Miracle-dz/UniFAR-FTUs huggingface dataset:
Formation of pressure‐balanced structures and fast waves from nonlinear Alfvén waves

In the solar wind, Alfvenic fluctuations are typically observed in association with small fluctuations of the density (ρ) and magnetic field strength (B), which tend to be anticorrelated and in approximate pressure balance. One would not expect any finite δρ and δB among pure Alfven waves propagating strictly outward from the Sun. Our paper shows how Alfven waves can nonlinearly produce structures in pressure balance. We present a second-order analysis of the pure magnetohydrodynamic equations and hybrid simulations which show that nonlinear Alfven waves traveling in different directions but with equal group velocity can generate pressure-balanced structures with wave vectors perpendicular to the background magnetic field B 0 . Homogeneous fast waves are also generated in this direction in order to satisfy initial conditions. They cannot be Landau or transit-time damped and so cause the values of B and ρ to vary with time as they beat with the pressure-balanced structures. However, we find δρδB < 0 is satisfied most of the time, and this can partly explain the tendency for anticorrelation observed in the solar wind. In directions away from the perpendicular one, Alfven waves produce driven fast waves which give constant B and ρ to second order. Homogeneous fast and slow waves are also produced in these directions but Landau damp away in large β plasmas. Thus an equilibrium or steady propagating waveform at second order can be produced where B and ρ vary only in the perpendicular direction. If transverse magnetic structures with wave vectors perpendicular to B 0 are included at the same order as the initial Alfven waves, then these evolve to pressure-balanced structures and can also coexist with the Alfven waves. However, an equilibrium is obtained generally only when these structures also have velocity fluctuations equivalent of those of the Alfven waves.
On the freeness of rational cuspidal plane curves

We bring additional support to the conjecture saying that a rational cuspidal plane curve is either free or nearly free. This conjecture was confirmed for curves of even degree, and in this note we prove it for many odd degrees. In particular, we show that this conjecture holds for the curves of degree at most 34.
Gaussian white noise as a many-particle process: the Kardar-Parisi-Zhang equation

A new approach is proposed to derive a stochastic differential equation from a master equation. Starting from the Liouvillian in a Fock space formulation and using a functional integral representation in terms of coherent states the authors get the corresponding Langevin equation. As examples aggregation and segregation processes with different probability rates are analyzed. In the case of a state dependent growth rate it results in a generalized Kardar-Zhang equation including the kind of noise which is a purely Gaussian one in this model.
THE FRACTION OF CLOSE BINARIES AMONG HUBBLE SPACE TELESCOPE GUIDE STARS - OPERATIONAL CONSEQUENCES, WORKAROUNDS, AND SUGGESTIONS FOR DESIGNERS OF FUTURE SPACE OBSERVATORIES

It is observationally determined that a significant number of guide stars which will be used by the Hubble Space Telescope are close binaries which can prevent a Fine-Guidance-Sensor fine lock. This is because the Fine Guidance Sensors (FGSs) operate as white-light interferometers, and the fringe patterns of binaries will result in a reduction in the loop gain in the FGS control system. Consequently, multiple guide stars must be attempted to ensure a successful acquisition. The limited HST on-board computer memory may restrict the number of guide stars which can be attempted, resulting in a possible loss of several hundred hours per year of observing time. The FGSs of the next-generation (and presumably larger) space-telescopes would be even more susceptible to the binary problem. Other types of guidance systems (such as quadrant detectors) deserve serious consideration for future space observatories.
Effects of broad-waveguide structure in 0.8 μm high-power InGaAsP/InGaP/AlGaAs lasers

Systematic study on the effects of the waveguide thickness Wg has been carried out for 200-μm-wide stripe separate-confinement-heterostructure lasers in the range of Wg=0.22–1.2 μm while the width of single quantum well is kept constant at 10 nm. The internal loss αi is reduced from 1.7 to 1 cm−1 when Wg is increased from 0.22 to 1.2 μm. It is shown that αi is not determined by the free-carrier absorption of clad layers, but primarily by Γ, the optical confinement factor, most probably due to scattering at the quantum well/waveguide interfaces. The external differential quantum efficiency ηd monotonically increases with Wg for pulsed operation. By contrast, ηd is maximum at Wg=0.8 μm for continuous-wave (cw) operation. Both the threshold carrier density and the threshold temperature sensitivity increases with Wg for Wg⩾0.8 μm, which decreases ηd in cw operation. When 200-μm-wide devices (20%/97% coated) were life tested at 2 W and 30 °C, the median degradation rate shows a minimal value of 3×10−6 h−1 at W.
The Einstein Observatory Extended Medium-Sensitivity Survey. II - The optical identifications

The optical identifications are presented of the Einstein Extended Medium-Sensitivity Survey (EMSS), including the methodology used to optically identify the EMSS sources and the uncertainties involved with that process. The optical properties of the classes of X-ray, optical, and radio data for each of the identified and, as yet, unidentified sources of the survey are described. A new class of X-ray emitters, cooling flow galaxies, is proposed. The criteria used to determine whether the proposed optical counterpart to the X-ray source is a plausible identification are described. Plausibility is based on the optical classification of the counterpart, e.g., AGN, cluster, G star, and the X-ray-to-optical flux ratios previously observed for these classes of X-ray emitters. Two independent schemes of optical classification of the counterparts are used to check the plausibility of these identifications; one is based on moderate-resolution optical spectroscopy, and the other, on inferred X-ray luminosity and the overall energy distribution. 110 refs.
k-Version Least Squares Finite Element Processes for 2-D Generalized Newtonian Fluid Flows

In this paper, a mathematical and computational framework based on h, p, k and variationally consistent (VC) integral form is utilized to present a finite element computational process for two dimensional steady, isothermal as well as non-isothermal fluid flows for power law and Carreau models of viscosity. Strong form of the governing differential equations is presented and utilized in dependent variables P, u, v and T. Since the differential operator is non-linear, Galerkin method, Petrov Galerkin method, method of weighted residuals and Galerkin method with weak forms yield integral form that are variationally inconsistent (VIC). Least Squares Processes on the other hand, yield integral forms that are VC. Computational processes based on VC integral forms are unconditionally stable and non-degenerate and hence do not require the use of problem dependent upwinding methods. The parameter k controlling global differentiability of the approximation permits higher order global approximations, which are necessitated by the physics in governing differential equations (GDEs). The behavior of the power law and Carreau models of shear thinning fluid behavior is investigated using theoretical solutions (when possible) as well as numerical simulations using the proposed methodology. Fully developed flow between parallel plates, steady pressure driven Couette flow and lid driven cavity are used as model problems.
A proof of a support theorem for stochastic wave equations in Holder norm with some general noises.

In this paper, we characterize the topological support in Holder norm of the law of the solution to a stochastic wave equation with three-dimensional space variable is proved. This note is a continuation of [9] and [10]. The result is a consequence of an approximation theorem, in the convergence of probability, for a sequence of evolution equations driven by a family of regularizations of the driving noise. We extend two previous results on this subject. The first extension is that we cover the case of multiplicative noise and non-zero initial conditions. The second extension is related to the covariance function associated with the noise, here we follow the approach of Hu, Huang and Nualart and ask conditions in terms the of the mean Holder continuity of such covariance function.
Connectedness of Brill-Noether loci via degenerations

We show that limit linear series spaces for chains of curves are reduced. Using new advances in the foundations of limit linear series, we then use degenerations to study the question of connectedness for spaces of linear series with imposed ramification at up to two points. We find that in general, these spaces may not be connected even when they have positive dimension, but we prove a criterion for connectedness which generalizes the theorem previously proved by Fulton and Lazarsfeld in the case without imposed ramification.
Dilations of Markovian semigroups of Fourier multipliers on locally compact groups

We prove that any weak* continuous semigroup $(T_t)_{t \geq 0}$ of Markov Fourier multipliers acting on a group von Neumann algebra $\mathrm{VN}(G)$ associated to a locally compact group $G$ can be dilated by a weak* continuous group of Markov $*$-automorphisms on a bigger von Neumann algebra. Our construction relies on probabilistic tools and is even new for the group $\mathbb{R}^n$. Our results imply the boundedness of the McIntosh's $\mathrm{H}^\infty$ functional calculus of the generators of these semigroups on the associated noncommutative $\mathrm{L}^p$-spaces.
Back stable Schubert calculus

We study the back stable Schubert calculus of the infinite flag variety. Our main results are: – a formula for back stable (double) Schubert classes expressing them in terms of a symmetric function part and a finite part; – a novel definition of double and triple Stanley symmetric functions; – a proof of the positivity of double Edelman–Greene coefficients generalizing the results of Edelman–Greene and Lascoux–Schützenberger; – the definition of a new class of bumpless pipedreams, giving new formulae for double Schubert polynomials, back stable double Schubert polynomials, and a new form of the Edelman–Greene insertion algorithm; – the construction of the Peterson subalgebra of the infinite nilHecke algebra, extending work of Peterson in the affine case; – equivariant Pieri rules for the homology of the infinite Grassmannian; – homology divided difference operators that create the equivariant homology Schubert classes of the infinite Grassmannian.
Gradient methods with regularization for constrained optimization problems and their complexity estimates

Abstract We suggest simple implementable modifications of conditional gradient and gradient projection methods for smooth convex optimization problems in Hilbert spaces. Usually, the custom methods attain only weak convergence. We prove strong convergence of the new versions and establish their complexity estimates, which appear similar to the convergence rate of the weakly convergent versions. Preliminary results of computational tests confirm efficiency of the proposed modification.
Implementation of a Rogowski coil for the measurement of partial discharges

In order to obtain partial discharge (PD) measurements a PD measuring probe based on a Rogowski coil was constructed. Up to now, Rogowski coils had been used to measure high level currents. In this article, the design of a Rogowski coil to measure very low currents, but with a very high frequency, such as partial dischages, is exposed. The Rogowski coil used as a PD transducer is very advantageous because it is inexpensive and easy to use. Besides, it provides the needed bandwidth for this application.
UNIVERSAL HOMOMORPHISMS, UNIVERSAL STRUCTURES, AND THE POLYMORPHISM CLONES OF HOMOGENEOUS STRUCTURES

Using a categorial version of Fra¨osse's theorem due to Droste and Gobel, we derive a criterion for a comma-category to have universal homoge- neous objects. As a first application we give new existence result for universal structures and for @0-categorical universal structures. As a second application we characterize the retracts of a large class of homogeneous structures, extending previous results by Bonato, Delic, Dolinka, and Kubis. As a third application we show for a large class of homogeneous structures that their polymorphism clone is generated by polymorphisms of bounded arity, generalizing a classical result by Sierpinski that the clone of all functions on a given set is generated by its binary part. Further we study the cofinality and the Bergman property for clones and we give sufficient conditions on a homogeneous structure to havea polymorphism clone that has uncountable cofinality and the Bergman property.
A Q-analogue and a Symmetric Function Analogue of a Result by Carlitz, Scoville and Vaughan

We derive an equation that is analogous to a well-known symmetric function identity: $\sum_{i=0}^n(-1)^ie_ih_{n-i}=0$. Here the elementary symmetric function $e_i$ is the Frobenius characteristic of the representation of $\mathcal{S}_i$ on the top homology of the subset lattice $B_i$, whereas our identity involves the representation of $\mathcal{S}_n\times \mathcal{S}_n$ on the Segre product of $B_n$ with itself. We then obtain a q-analogue of a polynomial identity given by Carlitz, Scoville and Vaughan through examining the Segre product of the subspace lattice $B_n(q)$ with itself. We recognize the connection between the Euler characteristic of the Segre product of $B_n(q)$ with itself and the representation on the Segre product of $B_n$ with itself by recovering our polynomial identity from specializing the identity on the representation of $\mathcal{S}_i\times \mathcal{S}_i$.
Electric‐field‐induced phase changes in poly(vinylidene fluoride)

The antipolar crystal form of poly(vinylidene fluoride) can be made piezoelectric and pyroelecric by the temporary application of electric fields in excess of 1 MV/cm at room temperature. Infrared and x‐ray diffraction data reveal that the polarization occurs in two stages. At fields near 1 MV/cm, a phase transition to a polar form II occurs with presumably no change in chain conformation. Fields near 5 MV/cm cause a change in conformation to produce form I. Our results indicate that at least a portion of the residual polarization occurs within the crystal phase of the polymer.
The Heegner point Kolyvagin system

In Bull. Soc. Math. France 115 (1987), 399–456, Perrin-Riou formulates a form of the Iwasawa main conjecture which relates Heegner points to the Selmer group of an elliptic curve defined over $\mathbb{Q}$, as one goes up the anticyclotomic $\mathbb{Z}_p$-extension of a quadratic imaginary field K. Building on the earlier work of Bertolini on this conjecture, and making use of the recent work of Mazur and Rubin on Kolyvagin's theory of Euler systems, we prove one divisibility of Perrin-Riou's conjectured equality. As a consequence, one obtains an upper bound on the rank of the Mordell–Weil group E(K) in terms of Heegner points.
Clinical examination and necropsy findings of a mountain hawk-eagle (Nisaetus nipalensis) that died during rehabilitation

We examined the clinical signs and necropsy findings of a mountain hawk-eagle (Nisaetus nipalensis) that died during rehabilitation. The bird was rescued and treated for open fracture of the right forearm. During rehabilitation, the bird could not stand up or fly. Part of the right secondary and left and right primary feathers were removed during rehabilitation; additional fracture was found in the right tibiotarsus and treated. However, the bird died 92 days after rescue and necropsy was performed. Severe hepatic lipidosis and capture myopathy were confirmed by histopathological examinations. These lesions may be associated with the cause of death of this animal. Accumulation of information is expected to contribute to the improvement of effective rehabilitation techniques for raptors.
An Observational Study of Strong Vertical Wind Shear over North America during the 1983/84 Cold Season

Abstract The phenomenon of strong vertical wind sheer (SWS) over the North American continent is documented with conventional rawinsonde data for the period 1 October 1983 through 31 March 1984. One of the objectives of this work is to describe the three-dimensional distribution of frontal zones. Since it is not possible to use the coarse horizontal resolution of the sounding network to document fully the existence of frontal zones, we instead use the excellent vertical resolution of the winds to infer the existence of these strong baroclinic zones through use of the thermal wind relation. SWS, defined as a shear exceeding that associated with a horizontal temperature gradient of 1 5.5°C/500 km, is most frequently observed in the lower and upper troposphere, though secondary frequency peaks are observed in the middle troposphere. The SWS phenomenon is preferentially located in the middle latitudes where the strongest baroclinity is typically found. Monthly fields of SWS show the frequency maxima to he clo.
The Weyl expansion for systems of independent identical particles

We present a novel analytical approach for the calculation of the mean density of states in many-body systems consisting of confined indistinguishable and independent particles. Our method makes explicit the intrinsic geometry inherent in the symmetrization postulate. In the spirit of the usual Weyl expansion for the smooth part of the density of states in confined single-particle systems, our results take the form of a sum over clusters of particles moving freely around manifolds in configuration space invariant under permutations. In our approach the emergence of the fermionic ground state is a consequence of a delicate cancellation effect of cluster contributions. As an asymptotic expansion, our approximation gives increasingly better results for large excitation energies, and we show that it coincides with the Bethe estimate in the appropriate region. Moreover, our construction gives the correct high-energy asymptotics expected from general considerations. Our expansion in cluster zones is naturally incorporated for systems of interacting particles, opening an alternative road to address the interplay between symmetry, confinement and interactions in many-body systems of identical bosonic or fermionic particles.
Metal–insulator transition in one-dimensional In-chains on Si(111): combination of a soft shear distortion and a double-band Peierls instability

The most stable geometries for the (4 × 1) and (4 × 2) phases of the In/Si(111) surface have been reanalysed using DFT-annealing. A very efficient local orbital method (FIREBALL) has allowed us to explore the geometrical phase space and look for new absolute minima. The most stable theoretical structure is a new In/Si(111)-(4 × 2) geometry that presents a semiconducting band structure. This (4 × 2) surface, qualitatively very similar to the structural model proposed by Kumpf et al (2000 Phys. Rev. Lett. 85 4916), is found to be the result of the combination of a soft shear distortion, whereby the two zigzag In-rows are displaced in opposite directions along the In-chains, and a pairing of the outer In atoms associated with a double-band Peierls distortion.
Monotone and Convex Stochastic Orders for Processes with Independent Increments

We study monotone and convex stochastic orders for processes with independent increments. Our contributions are twofold: First, we relate stochastic orders of the Poisson component to orders of their (generalized) Levy measures. The relation is proven using an interpolation formula for infinitely divisible laws. Second, we derive explicit conditions on the characteristics of the processes. In this case, we prove the conditions via constructions of couplings.
Volume inside old black holes

Black holes that have nearly evaporated are often thought of as small objects, due to their tiny exterior area. However, the horizon bounds large spacelike hypersurfaces. A compelling geometric perspective on the evolution of the interior geometry was recently shown to be provided by a generally covariant definition of the volume inside a black hole using maximal surfaces. In this article, we expand on previous results and show that finding the maximal surfaces in an arbitrary spherically symmetric spacetime is equivalent to a 1+1 geodesic problem. We then study the effect of Hawking radiation on the volume by computing the volume of maximal surfaces inside the apparent horizon of an evaporating black hole as a function of time at infinity: while the area is shrinking, the volume of these surfaces grows monotonically with advanced time, up to when the horizon has reached Planckian dimensions. The physical relevance of these results for the information paradox and the remnant scenarios are discussed.
Two-and multi-phase quadrature surfaces

In this paper we shall initiate the study of the two-and multi-phase quadrature surfaces (QS), which amounts to a two/multi-phase free boundary problems of Bernoulli type. The problem is studied mostly from a potential theoretic point of view that (for two-phase case) relates to integral representation \begin{document}$\int_{\partial Ω^+} g h (x) \ dσ_x - \int_{\partial Ω^-} g h (x) \ dσ_x= \int h dμ \ ,$ \end{document} where \begin{document} $dσ_x$ \end{document} is the surface measure, \begin{document} $μ= μ^+ - μ^-$ \end{document} is given measure with support in (a priori unknown domain) \begin{document} $Ω=Ω^+\cupΩ^-$ \end{document} , \begin{document} $g$ \end{document} is a given smooth positive function, and the integral holds for all functions \begin{document} $h$ \end{document} , which are harmonic on \begin{document} $\overline Ω$ \end{document} . Our approach is based on minimization of the corresponding two-and multi-phase functional and the use of its one-phase version as a barrier. We prove several results concerning existence, qualitative behavior, and regularity theory for solutions. A central result in our study states that three or more junction points do not appear.