Initial Momentum Research Articles

Quantum decay of an optical soliton

Optical solitons are known to be classically stable objects which are robust to perturbations. In this work, we show that due to quantum mechanical effects, an optical soliton that is initially in a classical soliton coherent state will shed photons into the continuum and hence decay. The standard formulation of the quantized soliton uses the linearized version of the quantum nonlinear Schrodinger equation in the background of the classical soliton, and the quantized soliton remains stable in this approximation. We show that if higher-order interaction terms are taken into account, the soliton is no longer stable, and its photon number decreases quadratically as a function of the number of soliton cycles. We compute the power spectrum for the continuum radiation and find a narrow band that is localized about the initial soliton momentum with a cut-off that is inversely proportional to the initial soliton width.

Nonlinear Thomson scattering in an arbitrary polarized laser field with a background magnetic field

The nonlinear Thomson scattering of an electron motion in a combining field constituted by an elliptically polarized laser and a background magnetic field is investigated. The dependence of electron trajectories, fundamental frequency, maximum radiation power in the spatial distribution, and the corresponding spatial angle on ellipticity are obtained. In addition, we find that the angular distributions of scattering spectra with respect to the azimuthal angle exhibit symmetry regardless of the order of harmonics, laser intensity, magnetic resonance parameter, and initial axial momentum. Meanwhile, the polar angle distribution of the spectra increasingly approaches the laser propagation direction with the laser intensity, magnetic resonance parameter, and initial axial momentum. The maximum radiated power increases, and the corresponding polar angle decreases. The optimal angle for the maximum radiated power per unit of solid, the corresponding photon number, and the photon brightness can be obtained, which implies that high-quality extreme ultraviolet (XUV) and/or x rays can be generated by the studied scheme when suitable parameters are chosen.

Flows for the masses: A multi-fluid non-linear perturbation theory for massive neutrinos

Velocity dispersion of the massive neutrinos presents a daunting challenge for non-linear cosmological perturbation theory. We consider the neutrino population as a collection of non-linear fluids, each with uniform initial momentum, through an extension of the Time Renormalization Group perturbation theory. Employing recently-developed Fast Fourier Transform techniques, we accelerate our non-linear perturbation theory by more than two orders of magnitude, making it quick enough for practical use. After verifying that the neutrino mode-coupling integrals and power spectra converge, we show that our perturbation theory agrees with N-body neutrino simulations to within 10% for neutrino fractions Ω ν,0 h 2 ≤ 0.005 up to wave numbers of k = 1 h/Mpc, an accuracy consistent with ≤ 2.5% errors in the neutrino mass determination. Non-linear growth represents a > 10% correction to the neutrino power spectrum even for density fractions as low as Ω ν,0 h 2 = 0.001, demonstrating the limits of linear theory for accurate neutrino power spectrum predictions. Our code FlowsForTheMasses is avaliable online at github.com/upadhye/FlowsForTheMasses.

Collisional dynamics of two-dimensional vortex quantum droplets

A quantum droplet is a self-bound state balanced by the mean-field interaction and Lee–Huang–Yang correction in a Bose–Bose mixture. In this paper, we study the collisional dynamics of two-dimensional quantum droplets with a vortex. By adjusting the initial momentum, the initial phase difference, the topological charge of the quantum droplets, and the total number of particles, we identify three dynamic mechanisms of collisions, namely, splitting, no-splitting, and their crossover according to the states after collision, which are significantly different from the merging, separation, and evaporation of the collisional dynamics of vortex-free droplets. The initial phase difference of the two droplets changes the interference fringes and the manner of splitting of the droplets. We also show that the three-body loss of atoms does not affect the result.

EDUKASI PEMBELAJARAN MATEMATIKA KEPADA SISWA KELAS 1 SEKOLAH DASAR NEGERI 4 TIGA, KECAMATAN SUSUT, BANGLI

Elementary education or elementary school is the initial momentum for children to improve their abilities, from elementary school they get learning immunity which then becomes a habit for them to do in the future. Learning language in elementary schools is an activity to equip students from the start on an ongoing basis so that students have discipline in thinking and speaking, most language teachers are not very aware of the importance of coaching writing training so that it causes students to have low writing creativity. Based on the results of observations at SDN 4 Tiga, Bangli, it was found that students in grade I had low creativity and writing skills. Keywords: Education, Elementary School, Students

The Essence And Curriculum Of Learning Indonesian Language In Elementary Schools

Education in elementary schools is the initial momentum for students to improve all the abilities inherent in children. Starting at the time of learning in early childhood (kindergarten ) and then continued and strengthened in elementary school. Habits that children carry out every day, both in the home, community and school environment, are important in forming natural potential, especially in the field of children's language. Language skills that are expected to be assisted, grown, and used as development material for elementary school teachers include listening or listening skills, speaking, reading, and writing. These four skills are so important to be given at the elementary school level as a form of teaching Indonesian according to the current education curriculum. Learning activities in schools are also expected to be able to integrate this unified language in all intra- and extra-curricular activity programs so that their benefits are increasingly visible and meaningful in harmony with the social life of students.

Dynamics of liquid dispersion in a rotating packed bed with single‐layer wire mesh

AbstractThe improvement of liquid dispersion by rotating wire mesh is one of the major causes for the mass transfer and micromixing intensification in rotating packed beds (RPBs). In particular, the initial dispersion region has been proved to have the greatest mass transfer and micromixing efficiency. However, the dispersion mechanism has not been revealed. This study investigated the dynamics of liquid dispersion in an RPB with single‐layer wire mesh. The liquid dispersion behaviors were obtained by high‐speed photography and numerical simulation. The liquid was found to stretch into ligaments and break into the main droplet and several satellite droplets. A new theoretical model was established to reveal the dispersion mechanism of these two stages. The stretching stage depends on the liquid initial momentum and acquired impulse, while the breakup stage was determined by the competition of ligaments recoil and pinch‐off behaviors. The model was validated in good agreement with the experimental and simulation results of the dispersion characteristics.

Thermals from finite sources in stable and unstable environments

The rise of thermals in the atmosphere has attracted a lot of attention since the early work of Morton et al. (Proc. R. Soc. Lond. A, vol. 234, 1956, pp. 1–23), who proposed that entrainment into a thermal was proportional to the surface area of the thermal and to the mean vertical velocity of the thermal. This paper presents new analytical solutions for the heights of rise of buoyant thermals in both stably and unstably stratified environments, for both negatively and positively buoyant sources, and where the sources have different size and strength (momentum) characteristics. The limiting cases of these analytical solutions are consistent with previous work. These analytical solutions do not appear elsewhere, and provide a compact set of equations that are easy to apply to a wide range of circumstances. The solutions are dependent upon the entrainment hypothesis, which is of course only an approximation, but the simplicity of the analytical solutions allows easy calculation and additional insights. These include the fact that while heights of rise are strongly dependent on both source strength and size for flows in stable environments, the dilution at the top of rise is independent of the source momentum. Further, in a stable environment, there is a conserved quantity that has dimensions proportional to vertical momentum. For negatively buoyant flows in an unstably stratified environment, thermals having low initial momentum will reach a maximum height, while thermals with high initial momentum will entrain sufficient buoyant environmental fluid that they will eventually become positively buoyant and continue to rise indefinitely.

Deposition behaviour of inclined momentum sediment-laden jet

As wastewater is commonly disposed of in the form of sediment-laden jet from a submarine outfall, the sediment movement when the jet evolves in the ambient water and its final deposition are of great importance to marine engineers. This study aims to investigate the settling mechanism of the sediment from an inclined discharge nozzle and quantify the deposition profile for various jet conditions in the hydrostatic environment through physical experiments and dimensional analysis. In the experimental tests, separate flow visualizations for the fluid and sediment phases are achieved to enable the simultaneous observation of sediment particles and jet fluid movement, through which the analysis of the relationship between the fluid and the sediment movement is carried out. The results show that at locations close to the nozzle (s/D = 5), sediment mean velocity has an inverse relationship with the turbulence intensity while positively correlated with the initial jet momentum. The discharge angle is found to have dominant effect on alternating the sediment velocity profile from symmetrical to asymmetrical. With the newly defined momentum settling length scale lmi, the non-dimensional formulations for deposition rate and accumulated deposition profile involving the nozzle inclination have been validated by the experimental data and are potential to be applied to the prediction of depositional rate and final deposition distribution near the outfall for the full-scale wastewater discharge events.

Application and Development of QKD-Based Quantum Secure Communication.

Quantum key distribution (QKD) protocols have unique advantages of enabling symmetric key sharing with information-theoretic security (ITS) between remote locations, which ensure the long-term security even in the era of quantum computation. QKD-based quantum secure communication (QSC) enhancing the security of key generation and update rate of keys, which could be integrated with a variety of cryptographic applications and communication protocols, has become one of the important solutions to improve information security. In recent years, the research on QKD has been active and productive, the performance of novel protocol systems has been improved significantly, and the feasibility of satellite-based QKD has been experimentally verified. QKD network construction, application exploration, and standardization have been carried out in China as well as other countries and regions around the world. Although QKD-based QSC applications and industrialization are still in the initial stage, the research and exploration momentum is positive and more achievements could be expected in the future.

Crystal-Momentum-Resolved Contributions to Harmonics in Laser-Driven Graphene

We investigate the crystal-momentum-resolved contributions to high-order harmonic generation in laser-driven graphene by semi-conductor Bloch equations in the velocity gauge. It is shown that each harmonic is generated by electrons with the specific initial crystal momentum. The higher harmonics are primarily contributed by the electrons of larger initial crystal momentum because they possess larger instantaneous energies during the intra-band motion. Particularly, we observe circular interference fringes in the crystal-momentum-resolved harmonics spectrum, which result from the inter-cycle interference of harmonic generation. These circular fringes will disappear if the inter-cycle interference is disrupted by the strong dephasing effect. Our findings can help to better analyze the mechanism of high harmonics in graphene.

The Effects of Gas Angular Momentum on the Formation of Magnetically Arrested Disks and the Launching of Powerful Jets

In this letter, we investigate Bondi-like accretion flows with zero or low specific angular momentum by performing 3D general relativistic magnetohydrodynamic simulations. In order to check if relativistic jets can be launched magnetically from such flows, we insert a large-scale poloidal magnetic field into the accretion flow and consider a rapidly spinning black hole. We demonstrate that under such conditions the accretion flow needs to initially have specific angular momentum above a certain threshold to eventually reach and robustly sustain the magnetically arrested disk state. If the flow can reach such a state, it can launch very powerful jets at ≳100% energy efficiency. Interestingly, we also find that even when the accretion flow has initial specific angular momentum below the threshold, it can still launch episodic jets with an average energy efficiency of ∼10%. However, the accretion flow has nontypical behaviors such as having different rotation directions at different inclinations and exhibiting persistent outflows along the midplane even in the inner disk region. Our results give plausible explanations as to why jets can be produced from various astrophysical systems that likely lack large gas specific angular momenta, such as Sgr A*, wind-fed X-ray binaries, tidal disruption events, and long-duration gamma-ray bursts.

The ellipticity dependence of Rydberg state excitation of noble gas atoms subject to strong laser fields

In this work, we theoretically investigate the ellipticity dependence of the Rydberg state excitation (RSE) and ionization of noble gas atoms subject to strong laser fields at a series of intensities and wavelengthes by a semiclassical model, where the nonadiabtic effect is considered or ignored. Our results demonstrate that, if the nonadiabatic effect has been ignored, the ratio between RSE and ionization yields exhibits an anomalous maximum at a nonzero ellipticity. On the other hand, if the nonadiabatic effect has been considered, this anomalous behavior disappears. The analysis indicates that the absence of this anomalous behavior can be attributed to the nonadiabatic corrections of instantaneous ionization rate and the initial photoelectron momentum distribution at the tunnel exit.

Helicity and vorticity in heavy-ion collisions at energies available at the JINR Nuclotron-based Ion Collider facility

Heavy-ion collisions at center-of-mass nucleon collision energies 4.5--11.5 GeV are analyzed within the parton-hadron-string dynamics (PHSD) transport model. Spectator nucleons are separated, and the transfer of the initial angular momentum of colliding nuclei to the fireball formed by participants is studied. The maximal angular momentum is carried by the fireball in gold-gold collisions with the impact parameter about 5 fm corresponding to centrality class 10--20%. The obtained participant distributions were fluidized and the energy and baryon number densities, temperature, and velocity fields are obtained in the Landau frame. It is shown that the velocity field has dominantly Hubble-like transversal and longitudinal expansion with the vortical motion being only a small correction on top of it. The vorticity field is calculated and illustrated in detail. The formation of two oppositely rotating vortex rings moving in opposite directions along the $z$ axis is demonstrated. Other characteristics of the vortical motion such as the Lamb vector field and the kinematic vorticity number are considered. The magnitude of the latter one is found to be smaller than that for the Poiseuille flow and close to the pure shear deformation corresponding to just a flattening of fluid cells. The field of hydrodynamic helicity, which is responsible for the axial vortex effect, is calculated. The separation of positive and negative helicities localized in upper and lower semiplanes with respect to the reaction plane is shown. It is proved that the areas with various helicity signs can be probed by the selection of $\mathrm{\ensuremath{\Lambda}}$ hyperons with positive and negative projections of their momenta orthogonal to the reaction plane.

Hybrid multi-fluid-particle simulations of the cosmic neutrino background

Simulation of the cosmic clustering of massive neutrinos is a daunting task, due both to their large velocity dispersion and to their weak clustering power becoming swamped by Poisson shot noise. We present a new approach, the multi-fluid hybrid-neutrino simulation, which partitions the neutrino population into multiple flows, each of which is characterised by its initial momentum and treated as a separate fluid. These fluid flows respond initially linearly to nonlinear perturbations in the cold matter, but slowest flows are later converted to a particle realisation should their clustering power exceed some threshold. After outlining the multi-fluid description of neutrinos, we study the conversion of the individual flows into particles, in order to quantify transient errors, as well as to determine a set of criteria for particle conversion. Assembling our results into a total neutrino power spectrum, we demonstrate that our multi-fluid hybrid-neutrino simulation is convergent to < 3% if conversion happens at z = 19 and agrees with more expensive simulations in the literature for neutrino fractions as high as Ω νh 2 = 0.005. Moreover, our hybrid-neutrino approach retains fine-grained information about the neutrinos' momentum distribution. However, the momentum resolution is currently limited by free-streaming transients excited by missing information in the neutrino particle initialisation procedure, which restricts the particle conversion to z ≳ 19 if percent-level resolution is desired.

Investigation on the concentration prediction model and personnel hazard range of LNG leakage from tankers in the tunnel

Liquid natural gas (LNG) leaks from tanker in the tunnel could result in more severe fire and explosion catastrophes than those that occur in unconfined space. Investigating the gas concentration distribution law and the accompanying personnel hazard range is crucial to provide guidelines for personnel escape and fire rescue in such accidents. In this paper, to provide a rapid technique for concentration estimation, the virtual source approach and the fluid settlement theory are applied to put forward a new model, which is based on the Gaussian plume model. Three batches of LNG diffusion tests were carried out in a 5 m long wind tunnel with a cross-section of 1 m × 1 m. The comparison results show that the prediction accuracy of the proposed model in the far region of the leakage source is better than that in the near region, with the error within ±16%, which demonstrated an accurate prediction performance of the proposed model. The numerical model of LNG leakage from tanker in the tunnel is established, and the influence of leakage direction, leakage aperture, and tunnel cross-section on concentration distribution law is discussed. The findings indicate that when the leakage direction changes from horizontal to vertical, the gas is more likely to accumulate in the tunnel due to the greater attenuation of the initial momentum of the gas, which causes the combustible range to increase by about 2 times. When the leakage aperture is 50 mm, the mass of combustible gas reaches the maximum value of 320.91 kg in 85.9 s, which indicates that the explosion intensity is not proportional to the leakage aperture. Excessive leakage aperture causes the concentration to surpass the Upper Flammable Limit, and the similar trends occur when the tunnel cross-section reduces. Based on the numerical results, the calculation model of the personnel hazard range suitable for various tunnel cross-sections and leakage apertures is derived by data fitting.

Orbital-resolved photoelectron momentum distributions of F- ions in a counter-rotating bicircular field.

We present a theoretical study of the orbital-resolved photoelectron momentum distributions (PMDs) of F- ions by a two-color counter-rotating circularly polarized field. We show that the PMDs of F- ions can be modulated from an isotropic symmetric distribution into a three-lobe one by adding a weak fundamental counter-rotating field to the intense second harmonic circularly polarized field, and this modulation strongly depends on the initial atomic orbital. The PMDs simulated by the strong-field approximation method show good agreement with those obtained by solving the time-dependent Schrödinger equation. Based on the strong-field approximation method, we find that the radial momentum shift of PMDs for different orbitals is the fingerprint of orbital-dependent initial momentum at the tunnel exit. More importantly, we demonstrate that the lobes in PMDs appear in sequential order, highlighting that the scheme can be viewed as controllable rotating temporal Young's two-slit interferometer.

Features of gravitational interaction as the basis of “Dark Energy” in the gas of null strings

In this work, the influence of the shape of the null strings that form the gas on the gravitational properties and evolution of the null string gas was investigated. An interesting result of the study is that the test null string, being in the interaction zone, can only have a shape that exactly repeats the shape of the source string. As a result, null strings having different spatial forms can be located in the gas only outside the zone of interaction with each other. The “size” (width) of the zone of interaction of each null string in the gas is determined by the value of its initial momenta, and for some critical values it can occupy the entire space. The size (width) and “impenetrability” of the interaction zones for null strings having different spatial shapes can be a physical source of “strong” gravitational repulsion in the gas of null strings. In turn, the “strong” gravitational repulsion between null strings with different spatial shapes can be a source of a long-term accelerated expansion of such a gas (a source of “dark energy”).

Evaluation of mixing of a secondary solid phase in a circulating fluidized bed riser

Mixing of the secondary solids phase, i.e. fuel or sorbent is crucial in fluidized bed reactors due to its effect on the performance of the reactor. Fluctuations in the gas-particle flow affect mixing, thus modeling this is essential for the analysis of mixing. However, simplified mixing models are used for large circulating fluidized bed (CFB) reactors, which causes uncertainties. A novel averaging method is presented to obtain representative results of transient secondary solid phase mixing in CFBs, acknowledging the effect of fluctuations. A parametric study is performed to investigate the effect of particle size, density, and inlet velocity on mixing and for insight into the mixing process. Additionally, the presented approach is used to compare different steady-state mixing methods to evaluate their applicability for modeling mixing in CFB reactors. Initial momentum and elutriation tendency of fuel were found to affect the mixing behavior, with two distinct routes identified.

Antiproton collisions with excited positronium

We present results of calculations of several processes resulting from positronium (Ps) collisions with antiprotons: antihydrogen formation, Ps breakup, and ${n}_{\mathrm{Ps}}$-changing collisions. Calculations utilize the quantum convergent close-coupling (CCC) method and the classical trajectory Monte Carlo (CTMC) method. We identify a region of Ps principal quantum numbers ${n}_{\mathrm{Ps}}$ and Ps energies where the classical description is valid and where the CCC calculations become computationally too expensive. This allows us to present the most complete and reliable set of cross sections in a broad range of ${n}_{\mathrm{Ps}}$ and initial orbital momentum quantum numbers ${l}_{\mathrm{Ps}}$ which are necessary for experiments with antihydrogen at CERN.