Miracle-dz/UniFAR-FTUs huggingface dataset:
Interaction Screening for Ultrahigh-Dimensional Data

In ultrahigh-dimensional data analysis, it is extremely challenging to identify important interaction effects, and a top concern in practice is computational feasibility. For a dataset with n observations and p predictors, the augmented design matrix including all linear and order-2 terms is of size n × (p2 + 3p)/2. When p is large, say more than tens of hundreds, the number of interactions is enormous and beyond the capacity of standard machines and software tools for storage and analysis. In theory, the interaction-selection consistency is hard to achieve in high-dimensional settings. Interaction effects have heavier tails and more complex covariance structures than main effects in a random design, making theoretical analysis difficult. In this article, we propose to tackle these issues by forward-selection-based procedures called iFOR, which identify interaction effects in a greedy forward fashion while maintaining the natural hierarchical model structure. Two algorithms, iFORT and iFORM, are studied. Computationally, the iFOR procedures are designed to be simple and fast to implement. No complex optimization tools are needed, since only OLS-type calculations are involved; the iFOR algorithms avoid storing and manipulating the whole augmented matrix, so the memory and CPU requirement is minimal; the computational complexity is linear in p for sparse models, hence feasible for p ≫ n. Theoretically, we prove that they possess sure screening property for ultrahigh-dimensional settings. Numerical examples are used to demonstrate their finite sample performance. Supplementary materials for this article are available online.
Bifurcation of attritional and large losses in an additive IBNR environment

In certain segments, IBNR calculations on paid triangles are more stable than on incurred triangles. However, calculations on payments often do not adequately take large losses into account. An IBNR method which separates large and attritional losses and thus allows to use payments for the attritional and incurred amounts for the large losses has been introduced by Riegel (see Riegel, U. (2014). A bifurcation approach for attritional and large losses in chain ladder calculations. Astin Bulletin 44, 127–172). The method corresponds to a stochastic model that is based on Mack’s chain ladder model. In this paper, we analyse a quasi-additive version of this model, i.e. a version which is in essence based on the assumptions of the additive (or incremental loss ratio) method. We describe the corresponding IBNR method and derive formulas for the mean squared error of prediction.
Electrical and optical properties of MoS$_{2}$,MoO$_{x=2,3}$(MoSO)/RGO heterostructure

We report on transport properties of the controllable large area MoSO/Reduced graphene oxide(RGO) heterostructures electrodeposited on FTO substrates and its comparision with theoretical calculations on MoSo/Gr. I-V characteristics of the heterostructure made by P or n-type MoSO, exhibit Schottkey behavior in the interface similar to the MoS$_{2}$/Gr ones. Theoretical calculations show significant effects of lateral layer size as well as layer number in the electronic properties. In monolayer MoS$_{2}$/Gr by increasing the lateral size the energy gap disappears and the Fermi level shifts towards valence band. In the case of bilayer MoS$_{2}$ on bilayer Gr structure, the Fermi level shift is again towards valence band but, the gap is slightly higher than the monolayer structure. We found that the experimentally obtained results for n-type MoSO/RGO results are qualitatively in agreement with theoretical calculations of the MoS$_{2}$/Gr heterostructure. These results are beneficial to understand and design the high quality and low cost MoSO/RGO based electronic, optoelectronic and energy storage devices or cocatalysts.
GalMod: A Galactic Synthesis Population Model

We present a new Galaxy population synthesis Model, GalMod. GalMod is a star-count model featuring an asymmetric bar/bulge as well as spiral arms and related extinction. The model, initially introduced in Pasetto et al., has been here completed with a central bar, a new bulge description, new disk vertical profiles, and several new bolometric corrections. The model can generate synthetic mock catalogs of visible portions of the Milky Way, external galaxies like M31, or N-body simulation initial conditions. At any given time, e.g., at a chosen age of the Galaxy, the model contains a sum of discrete stellar populations, namely the bulge/bar, disk, and halo. These populations are in turn the sum of different components: the disk is the sum of the spiral arms, thin disks, a thick disk, and various gas components, while the halo is the sum of a stellar component, a hot coronal gas, and a dark-matter component. The Galactic potential is computed from these population density profiles and used to generate detailed kinematics by considering up to the first four moments of the collisionless Boltzmann equation. The same density profiles are then used to define the observed color–magnitude diagrams in a user-defined field of view (FoV) from an arbitrary solar location. Several photometric systems have been included and made available online, and no limits on the size of the FoV are imposed thus allowing full-sky simulations, too. Finally, we model the extinction by adopting a dust model with advanced ray-tracing solutions. The model's Web page (and tutorial) can be accessed at www.GalMod. org and support is provided at Galaxy.Model@yahoo.com.
Free-carrier screening of polarization fields in wurtzite GaN/InGaN laser structures

The free-carrier screening of macroscopic polarization fields in wurtzite GaN/InGaN quantum well lasers is investigated via a self-consistent tight-binding approach. We show that the high carrier concentrations found experimentally in nitride laser structures effectively screen the built-in spontaneous and piezoelectricpolarization fields, thus inducing a “field-free” band profile. Our results explain some heretofore puzzling experimental data on nitride lasers, such as the unusually high lasing excitation thresholds and emission blue shifts for increasing excitation levels.
Initiation and Development of Rear Inflow within the 28-29 June 1989 North Dakota Mesoconvective System

Abstract Five dual-Doppler analyses spanning a period of 1.5 h are used to document the initiation and development of rear inflow within a High Plains squall line. The squall line developed as part of the 28-29 June 1989 mesoconvective system that passed through the North Dakota Thunderstorm Project observational network. This storm was explosively initiated along a preexisting, isolated gust front in an environment of much instability and weak upper-air flow, and moved within dual-Doppler coverage soon after its initiation. The kinematic analyses were performed over a 90-min period as the squall line continued to develop and move to the east-northeast. The Doppler analyses reveal that the rear inflow was initiated near the high-reflectivity cores of the squall line, within 20 min of the formation of the system. With time, the, rear inflow expanded rearward, increased in intensity, and descended to near the surface behind the northern section of the squall line. In regions where the squall line dissipated.
HIP 21539 is not a past very close neighbour of the Sun

Aims: A previous study claimed that the star HIP 21539 passed close to the Sun, at a distance of 1.9 pc, around 0.14 Myr ago. We show that this is not the case. Methods: We redetermined the trajectory of the star relative to the Sun using a new accurate radial velocity from the HARPS spectrograph combined with the recent Gaia-TGAS astrometry. Results: With this new data, the closest approach of HIP 21539 to the Sun is now 17 pc, instead of 1.9 pc. Conclusions: At this distance, the star has not perturbed the Oort cloud.
Magnus: A New Resistive MHD Code with Heat Flow Terms

We present a new magnetohydrodynamic (MHD) code for the simulation of wave propagation in the solar atmosphere, under the effects of electrical resistivity—but not dominant—and heat transference in a uniform 3D grid. The code is based on the finite-volume method combined with the HLLE and HLLC approximate Riemann solvers, which use different slope limiters like MINMOD, MC, and WENO5. In order to control the growth of the divergence of the magnetic field, due to numerical errors, we apply the Flux Constrained Transport method, which is described in detail to understand how the resistive terms are included in the algorithm. In our results, it is verified that this method preserves the divergence of the magnetic fields within the machine round-off error ( ). For the validation of the accuracy and efficiency of the schemes implemented in the code, we present some numerical tests in 1D and 2D for the ideal MHD. Later, we show one test for the resistivity in a magnetic reconnection process and one for the thermal conduction, where the temperature is advected by the magnetic field lines. Moreover, we display two numerical problems associated with the MHD wave propagation. The first one corresponds to a 3D evolution of a vertical velocity pulse at the photosphere–transition–corona region, while the second one consists of a 2D simulation of a transverse velocity pulse in a coronal loop.
Distant clusters of galaxies in the 2XMM/SDSS footprint: follow-up observations with the LBT

Context. Galaxy clusters at high redshift are important to test cosmological models and models for the growth of structure. They are difficult to find in wide-angle optical surveys, however, leaving dedicated follow-up of X-ray selected candidates as one promising identification route. Aims. We aim to increase the number of galaxy clusters beyond the SDSS-limit, z ~ 0.75. Methods. We compiled a list of extended X-ray sources from the 2XMMp catalogue within the footprint of the Sloan Digital Sky Survey. Fields without optical counterpart were selected for further investigation. Deep optical imaging and follow-up spectroscopy were obtained with the Large Binocular Telescope, Arizona (LBT), of those candidates not known to the literature. Results. From initially 19 candidates, selected by visually screening X-ray images of 478 XMM-Newton observations and the corresponding SDSS images, 6 clusters were found in the literature. Imaging data through r,z filters were obtained for the remaining candidates, and 7 were chosen for multi-object (MOS) spectroscopy. Spectroscopic redshifts, optical magnitudes, and X-ray parameters (flux, temperature, and luminosity) are presented for the clusters with spectroscopic redshifts. The distant clusters studied here constitute one additional redshift bin for studies of the L X − T relation, which does not seem to evolve from high to low redshifts. Conclusions. The selection method of distant galaxy clusters presented here was highly successful. It is based solely on archival optical (SDSS) and X-ray ( XMM-Newton ) data. Out of 19 selected candidates, 6 of the 7 candidates selected for spectroscopic follow-up were verified as distant clusters, a further candidate is most likely a group of galaxies at z ~ 1.21. Out of the remaining 12 candidates, 6 were known previously as galaxy clusters, one object is a likely X-ray emission from an AGN radio jet, and for 5 we see no clear evidence for them to be high-redshift galaxy clusters.
Comprehensive comparison of numerical relativity and effective-one-body results to inform improvements in waveform models for binary neutron star systems

We present a detailed comparison between tidal effective-one-body (EOB) models and new state-of-the-art numerical relativity simulations for non-spinning binary neutron star systems. This comparison is the most extensive one to date, covering a wide range in the parameter space and encompassing the energetics of the binary, the periastron advance, the time and frequency evolution of the gravitational wave phase for the dominant mode, and several subdominant modes. We consider different EOB models with tidal effects that have been proposed, including the model with dynamical tides of [Phys.Rev.Lett. 116 (2016) no.18, 181101] and the gravitational self-force (GSF) inspired tidal EOB model of [Phys.Rev.Lett. 114 (2015) no.16, 161103]. The EOB model with dynamical tides leads to the best representation of the systems considered here, however, the differences to the GSF-inspired model are small. A common feature is that for systems where matter effects are large, i.e. stiff equations of state or small total masses, all EOB models underestimate the tidal effects and differences to the results from numerical relativity simulations become noticeable near the merger. We analyze this regime to diagnose the shortcomings of the models in the late inspiral, where the two neutron stars are no longer isolated bodies moving in vacuum. Our work will serve to guide further advances in modeling these systems.
Heegaard Floer homology and integer surgeries on links

Let L be a link in an integral homology three-sphere. We give a description of the Heegaard Floer homology of integral surgeries on L in terms of some data associated to L, which we call a complete system of hyperboxes for L. Roughly, a complete systems of hyperboxes consists of chain complexes for (some versions of) the link Floer homology of L and all its sublinks, together with several chain maps between these complexes. Further, we introduce a way of presenting closed four-manifolds with b_2^+ > 1 by four-colored framed links in the three-sphere. Given a link presentation of this kind for a four-manifold X, we then describe the Ozsvath-Szabo mixed invariants of X in terms of a complete system of hyperboxes for the link. Finally, we explain how a grid diagram produces a particular complete system of hyperboxes for the corresponding link.
The spectrum of the brown dwarf candidate PC0025+0447

A spectrum of the cool dwarf star PC0025+0447 obtained with the Low Resolution Imaging Spectrograph at the Keck telescope yields an upper limit on the lithium to hydrogen ratio. The limit is temperature dependent and ranges from 5X10“ 10 for an effective temperature of 2500 K to IX10“ 10 at 1900 K. A definitive spectrum of the star’s chromospheric emission is presented, but the prominence of the Balmer series is due to the weak thermal emission of the photosphere, rather than extraordinary activity. PC0025+0447 dwarf.
Multi-wavelength study of the gravitational lens system RXS J113155.4-123155. I. Multi-epoch optical and near infrared imaging

Aims. RXS J113155.4-123155 (z = 0.66) is a quadruply imaged lensed quasar with a resolved Einstein Ring. The goal of this paper is to provide a full characterization of this system, and more particularly accurate astrometry and photometry. These observational constraints constitute a mandatory ingredient for the precise determination of the lens mass profile, the derivation of the Hubble constant H0 from time delay measurements and investigations on the presence of massive substructures in the lensing galaxy. Methods. Visible and near-infrared imaging observations of RXS J113155.4-123155 were carried out at various epochs using several ground based telescopes and the HST. The frames have been deconvolved using the MCS algorithm. A Singular Isothermal Ellipsoid (SIE) + external shear has been used to model the lensing galaxy potential. Results. MCS deconvolution enables us to separate the flux of the QSO (point-like images) from that of its host galaxy and to accurately track the flux variations of the point-like images in various filters. The deconvolved frames unveil several multiply imaged structures in the Einstein ring and an unidentified object in the vicinity of the lensing galaxy. We discuss the lightcurves and the chromatic flux ratio variations and deduce that both intrinsic variability and microlensing took place during a span longer than one year. We demonstrate that microlensing may easily account for the so called anomalous flux ratios presented in the discovery paper. However, the observed flux ratios are still poorly reproduced when modeling the lens potential with a SIE+shear. We argue that this disagreement can hardly be explained by milli-lensing caused by substructures in the lensing galaxy. A solution proposed in Paper II consists in a more complex lens model including an octupole term to the lens gravitational potential.
Galactic Planetary Nebulae as Probes of Radial Metallicity Gradients and Other Abundance Patterns

We use planetary nebulae (PNe) as probes to determine the Galactic radial oxygen gradients and other abundance patterns. We select data homogeneously from recent data sets, including PNe at large Galactocentric distances. The radial oxygen gradient calculated for the general PN population, which probes the region from the Galactic center out to ∼28 kpc, is shallow, with slope ∼−0.02 dex kpc−1, in agreement with previous findings. We looked for time evolution of the metallicity gradient using PNe with different age progenitors as metallicity probes. We identify PNe whose progenitor stars are younger than 1 Gyr (YPPNe) and those whose progenitor stars are older than 7.5 Gyr (OPPNe) based on the comparison between evolutionary yields and elemental abundances of the PNe. By studying OPPNe and YPPNe separately, we found that (i) the OPPNe oxygen gradient is shallower (∼−0.015 dex kpc−1) than that derived from YPPNe (∼−0.027 dex kpc−1); (ii) the OPPNe inner radial distribution of oxygen is compatible with no gradient to the radial extent of the thick disk population (∼10 kpc), similarly to what has been observed in thick disk stars; and (iii) PNe (especially OPPNe) indicate that significant gradient slope is limited to Galactocentric distances between ∼10 and ∼13.5 kpc, as observed for open clusters and field stars. Outside this range, the distribution is almost flat. We found that the radial oxygen gradient is steeper for a PN population closer to the Galactic disk, similar to what is observed in the general stellar population by the SEGUE survey. We use our novel population dating to compare our results with current chemical evolutionary models and gradients from other Galactic populations for insight on galaxy chemical evolution.
Second order Galilean fluids and Stokes’ law

We study the second derivative effects on the constitutive relations of an uncharged parity-even Galilean fluid using the null fluid framework. Null fluids are an equivalent representation of Galilean fluids in terms of a higher dimensional relativistic fluid, which makes the Galilean symmetries manifest and tractable. The analysis is based on the off-shell formalism of hydrodynamics. We use this formalism to work out a generic algorithm to obtain the constitutive relations of a Galilean fluid up to arbitrarily high derivative orders, and later specialize to second order. Finally, we study the Stokes’ law which determines the drag force on an object moving through a fluid, in presence of certain second order terms. We identify the second order transport coefficients which leave the drag force invariant.
An Upper Limit on the Milky Way Mass from the Orbit of the Sagittarius Dwarf Satellite

As one of the most massive Milky Way (MW) satellites, the Sagittarius dwarf galaxy played an important role in shaping the Galactic disk and stellar halo morphologies. The disruption of Sagittarius over several close-in passages has populated the halo of our Galaxy with large-scale tidal streams and offers a unique diagnostic tool for measuring its gravitational potential. Here, we test different progenitor mass models for the MW and Sagittarius by modeling the full infall of the satellite. We constrain the mass of the Galaxy based on the kinematics of the satellite remnant and multiple tidal streams of Sagittarius. Our semianalytic modeling of the orbital dynamics agrees with full N-body simulations, and favors low values for the MW mass, . This conclusion eases the tension between ΛCDM and the observed parameters of the MW satellites.
SDSS-IV MaNGA: Environmental Dependence of the Mgb/ – Relation for Nearby Galaxies

We use a sample of ∼3000 galaxies from the MaNGA MPL-7 internal data release to study the α abundance distribution within low-redshift galaxies. We use the Lick index ratio Mgb/ as an α abundance indicator to study relationships between the α abundance distribution and galaxy properties such as effective stellar velocity dispersion within 0.3 effective radii (σ*), galaxy environment, and dark matter halo formation time (zf). We find that (1) all galaxies show a tight correlation between Mgb/ and (2) “old” (Hβ < 3) low-σ* galaxies in high local density environment and inner regions within galaxy groups are enhanced in Mgb/ , while “young” (Hβ > 3) galaxies and high-mass galaxies show no or less environmental dependence; (3) “old” galaxies with high-zf show enhanced Mgb/ over low- and medium-zf; and (4) Mgb/ gradients are close to zero and show dependence on σ* but no obvious dependence on the environment or zf. Our study indicates that stellar velocity dispersion or galaxy mass is the main parameter driving the Mgb/ enhancement, although environments appear to have modest effects, particularly for low- and medium-mass galaxies.
Dynamical topological quantum phase transitions for mixed states

We introduce and study dynamical probes of band structure topology in the post-quench time-evolution from mixed initial states of quantum many-body systems. Our construction generalizes the notion of dynamical quantum phase transitions (DQPTs), a real-time counterpart of conventional equilibrium phase transitions in quantum dynamics, to finite temperatures and generalized Gibbs ensembles. The non-analytical signatures hallmarking these mixed state DQPTs are found to be characterized by observable phase singularities manifesting in the dynamical formation of vortex-antivortex pairs in the interferometric phase of the density matrix. Studying quenches in Chern insulators, we find that changes in the topological properties of the Hamiltonian can be identified in this scenario, without ever preparing a topologically non-trivial or low-temperature initial state. Our observations are of immediate relevance for current experiments aimed at realizing topological phases in ultracold atomic gases.
Constraints on massive axion-like particles from X-ray observations of NGC 1275

If axion-like particles (ALPs) exist, photons can convert to ALPs on passage through regions containing magnetic fields. The magnetised intracluster medium of large galaxy clusters provides a region that is highly efficient at ALP-photon conversion. X-ray observations of Active Galactic Nuclei (AGNs) located within galaxy clusters can be used to search for and constrain ALPs, as photon-ALP conversion would lead to energy-dependent quasi-sinusoidal modulations in the X-ray spectrum of an AGN. We use Chandra observations of the central AGN of the Perseus Cluster, NGC1275, to place bounds on massive ALPs up to ma ∼ 10−11eV, extending previous work that used this dataset to constrain massless ALPs.
Nonlinear electrodynamics and FRW cosmology

Maxwell electrodynamics, considered as a source of the classical Einstein field equations, leads to the singular isotropic Friedmann solutions. We show that this singular behavior does not occur for a class of nonlinear generalizations of the electromagnetic theory. A mathematical toy model is proposed for which the analytical nonsingular extension of FRW solutions is obtained.