bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the value of the Immirzi parameter and the horizon entropy
Authors: Pigozzo Cássio , Bacelar Flora S , Carneiro Saulo 
Published: November 2020

Abstract
In loop quantum gravity (LQG) the quantisation of general relativity leads to precise predictions for the eigenvalues of geometrical observables like volume and area, up to the value of the only free parameter of the theory, the Barbero–Immirzi (BI) parameter. With the help of the eigenvalues equation for the area operator, LQG successfully derives the Bekenstein–Hawking entropy of large black holes with isolated horizons, fixing at this limit the BI parameter as γ ≈ 0.274. In the present paper we show some evidence that a black hole with angular momentum ℏ and Planck mass is an eigenstate of the area operator provided that

γ
=

3

/
6
≈
1.05
×
0.274

. As the black hole is extremal, there is no Hawking radiation and the horizon is isolated. We also suggest that such a black hole can be formed in the head-on scattering of two parallel standard model neutrinos in the mass state m
2 (assuming m
1 = 0). Furthermore, we use the obtained BI parameter to numerically compute the entropy of isolated horizons with areas ranging up to

250

l

P

2

, by counting the number of micro-states associated to a given area. The resulting entropy has a leading term

S
≈
0.25

A

, in agreement to the Bekenstein–Hawking entropy. As the identification of the above eigenstate rests on the matching between classical areas and quantum area eigenvalues, we also present, on the basis of an effective quantum model for the Schwarzschild black hole recently proposed by Ashtekar, Olmedo and Singh, an expression for the quantum corrected area of isolated horizons, valid for any black hole mass. Quantum corrections are shown to be negligible for a Planck mass black hole, of order 10−3 relative to the classical area.
Reply to Comment on ‘Forces on hockey players: vectors, work, energy and angular momentum’
Authors: Nässén Nina , Nässén Hans-Åke , Eriksson Urban , Pendrill Ann-Marie 
Published: November 2020

Abstract
Bracko has commented on our paper ‘forces on hockey players: vectors, work, energy and angular momentum’and refers to extensive studies on skaters using traditional techniques. We note that results based on one skating technique, such as a correlation between stride rate and speed, cannot be immediately applied to a different technique.
Forced precession of a gyroscope and its application to Laithwaite’s engine
Authors: Provatidis Christopher G 
Published: November 2020

Abstract
The forced precession of a symmetrical gyroscope is studied for the particular case in which the axle of a flywheel is pivoted by a hinge joint and follows a horizontal circular path of a given radius. The aforementioned setup appears in the so-called Laithwaite engine, the detailed mechanics of which are still an enigma. Instead of applying Lagrangian equations, Newton’s second law is applied to the rotating gyroscope with respect to its center of mass. Three novel Euler equations are developed that are much longer than those found in textbooks. In this mechanical system, which is characterized by one degree of freedom, the main nonlinear governing equation is identified and then MATLAB code is developed to obtain and visualize the numerical solution. Under particular conditions that ensure small oscillations of the gyroscope’s axle (a maximum oscillation of eight degrees in the lean angle) near the horizontal plane through the pivot, a linearization is performed and is successfully compared with the aforementioned nonlinear numerical solution. The computer program facilitates the understanding and calculation of physical quantities such as the internal forces and moments, support forces and power transmission from the drive motor. In particular, it is shown that, for a hinge joint, the period of oscillation differs from that of a rotating pivot, which is crucial to the debate about whether such an engine may produce a net thrust, or not. A relevant paradox is resolved.
Oversmoothing Tikhonov regularization in Banach spaces
*
Authors: Chen De-Han , Hofmann Bernd , Yousept Irwin 
Published: November 2020

Abstract
This paper develops a Tikhonov regularization theory for nonlinear ill-posed operator equations in Banach spaces. As the main challenge, we consider the so-called oversmoothing state in the sense that the Tikhonov penalization is not able to capture the true solution regularity and leads to the infinite penalty value in the solution. We establish a vast extension of the Hilbertian convergence theory through the use of invertible sectorial operators from the holomorphic functional calculus and the prominent theory of interpolation scales in Banach spaces. Applications of the proposed theory involving ℓ
1, Bessel potential spaces, and Besov spaces are discussed.
Theoretical study of the control of absorption, transparency, and amplification in a microwave- and RF-driven four-level (Δ + ∇)-type closed-contour interaction system
Authors: Das Aparajita , Saha Jayanta K , Hossain Md Mabud 
Published: November 2020

Abstract
This paper describes a theoretical study of the optical responses of an atomic medium to the probe field in a four-level (Δ + ∇)-type closed-contour interaction system driven by two pump laser fields (P1, P2), one probe laser field (Pr) and two microwave or radio frequency (RF) coupling fields (L, U). Here, L and U are considered to connect the forbidden electric dipole transitions, i.e. two hyperfine ground states of the Δ subsystem and two hyperfine excited states of the ∇ subsystem, respectively. Since each subsystem is a closed-loop system, relative phases are thought to be present between the optical fields (pump and probe fields), and the microwave or RF fields. The manipulation of the quantum coherence of the system by the strengths of coupling fields along with the relative phases is demonstrated in terms of the changes occurring in the absorption of the probe field by the medium. The probe absorption and dispersion profiles are extracted by numerically solving the optical Bloch equations for the system under steady-state conditions. In this study, we start by illuminating the system with the probe only, and then, by applying the pump fields and the coupling fields one by one, the changes in the absorptive and dispersive probe line profiles are investigated for two distinct cases that depend on the relative strengths of the pump fields, e.g. when P2 is stronger than P1 and vice versa. Furthermore, the individual effects of the strengths and phases of the coupling fields on the probe absorption, transparency and amplification are also explored for both cases. All the changes that appear in the probe signal as a result of the application of different fields are explained by the modified interaction fields or the corresponding effective Rabi frequencies obtained from the partial dressed-state analysis.
Exploration of the high-order harmonic generation from periodic potentials by Bohmian trajectories
Authors: Pan Xue-Fei , Li Bo , Qi Tong , Zhang Jun , Liu Xue-Shen 
Published: November 2020

Abstract
The recombination processes of the electrons in solid are illustrated by solving the time-dependent Schrödinger equation. The results show that the Bohmian trajectories and the time evolution of the electronic probability density agrees very well, which demonstrates that we can use the Bohmian trajectories to investigate the recombination processes of the electrons in solid. We select the region where the probability density of the electron reached the strongest and the weakest as the initial position of the calculated Bohmian trajectories, one can see that the Bohmian trajectories have similar structures. In addition, our results show that the emission time of the solid high-order harmonic generation (HHG) spectra from the time-frequency distribution agrees well with the time that the Bohmian trajectories change direction. By regulating the phase of the electric field, the electrons can move farther, which will result in the broad cutoff of the HHG. We have also demonstrated that the similar structure of the Bohmian trajectories of the solid with a defect for different initial positions disappears due to the broken periodic structure, which further illustrates that the motion processes of the electrons in solid depend on the structure of the solid.
Voltage tunable low damping YIG/PMN-PT multiferroic heterostructure for low-power RF/microwave devices
Authors: Zhao Yanan , Li Yaojin , Zhu Shukai , Chen Chen , Yao Mouteng , Zhao Yifan , Hu Zhongqiang , Peng Bing , Liu Ming , Zhou Ziyao 
Published: November 2020

Abstract
Voltage-tunable RF/microwave devices attract great attention due to their low power consumption; however, they still suffer from the fundamental dilemma between large tunability and low insertion loss. In this paper, yttrium iron garnet (YIG) polycrystalline thin films with low microwave loss (<3 × 10−4) were directly deposited on mica substrates via a van der Waals force and then transferred onto PMN-PT substrates. The in-plane magnetic anisotropy of YIG was tuned by the in-plane biaxial stress of PMN-PT, and an improved voltage tunability (175 MHz) of in-plane FMR fr
was obtained due to the removal of the substrate clamping effect. Moreover, our samples still represent good frequency stability (4–12 GHz) during the tuning process. It is of significance for exploiting novel, portable, low-loss RF/microwave devices in the future.
Microstructural dependence of residual stress in reactively sputtered epitaxial GaN films
Authors: Monish M , Major S S 
Published: November 2020

Abstract
Epitaxial GaN films were grown on c-sapphire by rf magnetron reactive sputtering of GaAs at different partial pressures of nitrogen in Ar–N2 sputtering atmosphere. High-resolution x-ray diffraction and φ-scans reveal the mosaic growth of c-axis oriented, wurtzite GaN films. The c and a parameters were independently determined to obtain the corresponding in-plane and out-of-plane strain components. Raman measurements confirmed the in-plane strain behavior. The surface morphology and elemental composition of films were studied by atomic force microscopy and secondary ion mass spectroscopy, respectively. High-resolution ω-2θ, ω, and in-plane φ-rocking curve scans were used to obtain micro-strain, screw and edge dislocation densities, respectively. The films grown at 30%–100% N2 reveal dominance of edge (∼1012 cm−2) over screw (∼1010 cm−2) dislocations, with both approaching similar densities at lower N2 percentages. The strain data has been analyzed to separate the hydrostatic and biaxial contributions and their dependences on N2 percentage. The film grown at 100% N2 displays large hydrostatic strain and micro-strain due to the presence of excess/interstitial nitrogen. The hydrostatic strain and micro-strain decrease substantially with initial decrease of N2 percentage, but increase slightly in the films grown below 30% N2, primarily due to the incorporation of Ar. The films grown below 75% N2 display growth-related intrinsic tensile stress, originating from crystallite coalescence. The stress reversal from tensile to compressive, seen in the films grown at higher N2 percentages is primarily attributed to the incorporation of excess/interstitial nitrogen into grain boundaries and the tensile side of edge dislocations. The decrease of intrinsic tensile stress in the films grown below 30% N2 is attributed to the incorporation of Ar and their voided structure.
Coupled mechanisms of the keyhole, energy transfer and compositional change associated with the variable polarity plasma arc process
Authors: Wu Dongsheng , Tashiro Shinichi , Hua Xueming , Tanaka Manabu 
Published: November 2020

Abstract
A three-dimensional numerical model that coupled the arc, keyhole and weld pool was developed to investigate the keyhole behavior and energy transfer of an aluminum alloy in a variable polarity plasma arc welding process. The convective pattern in the weld pool was measured using an advanced x-ray transmission system. The elemental distribution of the bead was determined using an electron-probe microanalyzer. The coupled mechanisms of the keyhole, energy transfer, and compositional change were revealed. With a keyhole, both the arc energy loss and energy input increase, while the total energy transported from the arc to the weld pool decreases a bit, so the arc energy efficiency decreases. The heat flux at the keyhole is low and decentralized, resulting in low keyhole temperature; thus, the loss of elements with low boiling points due to evaporation can be ignored. Elements can be sufficiently mixed and distributed uniformly throughout the bead.
Alternative formulation of the induced surface and curvature tensions approach
Authors: Bugaev Kyrill A 
Published: November 2020

Abstract
We develop a novel method to analyze the excluded volume of the multicomponent mixtures of classical hard spheres in the grand canonical ensemble. The method is based on the Laplace–Fourier transform technique and allows one to account for the fluctuations of the particle number density for the induced surface and curvature tensions equation of state. As a result one can go beyond the Van der Waals (VdW) approximation by obtaining the suppression of the induced surface and curvature tensions coefficients at moderate and high packing fractions. In contrast to the standard induced surface and curvature tensions equation of state the suppression of these coefficients is not the exponential, but a power-like one. The obtained alternative equation of state is further generalized to account for higher virial coefficients. This result is straightforwardly generalized to the case of quantum statistics.
Understanding charged vesicle suspensions as Wigner glasses: dynamical aspects
Authors: Porpora G , Rusciano F , Guida V , Greco F , Pastore R 
Published: November 2020

Abstract
Suspensions of charged vesicles in water with added salt are widespread in nature and industrial production. Here we investigate, via Brownian dynamics simulations, a model that grasps the key features of these systems, with bidisperse colloidal beads interacting via a hard-core and an electrostatic double layer potential. Our goal is to focus on a set of interaction parameters that is not generic but measured in recent experiments, and relevant for a class of consumer products, such as liquid fabric softeners. On increasing the volume fraction in a range relevant to real formulation, we show that the dynamics become progressively slower and heterogeneous, displaying the typical signatures of an approaching glass transition. On lowering the salt concentration, which corresponds to increasing the strength and range of the electrostatic repulsion, the emergence of glassy dynamics becomes significantly steeper, and, remarkably, occurs at volume fractions well below the hard-sphere glass transition. The volume fraction dependence of the structural relaxation time at different salt concentration is well described through a functional law inspired by a recently proposed model (Krausser et al 2015 Proc. Natl Acad. Sci. USA
112 13762). According to our results, the investigated system may be thought of as a Wigner glass, i.e. a low-density glassy state stabilized by long-range repulsive interactions. Overall, our study suggests that glassy dynamics plays an important role in controlling the stability of these suspensions.
Damping via the hyperfine interaction of a spin-rotation mode in a two-dimensional strongly magnetized electron plasma
Authors: Dickmann S 
Published: November 2020

Abstract
We address damping of a Goldstone spin-rotation mode emerging in a quantum Hall ferromagnet due to laser pulse excitation. Recent experimental data show that the attenuation mechanism, dephasing of the observed Kerr precession, is apparently related not only to spatial fluctuations of the electron Landé factor in the quantum well, but to a hyperfine interaction with nuclei, because local magnetization of GaAs nuclei should also experience spatial fluctuations. The motion of the macroscopic spin-rotation state is studied microscopically by solving a non-stationary Schrödinger equation. Comparison with the previously studied channel of transverse spin relaxation (attenuation of Kerr oscillations) shows that relaxation via nuclei involves a longer quadratic stage of time-dependance of the transverse spin, and, accordingly, an elongated transition to a linear stage, so that a linear time-dependance may not be revealed.
Collective excitations in spin-polarized bilayer graphene
Authors: Van Men Nguyen , Khanh Nguyen Quoc , Kim Phuong Dong Thi 
Published: November 2020

Abstract
We calculate the plasmon frequency ω and damping rate γ of plasma oscillations in a spin-polarized BLG system. Using the long wavelength approximation for dynamical dielectric function, we obtain an analytical expression for plasmon frequency showing that degree of spin polarization P has negligible effect on the long wavelength plasmon frequency. Numerical calculations demonstrate that the plasmon frequency increases (decreases) noticeably (slightly) with the increase in spin polarization in large (small) wave-vector q region. We also find that the damping rate and the shape of γ as a function of q depend strongly on P. The increase in carrier density decreases significantly both plasmon frequency and damping rate independently of the spin polarization. The numerically calculated critical wave vector, at which the plasmon dispersion curve hits the edge of electron–hole continuum, decreases with P and can be used to experimentally determine the degree of spin polarization.
Tuning electrical and thermal conductivities of the two-dimensional electron gas in AlN/GaN heterostructures by piezoelectricity
Authors: Abou-Hamdan L , Hamyeh S , Iskandar A , Tauk R , Brault J , Tabbal M , Adam P-M , Kazan M 
Published: November 2020

Abstract
We investigate the electrical and thermal conductivities of the two-dimensional electron gas (2DEG) confined in the quantum well formed at the heterojunction between a thin GaN layer and an AlN layer strained by an Al
x
Ga1−x
N capping layer in the temperature range from 10 to 360 K. The experimental protocol developed to deduce from calorimetric and Hall-effect measurements at a variable temperature the critical characteristics and transport properties of the confined 2DEG is presented. It is found that, in the measured temperature range (10–360 K), the electrical conductivity of the 2DEG is temperature-independent, due to the predominance of scattering processes by interface defects. However, the thermal conductivity shows a linear temperature dependence, mirroring the specific heat of free electrons. The temperature-independent relaxation time associated with the overall electron scattering means that the values obtained for electrical and thermal conductivities are in excellent agreement with those stipulated by the Weidemann–Franz law. It is also found that for weak strain fields in the AlN layer, both the electrical and thermal conductivities of the two-dimensional interfacial electrons increase exponentially with strain. The importance of 2DEG in AlN/GaN quantum wells lies in the fact that the strong piezoelectricity of AlN allows the transport properties of the 2DEG to be tuned or modulated by a weak electric field even with the high density of lattice mismatch induced defects at the AlN-GaN interface .
A one-step synthesis of ultra-long silver nanowires with ultra-high aspect ratio above 2000 and its application in flexible transparent conductive electrodes
Authors: Zhang Lu , Jiang Fuliang , Wu Bisheng , Lv Chencheng , Wu Minghua 
Published: November 2020

Abstract
Silver nanowires (AgNWs), appear as an extremely promising candidate for the next generation of flexible transparent conductive electrodes (FTCEs). However, the performance of AgNWs-FTCEs was severely limited by the aspect ratio of AgNWs, while it was still a big challenge to fabricate AgNWs with high aspect ratio nowadays. To improve the aspect ratio of AgNWs, bromide ion (Br−), cupric ion (Cu2+) and polyvinylpyrrolidone (PVP, Mw ≈ 1300 000) which are beneficial for the synthesis of high aspect ratio AgNWs, were introduced in this article. The high quality and uniform AgNWs with the average diameter of 77.6 nm and the aspect ratio above 2000 were fabricated via a one-step solvothermal method. The effects of reaction time, molar ratio of AgNO3 to PVP and the concentration of CuBr2 on the aspect ratio of AgNWs were discussed. The mechanism of the synthesis of high aspect ratio AgNWs was explored. After that, the prepared AgNWs were spin-coated on the surface of PET film, the FTCEs based on the ultra-high aspect ratio AgNWs without any post-treatments exhibits relatively high transmittance, low haze and low sheet resistance, and the AgNWs have little effect on the optical performance of pristine PET film. The outstanding performance of the prepared FTCEs indicated that the ultra-high aspect ratio AgNWs are ideal materials in the application of FTCEs, and the method of fabricating AgNWs could provide a direction to the high aspect ratio AgNWs.
Hole-transmission enhancement in 4H-silicon carbide light triggered thyristor for low loss
*
Authors: Xi Wang , Hongbin Pu , Jichao Hu , Qing Liu , Chunlan Chen , Bei Xu 
Published: November 2020

Abstract
In this paper, a 20 kV silicon carbide (SiC) light triggered thyristor (LTT) with n-type blocking base is simulated using Synopsys Sentaurus TCAD. In order to reduce the power dissipation, a method that enhances the hole-transmission through electric field induced by gradual doping profile in the n-buffer layer is proposed. The results indicate that the method enhancing the hole-transmission is effective in reducing the power loss of SiC LTT with n-type blocking base. By changing the doping profile of n-buffer layer from uniform to gradual, both on-state loss and switching loss are efficiently reduced. Compared to the conventional SiC LTT with 2.5 μm thick n-buffer layer, when the doping gradient is 1.0 × 1021 cm−4, the on-state and the switching losses of the hole-transmission enhanced SiC LTT are reduced by 34.7% and 17.9%, respectively.
Ab initio investigation of hydrogen-based high T
c superconductor that is stable under ambient environment
Authors: Zhang Ting 
Published: November 2020

Abstract
We report an ab initio investigation of a hydrogen-based high-T
c superconductor candidate—crystalized C4H4 in the cubic-gauche (cg-C4H4) structure, with the symmetry of space group I213. We find the cg-C4H4 structure to be stable under ambient environment; and the evaluation of the electron-phonon coupling strength indicates that the heavily doped cg-C4H4 can generate superconductivity with a T
c ∼ 72 K. The high frequency vibrational modes of hydrogen atoms are found to play an important role in the total electron-phonon interaction strength, and the reduction of structural symmetry compared with graphene further enhances the electron–phonon coupling of the carbon framework. Our investigation illustrates a BCS route to realizing the hydrogen-based high T
c superconductivity.
Work relation in instantaneous-equilibrium transition of forward and reverse processes
Authors: Albay John A C , Kwon Chulan , Lai Pik-Yin , Jun Yonggun 
Published: November 2020

Abstract
Realizing quasistatic processes in finite times requires additional control parameters to keep the system in instantaneous equilibrium (ieq). However, the finite-rate ieq transition of the reverse process is not just the time-reversal of the ieq forward process due to the odd-parity of controlling parameters. We theoretically show a work relation that the dissipated work of the ieq transition of the forward process is the same as that of the corresponding reverse process. The work relation can be interpreted as a generalization of equilibrium (quasistatic) processes. The work relation and the associated statistics of nonequilibrium work are experimentally confirmed in three different Brownian systems: the time-varying harmonic and non-harmonic potentials and the Brownian harmonic transport, which are manipulated by the optical feedback trap.