Miracle-dz/UniFAR-FTUs huggingface dataset:
Transport properties of iron at the Earth's core conditions: the effect of spin disorder

The electronic and thermal transport properties of the Earth's core are crucial for many geophysical models such as the geodynamo model of the Earth's magnetic field and of its reversals. Here we show, by considering bcc iron and an iron-rich iron-silicon alloy as a representative of the Earth's core composition and applying first-principles modeling, that the spin disorder at the Earth's core conditions not considered previously provides an essential contribution, of order 20 $\ensuremath{\mu}\mathrm{\ensuremath{\Omega}}$ cm, to the electrical resistivity. This value is comparable in magnitude with the electron-phonon and with the recently estimated electron-electron scattering contributions. The origin of the spin-disorder resistivity (SDR) consists of the existence of fluctuating local moments that are stabilized at high temperatures by the magnetic entropy even at pressures at which the ground state of iron is nonmagnetic. We find that electron-phonon and SDR contributions are not additive at high temperatures. We thus observe a large violation of the Matthiessen rule, not common in conventional metallic alloys at ambient conditions.
Multicritical behaviour of the diluted contact process

We study a contact process on a two-dimensional square lattice which is diluted by randomly removing bonds with probability p. For p<1/2 and varying birth rate λ the model was shown to exhibit a continuous phase transition which belongs to the universality class of strongly disordered directed percolation. The phase transition line terminates in a multicritical point at p = 1/2 and λ = λ* = 3.55(1), where the model can be interpreted as a critical directed percolation process running on a critical isotropic percolation cluster. In the present work we study the multicritical point and its neighbourhood by numerical simulations, discussing possible scaling forms which could describe the critical behaviour at the transition.
Application of Pocklington's equation to analysis of dipole frequency-selective surfaces of finite size

Pocklington's equation is applied to arrays of linear dipoles. An integral equation for the currents induced in each dipole is derived for plane-wave illumination. The equation is solved by the method of moments. The current mode amplitudes for a 5 × 5 array and a 20 × 5 array are compared with those given by the standard modal analysis of an infinite periodic array using the same set of basis functions. In the latter case predicted transmission responses in the frequency range 18-40 GHz link the calculations to experiment. The effect of the edge region on the induced current phasors and on the scattered fields is discussed. Near the resonance frequency for TE incidence there is a pronounced amplitude variation across the 20 × 5 array. The analysis described in the paper is not restricted to periodic lattices.
High-Energy Emission from the PSR B1259-63 System near Periastron

We report the results of a CGRO 3-week observation of the binary system containing the 47 ms pulsar PSR B1259-63 orbiting around a Be star companion in a very eccentric orbit. The PSR B1259-63 binary is a unique system for the study of the interaction of a rapidly rotating pulsar with time-variable nebular surroundings. CGRO observed the PSR B1259-63 system in coincidence with its most recent periastron passage (January 3-23, 1994). Unpulsed and non-thermal hard X-ray emission was detected up to 200 keV, with a photon index $1.8 \pm 0.2$ and a flux of ~4 mCrab, corresponding to a luminosity of a few 10^{34} erg/s at the distance of 2 kpc. The hard X-ray flux and spectrum detected by CGRO agrees with the X-ray emission measured by simultaneous ASCA observations. EGRET upper limits are significant, and exclude strong inverse Compton cooling in the PSR B1259-63 system. We interpret the observed non-thermal emission as synchrotron radiation of shocked electron/positron pairs of the relativistic pulsar wind interacting with the mass outflow from the Be star. Our results clearly indicate, for the first time in a binary pulsar, that high energy emission can be shock-powered rather than caused by accretion. The lack of X-ray/gamma-ray pulsations constrains models of high-energy emission from rapidly rotating pulsars.
Is SAX J1808.4-3658 a Strange Star ?

The possibility of strange stars is one of the most important issues in the study of compact objects. Here we use the observations of the newly discovered millisecond x-ray pulsar SAX J1808.4-3658 to constrain the radius of the compact star. Comparing the mass-radius relation of SAX J1808.4-3658 with theoretical models for both neutron stars and strange stars, we argue that a strange star model could be more consistent with SAX J1808.4-3658, and suggest that it is a likely strange star candidate. Our results are useful in constraining microscopic chiral symmetry restoration parameters in the quantum chromodynamics (QCD) modeling of strange matter.
The Structure and Evolution of Lyman-alpha Forest Clouds in the Minihalo Model

Results are presented for one-dimensional numerical hydrodynamics computations of the structure and evolution of Lya forest clouds gravitationally confined by dark matter minihalos. The clouds are developed from linear perturbations at high redshift and exposed to either a QSO- or galaxy-dominated metagalactic radiation field at moderate redshifts. While the emphasis is on spherical systems, slab symmetry is also considered. Three zones may be identified in a collapsed cloud: (1) a quasi-hydrostatic core in thermal equilibrium, (2) a nonhydrostatic intermediate zone out of thermal equilibrium, and (3) a cosmological accretion layer joining onto the Hubble expansion. Most of the measured Lya forest column densities arise in the intermediate zone. The development of the core would result in a flattening in the column density distribution near an HI column density of 10**15-10**16 cm**-2. The cloud diameters corresponding to an HI column density of 10**14 cm**-2 lie in the range 10-60 kpc, while systems with column densities exceeding 10**15 cm**-2 have diameters smaller than 10 kpc. Systems with circular velocities exceeding 50 km/s result in clouds which contract until they become Jeans unstable and collapse. The critical column density for collapse is 10**17-10**18 cm**-2. A mild correlation of Doppler parameter with neutral hydrogen column density is found in several models for systems with column densities less than 10**13.5 cm**-2, with Doppler parameters occurring as low as b > 20 km/s for 10**13 cm**-2 column density systems. No lines with b < 15 km/s are found.
Impact of Junction Depth and Abruptness on the Activation and the Leakage Current in Germanium n$^{+}$/p Junctions

The phosphorous activation in Ge n$^{+}$/p junctions is compared in terms of junction depth, by using laser spike annealing at 860°C for 400$\mu$s. The reverse junction leakage is found to strongly depend on the abruptness of dopant profiles. A shallow and abrupt junction is shown to have lower phosphorous activation level, due to surface dose loss, and higher band-to-band tunneling (BTBT) leakage, when compared to the deep junction. Simulations were carried out to evaluate the lowest achievable OFF-state currents (I$_{OFF}$) for Ge double-gate FETs when using such an abrupt junction. Our results indicate that a Ge body thickness smaller than 5 nm is required to suppress the BTBT leakage and meet the requirement for the high performance devices defined by the International Technology Roadmap for Semiconductors (I$_{OFF}$ = 10$^{-7}$ A/$\mu$m).
Rossby Wave Instability of Thin Accretion Disks. II. Detailed Linear Theory

In an earlier work we identified a global, nonaxisymmetric instability associated with the presence of an extreme in the radial profile of the key function ℒ(r) ≡ (ΣΩ/κ2)S2/Γ in a thin, inviscid, nonmagnetized accretion disk. Here Σ(r) is the surface mass density of the disk, Ω(r) is the angular rotation rate, S(r) is the specific entropy, Γ is the adiabatic index, and κ(r) is the radial epicyclic frequency. The dispersion relation of the instability was shown to be similar to that of Rossby waves in planetary atmospheres. In this paper, we present the detailed linear theory of this Rossby wave instability and show that it exists for a wider range of conditions, specifically, for the case where there is a "jump" over some range of r in Σ(r) or in the pressure P(r). We elucidate the physical mechanism of this instability and its dependence on various parameters, including the magnitude of the "bump" or "jump," the azimuthal mode number, and the sound speed in the disk. We find a large parameter range where the disk is stable to axisymmetric perturbations but unstable to the nonaxisymmetric Rossby waves. We find that growth rates of the Rossby wave instability can be high, ~0. 2ΩK for relative small jumps or bumps. We discuss possible conditions which can lead to this instability and the consequences of the instability.
A Subarcsecond Companion to the T Tauri Star AS 353B

Adaptive optics imaging of the bright visual T Tauri binary AS 353 with the Subaru Telescope shows that it is a hierarchical triple system. The secondary component, located 5. ″6 south of AS 353A, is resolved into a subarcsecond binary, AS 353 Ba and Bb, separated by 0. ″24. Resolved spectroscopy of the two close components shows that both have nearly identical spectral types of about M1.5. Whereas AS 353A and Ba show clear evidence of an infrared excess, AS 353 Bb does not. We discuss the possible role of multiplicity in launching the large Herbig-Haro flow associated with AS 353A.
Surface tension of small bubbles and droplets and the cavitation threshold

In this paper, using an unified approach, estimates are given of the magnitude of the surface tension of water for planar and curved interfaces in the pairwase interaction approximation based on the Lennard-Jones potential. It is shown that the surface tensions of a bubble and droplet have qualitatively different dependences on the curvature of the surface: for the bubble, as the radius of the surface's curvature decreases, the surface tension decreases, whereas it increases on the droplet. The corresponding values of the Tolman corrections are also determined. In addition, it is shown that the dependence of the surface tension on the surface's curvature is important for evaluating the critical negative pressure for the onset of cavitation.
Feature Selection for Predicting Building Energy Consumption Based on Statistical Learning Method

Machine learning methods are widely studied and applied to predict building energy consumption. Since the factors associated with building energy behaviors are quite abundant and complex, this paper investigates for the first time how the selection of subsets of features influence the model performance when statistical learning method is adopted to derive the model. In this paper the optimal features are selected based on the feasibility of obtaining them and on the scores they provide under the evaluation of some filter methods. The selected subset is then evaluated on three data sets by support vector regression involving two kernel functions: radial basis function and polynomial function. Experimental results confirm the validity of the selected subset and show that the proposed feature selection method can guarantee the prediction accuracy and reduces the computational time for data analyzing.
Model calculations of superlubricity of graphite

In this paper, friction between a finite, nanometer-sized, rigid graphite flake and a rigid graphite surface is analyzed theoretically in the framework of a modified Tomlinson model. Lateral forces are studied as a function of orientational misfit between flake and surface lattices, pulling direction of the flake, flake size and flake shape. The calculations show that the orientation dependence of the friction provides information on the contact size and shape. We find good agreement between the calculations and the experimental results, discussed in a recent publication by Dienwiebel et al. [M. Dienwiebel, G. S. Verhoeven, N. Pradeep, J. W. M. Frenken, J. A. Heimberg, and H. W. Zandbergen, Phys. Rev. Lett. 92, 126101(2004)].
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We provide a cohomological framework for contextuality of quantum mechanics that is suited to describing contextuality as a resource in measurement-based quantum computation. This framework applies to the parity proofs first discussed by Mermin, as well as a different type of contextuality proofs based on symmetry transformations. The topological arguments presented can be used in the state-dependent and the state-independent case.
Quantum modeling

We present a modificaton of Simon's Algorithm that in some cases is able to fit experimentally obtained data to appropriately chosen trial functions with high probability. Modulo constants pertaining to the reliability and probability of success of the algorithm, the algorithm runs using only O[polylog(|Y|)] queries to the quantum database and O[polylog(|X|,|Y|)] elementary quantum gates where |X| is the size of the experimental data set and |Y| is the size of the parameter space. We discuss heuristics for good performance, analyze the performance of the algorithm in the case of linear regression, both one-dimensional and multidimensional, and outline the algorithm's limitations.
Quantum simulation / Simulation quantique Artificial gauge fields in materials and engineered systems

Artificial gauge fields are currently realized in a wide range of physical settings. This includes solid-state devices but also engineered systems, such as photonic crystals, ultracold gases and mechanical setups. It is the aim of this review to offer, for the first time, a unified view on these various forms of artificial electromagnetic fields and spinorbit couplings for matter and light. This topical review provides a general introduction to the universal concept of engineered gauge fields, in a form which is accessible to young researchers entering the field. Moreover, this work aims to connect different communities, by revealing explicit links between the diverse forms and realizations of artificial gauge fields.
Compressible Invariant Solutions In Open Cavity Flows

A family of compressible exact periodic solutions is reported for the first time in an open cavity flow setup. These are found using a novel framework which permits the computation of such solutions in an arbitrary complex geometry. The periodic orbits arise from a synchronised concatenation of convective and acoustic events which strongly depend on the Mach number. This flow-acoustic interaction furnishes the periodic solutions with a remarkable stability and it is found to completely dominate the system's dynamics and the sound directivity. The periodic orbits, which could be called `exact Rossiter modes', collapse with a family of equilibrium solutions at a subcritical Hopf bifurcation, occurring in the quasi-incompressible regime. This shows compressibility has a destabilising effect in cavity flows, which we analyse in detail. By establishing a connection with previous 2D and 3D stability studies of cavity flows, we are able to isolate the effect of purely compressible two-dimensional flow phenomena across Mach number. A linear stability analysis of the equilibria provides insight into the compressible flow mechanisms responsible for the instability. A close look at the adjoint modes suggests that an eigenvalue merge occurs at a Mach number between 0.35 and 0.4, which boosts the receptivity of the leading mode and determines the onset of the unstable character of the system. The effect of the choice of base flow over the transition dynamics is also discussed, where in the present case, the frequencies associated to the leading eigenmodes show a strong connection with the frequencies of the periodic orbits at the same Mach numbers.
Motion of magnetically charged particles in a magnetically charged stringy black hole spacetime

We study the motion of massive particles with electric and magnetic charges in the background of a magnetically charged Garfinkle-Horowitz-Strominger stringy black hole. We solve analytically the equations of motion of the test particles and we describe the orbital motion in terms of the Weierstrass elliptic functions. We find that there are critical values of the magnetic charge of the black hole and the magnetic charge of the test particle which characterize the bound and unbound orbits and we study two observables, the perihelion shift and the Lense-Thirring effect. The trajectories depend on the electric and magnetic charges of the test particle. While the angular-motion depends on the electric charge of the test particle, the $r$ and $t$-motion depends on the mass and the magnetic charge of the test particle.
Droplet ripening in concentration gradients

Living cells use phase separation and concentration gradients to organize chemical compartments in space. Here, we present a theoretical study of droplet dynamics in gradient systems. We derive the corresponding growth law of droplets and find that droplets exhibit a drift velocity and position dependent growth. As a consequence, the dissolution boundary moves through the system, thereby segregating droplets to one end. We show that for steep enough gradients, the ripening leads to a transient arrest of droplet growth that is induced by a narrowing of the droplet size distribution.
A computational model for exploring particle acceleration during reconnection in macroscale systems

A new computational model is presented suitable for exploring the self-consistent production of energetic electrons during magnetic reconnection in macroscale systems. The equations are based on the recent discovery that parallel electric fields are ineffective drivers of energetic particles during reconnection so that the kinetic scales which control the development of such fields can be ordered out of the equations. The resulting equations consist of a magnetohydrodynamic (MHD) backbone with the energetic component represented by macro-particles described by the guiding center equations. Crucially, the energetic component feeds back on the MHD equations so that the total energy of the MHD fluid and the energetic particles is conserved. The equations correctly describe the firehose instability, whose dynamics plays a key role in throttling reconnection and in controlling the spectra of energetic particles. The results of early tests of the model, including the propagation of Alfven waves in a system with pressure anisotropy and the growth of firehose modes, establish that the basic algorithm is stable and produces reliable physics results in preparation for further benchmarking with particle-in-cell models of reconnection.
Exact solution and precise asymptotics of a Fisher–KPP type front

The present work concerns a version of the Fisher–KPP equation where the nonlinear term is replaced by a saturation mechanism, yielding a free boundary problem with mixed conditions. Following an idea proposed in Brunet and Derrida (2015 J. Stat. Phys. 161 801), we show that the Laplace transform of the initial condition is directly related to some functional of the front position μt. We then obtain precise asymptotics of the front position by means of singularity analysis. In particular, we recover the so-called Ebert and van Saarloos correction (Ebert and van Saarloos 2000 Physica D 146 1), we obtain an additional term of order log⁡t/t in this expansion, and we give precise conditions on the initial condition for those terms to be present.
Quantum learning and universal quantum matching machine

Suppose that three kinds of quantum systems are given in some unknown states $|f{〉}^{\ensuremath{\bigotimes}N},$ $|{g}_{1}{〉}^{\ensuremath{\bigotimes}K},$ and $|{g}_{2}{〉}^{\ensuremath{\bigotimes}K},$ and we want to decide which template state $|{g}_{1}〉$ or $|{g}_{2}〉,$ each representing the feature of the pattern class ${\mathcal{C}}_{1}$ or ${\mathcal{C}}_{2},$ respectively, is closest to the input feature state $|f〉. $ This is an extension of the pattern matching problem into the quantum domain. Assuming that these states are known a priori to belong to a certain parametric family of pure qubit systems, we derive two kinds of matching strategies. The first one is a semiclassical strategy that is obtained by the natural extension of conventional matching strategies and consists of a two-stage procedure: identification (estimation) of the unknown template states to design the classifier (learning process to train the classifier) and classification of the input system into the appropriate pattern class based on the estimated results. The other is a fully quantum strategy without any intermediate measurement, which we might call as the universal quantum matching machine. We present the Bayes optimal solutions for both strategies in the case of $K=1,$ showing that there certainly exists a fully quantum matching procedure that is strictly superior to the straightforward semiclassical extension of the conventional matching strategy based on the learning process.
ALMA observation of the disruption of molecular gas in M87

We present the results from Atacama Large Millimeter Array (ALMA) observations centred 40 arcsec (3 kpc in projection) south-east of the nucleus of M87. We report the detection of extended CO (2-1) line emission with a total flux of (5.5 +/- 0.6) x 10(-18) erg s(-1) cm(-2) and corresponding molecular gas mass M-H2 (4.7 +/- 0.4) x 10(5) M-circle dot, assuming a Galactic CO to H-2 conversion factor. ALMA data indicate a line-of-sight velocity of -129 +/- 3 km s(-1), in good agreement with measurements based on the [C-II] and H alpha+[N-II] lines, and a velocity dispersion of sigma = 27 +/- 3 km s(-1). The CO (2-1) emission originates only outside the radio lobe of the active galactic nucleus (AGN) seen in the 6 cm Very Large Array image, while the filament prolongs further inwards at other wavelengths. The molecular gas in M87 appears to be destroyed or excited by AGN activity, either by direct interaction with the radio plasma, or by the shock driven by the lobe into the X-ray emitting atmosphere. This is an important piece of the puzzle in understanding the impact of the central AGN on the amount of the coldest gas from which star formation can proceed.
Binormal Model of Ensemble Partial Cloudiness

Abstract A new formulation of partial cloudiness parameterization has been introduced that agrees with that for a random model in one limit and approaches the simple updraft/downdraft model of larger-scale models in the limit of very highly skewed flow. Each of the conserved variables, liquid potential temperature and total humidity, along with the vertical velocity, are assumed to have probability distributions that may be parameterized as combinations of two multivariate normal distributions. This allows the skewness of the variables to be controlled by the bias between the means of the two normals and their relative fractions. It also provides a smooth transition between the normal distribution and the two limiting delta function distribution of the updraft/downdraft model. Comparisons with large-eddy-simulation data show this new model to be valid over a much wider range of conditions than the single normal distribution. When a simple cloud-top entrainment instability (CTEI) analysis is made using the.