMIC REIONIZATION, AND MISSING SATELLITES

We provide a holistic view of galaxy evolution at high redshifts z ≳ 4, which incorporates the constraints from various astrophysical/cosmological probes, including the estimate of the cosmic star formation rate (SFR) density from UV/IR surveys and long gamma-ray burst (GRBs) rates, the cosmic reionization history following the latest Planck measurements, and the missing satellites issue. We achieve this goal in a model-independent way by exploiting the SFR functions derived by Mancuso et al. on the basis of an educated extrapolation of the latest UV/far-IR data from HST/Herschel, and already tested against a number of independent observables. Our SFR functions integrated down to a UV magnitude limit MUV ≲ −13 (or SFR limit around 10−2 M⊙ yr−1) produce a cosmic SFR density in excellent agreement with recent determinations from IR surveys and, taking into account a metallicity ceiling Z ≲ Z⊙/2, with the estimates from long GRB rates. They also yield a cosmic reionization history consistent with that implied by the recent measurements of the Planck mission of the electron scattering optical depth τes ≈ 0.058; remarkably, this result is obtained under a conceivable assumption regarding the average value fesc ≈ 0.1 of the escape fraction for ionizing photons. We demonstrate via the abundance-matching technique that the above constraints concurrently imply galaxy formation becoming inefficient within dark matter halos of mass below a few 108 M⊙; pleasingly, such a limit is also required so as not to run into the missing satellites issue. Finally, we predict a downturn of the Galaxy luminosity function faintward of MUV ≲ −12, and stress that its detailed shape, to be plausibly probed in the near future by the JWST, will be extremely informative on the astrophysics of galaxy formation in small halos, or even on the microscopic nature of the dark matter.
Accreting Double White Dwarf Binaries: Implications for LISA

We explore the long-term evolution of mass-transferring white dwarf (WD) binaries undergoing both direct-impact and disk accretion and explore implications of such systems to gravitational-wave (GW) astronomy. We cover a broad range of initial component masses and show that these systems, the majority of which lie within the Laser Interferometer Space Antenna (LISA) sensitivity range, exhibit prominent negative orbital frequency evolution (chirp) for a significant fraction of their lifetimes. Using a galactic population synthesis, we predict ∼2700 of these systems will be observable with a negative chirp of 0.1 yr−2 by a space-based GW detector like LISA. We also show that detections of mass-transferring double WD systems by LISA may provide astronomers with unique ways of probing the physics governing close compact object binaries.
NOVEL QUANTUM COMPRESSOR DESIGNS USING NEW GENETIC ALGORITHM-BASED SIMULATOR, ANALYZER AND SYNTHESIZER SOFTWARE IN NANOTECHNOLOGY

Quantum and reversible logic circuits have found emerging attentions in nanotechnology, optical computing, quantum computing, and low power CMOS design. In this paper, we propose some new quantum and reversible compressors using our new genetic algorithm-based simulator, analyzer, and synthesizer software. The proposed quantum 4:2 and 6:2 compressor circuits are compared with the existing counterparts in terms of number of constant inputs, number of garbage outputs, delay and the quantum cost (QC). We have also designed quantum 7:2 compressor for the first time. The proposed quantum compressors are optimized in terms of QC and delay. The proposed designs can be used as a basic block in complex systems like multipliers, and can execute complicated operations better than the existing designs in literature.
Reducing antenna mechanical noise in precision spacecraft tracking

Doppler tracking of deep space probes is central to spacecraft navigation and many radio science investigations. The most sensitive Doppler observations to date were taken using the NASA/JPL Deep Space Network antenna DSS 25 (a 34 m diameter beam‐waveguide station instrumented with simultaneous X‐ and Ka‐band uplink and tropospheric scintillation calibration equipment) tracking the Cassini spacecraft. Those observations achieved Doppler fractional frequency stability (Doppler frequency fluctuation divided by center frequency, Δf/fo) ≈ 3 X 10−15 at 1000 s integration time. The leading noise in these very‐high‐sensitivity tracks was time‐dependent unmodeled motion of the ground antenna's phase center (caused, e.g., by antenna sag as elevation angle changes, unmodeled subreflector motion, wind loading, bulk motion of the antenna as it rolled over irregularities in its azimuth ring, etc.). This antenna mechanical noise has seemed irreducible since it is not clear how to build a large, moving, steel structure with intrinsic mechanical stability better than that of current tracking stations. Here we show how intrinsic mechanical noise of a large tracking antenna can be suppressed when two‐way Doppler tracking data and receive‐only Doppler data from a stiffer antenna are combined with suitable delays. Using this time delay correction procedure, the mechanical noise in the final Doppler observable can be reduced to that of the stiffer antenna. We demonstrate proof‐of‐concept experimentally and briefly discuss some practical considerations.
On the number of subgraphs of the Barabási-Albert random graph

We study a model of a random graph of the type of the Barabási-Albert preferential attachment model. We develop a technique that makes it possible to estimate the mathematical expectation for a fairly wide class of random variables in the model under consideration. We use this technique to prove a theorem on the asymptotics of the mathematical expectation of the number of subgraphs isomorphic to a certain fixed graph in the random graphs of this model.
The Hard X-Ray Emission of the Blazar PKS 2155–304

The synchrotron peak of the X-ray bright High Energy Peaked Blazar PKS 2155–304 occurs in the UV-EUV region and hence its X-ray emission (0.6–10 keV) lies mostly in the falling part of the synchrotron hump. We aim to study the X-ray emission of PKS 2155–304 during different intensity states in 2009–2014 using the XMM-Newton satellite. We studied the spectral curvature of all of the observations to provide crucial information on the energy distribution of the nonthermal particles. Most of the observations show curvature or deviation from a single power law and can be well modeled by a log parabola model. In some of the observations, we find spectral flattening after 6 keV. In order to find the possible origin of the X-ray excess, we built the Multiband Spectral Energy distribution. We find that the X-ray excess in PKS 2155–304 is difficult to fit in the one zone model but, could be easily reconciled in the spine/layer jet structure. The hard X-ray excess can be explained by the inverse Comptonization of the synchrotron photons (from the layer) by the spine electrons.
Determination of the neutral number density in the Io torus from Galileo‐EPD measurements

During the GALILEO spacecraft encounter with Io in December 1995, the Energetic Particles Detector (EPD) [Williams et al., 1992] measured pitch angle distributions with high spatial and temporal resolution. All ion and electron channels show a depletion of field‐aligned particles due to the interaction of trapped particles with the ionosphere / atmosphere of Jupiter. The medium nuclei channels, containing mainly sulphur and oxygen ions, show a second minimum for particles moving perpendicular to the magnetic field direction. This observation indicates that charge exchange between the singly‐charged energetic ions and neutral atoms in the Io torus represents an important loss mechanism for energetic ions within the Io torus regions. Additionally, knowing the cross‐sections of the involved charge exchange reactions it is possible to calculate the average neutral number density in the Io torus. The obtained result of ≈35 cm−3 is in good agreement with density estimations using ground based measurements.
Verifying and reporting Fast Radio Bursts

Fast Radio Bursts (FRBs) are a class of short-duration transients at radio wavelengths with inferred astrophysical origin. The prototypical FRB is a broadband signal that occurs over the extent of the receiver frequency range, is narrow in time, and is highly dispersed, following a $\nu^{-2}$ relation. However, some FRBs appear band-limited, and show apparent scintillation, complex frequency-dependent structure, or multi-component pulse shapes. While there is sufficient evidence that FRBs are indeed astrophysical, their one-off nature necessitates extra scrutiny when reporting a detection as bona fide and not a false positive. Currently, there is no formal validation framework for FRBs, rather a set of community practices. In this article, we discuss potential sources of false positives, and suggest a framework in which FRB-like events can be evaluated as real or otherwise. We present examples of false-positive events in data from the Arecibo, LOFAR, and Nanshan telescopes, which while FRB-like, are found to be due to instrumental variations, noise, and radio-frequency interference. Differentiating these false-positive detections from astrophysical events requires knowledge and tests beyond thresholded single-pulse detection. We discuss post-detection analyses, verification tests, and datasets which should be provided when reporting an FRB detection.
Evidence for a Z$_2$ topological ordered quantum spin liquid in a kagome-lattice antiferromagnet

A quantum spin liquid with a $Z_2$ topological order has long been thought to be important for the application of quantum computing and may be related to high-temperature superconductivity. While a two-dimensional kagome antiferromagnet may host such a state, strong experimental evidences are still lacking. Here we show that the spin excitations from the kagome planes in magnetically ordered Cu$_4$(OD)$_6$FBr and non-magnetically ordered Cu$_3$Zn(OD)$_6$FBr are similarly gapped although the content of inter-kagome-layer Cu$^{2+}$ ions changes dramatically. This suggests that the spin triplet gap and continuum of the intrinsic kagome antiferromagnet are robust against the interlayer magnetic impurities. Our results show that the ground state of Cu$_3$Zn(OD)$_6$FBr is a gapped quantum spin liquid with Z$_2$ topological order.
Identification of two hard X-ray emitting Be stars using the HEAO 1 scanning modulation collimator

Using precise positions from the HEAO 1 Scanning Modulation Collimator experiment, two hard X-ray sources, 4U 0728 - 25 = 3A 0726 - 260 and 4U 2206 + 54 = 3A 2206 + 543, are identified with early-type stars. In both cases broad (10 A FWHM) H-alpha emission is detected. The UBV colors suggest that the optical counterparts are main-sequence B0-B2 stars at 2-6 kpc, implying a mean X-ray luminosity of order 10 to the 35th ergs/sq cm s (2-10 keV). The X-ray emission in both cases is highly variable, and it is suggested that they belong to the class of X-ray emitting Be stars, containing a neutron star in a widely separated binary system.
Instability of the Proca field on Kerr spacetime

The field of a massive vector boson in the vicinity of a rotating black hole is known to suffer an instability, due to the exponential amplification of (co-rotating, low-frequency) bound state modes by black hole superradiance. Here we calculate the bound state spectrum by exploiting the separation of variables recently achieved by Frolov, Krtou, Kubiz'ak and Santos (FKKS) for the Proca field on Kerr-(A)dS-NUT spacetimes of arbitrary dimension. Restricting to the 4D Kerr case, we first establish the relationship between the FKKS and Teukolsky variables in the massless case; obtain exact results for the angular eigenvalues in the marginally-bound case; and present a spectral method for solving the angular equation in the general case. We then demonstrate that all three physical polarizations can be recovered from the FKKS ansatz, resolving an open question. We present numerical results for the instability growth rate for a selection of modes of all three polarizations, and discuss physical implications.
A search for gravitationally lensed quasars and quasar pairs in Pan-STARRS1: spectroscopy and sources of shear in the diamond 2M1134−2103

We present results of a systematic search for gravitationally lensed quasars in Pan-STARRS1. Our final sample of candidates comprises of 91 systems, not including 25 rediscovered lensed quasars and quasar pairs. In the absence of spectroscopy to verify the lensing nature of the candidates, the main sources of contaminants are likely to be quasar pairs, which we consider to be a byproduct of our work, and a smaller number of quasar + star associations. Among the independently discovered quads is 2M1134−2103, for which we obtained spectroscopy for the first time, finding a redshift of 2.77 for the quasar. There is evidence for microlensing in at least one image. We perform detailed mass modelling of this system using archival imaging data, and find that the unusually large shear responsible for the diamond-like configuration can be attributed mainly to a faint companion ∼4 arcsec away, and to a galaxy group/cluster ∼30 arcsec away. We also set limits of z ∼ 0.5–1.5 on the redshift of the lensing galaxy, based on its brightness, the image separation of the lensed images, and an analysis of the observed photometric flux ratios.
Paramagnetic Meissner effect in multiply-connected superconductors

We have measured a paramagnetic Meissner effect in $\mathrm{Nb}\char21{}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}\char21{}\mathrm{Nb}$ Josephson-junction arrays using a scanning superconducting quantum interference device microscope. The arrays exhibit diamagnetism for some cooling fields and paramagnetism for other cooling fields. The measured mean magnetization is always small, $〈{\ensuremath{\Phi}}_{\mathrm{tot}}\ensuremath{-}{\ensuremath{\Phi}}_{\mathrm{ext}}〉l0.3{\ensuremath{\Phi}}_{0}$ (in terms of flux per unit cell of the array, where ${\ensuremath{\Phi}}_{0}$ is the flux quantum), for the range of cooling fields investigated $(\ensuremath{-}12{\ensuremath{\Phi}}_{0}$ to $12{\ensuremath{\Phi}}_{0}). $ We demonstrate that a different model of magnetic screening, valid for multiply-connected superconductors, reproduces all of the essential features of paramagnetism that we observe and that no exotic mechanism, such as d-wave superconductivity, is needed for paramagnetism.