Miracle-dz/UniFAR-FTUs huggingface dataset:
Studying the accretion geometry of EXO 2030+375 at luminosities close to the propeller regime

The Be X-ray binary EXO 2030+375 was in an extended low luminosity state during most of 2016. We observed this state with NuSTAR and Swift, supported by INTEGRAL observations as well as optical spectroscopy with the NOT. We present a comprehensive spectral and timing analysis of these data here to study the accretion geometry and investigate a possible onset of the propeller effect. The H-alpha data show that the circumstellar disk of the Be-star is still present. We measure equivalent widths similar to values found during more active phases in the past, indicating that the low-luminosity state is not simply triggered by a smaller Be disk. The NuSTAR data, taken at a 3-78 keV luminosity of ~6.8e35 erg/s (for a distance of 7.1 kpc), are well described by standard accreting pulsar models, such as an absorbed power-law with a high-energy cutoff. We find that pulsations are still clearly visible at these luminosities, indicating that accretion is continuing despite the very low mass transfer rate. In phase-resolved spectroscopy we find a peculiar variation of the photon index from ~1.5 to ~2.5 over only about 3% of the rotational period. This variation is similar to that observed with XMM-Newton at much higher luminosities. It may be connected to the accretion column passing through our line of sight. With Swift/XRT we observe luminosities as low as 1e34 erg/s during which the data quality did not allow us to search for pulsations, but the spectrum is much softer and well described by either a blackbody or soft power-law continuum. This softer spectrum might be due to the fact that accretion has been stopped by the propeller effect and we only observe the neutron star surface cooling.
Frequency shift and mode coupling in the nonlinear dynamics of a Bose condensed gas

We investigate the behavior of large amplitude oscillations of a trapped Bose-condensed gas of alkali atoms at zero temperature, by solving the equations of hydrodynamics for collective modes. Due to the atom-atom interaction, the equations of motion are nonlinear and give rise to significant frequency shift and mode coupling. We provide analytic expressions for the frequency shift, pointing out the crucial role played by the anisotropy of the confining potential. For special values of the anisotropy parameter the mode coupling is particularly strong and the frequency shift becomes large, revealing a peculiar behavior of the Bose-condensed gas. Consequences on the theory of collapse and revival of collective excitations are also discussed. 3.75. Fi, 67.40. Db
Network Topology of the Austrian Airline Flights

The information of the Austrian airline flights was collected and quantitatively analyzed by the concepts of complex network. It displays some features of small-world networks, namely large clustering coefficient and small average shortest-path length. The degree distributions of the networks reveal power law behavior with exponent value of 2 $\sim$ 3 for the small degree branch but a flat tail for the large degree branch. Similarly, the flight weight distributions show power-law behavior for the small weight branch. Furthermore, we found that the clustering coefficient $C$, 0.206, of this flight network is greatly larger than that of a random network, 0.01, which has the same numbers of the airports ($N$) and mean degree ($ $), and the diameter $D$, 2.383, of the flight network is significantly smaller than the value of the same random network, 18.67. In addition, the degree-degree correlation analysis shows the network has disassortative behavior, i.e. the large airports are likely to link to smaller airports. Furthermore, the clustering coefficient analysis indicates that the large airports reveal the hierarchical organization.
DARK VISCOUS FLUID DESCRIBED BY A UNIFIED EQUATION OF STATE IN COSMOLOGY

We generalize the ΛCDM model by introducing a unified EOS to describe the Universe contents modeled as dark viscous fluid, motivated by the fact that a single constant equation of state (EOS) p = -p0 (p0 > 0) reproduces the ΛCDM model exactly. This EOS describes the perfect fluid term, the dissipative effect, and the cosmological constant in a unique framework and the Friedmann equations can be analytically solved. Especially, we find a relation between the EOS parameter and the renormalizable condition of a scalar field. We develop a completely numerical method to perform a χ2 minimization to constrain the parameters in a cosmological model directly from the Friedmann equations, and employ the SNe data with the parameter $\mathcal{A}$ measured from the SDSS data to constrain our model. The result indicates that the dissipative effect is rather small in the late-time Universe.
Picosecond and femtosecond Fourier pulse shape synthesis

2014 We review our work on the synthesis of arbitrarily shaped, coherent optical pulses, by spatial filtering in a grating pulse compressor. We describe picosecond pulses shaped using a fiber and grating pulse compressor and femtosecond pulses shaped using a nondispersive grating compressor. The discussion includes generation of coherent square pulses and abruptly phase-modulated « odd » pulses, two slit temporal interference measurements of the optical phase spectrum, and ultrashort pulse encryption and decoding by phase scrambling. We conclude with a proposal for an ultrafast optical self-routing switch based upon frequency domain phase coding of ultrashort pulses. Revue Phys. Appl. 22 (1987) -1628 DÉCEMBRE 1987, PAGE 1619
Cosmological Velocity Bias

Velocity bias is a reduction of the velocity dispersion of tracer galaxies in comparison to the velocity dispersion of the underlying mass field. There are two distinct forms of velocity bias. The single particle velocity reduction, $b_v(1)$, is the result of energy loss of a tracer population, and in virialized regions, such as galaxy clusters, is intimately associated with mass segregation which together lead to cluster mass underestimates. The pairwise velocity bias, $b_v(2)$, has an additional statistical reduction if the total mass per galaxy rises with velocity dispersion of the virialized cluster. Values of the velocity bias are estimated from n-body simulations, finding $b_v(1)\simeq 0.85\pm0.1$ and $b_v(2)\simeq 0.6\pm0.2$. The value of $b_v(1)$ is relatively secure and predicts that the virial radius of the cluster light is about 20\% of the cluster mass, which can be tested with observations of cluster mass profiles beyond the apparent virial radius. The value of $b_v(2)$ is sensitive to the formation efficiency of galaxies over environments ranging from voids to rich clusters, the latter of which are not yet well resolved in simulations. An $n=1$, $\Omega=1$, COBE normalized CDM spectrum requires $b_v(2)\simeq0.20(15\mu K/Q)(\sigma_{12}/317 \kms)$ which is well below the measured range of $b_v(2)$. The pairwise velocities at 1 \hmpc\ allow $\Omega=1$ for a galaxy clustering bias near unity if $b_v(2)\simeq0.6$.
Stability of ferromagnetic state of epitaxially grown ordered FeRh thin films

We report on the magnetic properties of B2-type ordered FeRh epitaxial thin films deposited on MgO(001) substarates as a function of film thickness. All the films show a clear magnetic phase transition from the antiferromagnetic state to the ferromagnetic state with increasing temperature while the transition temperature of a 10-nm-thick film decreases down to 300K. The 10-nm-thick film also shows a large magnetization even in the antiferromagnetic state compared with other thicker films. These magnetization data indicate that the ferromagnetic state is becoming more stable than the antiferromagnetic state with decreasing film thickness. Such thickness dependent magnetic properties are qualitatively compatible with a theoretical prediction for FeRh(001) thin layers.
Magnetorotational collapse of massive stellar cores to neutron stars : Simulations in full general relativity

We study magnetohydrodynamic (MHD) effects arising in the collapse of magnetized, rotating, massive stellar cores to proto-neutron stars (PNSs). We perform axisymmetric numerical simulations in full general relativity with a hybrid equation of state. The formation and early evolution of a PNS are followed with a grid of $2500\ifmmode\times\else\texttimes\fi{}2500$ zones, which provides better resolution than in previous (Newtonian) studies. We confirm that significant differential rotation results even when the rotation of the progenitor is initially uniform. Consequently, the magnetic field is amplified both by magnetic winding and the magnetorotational instability (MRI). Even if the magnetic energy ${E}_{\mathrm{EM}}$ is much smaller than the rotational kinetic energy ${T}_{\mathrm{rot}}$ at the time of PNS formation, the ratio ${E}_{\mathrm{EM}}/{T}_{\mathrm{rot}}$ increases to 0.1\char21{}0.2 by the magnetic winding. Following PNS formation, MHD outflows lead to losses of rest mass, energy, and angular momentum from the system. The earliest outflow is produced primarily by the increasing magnetic stress caused by magnetic winding. The MRI amplifies the poloidal field and increases the magnetic stress, causing further angular momentum transport and helping to drive the outflow. After the magnetic field saturates, a nearly stationary, collimated magnetic field forms near the rotation axis and a Blandford-Payne\char21{}type outflow develops along the field lines. These outflows remove angular momentum from the PNS at a rate given by $\stackrel{\ifmmode \dot{}\else \textperiodcentered \fi{}}{J}\ensuremath{\sim}\ensuremath{\eta}{E}_{\mathrm{EM}}{C}_{B}$, where $\ensuremath{\eta}$ is a constant of order $\ensuremath{\sim}0.1$ and ${C}_{B}$ is a typical ratio of poloidal to toroidal field strength. As a result, the rotation period quickly increases for a strongly magnetized PNS until the degree of differential rotation decreases. Our simulations suggest that rapidly rotating, magnetized PNSs may not give rise to rapidly rotating neutron stars.
Radial drift of dust in protoplanetary discs: the evolution of ice lines and dead zones

We have developed a new model for the astrochemical structure of a viscously evolving protoplanetary disk that couples an analytic description of the disk's temperature and density profile, chemical evolution, and an evolving dust distribution. We compute evolving radial distributions for a range of dust grain sizes, which depend on coagulation, fragmentation and radial drift processes. In particular we find that the water ice line plays an important role in shaping the radial distribution of the maximum grain size because ice coated grains are significantly less susceptible to fragmentation than their dry counterparts. This in turn has important effects on disk ionization and therefore on the location of dead zones. In comparison to a simple constant gas-to-dust ratio model for the dust as an example, we find that the new model predicts an outer dead zone edge that moves in by a factor of about 3 at 1 Myr (to 5 AU) and by a factor of about 14 by 3 Myr (to 0.5 AU). We show that the changing position of the dead zone and heat transition traps have important implications for the formation and trapping of planets in protoplanetary disks. Finally, we consider our results in light of recent ALMA observations of HL Tau and TW Hya.
Electronic structure ofd-wave superconducting quantum wires

We present analytical and numerical results for the electronic spectra of wires of a d-wave superconductor on a square lattice. The spectra of Andreev and other quasiparticle states, as well as the spatial and particle-hole structures of their wave functions, depend on interference effects caused by the presence of the surfaces and are qualitatively different for half-filled wires with even or odd number of chains. For half-filled wires with an odd number of chains N at (110) orientation, spectra consist of N doubly degenerate branches. By contrast, for even N wires, these levels are split, and all quasiparticle states, even the ones lying above the maximal gap, have the characteristic properties of Andreev bound states. These Andreev states above the gap can be interpreted as a consequence of an infinite sequence of Andreev reflections experienced by quasiparticles along their trajectories bounded by the surfaces of the wire. Our microscopic results for the local density of states display atomic-scale Friedel oscillations due to the presence of the surfaces, which should be observable by scanning tunneling microscopy. For narrow wires the self-consistent treatment of the order parameter is found to play a crucial role. In particular, we find that for small wire widths the finite geometry may drive strong fluctuations or even stablilize exotic quasi-1D pair states with spin triplet character.
A New Instability of Accretion Disks around Magnetic Compact Stars

Aperiodic variability and quasi-periodic oscillations (QPOs) are observed from accretion disks orbiting white dwarfs, neutron stars, and black holes, suggesting that the flow is universally broken up into discrete blobs. We consider the interaction of these blobs with the magnetic field of a compact, accreting star, where diamagnetic blobs suffer a drag. We show that when the magnetic moment is not aligned with the spin axis, the resulting force is pulsed, and this can lead to resonance with the oscillation of the blobs around the equatorial plane; a resonance condition where energy is effectively pumped into nonequatorial motions is then derived. We show that the same resonance condition applies for the quadrupolar component of the magnetic field. We discuss the conditions of applicability of this result, showing that they are quite wide. We also show that realistic complications, such as chaotic magnetic fields, buoyancy, radiation pressure, evaporation, Kelvin-Helmholtz instability, and shear stresses due to differential rotation do not affect our results. In accreting neutron stars with millisecond periods, we show that this instability leads to Lense-Thirring precession of the blobs and that damping by viscosity can be neglected.
Overshooting in the Core Helium-burning Stage of a 30 M⊙ Star Using the k-ω Model

Overshooting and semiconvection are among the most noteworthy uncertainties in the evolution of massive stars. Complete mixing over a certain distance beyond the convective boundary and an exponentially decaying diffusion outside the convection zone are commonly adopted for the overshoot mixing. Recently, Li developed the k-ω model, which can be used in both convection zones and overshooting regions. We incorporated it in calculations of 30 M⊙ stellar models. We find that in the main-sequence stage, models with the k-ω model are almost identical to models with complete mixing in the overshooting region beyond the convective core, and the overshooting in the k-ω model is equivalent to an overshooting distance of about 0.15 HP. In the post -main-sequence stage, we find that the overshooting below the bottom of the intermediate convection zone beyond the hydrogen-burning shell can significantly restrict the size of the hydrogen-depleted core, and can penetrate effectively into the hydrogen-burning shell. These two effects are crucial for the evolution of the core helium-burning stage. During the core helium-burning stage, we find that the overshooting model based on the k-ω model results in a similar complete mixing region but a much wider partial mixing region than the overshooting model based on Herwig. In particular, the overshooting distance in the core helium-burning stage may be significantly smaller than that in the main-sequence phase for massive stars.
Noncommutative radial waves

We study radial waves in a (2+1)-dimensional noncommutative scalar field theory, using operatorial methods. The waves propagate along a discrete radial coordinate and are described by finite series deformations of Bessel-type functions. At radius much larger than the noncommutativity scale , one recovers the usual commutative behaviour. At small distances, classical divergences are smoothed out by noncommutativity.
PIS-YOLO: Real-Time Detection for Medical Mask Specification in an Edge Device

Wearing masks in a crowded environment can reduce the risk of infection; however, wearing nonstandard cloud does not have a good protective effect on the virus, which makes it necessary to monitor the wearing of masks in real time. You only look once (YOLO) series models are widely used in various edge devices. The existing YOLOv5s method meets the requirements of inference time, but it is slightly deficient in terms of accuracy due to its generality. Considering the characteristics of our driver medical mask dataset, a position insensitive loss which is cloud extract shared area feature in different categories and half deformable convolution net methods with cloud concern noteworthy features were introduced into YOLOv5s to improve accuracy, with an increase of 6.7% mean average in @. 5 (mAP@.5) and 8.3% in mAP@. 5:. 95 for our dataset. To ensure that our method can be applied in a real scenario, TensorRT and CUDA were introduced to reduce the inference time in two edge devices (Jetson TX2 and Jetson Nano) and one desktop device, whose inference time was faster than that of previous methods.
Mass growth and density profiles of dark matter haloes in hierarchical clustering

We develop a model for the growth of dark matter haloes and use it to study their evolved density profiles. In this model, haloes are spherical and form by quiescent accretion of matter in clumps, which are called satellites. The halo mass as a function of redshift is given by the mass of the most massive progenitor, and is determined from Monte Carlo realizations of the merger-history tree. Inside the halo, satellites move under the action of the gravitational force of the halo and a dynamical friction drag force. The associated equation of motion is solved numerically. The energy lost to dynamical friction is transferred to the halo in the form of kinetic energy. As satellites sink into the halo, they continually lose matter as a result of tidal stripping. The stripped matter moves inside the halo free of dynamical friction. The evolved density profiles are steeper than those obtained by assuming that, once they have been accreted on to the parent halo, satellites remain at a fixed distance from the halo centre. We find that the final density profile depends mainly on the rate of infall of matter on to the halo. This, in turn, depends on the initial fluctuation field as well as on cosmology. For mass scales where the effective spectral index of the initial density field is less than -1, the model predicts a profile that can only be approximately matched by the one-parameter family of curves suggested by Navarro, Frenk and White. For scale-free power spectra with initial slope n, the density profile, within about 1 per cent of the virial radius, is ρ∝ r-β, with 3(3+n)/(5+n)≤β≤ 3(3+n)/(4+n).
Dwarf carbon stars are likely metal-poor binaries and unlikely hosts to carbon planets

Dwarf carbon stars make up the largest fraction of carbon stars in the Galaxy with around 1200 candidates known to date primarily from the Sloan Digital Sky Survey. They either possess primordial carbon-enhancements, or are polluted by mass transfer from an evolved companion such that C/O is enhanced beyond unity. To directly test the binary hypothesis, a radial velocity monitoring survey has been carried out on 28 dwarf carbon stars, resulting in the detection of variations in 21 targets. Using Monte Carlo simulations, this detection fraction is found to be consistent with a 100% binary population and orbital periods on the order of hundreds of days. This result supports the post-mass transfer nature of dwarf carbon stars, and implies they are not likely hosts to carbon planets.
Nuclear matrix element of neutrinoless double-β decay : relativity and short-range correlations

CITATION: Song, L. S. , et al. 2017. Nuclear matrix element of neutrinoless double-β decay : relativity and short-range correlations. Physical Review C, 95(1):1-10, doi:10.1103/PhysRevC.95. 024305.
Self-acousto-optic modulation and orthogonality violation in the transverse modes of a broad-area Nd-doped yttrium-aluminum-garnet single-shot laser

Self-acousto-optic Raman-Nath modulation and nonorthogonal transversal modes are found in a broad-area Nd:YAG single-shot laser. The device is free from the thermal-induced effects previously related to orthogonality violation and the acousto-optic modulation comes from a shock wave produced by the discharge of the flash lamps that optically pump the laser. The experimental findings are reproduced by a general model of a class B laser.
Geometric models of (d+1)-dimensional relativistic rotating oscillators

Geometric models of quantum relativistic rotating oscillators in arbitrary dimensions are deﬁned on backgrounds with deformed anti-de Sitter metrics. It is shown that these models are analytically solvable, deriving the formulas of the energy levels and corresponding normalized energy eigenfunctions. An important property is that all these models have the same nonrelativistic limit, namely the usual harmonic oscillator.
Three-dimensionally perturbed vortex tubes in a rotating flow

Numerical experiments are used to study the evolution of perturbed vortex tubes in a rotating environment in order to better understand the process of two-dimensionalization of unsteady rotating flows. We specifically consider non-axisymmetric perturbations to columnar vortices aligned along the axis of rotation. The basic unperturbed vortex is chosen to have a Gaussian cross-sectional vorticity distribution. The experiments cover a parameter space in which both the strength of the initial perturbation and the Rossby number are varied. The Rossby number is defined here as the ratio of the maximum amplitude of vorticity in the Gaussian vorticity profile to twice the ambient rotation rate. For small perturbations and small Rossby numbers, both cyclones and anticyclones behave similarly, relaxing rapidly back toward two-dimensional columnar vortices. For large perturbations and small Rossby numbers, a rapid instability occurs for both cyclones and anticyclones in which antiparallel vorticity is created. The tubes break up and then re-form again into columnar vortices parallel to the rotation axis (i.e. into a quasi-two-dimensional flow) through nonlinear processes. For Rossby numbers greater than 1, even small perturbations result in the complete breakdown of the anticyclonic vortex through centrifugal instability, while cyclones remain stable. For a range of Rossby numbers greater than 1, after the breakdown of the anticyclone, a new weaker anticyclone forms, with a small-scale background vorticity of spectral shape given approximately by the −5/3 energy spectral law.