Miracle-dz/UniFAR-FTUs huggingface dataset:
Covering theorems for open continuous mappings having two valences between orientable surfaces

LetX be an open orientable surface with nite genus and nite number of boundary components, and letY be a closed orientable surface. An open continuous function from X to Y is termed a (p;q)-map, 0 <q<p , if it has a nite number of branch points and assumes every point in Y either p or q times, counting multiplicity, with possibly a nite number of exceptions. These comprise the most general class of all nontrivial functions having two valences betweenX andY. In this paper we generalize and prove in a unied manner almost all the earlier covering and existence results involving (p;q)-maps between orientable surfaces. Our main tools are (i) a generalized embedding theorem (see Lyzzaik, 1995) which asserts that image surfaces of (p;q)-maps embed in pfold closed coverings possibly having branch points o the image surfaces, and (ii) results (see Lyzzaik and Stephenson, and Lyzzaik, 1996) \modifying" general (p;q)-maps to \simplicial" ones having the same covering structures. This leads us to combinatorial results of (p;q)-maps relating their branch orders and exceptional sets of points to the valences p, q and the topological invariants of X and Y. The paper ends with open questions.
Stability and lifetime of antiferromagnetic skyrmions

The two-dimensional Heisenberg exchange model with out-of-plane anisotropy and Dzyaloshinskii-Moriya interaction is employed to investigate the lifetime and stability of antiferromagnetic (AFM) skyrmion as a function of temperature and external magnetic field. An isolated AFM skyrmion is shown to be metastable at zero temperature in a certain parameter range set by two boundaries separating the skyrmion state from the uniform AFM phase and a stripe domain state. The distribution of the energy barriers for the AFM skyrmion decay into the uniform AFM state complements the zero-temperature stability diagram and demonstrates that the skyrmion stability region is significantly narrowed at finite temperatures. We show that the AFM skyrmion stability can further be enhanced by an application of magnetic field, which strength is comparable with the spin-flop field. This stabilization of AFM skyrmions in external magnetic fields is in sharp contrast to the behavior of their ferromagnetic counterparts. Furthermore, we demonstrate that the AFM skyrmions are stable on the timescales of milliseconds below 50 K for realistic material parameters, making it feasible to observe them in modern experiments.
An Empirical Fitting Method for Type Ia Supernova Light Curves: A Case Study of SN 2011fe

We present a new empirical fitting method for the optical light curves of Type Ia supernovae (SNe Ia). We find that a variant broken-power-law function provides a good fit, with the simple assumption that the optical emission is approximately the blackbody emission of the expanding fireball. This function is mathematically analytic and is derived directly from the photospheric velocity evolution. When deriving the function, we assume that both the blackbody temperature and photospheric velocity are constant, but the final function is able to accommodate these changes during the fitting procedure. Applying it to the case study of SN 2011fe gives a surprisingly good fit that can describe the light curves from the first-light time to a few weeks after peak brightness, as well as over a large range of fluxes (∼5 mag, and even ∼7 mag in the g band). Since SNe Ia share similar light-curve shapes, this fitting method has the potential to fit most other SNe Ia and characterize their properties in large statistical samples such as those already gathered and in the near future as new facilities become available.
Measurement of degree of orientation of high polymer using rotating linear polarization imaging

Degree of orientation is an important parameter for the oriented high polymer, determining shock strength and elongation at break. An optical method sensitive to the well-oriented sample, was originated at our lab, and named as rotating linear polarization imaging. This method expresses the polarization difference as a function of multi-incident and multi-detection polarization angles. A parameter, α, is fitted and the resulting α image shows the 2-dimensional spatial distribution of the orientation of sample. Experiments are designed to acquire the α images when stretching is performed under different directions according to changes of the degree of orientation; and these α images are compared with the normal case in which no stretching is performed. The acquired α images show that when stretching along the orientation of sample (enlarge degree of orientation), the values of α become larger than the normal case, and at the perpendicularity direction (reduce degree of orientation), the values are smaller. Experiments show that á could characterize the degree of orientation well and indicate the potential of our method to measure the degree of orientation of high polymer.
Discovery of a glitch in the accretion-powered pulsar SXP 1062

We present timing analysis of the accretion powered pulsar SXP 1062, based on the observations of \textit{Swift}, \textit{XMM-Newton} and \textit{Chandra} satellites covering a time span of about 2 years. We obtain a phase coherent timing solution which shows that SXP 1062 has been steadily spinning down with a rate $-\,4.29(7) \times 10^{-14}$ Hz s$^{-1}$ leading to a surface magnetic field estimate of about $1.5 \times 10^{14}$ G. We also resolve the binary orbital motion of the system from X-ray data which confirms an orbital period of 656(2) days. On MJD 56834.5, a sudden change in pulse frequency occurs with $\Delta\nu = 1.28(5) \times 10^{-6} $ Hz, which indicates a glitch event. The fractional size of the glitch is $\Delta \nu / \nu \! \sim \! 1.37(6) \times 10^{-3}$ and SXP 1062 continues to spin-down with a steady rate after the glitch. A short X-ray outburst 25 days prior to the glitch does not alter the spin-down of the source; therefore the glitch should be associated with the internal structure of the neutron star. While glitch events are common for isolated pulsars, the glitch of SXP 1062 is the first confirmation of the observability of this type of events among accretion powered pulsars. Furthermore, the value of the fractional change of pulse frequency ensures that we discover the largest glitch reported up to now.
Acta Polytechnica

Abstract. We revisit the algebraic description of shape invariance method in one-dimensional quantum mechanics. In this note we focus on four particular examples: the Kepler problem in flat space, the Kepler problem in spherical space, the Kepler problem in hyperbolic space, and the Rosen–Morse potential problem. Following the prescription given by Gangopadhyaya et al., we first introduce certain nonlinear algebraic systems. We then show that, if the model parameters are appropriately quantized, the bound-state problems can be solved solely by means of representation theory.
A sliced-finite difference method for the American option

It is generally accepted that the Black-Scholes model for American option pricing is a free-boundary problem involving a partial differential equation. Approximate solutions may be obtained using numerical methods, but the precision and stability of these solutions is hard to control since they are significantly affected by the singularity at the exercise boundary near the expiration date. We propose a Sliced-Finite Difference (SFD) numerical method, to solve the pricing problem of American put options. The proposed method combines the advantages of the semi-analytical method and the sliced-fixed boundary finite difference method and overcomes their deficiencies. Using the SFD method, we can resolve the problem that results from the singularity near the optimal exercise boundary. Numerical experiments show that the SFD method is more accurate than other numerical methods. The proposed method is targeted at American put options but it is also applicable to other types of options.
Fast Radio Bursts’ Recipes for the Distributions of Dispersion Measures, Flux Densities, and Fluences

We investigate how the statistical properties of dispersion measure (DM) and apparent flux density/fluence of (nonrepeating) fast radio bursts (FRBs) are determined by unknown cosmic rate density history [ρFRB(z)] and luminosity function (LF) of the transient events. We predict the distributions of DMs, flux densities, and fluences of FRBs taking account of the variation of the receiver efficiency within its beam, using analytical models of ρFRB(z) and LF. Comparing the predictions with the observations, we show that the cumulative distribution of apparent fluences suggests that FRBs originate at cosmological distances and ρFRB increases with redshift resembling the cosmic star formation history (CSFH). We also show that an LF model with a bright-end cutoff at log10Lν (erg s−1 Hz−1) ∼ 34 are favored to reproduce the observed DM distribution if ρFRB(z) ∝ CSFH, although the statistical significance of the constraints obtained with the current size of the observed sample is not high. Finally, we find that the correlation between DM and flux density of FRBs is potentially a powerful tool to distinguish whether FRBs are at cosmological distances or in the local universe more robustly with future observations.
Exact Solutions of Klein–Gordon Equation with Scalar and Vector Rosen–Morse-Type Potentials

We obtain an exact analytical solution of the Klein–Gordon equation for the equal vector and scalar Rosen– Morse and Eckart potentials as well as the parity-time (PT) symmetric version of the these potentials by using the asymptotic iteration method. Although these PT symmetric potentials are non-Hermitian, the corresponding eigenvalues are real as a result of the PT symmetry.
Atlas of quasar energy distributions

We present an atlas of the spectral energy distributions (SEDs) of normal, nonblazar, quasars over the whole available range (radio to 10 keV X-rays) of the electromagnetic spectrum. The primary (UVSX) sample includes 47 quasars for which the spectral energy distributions include X-ray spectral indices and UV data. Of these, 29 are radio quiet, and 18 are radio loud. The SEDs are presented both in figures and in tabular form, with additional tabular material published on CD-ROM. Previously unpublished observational data for a second set of quasars excluded from the primary sample are also tabulated. The effects of host galaxy starlight contamination and foreground extinction on the UVSX sample are considered and the sample is used to investigate the range of SED properties. Of course, the properties we derive are influenced strongly by the selection effects induced by quasar discovery techniques. We derive the mean energy distribution (MED) for radio-loud and radio-quiet objects and present the bolometric corrections derived from it. We note, however, that the dispersion about this mean is large (approximately one decade for both the infrared and ultraviolet components when the MED is normalized at the near-infrared inflection). At least part of the dispersion in the ultraviolet may be due to time variability, but this is unlikely to be important in the infrared. The existence of such a large dispersion indicates that the MED reflects only some of the properties of quasars and so should be used only with caution.
Measurement of Trap Stiffness of Holographic Optical Tweezers with Power Spectrum Method

A microsphere trapped by optical tweezers moves according to the Brownian motion law, which can be described by the Langevin equation. Based on it, a quadrant photodiode (QD) is used to track the displacement of the microsphere with a diameter of 2.5um trapped by holographic optical tweezers, and power spectrum method is adopted to obtain radial trap stiffness. Experiments show that the trap stiffness increases with the increase of the laser power, and decreases as the distance between the optical trap and the inside bottom surface of the sample cell increases.
Cosmic String Wake Detection using 3D Ridgelet Transformations

Three-dimensional ridgelet statistics are used to search for the signals of cosmic string wakes in the distribution of dark matter. We compare N-body simulations of the dark matter distribution in cosmological models with and without a cosmic string wake, assuming that the dominant sources of fluctuations are those predicted in the standard $\Lambda$CDM model. Cosmic string wakes lead to overdense regions with planar topology, and hence three-dimensional ridgelet statistics are a promising analysis tool. The string signal is easier identifiable for larger string tensions and at higher redshift. We find that a wake produced by a string of tension $G\mu = 10^{-7}$ (a value slightly lower than the best current robust upper bound) can be detected at $6 \, \sigma$ confidence level at a cosmological redshift $z = 10$.
Use of genetic algorithms for the vibroacoustic optimization of a plate carrying point-masses

Optimal design of mechanical structures for vibration or noise reduction often requires finding the minima of highly nonlinear multi-dimensional functions. In this paper, genetic algorithms are introduced as a new promising tool for numerical optimization of such problems. The application presented is on the control of the vibroacoustic response of a plate carrying point-masses. Genetic algorithms have been used to determine the optimal positions of the masses on the plate. Several cases are presented, using various optimization criteria, showing the importance of selecting the most appropriate criterion.
Hierarchical Vector Autoregression

Vector autoregression (VAR) is a fundamental tool for modeling the joint dynamics of multivariate time series. However, as the number of component series is increased, the VAR model quickly becomes overparameterized, making reliable estimation difficult and impeding its adoption as a forecasting tool in high dimensional settings. A number of authors have sought to address this issue by incorporating regularized approaches, such as the lasso, that impose sparse or low-rank structures on the estimated coefficient parameters of the VAR. More traditional approaches attempt to address overparameterization by selecting a low lag order, based on the assumption that dynamic dependence among components is short-range. However, these methods typically assume a single, universal lag order that applies across all components, unnecessarily constraining the dynamic relationship between the components and impeding forecast performance. The lasso-based approaches are more flexible but do not incorporate the notion of lag order selection. We propose a new class of regularized VAR models, called hierarchical vector autoregression (HVAR), that embed the notion of lag selection into a convex regularizer. The key convex modeling tool is a group lasso with nested groups which ensure the sparsity pattern of autoregressive lag coefficients honors the ordered structure inherent to VAR. We provide computationally efficient algorithms for solving HVAR problems that can be parallelized across the components. A simulation study shows the improved performance in forecasting and lag order selection over previous approaches, and a macroeconomic application further highlights forecasting improvements as well as the convenient, interpretable output of a HVAR model.
An Integral-type Dynamic Localization Two-parameter Subgrid-scale Model: Formulation and Simulation

The dynamic two-parameter mixed model (DMM2) has been recently introduced into the large eddy simulation (LES) by Salvetti and Banerjee [“a priori Tests of A New Dynamic Subgrid-Scale Model for Finite-Difference Large-Eddy Simulations”, Phys. Fluids, 7 (1995) pp. 2831–2847], Horiuti [“A New Dynamic Two-Parameter Mixed Model for Large-Eddy Simulation”, Phys. Fluids, 9 (1997) pp. 3443–3464], Meneveau and Katz [“Dynamic Testing of Subgrid Models in Large Eddy Simulation Based on the Cermano Identity”, Phys. Fluids, 11 (1999) pp. 245–247], Sarghini et al. [“Scale-Similar Models for Large-eddy Simulations”, Phys. Fluids, 11 (1999) pp. 1596–1607], and Morinishi and Vasilyev [“A Recommended Modification to the Dynamic Two-Parameter Mixed Subgrid Scale Model for Large Eddy Simulation of Wall Bounded Turbulent Flow”, Phys. Fluids, 13 (2001) pp. 3400–3410]. However, current approaches in the literature are mathematically inconsistent. In this paper, the DMM2 has been optimized using the functional variational method. The mathematical inconsistency has been removed and a governing system of two integral equations for the model coefficients of the DMM2 has been obtained. Numerical simulation of turbulent Couette flow is used to validate the new optimal DMM2. The numerical results agree with the direct numerical simulation (DNS) data, the classical wall law and experimental correlations that are available in the literature.
Universality class of an S=1/2 quantum spin ladder system with four-spin exchange

We study a $s=\frac{1}{2}$ Heisenberg spin ladder with four-spin exchange. Combining numerical results with conformal field theory, we find a phase transition with central charge $c=\frac{3}{2}. $ Since this system has an SU(2) symmetry, we can conclude that this critical theory is described by $k=2$ SU(2) Wess-Zumino-Witten model with ${Z}_{2}$ symmetry breaking.
Fusion of finite impulse response filter and adaptive Kalman filter to suppress angle random walk of fiber optic gyroscopes

Abstract. We present a new fusion structure of finite impulse response (FIR) filter and adaptive Kalman filter to suppress the angle random walk (ARW) of the fiber optic gyroscopes (FOGs). In our proposed fusion filter, a low-pass FIR filter first decomposes the discrete-time rotation rate into an approximation part and a detailed part. The detailed part is then put into an adaptive Kalman filter, which generates an increment part to compensate the high-frequency components of the rotation rate suppressed by the FIR filter. Different from the existing adaptive mechanism that modifies the covariance matrix of the error in the predicted estimate to cover model error, our proposal adaptively modifies the state equation of the Kalman filter to give a more accurate model. Therefore, it has the ability to distinguish the high-frequency components of the rotate rate from the high-frequency ARW noise. The new fusion structure integrates the advantages of these two filters. Experiments showed that with this new proposal, the ARW of a specific FOG had been reduced from 0.03741 deg/h to 0.00976 deg/h when the tap order M reached 1000, and the tracking error in dynamic cases was smaller than the digital resolution of the FOG.
Strain-induced band gap shrinkage in Ge grown on Si substrate

Band gap shrinkage induced by tensile strain is shown for Ge directly grown on Si substrate. In Ge-on-Si pin diodes, photons having energy lower than the direct band gap of bulk Ge were efficiently detected. According to photoreflectance measurement, this property is due to band gap shrinkage. The origin of the shrinkage is not the Franz–Keldysh effect but rather tensile strain. It is discussed that the generation of such a tensile strain can be ascribed to the difference of thermal expansion between Ge and Si. Advantages of this tensile Ge for application to photodiode are also discussed.
Precession of perihelion of a planetesimal perturbed by a circumstellar disk

In questo lavoro di tesi abbiamo trattato dei modelli di costruzione del potenziale indotto di un giovane disco circumstellare in modo da calcolare la velocita di precessione del perielio di un planeterismo da esso perturbato. Inizialmente affronteremo i modelli di Binney e Tremaine, e Ward che partono da una densita superficiale di massa dipendente da una non specificata potenza della distanza dalla stella. In seguito di specializzeremo nel caso in cui la potenza e -1, e studieremo la precessione di questi due modelli unitamente a quello di Mestel, e confronteremo con una simulazione i risultati. Calcoleremo il tutto anche per indice -1.5 (quella della Minimum Mass Solar Nebula) insieme ad una semplificazione del modello di Ward, fatto da Rafikov e confronteremo le previsioni.
Optimal technique for estimating the reachable set of a controlled n-dimensional linear system

The reachable set from a given point of a controlled dynamical system is the set of all states to which the system can be driven from that point in a finite time by the allowed controls. A technique is presented Tor estimating the reachable set from the asymptotically-stable origin of a class of n-dimensional linear systems under bounded control. The technique is an optimal version of a Lyapunov method, and provides an (over-)estimate of the full reachable set; it involves the minimization of a quadratic constraint, followed by the maximization of a quadratic form subject to this constraint. The non-linear optimization problems can be routinely solved by means of computer algebra and commonly available computer software. In general, the technique produces a much-improved estimate of the reachable set compared to that given by the standard Lyapunov method. Another advantage of the technique is that it is truly applicable to higher-dimensional systems (n ≥ 3). Since the estimate produced is in the convenien.
New Tools for Computing Tight Bounds on the Real Structured Singular Value

New tools are presented for the computation of tight lower bounds on the structured singular value π, for highorder plants subject to purely real parametric uncertainty. The e rst approach uses the π-sensitivity function to systematically reduce the order of the real uncertainty matrix, so that exponential time lower bound algorithms can be applied. The second approach formulates the search for a worst-case real destabilizing perturbation as a constrained nonlinearoptimization problem.Both approachesareapplied to theproblem ofanalyzing thestability robustness properties of an integrated e ight and propulsion control system for an experimental vertical/short takeoff and landing aircraft cone guration. Currently available software tools for calculating lower bounds on real π fail for this problem, whereas both new approaches deliver tight bounds over the frequency range of interest.
Criteria for Combining Inverse and Rayleigh Quotient Iteration

A method is presented to find selected eigenvalue-eigenvector pairs of the generalized problem $Ax = \lambda Bx$. Here A and B are real symmetric matrices and B is positive definite. It is further assumed that the matrices are large and sparse and that factorization of either of them is impractical. Our method finds an eigenvalue in a given interval $J = (\gamma - \eta ,\gamma + \eta )$ or determines that J is free of eigenvalues while computing an approximation to the eigenvalue closest to this interval. The corresponding eigenvector is also computed. The method consists of inverse and Rayleigh quotient iteration steps. The convergence is studied and it is shown how an inclusion theorem gives one of the criteria for switching from inverse to Rayleigh quotient iteration. The existence of an eigenvalue in the desired interval is guaranteed when this criterion is fulfilled. Some numerical experiments are reported which suggest that the method is optimal in the sense that when the mesh is refined the computa.
New implicit boundary procedures - Theory and applications

Analytical techniques for the application of implicit boundary conditions for inviscid flows to shock and body boundary layer conditions involving the Euler equations are presented. The theory of characteristics is used to update boundary points with spatial second order accuracy. The method is useful for implicit schemes which feature approximate factorization, and as such is incorporated into an existing PNS code. Examples are provided in terms of flows over a cone, over a maneuverable reentry vehicle, and over a finned vehicle. Improvements in the convergence rate are demonstrated for the conical flow solutions.