Miracle-dz/UniFAR-FTUs huggingface dataset:
Sign of viscous magnetoresistance in electron fluids

In sufficiently clean metals, it is possible for electrons to collectively flow as a viscous fluid at finite temperature. These viscous effects have been predicted to give a notable magnetoresistance, but whether the magnetoresistance is positive or negative has been debated. We argue that regardless of the strength of inhomogeneity, bulk magnetoresistance is always positive in the hydrodynamic regime. We also compute transport in weakly inhomogeneous metals across the ballistic-to-hydrodynamic crossover, where we also find positive magnetoresistance. The nonmonotonic temperature dependence of resistivity in this regime (a bulk Gurzhi effect) rapidly disappears upon turning on any finite magnetic field, suggesting that magnetotransport is a simple test for viscous effects in bulk transport, including at the onset of the hydrodynamic regime.
Exponential Decay and Lack of Analyticity for the System of the Kirchhoff Love Plates and Membrane Like Electric Network Equation with Fractional Partial Damping

The emphasis in this paper is on the Coupled System of a Kirchhoff Love Plate Equation with the Equation of a Membrane like Electrical Network, where the coupling is of higher order given by the Laplacian of the displacement velocity $-\gamma\Delta u_t$ and the Laplacian of the electric potential field $\gamma\Delta v_t$, here only one of the equations is conservative and the other has dissipative properties. The dissipative mechanism is given by an intermediate damping $(- \Delta)^\theta v_t$ between the electrical damping potential for $\theta=0$ and the Laplacian of the electric potential for $\theta=1$. We show that $S(t)=e^{\mathbb{B}t}$ is not analytic for $\theta\in[0,1]$, however $S(t)$ decays exponentially for $0\leq\theta\leq 1$.
Why Should the Q-method be Integrated Into the Design Science Research? A Systematic Mapping Study

The Q-method has been utilized over time in various areas, including information systems. In this study, we used a systematic mapping to illustrate how the Q-method was applied within Information Systems (IS) community and proposing towards integration of Q-method into the Design Sciences Research (DSR) process as a tool for future research DSR-based IS studies. In this mapping study, we collected peer-reviewed journals from Basket-of-Eight journals and the digital library of the Association for Information Systems (AIS). Then we grouped the publications according to the process of DSR, and different variables for preparing Q-method from IS publications. We found that the potential of the Q-methodology can be used to support each main research stage of DSR processes and can serve as the useful tool to evaluate a system in the IS topic of system analysis and design.
The Accretion History of AGN: A Newly Defined Population of Cold Quasars

Quasars are the most luminous of active galactic nuclei, and are perhaps responsible for quenching star formation in their hosts. The Stripe 82X catalog covers 31.3 deg2 of the Stripe 82 field, of which the 15.6 deg2 covered with XMM-Newton is also covered by Herschel/SPIRE. We have 2500 X-ray detected sources with multiwavelength counterparts, and 30% of these are unobscured quasars, with LX > 1044 erg s−1 and MB < −23. We define a new population of quasars that are unobscured, have X-ray luminosities in excess of 1044 erg s−1, have broad emission lines, and yet are also bright in the far-infrared, with a 250 μm flux density of S250 > 30 mJy. We refer to these Herschel-detected, unobscured quasars as “cold quasars. ” A mere 4% (21) of the X-ray- and optically selected unobscured quasars in Stripe 82X are detected at 250 μm. These cold quasars lie at z ∼ 1–3, have LIR > 1012 L⊙, and have star formation rates (SFRs) of ∼200–1400 M⊙ yr−1. Cold quasars are bluer in the mid-IR than the full quasar population, and 72% of our cold quasars have WISE W3 < 11.5 [Vega], while only 19% of the full quasar sample meets this criteria. Crucially, cold quasars have on average ∼nine times as much star formation as the main sequence of star-forming galaxies at similar redshifts. Although dust-rich, unobscured quasars have occasionally been noted in the literature before, we argue that they should be considered as a separate class of quasars due to their high SFRs. This phase is likely short-lived, as the central engine and immense star formation consume the gas reservoir. Cold quasars are type-1 blue quasars that reside in starburst galaxies.
Emission-line properties of the most luminous AGNs in massive galaxies at intermediate redshifts

We have analysed the emission-line properties of 6019 Type II active galactic nuclei (AGNs) at redshifts in the range 0.4–0.8 with [O iii] luminosities greater than $3 \times 10^8 \, \mathrm{L}_{\odot }$, characteristic of the Type II quasars first identified in population studies by Zakamska et al. The AGNs are drawn from the CMASS sample of galaxies with stellar masses greater than $10^{11} \, \mathrm{M}_{\odot }$ that were studied as part of the Baryon Oscillation Spectroscopic Survey (BOSS) and comprise 0.5 per cent of the total population of these galaxies. Individual spectra have low S/N, so the analysis is carried out on stacked spectra in bins of [O iii] luminosity and estimated stellar age. The emission line ratios of the stacks are well fit with simple uniform-density photoionization models with metallicities between solar and twice solar. In the stacks, a number of emission lines are found to have distinct broad components requiring a double Gaussian rather than a single Gaussian fit, indicative of outflowing ionized gas. These are: [O iii] λ4959, [O iii] λ5007, [O ii] λ3727,3729, and H αλ6563. Higher ionization lines such as [Ne iii] λ3869 and [Ne v] λ3345 are detected in the stacks, but are well fit by single Gaussians. The broad components typically contain a third of the total line flux and have widths of 600 km s−1 for the oxygen lines and 900 km s−1 for H α. The fraction of the flux in the broad component and its width are independent of [O iii] luminosity, stellar age, radio, and mid-IR luminosity. The stellar mass of the galaxy is the only parameter we could identify that influences the width of the broad line component.
GreyReID: A Two-stream Deep Framework with RGB-grey Information for Person Re-identification

In this paper, we observe that most false positive images (i.e., different identities with query images) in the top ranking list usually have the similar color information with the query image in person re-identification (Re-ID). Meanwhile, when we use the greyscale images generated from RGB images to conduct the person Re-ID task, some hard query images can obtain better performance compared with using RGB images. Therefore, RGB and greyscale images seem to be complementary to each other for person Re-ID. In this paper, we aim to utilize both RGB and greyscale images to improve the person Re-ID performance. To this end, we propose a novel two-stream deep neural network with RGB-grey information, which can effectively fuse RGB and greyscale feature representations to enhance the generalization ability of Re-ID. Firstly, we convert RGB images to greyscale images in each training batch. Based on these RGB and greyscale images, we train the RGB and greyscale branches, respectively. Secondly, to build up connections between RGB and greyscale branches, we merge the RGB and greyscale branches into a new joint branch. Finally, we concatenate the features of all three branches as the final feature representation for Re-ID. Moreover, in the training process, we adopt the joint learning scheme to simultaneously train each branch by the independent loss function, which can enhance the generalization ability of each branch. Besides, a global loss function is utilized to further fine-tune the final concatenated feature. The extensive experiments on multiple benchmark datasets fully show that the proposed method can outperform the state-of-the-art person Re-ID methods. Furthermore, using greyscale images can indeed improve the person Re-ID performance.
Robust Translational Force Control of Multi-Rotor UAV for Precise Acceleration Tracking

In this article, we introduce a translational force control method with disturbance observer (DOB)-based force disturbance cancellation for precise 3-D acceleration control of a multi-rotor unmanned aerial vehicle (UAV). The acceleration control of the multi-rotor requires conversion of the desired acceleration signal to the desired roll, pitch, and total thrust. However, because the attitude dynamics and the thrust dynamics are different, simple kinematic signal conversion without consideration of those difference can cause serious performance degradation in acceleration tracking. Unlike most existing translational force control techniques that are based on such simple inversion, our new method allows controlling the acceleration of the multi-rotor more precisely by considering the dynamics of the multi-rotor during the kinematic inversion. By combining the DOB with the translational force system that includes the improved conversion technique, we achieve robustness with respect to the external force disturbances that hinder the accurate acceleration control. $\mu $ -analysis is performed to ensure the robust stability of the overall closed-loop system, considering the combined effect of various possible model uncertainties. Both simulation and experiment are conducted to validate the proposed technique, which confirms the satisfactory performance to track the desired acceleration of the multi-rotor. Note to Practitioners—This article presents a method for controlling the acceleration of a multi-rotor accurately under the presence of translational force disturbance. Unlike the existing methods, the new signal conversion technique that considers the dynamics of the multi-rotor in the process of converting the target translational acceleration signal to the target roll, pitch, and thrust signal enables a more accurate translational force control. The DOB structure applied to the translational force control system overcomes the acceleration control performance deterioration caused by external translational force disturbance. Through the combination of the two techniques, the acceleration of the multi-rotor can be accurately controlled not only in the nominal environment but also in the presence of translational force disturbance.
Operator inequalities I. Models and ergodicity.

We discuss when an operator, subject to a rather general inequality in hereditary form, admits a unitarily equivalent functional model of Agler type in the reproducing kernel Hilbert space associated to the inequality. To the contrary to the previous work, the kernel need not be of Nevanlinna-Pick type. We derive some consequences concerning the ergodic behavior of the operator.
First demonstration of a bubble-assisted Liquid Hole Multiplier operation in liquid argon

We demonstrate, for the first time, the operation of a bubble-assisted Liquid Hole Multiplier (LHM) in liquid argon. The LHM, sensitive to both radiation-induced ionization electrons and primary scintillation photons, consists of a perforated electrode immersed in the noble liquid, with a stable gas-bubble trapped underneath. Electrons deposited in the liquid or scintillation-induced photoelectrons emitted from a photocathode on the electrode's surface, are collected into the holes; after crossing the liquid-gas interface, they induce electroluminescence within the bubble. After having validated in previous works the LHM concept in liquid xenon, we provide here first preliminary results on its operation in liquid argon. We demonstrate the bubble containment under a Thick Gas Electron Multiplier (THGEM) electrode and provide the detector response to alpha particles, recorded with SiPMs and with a PMT—under electroluminescence and with modest gas multiplication; the imaging capability is also demonstrated.
Existence and Asymptotics of Nonlinear Helmholtz Eigenfunctions

We prove the existence and asymptotic expansion of a large class of solutions to nonlinear Helmholtz equations of the form \begin{equation*} (\Delta - \lambda^2) u = N[u], \end{equation*} where $\Delta = -\sum_j \partial^2_j$ is the Laplacian on $\mathbb{R}^n$ with sign convention that it is positive as an operator, $\lambda$ is a positive real number, and $N[u]$ is a nonlinear operator that is a sum of monomials of degree $\geq p$ in $u$, $\overline{u}$ and their derivatives of order up to two, for some $p \geq 2$. Nonlinear Helmholtz eigenfunctions with $N[u]= \pm |u|^{p-1} u$ were first considered by Gutierrez. Such equations are of interest in part because, for certain nonlinearities $N[u]$, they furnish standing waves for nonlinear evolution equations, that is, solutions that are time-harmonic. We show that, under the condition $(p-1)(n-1)/2 > 2$ and $k > (n-1)/2$, for every $f \in H^{k+2}(\mathbb{S}^{n-1})$ of sufficiently small norm, there is a nonlinear Helmholtz function taking the form \begin{equation*} u(r, \omega) = r^{-(n-1)/2} \Big( e^{-i\lambda r} f(\omega) + e^{+i\lambda r} g(\omega) + O(r^{-\epsilon}) \Big), \text{ as } r \to \infty, \quad \epsilon > 0, \end{equation*} for some $g \in H^{k}(\mathbb{S}^{n-1})$. Moreover, we prove the result in the general setting of asymptotically conic manifolds.
Dynamics of Riemann waves with sharp measure-controlled damping.

This paper is concerned with locally damped semilinear wave equations defined on compact Riemannian manifolds with boundary. We present a construction of measure-controlled damping regions which are sharp in the sense that their summed interior and boundary measures are arbitrarily small. The construction of this class of open sets is purely geometric and allows us to prove a new observability inequality in terms of potential energy rather than the usual one with kinetic energy. A unique continuation property is also proved. Then, in three-dimension spaces, we establish the existence of finite dimensional smooth global attractors for a class of wave equations with nonlinear damping and forces with critical Sobolev growth. In addition, by means of an obstacle control condition, we show that our class of measure-controlled regions satisfies the well-known geometric control condition (GCC). Therefore, many of known results for the stabilization of wave equations hold true in the present context.
A General Prescription for Semi-Classical Holography

We present a version of holographic correspondence where bulk solutions with sources localized on the holographic screen are the key objects of interest, and not bulk solutions defined by their boundary values on the screen. We can use this to calculate semi-classical holographic correlators in fairly general spacetime regions, including flat space with timelike boundaries. In AdS, the distinction between our approach and the standard Dirichlet-like approach is superficial. But in more general settings, the analytic continuation of the Dirichlet Green function does not lead to a Feynman propagator in the bulk. Our prescription avoids this problem. Furthermore, in Lorentzian signature we find an additional homogeneous mode. This is a natural proxy for the AdS normalizable mode and allows us to do bulk reconstruction. Perturbatively adding bulk interactions to these discussions is straightforward. We conclude by elevating some of these ideas into a general philosophy about mechanics and field theory. We argue that localizing sources on suitable submanifolds can be an instructive alternative formalism to treating these submanifolds as boundaries.
A bayesian-like approach to derive chemical abundances in type-2 active galactic nuclei based on photoionization models

We present a new methodology for the analysis of the emission lines of the interstellar medium in the narrow-line regions around type-2 active galactic nuclei. Our aim is to provide a recipe that can be used for large samples of objects in a consistent way using different sets of optical emission lines that takes into the account possible variations from the O/H–N/O relation to use [N ii] lines. Our approach consists of a bayesian-like comparison between certain observed emission-line ratios sensitive to total oxygen abundance, nitrogen-to-oxygen ratio, and ionization parameter with the predictions from a large grid of photoionization models calculated under the most usual conditions in this environment. We applied our method to a sample of Seyfert 2 galaxies with optical emission-line fluxes and determinations of their chemical properties from detailed models in the literature. Our results agree within the errors with other results and confirm the high metallicity of the objects of the sample, with N/O values consistent with a large secondary production of N, but with a large dispersion. The obtained ionization parameters for this sample are much larger than those for star-forming object at the same metallicity.
HAYDN -- High-precision AsteroseismologY of DeNse stellar fields (ESA Voyage 2050 White Paper)

In the last decade, the Kepler and CoRoT space-photometry missions have demonstrated the potential of asteroseismology as a novel, versatile and powerful tool to perform exquisite tests of stellar physics, and to enable precise and accurate characterisations of stellar properties, with impact on both exoplanetary and Galactic astrophysics. Based on our improved understanding of the strengths and limitations of such a tool, we argue for a new small/medium space mission dedicated to gathering high-precision, high-cadence, long photometric series in dense stellar fields. Such a mission will lead to breakthroughs in stellar astrophysics, especially in the metal poor regime, will elucidate the evolution and formation of open and globular clusters, and aid our understanding of the assembly history and chemodynamics of the Milky Way's bulge and few nearby dwarf galaxies.
Three-dimensional Density Structure of a Solar Coronal Streamer Observed by SOHO/LASCO and STEREO/COR2 in Quadrature

Helmet streamers are a prominent manifestation of magnetic structures with current sheets in the solar corona. These large-scale structures are regions with high plasma density, overlying active regions and filament channels. We investigate the three-dimensional (3D) structure of a coronal streamer, observed simultaneously by white-light coronagraphs from two vantage points near quadrature (the Solar and Heliospheric Observatory (SOHO)/Large Angle and Spectrometric Coronagraph Experiment (LASCO) and the Solar Terrestrial Relations Observatory (STEREO)/Coronagraph 2 (COR2)). We design a forward model based on plausible assumptions about the 3D streamer structure taken from physical models (a plasma slab centered around a current sheet). The streamer stalk is approximated by a plasma slab, with an electron density that is characterized by three separate functions describing the radial, transverse, and face-on profiles, respectively. For the first time, we simultaneously fit the observational data from SOHO and STEREO using a multivariate minimization algorithm. The streamer plasma sheet contains a number of brighter and darker ray-like structures with the density contrast up to about a factor of 3 between them. The densities derived using polarized and unpolarized data are similar. We demonstrate that our model corresponds well to the observations.
Learning the best thermoelectric nanoscale heat engines through evolving network topology

The quest to identify the best heat engine has been at the center of science and technology. Thermoelectric nanoscale heat engines convert heat flows into useful work in the form of electrical power and promise the realization of on-chip power production. Considerable studies have so far revealed the potentials to yield an enhanced efficiency originating from quantum confinement effects and energy-dependent transport properties. However, the full benefit of many-body interactions in thermoelectric is yet to be investigated; identifying the optimal interaction is a hard problem due to combinatorial explosion of the search space, which makes brute-force searches infeasible. Here we tackle this problem with reinforcement learning of network topology in interacting electronic systems, and identify a set of the best thermoelectric nanoscale engines. Harnessing many-body interactions, we show that the maximum possible values of the thermoelectric figure of merit and the power factor can be enhanced by orders of magnitudes for generic single-electron levels. This allows for simple and flexible design of realizing the asymptotic Carnot efficiency with subextensive, but still nonzero and stable power. To realize the optimal nanoscale engines, we propose concrete physical setups based on quantum-dot arrays. The developed framework of reinforcement learning through evolving network topology thus enables one to identify full potential of nanoscale systems.
Correlation Clustering with Same-Cluster Queries Bounded by Optimal Cost

Several clustering frameworks with interactive (semi-supervised) queries have been studied in the past. Recently, clustering with same-cluster queries has become popular. An algorithm in this setting has access to an oracle with full knowledge of an optimal clustering, and the algorithm can ask the oracle queries of the form, "Does the optimal clustering put vertices $ u $ and $ v $ in the same cluster? " Due to its simplicity, this querying model can easily be implemented in real crowd-sourcing platforms and has attracted a lot of recent work. In this paper, we study the popular correlation clustering problem (Bansal et al., 2002) under this framework. Given a complete graph $G=(V,E)$ with positive and negative edge labels, correlation clustering objective aims to compute a graph clustering that minimizes the total number of disagreements, that is the negative intra-cluster edges and positive inter-cluster edges. Let $ C_{OPT} $ be the number of disagreements made by the optimal clustering. We present algorithms for correlation clustering whose error and query bounds are parameterized by $C_{OPT}$ rather than by the number of clusters. Indeed, a good clustering must have small $C_{OPT}$. Specifically, we present an efficient algorithm that recovers an exact optimal clustering using at most $2C_{OPT} $ queries and an efficient algorithm that outputs a $2$-approximation using at most $C_{OPT} $ queries. In addition, we show under a plausible complexity assumption, there does not exist any polynomial time algorithm that has an approximation ratio better than $1+\alpha$ for an absolute constant $\alpha >0$ with $o(C_{OPT})$ queries. We extensively evaluate our methods on several synthetic and real-world datasets using real crowd-sourced oracles. Moreover, we compare our approach against several known correlation clustering algorithms.