Miracle-dz/UniFAR-FTUs huggingface dataset:
The quiescent X-ray spectrum of accreting black holes

The quiescent state is the dominant accretion mode for black holes on all mass scales. Our knowledge of the X-ray spectrum is limited due to the characteristic low luminosity in this state. Herein, we present an analysis of the sample of dynamically-confirmed stellar-mass black holes observed in quiescence in the Chandra/XMM-Newton/Suzaku era resulting in a sample of 8 black holes with � 570 ks of observations. In contrast to the majority of AGN where observations are limited by contamination from diffuse gas, the stellar-mass systems allow for a clean study of the X-ray spectrum resulting from the accretion flow alone. The data are characterized using simple models. We find a model consisting of a power-law or thermal bremsstrahlung to both provide excellent descriptions of the data, where we measure = 2 . 06 ± 0.03 and kT = 5.03 +0.33 0.31 keV respectively in the 0.3 – 10 keV bandpass, at a median luminosity of Lx � 5.5×10 7 LEdd. This result in discussed in the context of our understanding of the accretion flow onto stellar and supermassive black holes at low luminosities.
Conical intersections for light and matter waves

Abstract We review the design, theory, and applications of two dimensional periodic lattices hosting conical intersections in their energy-momentum spectrum. The best known example is the Dirac cone, where propagation is governed by an effective Dirac equation, with electron spin replaced by a ‘fermionic’ half-integer pseudospin. However, in many systems such as metamaterials, modal symmetries result in the formation of higher order conical intersections with integer or ‘bosonic’ pseudospin. The ability to engineer lattices with these qualitatively different singular dispersion relations opens up many applications, including superior slab lasers, generation of orbital angular momentum, zero-index metamaterials, and quantum simulation of exotic phases of relativistic matter. Graphical Abstract
A Lower Bound for Relaxed Locally Decodable Codes

A locally decodable code (LDC) C:{0,1}^k -> {0,1}^n is an error correcting code wherein individual bits of the message can be recovered by only querying a few bits of a noisy codeword. LDCs found a myriad of applications both in theory and in practice, ranging from probabilistically checkable proofs to distributed storage. However, despite nearly two decades of extensive study, the best known constructions of O(1)-query LDCs have super-polynomial blocklength. The notion of relaxed LDCs is a natural relaxation of LDCs, which aims to bypass the foregoing barrier by requiring local decoding of nearly all individual message bits, yet allowing decoding failure (but not error) on the rest. State of the art constructions of O(1)-query relaxed LDCs achieve blocklength n = O(k^{1+ \gamma}) for an arbitrarily small constant \gamma. We prove a lower bound which shows that O(1)-query relaxed LDCs cannot achieve blocklength n = k^{1+ o(1)}. This resolves an open problem raised by Goldreich in 2004.
Systematic Study of Rogue Wave Probability Distributions in a Fourth-Order Nonlinear Schr\"odinger Equation

Nonlinear instability and refraction by ocean currents are both important mechanisms that go beyond the Rayleigh approximation and may be responsible for the formation of freak waves. In this paper, we quantitatively study nonlinear effects on the evolution of surface gravity waves on the ocean, to explore systematically the effects of various input parameters on the probability of freak wave formation. The fourth-order current-modified nonlinear Schr\"odinger equation (CNLS4) is employed to describe the wave evolution. By solving CNLS4 numerically, we are able to obtain quantitative predictions for the wave height distribution as a function of key environmental conditions such as average steepness, angular spread, and frequency spread of the local sea state. Additionally, we explore the spatial dependence of the wave height distribution, associated with the buildup of nonlinear development.
THE EFFECT OF GOOD GOVERNANCE IMPLEMENTATION, GOVERNMENT ACCOUNTING STANDARDS, EFFECTIVENESS OF INTERNAL CONTROL SYSTEM AND HUMAN RESOURCE QUALITY ON THE QUALITY OF REGIONAL TASK FORCE FINANCIAL STATEMENTS

The purpose of this research is examine the effect of implementation of Good Governance, Government Accounting Standards, Effectiveness of Internal Control System and Quality of Human Resources to the Quality of Financial Statements in the local municipality and regency (SKPD) Ambon, Maluku province. The population are 90 SKPD in the province of Maluku and each sample represented by one respondent. This research using quantitative approach, and data collection was done directly by using the questionnaire. Data were analyzed using Partial Least Square Equational Structural Models (PLS-SEM) with SmartPLS program. The results showed that the implementation of good governance, Government Accounting Standards, Quality of Human Resources positive significantly affect the Quality of Financial Statements Municipal area and the regency of Ambon, Maluku. Effectiveness of Internal Control System is not significant to the Quality of the Financial Statements in the local municipality and regency Ambon, Maluku.
Scalable and Efficient Hypothesis Testing with Random Forests

Throughout the last decade, random forests have established themselves as among the most accurate and popular supervised learning methods. While their black-box nature has made their mathematical analysis difficult, recent work has established important statistical properties like consistency and asymptotic normality by considering subsampling in lieu of bootstrapping. Though such results open the door to traditional inference procedures, all formal methods suggested thus far place severe restrictions on the testing framework and their computational overhead precludes their practical scientific use. Here we propose a permutation-style testing approach to formally assess feature significance. We establish asymptotic validity of the test via exchangeability arguments and show that the test maintains high power with orders of magnitude fewer computations. As importantly, the procedure scales easily to big data settings where large training and testing sets may be employed without the need to construct additional models. Simulations and applications to ecological data where random forests have recently shown promise are provided.
Active dry granular flows: Rheology and rigidity transitions

The constitutive relations of a dense granular flow composed of self-propelling frictional hard particles are investigated by means of DEM numerical simulations. We show that the rheology, which relates the dynamical friction μ and the volume fraction ϕ to the inertial number I, depends on a dimensionless number , which compares the active force to the confining pressure. Two liquid/solid transitions —in the Maxwell rigidity sense— are observed. As soon as the activity is turned on, the packing becomes an “active solid” with a mean number of particle contacts larger than the isostatic value. The quasi-static values of μ and ϕ decrease with . At a finite value of the activity , corresponding to the isostatic condition, a second “active rigidity transition” is observed beyond which the quasi-static values of the friction vanishes and the rheology becomes Newtonian. For \mathcal{A}_t$ ? > , we provide evidence for a highly intermittent dynamics of this “active fluid”.
Stochastic optimal control problem with infinite horizon driven by G-Brownian motion

The present paper considers a stochastic optimal control problem, in which the cost function is defined through a backward stochastic differential equation with infinite horizon driven by G-Brownian motion. Then we study the regularities of the value function and establish the dynamic programming principle. Moreover, we prove that the value function is the uniqueness viscosity solution of the related HJBI equation.
The heat kernel on asymptotically hyperbolic manifolds

Abstract Upper and lower bounds on the heat kernel on complete Riemannian manifolds were obtained in a series of pioneering works due to Cheng-Li-Yau, Cheeger-Yau and Li-Yau. However, these estimates do not give a complete picture of the heat kernel for all times and all pairs of points — in particular, there is a considerable gap between available upper and lower bounds at large distances and/or large times. Inspired by the work of Davies-Mandouvalos on we study heat kernel bounds on Cartan-Hadamard manifolds that are asymptotically hyperbolic in the sense of Mazzeo-Melrose. Under the assumption of no eigenvalues and no resonance at the bottom of the continuous spectrum, we show that the heat kernel on such manifolds is comparable to the heat kernel on hyperbolic space of the same dimension (expressed as a function of time t and geodesic distance r), uniformly for all and all In particular our upper and lower bounds are uniformly comparable for all distances and all times. The corresponding statement for asymptotically Euclidean spaces is not known to hold, and as we argue in the last section, it is very unlikely to be true in that geometry. As an application, we show boundedness on Lp of the Riesz transform for on such manifolds, for p satisfying For (the standard Riesz transform ), this was previously shown by Lohoué in a more general setting.
Studying the emergence of the red sequence through galaxy clustering: host halo masses at z > 2

We use the UKIDSS Ultra-Deep Survey, the deepest degree-scale near-infrared survey to date, to investigate the clustering of star-forming and passive galaxies to z ~ 3.5. Our new measurements include the first determination of the clustering for passive galaxies at z > 2, which we achieve using a cross-correlation technique. We find that passive galaxies are the most strongly clustered, typically hosted by massive dark matter halos with M_halo > 5 x 10^12 M_sun irrespective of redshift or stellar mass. Our findings are consistent with models in which a critical halo mass determines the transition from star-forming to passive galaxies. Star-forming galaxies show no strong correlation between stellar mass and halo mass, but passive galaxies show evidence for an anti-correlation; low-mass passive galaxies appear, on average, to be located in the most massive halos. These results can be understood if the termination of star formation is most efficient for galaxies of low stellar mass in very dense environments.
The Wolf-Rayet features and mass-metallicity relation of long-duration gamma-ray burst host galaxies

Aims. We gather optical spectra of 8 long-duration GRB host galaxies selected from the archival data of VLT/FORS2. We investigate whether or not Wolf-Rayet (WR) stars can be detected in these GRB host galaxies. We also estimate the physical properties of GRB host galaxies, such as metallicity. Methods. We identify the WR features in these spectra by fitting the WR bumps and WR emission lines in blue and red bumps. We identify the subtypes of the WR stars, estimate the numbers of stars in each subtype, and calculate the WR/O star ratios. The (O/H) abundances of GRB hosts are inferred from both the electron temperature (Te) and the metallicity-sensitive strong-line ratio (R23), for which we break the R23 degeneracy. We compare the environments of long-duration GRB host galaxies with those of other galaxies in terms of their luminosity (stellar mass)‐metallicity relations (L−Z, M∗−Z). Results. We detect WR stars in 5 GRB host galaxies with spectra of relatively high signal-to-noise ratios (S /N). In the comparison of L−Z, M∗−Z relations, we show that GRB hosts have lower metallicities than other samples of comparable luminosity and stellar mass. The presence of WR stars and the observed high WR/O star ratio, together with the low metallicity, support the “core-collapsar” model and imply that we are witnessing the first stage of star formation in the host regions of GRBs.
Joint Multi-UAV Path Planning and LoS Communication for Mobile-Edge Computing in IoT Networks With RISs

This article addresses a joint path planning and communication scheduling problem for a team of unmanned aerial vehicles (UAVs) equipped with central processing units and performing computing tasks for Internet of Things (IoT) devices located on uneven terrain. On such terrains, the Line of Sight (LoS) between a UAV and a ground IoT device may be blocked by buildings or mountains. In this article, reconfigurable intelligent surfaces (RISs) are deployed on the ground to improve wireless communication between UAVs and IoT devices. Computing tasks and their results can be sent to and from UAVs either directly or via RIS-reflected paths. The objective is to develop a joint multi-UAV path planning/transmission scheduling algorithm that maximizes the number of computing tasks successfully and timely performed by the UAVs and transmitted back to the IoT ground devices and minimizes the total energy consumption of the UAVs. An effective path planning algorithm for this optimization problem is proposed. A mathematically rigorous proof of its asymptotic optimality is given. The developed algorithm is computationally effective and easily implementable in real time. Computer simulations and comparisons with other effective methods prove the effectiveness of the developed approach.
Ionization degree and magnetic diffusivity in the primordial star-forming clouds

Magnetic fields play such roles in star formation as the angular momentum transport in star-forming clouds, thereby controlling circumstellar disc formation and even binary star formation efficiency. The coupling between the magnetic field and gas is determined by the ionization degree in the gas. Here, we calculate the thermal and chemical evolution of the primordial gas by solving chemical reaction network where all the reactions are reversed. We find that at ∼1014–1018 cm−3, the ionization degree becomes 100–1000 times higher than the previous results due to the lithium ionization by thermal photons trapped in the cloud, which has been omitted so far. We construct the minimal chemical network which can reproduce correctly the ionization degree as well as the thermal evolution by extracting 36 reactions among 13 species. Using the obtained ionization degree, we evaluate the magnetic field diffusivity. We find that the field dissipation can be neglected for global fields coherent over ≳ a tenth of the cloud size as long as the field is not so strong as to prohibit the collapse. With magnetic fields strong enough for ambipolar diffusion heating to be significant, the magnetic pressure effects to slow down the collapse and to reduce the compressional heating become more important, and the temperature actually becomes lower than in the no-field case.
Uniform bounds of discrete Birman–Schwinger operators

In this note, uniform bounds of the Birman-Schwinger operators in the discrete setting are studied. For uniformly decaying potentials, we obtain the same bound as in the continuous setting. However, for non-uniformly decaying potential, our results are weaker than in the continuous setting. As an application, we obtain unitary equivalence between the discrete Laplacian and the weakly coupled systems.
Gamma-ray constraints on effective interactions of the dark matter

Using an effective interaction approach to describe the interactions between the dark matter particle and the light degrees of freedom of the standard model, we calculate the gamma-ray flux due to the annihilation of the dark matter into quarks, followed by fragmentation into neutral pions which subsequently decay into photons. By comparison to the mid-latitude data released from the Fermi-LAT experiment, we obtain useful constraints on the size of the effective interactions and they are found to be comparable to those deduced from collider, gamma-ray line and anti-matter search experiments. However, the two operators induced by scalar and vector exchange among fermionic dark matter and light quarks that contribute to spin-independent cross sections are constrained more stringently by the recent XENON100 data.
Resonant cyclotron scattering in pulsar magnetospheres and its application to isolated neutron stars

Resonant cyclotron scattering (RCS) in pulsar magnetospheres is considered. The photon diffusion equation (Kompaneets equation) for RCS is derived. The photon system is modeled three dimensionally. Numerical calculations show that there exist not only up scattering but also down scattering of RCS, depending on the parameter space. RCS's possible applications to spectral energy distributions of magnetar candidates and radio quiet isolated neutron stars (INSs) are pointed out. The optical/UV excess of INSs may be caused by the down scattering of RCS. The calculations for RX J1856.5-3754 and RX J0720.4-3125 are presented and compared with their observational data. In our model, the INSs are proposed to be normal neutron stars, although the quark star hypothesis is still possible. The low pulsation amplitude of INSs is a natural consequence in the RCS model.
Machine Learning Based Efficient Qt-Mtt Partitioning for VVC Inter Coding

The Joint Video Experts Team (JVET) have standardized the Versatile Video Coding (VVC) in 2020 targeting efficient coding of the emerging video services and formats such as 8K and immersive video streaming applications. VVC standard enhances the coding efficiency by 40% at the cost of an encoder computational complexity increase estimated to 859%(x8) compared to the previous standard High Efficiency Video Coding (HEVC). This work aims at reducing the complexity of the VVC encoder under the Random Access (RA) configuration. The proposed method takes advantage of the inter prediction in order to predict the split probabilities through a convolutional neural network. Our solution reaches 31.8% of complexity reduction for a negligible bitrate increase of 1.11% outperforming state-of-the-art methods.
REMARKS ON ${\mathcal{Z}}$-STABLE PROJECTIONLESS C*-ALGEBRAS

Abstract It is shown that ${\mathcal{Z}}$-stable projectionless C*-algebras have the property that every element is a limit of products of two nilpotents. This is then used to classify the approximate unitary equivalence classes of positive elements in such C*-algebras using traces.
All-optical amplification in metallic subwavelength linear waveguides

Proposed all optical amplification scenario is based on the properties of light propagation in two coupled subwavelength metallic slab waveguides where for particular choice of waveguide parameters two propagating (symmetric) and non-propagating (antisymmetric) eigenmodes coexist. For such a setup incident beams realize boundary conditions for forming a stationary state as a superposition of mentioned eigenmodes. It is shown both analytically and numerically that amplification rate in this completely linear mechanism diverges for small signal values.
Polarization transfer in relativistic magnetized plasmas

The polarization transfer coefficients of a relativistic magnetized plasma are derived. These results apply to any momentum distribution function of the particles, isotropic or anisotropic. Particles interact with the radiation either in a non resonant mode when the frequency of the radiation exceeds their characteristic synchrotron emission frequency, or quasi resonantly otherwise. These two classes of particles contribute differently to the polarization transfer coefficients. For a given frequency, this dichotomy corresponds to a regime change in the dependence of the transfer coefficients on the parameters of the particle s population. The derivation of the transfer coefficients involves an exact expression of the conductivity tensor of the relativistic magnetized plasma that has not been used hitherto in this context. Suitable expansions valid at frequencies larger than the cyclotron frequency allow us to analytically perform the summation over all resonances at high harmonics of the relativistic gyrofrequency. The transfer coefficients are represented in the form of two variable integrals that can be conveniently computed for any set of parameters by using Olver s expansion of high order Bessel functions. We particularize our results to a number of distribution functions, isotropic, thermal or powerlaw, with different multipolar anisotropies of low order, or strongly beamed. For isotropic distributions, the Faraday coefficients are expressed in the form of a one variable quadrature over energy, for which we provide the kernels in the high-frequency limit and in the asymptotic low-frequency limit. A similar reduction to a one-variable quadrature over energy is derived at high frequency for a large class of anisotropic distribution functions that may form a basis on which any smoothly anisotropic distribution could be expanded.
Romanovski polynomials in selected physics problems

We briefly review the five possible real polynomial solutions of hypergeometric differential equations. Three of them are the well known classical orthogonal polynomials, but the other two are different with respect to their orthogonality properties. We then focus on the family of polynomials which exhibits a finite orthogonality. This family, to be referred to as the Romanovski polynomials, is required in exact solutions of several physics problems ranging from quantum mechanics and quark physics to random matrix theory. It appears timely to draw attention to it by the present study. Our survey also includes several new observations on the orthogonality properties of the Romanovski polynomials and new developments from their Rodrigues formula.
Reliability and Validity of a Novel Reactive Agility Test with Soccer Goalkeeper-Specific Movements

The purpose of this study was to develop a reactive agility test with soccer goalkeeper (GK)-specific movements (G-RAT) and to examine the reliability and validity of college-aged GKs. We designed a five-branch star-shaped course with diving and ball-catching movements under reactive conditions. In the setup, a start–goal line was set on the top of a branch and 3.5 m away from the center of the star-shaped setting. Content validity was assessed by six experts, and the item-content validity index (I-CVI) was calculated. Thirty-three male GKs performed the test trial twice. One test trial of G-RAT consists of three shuttles from the start–goal line to diving and ball-catching. For the reactive condition, GKs were instructed on which ball directions should dive when their body trunk reached 1.5 m away from the start–goal line. GKs were classified into regular (R) or non-regular (NR) groups. The intraclass correlation coefficient (ICC) and the receiver operating characteristic (ROC) curve analyses were used to assess the reliability and predictive power as convergent validity. The I-CVI was 0.83, which was greater than the acceptable level of 0.78. The ICC value was 0.94 (p < 0.01; 95% confidence interval (95%CI), 0.88–0.97). The GKs completed the test 14.3 ± 0.7 and 15.3 ± 1.0 s in the R and NR group (p < 0.01; Cohen’s d = 0.89), respectively. The area under the curves of G-RAT was 0.80 (95%CI, 0.64–0.96). These results show that a GK-specific agility test under reactive conditions would have sufficient reliability and both content and convergent validity in college-aged GKs.