Field Propagation Research Articles

Nondipole signatures in ionization and high-order harmonic generation

We analyze nondipole effects arising in ionization and high-order harmonic generation for a two-dimensional hydrogen atom irradiated with either low- or high-frequency laser pulses. In the low-frequency case, the electron wave packet dynamics is dominated by rescattering processes within the laser pulse. Here both odd- and even-order harmonics are generated in the direction of the laser field propagation and polarization, respectively. For high-frequency pulses, such rescattering processes can be neglected. We demonstrate that a significant portion of photoelectrons is detected opposite to the laser pulse propagation direction as a consequence of their postpulse wave packet spreading and interaction with the parent ion. This is accompanied by rich interference structures formed in the momentum distributions of photoelectrons. Our results follow from the numerical solution of the time-dependent Schr\"odinger equation, which is based on the Suzuki-Trotter scheme with the split-step Fourier approach. The method relies on a Hamiltonian decomposition, where except for the components depending exclusively on the momentum or on the position operators, there are also terms depending on both momentum and position operators in particular configurations. We demonstrate that, as long as the latter does not depend on noncommuting coordinates of the momentum and position operators, nondipole effects in laser-matter interactions can be studied without applying extra approximations and unitary operations.

Low-Temperature Gas Cooling Correction Trajectory Offset Technology of Laser-Induced Thermal Crack Propagation for Asymmetric Linear Cutting Glass

Laser-induced thermal crack propagation (LITP) is a high-quality and efficient processing method that has been widely used in fields such as glass cutting. However, the problem of trajectory deviation often arises in actual cutting operations, especially in asymmetric cutting. To address this issue, a low-temperature gas cooling trajectory deviation correction technique was proposed in this study. This technique modifies the temperature and stress distribution by spraying low-temperature gas onto the processing surface and maintaining a relative position with the laser, thereby correcting the trajectory deviation. The finite element simulation software ABAQUS was employed to numerically simulate the dynamic propagation of temperature fields, thermal stress, and cracks in the asymmetric linear cutting and circular cutting of soda-lime glass with the proposed low-temperature gas cooling trajectory deviation correction technique, and the correction mechanism was elucidated. In the simulation results, the optimal relative distance (ΔX) between the low-temperature gas and scanning laser was obtained by analyzing the transverse tensile stress. Based on the analysis of the experimental and numerical simulation results, it is concluded that the cryogenic gas cooling technique can effectively correct the trajectory deviation phenomenon of asymmetric linear cutting of soda lime glass by LITP.

Study on fracture characteristics of anchored sandstone with precast crack based on double K criterion

Fracture toughness is an important fracture mechanics parameter of rocks, the double K criterion can reasonably explain the fracture mechanism of rocks. To investigate the fracture mechanics behavior of the anchored rock with a pre-crack, three-point bending test was performed to analyze the mode I fracture process of the rock. A series of pre-cracked sandstone beams of the same size, strength, and different anchor parameters were tested. The evolution characteristics of deformation field and crack tip propagation during the entire fracture process were investigated using a non-contact optical measurement method, and rock fracture mechanics parameters corresponding to different anchoring conditions were obtained. The toughening mechanism of anchor bolt was discussed based on stress intensity factor theory. The double K criterion can be used to describe the fracture failure characteristics of rocks. By regarding the anchored rock as the composite material of bolt and rock, the anchoring composite fracture toughness can be obtained, and the stability of the anchored rock can be determined using the double K criterion. The toughening mechanism of the anchor bolt increases the threshold of crack initiation and instability of the entire anchored rock by increasing the stress intensity factor at the crack tip of the rock. The crack arrest mechanism of the bolt retards crack propagation via the transverse closing force. Investigating the anchoring effect of different anchoring parameters allows, the rock anchoring control mechanism to be revealed from the perspective of fracture mechanics, which can provide a reference for mining and tunnel engineering support.

Spontaneous symmetry breaking and ghost states in two-dimensional fractional nonlinear media with non-Hermitian potential

The interaction of fractional diffraction and parity-time ({{{{{mathcal{PT}}}}}}) symmetric would bring some unique properties to certain physical system. Here we report a spontaneous symmetry breaking (SSB) phenomenon and ghost states of solitons supported by the two-dimensional (2D) fractional nonlinear Schrödinger (FNLS) equation with focusing and defocusing Kerr media under 2D non-Hermitian {{{{{mathcal{PT}}}}}}-symmetric potential. The continuous asymmetric soliton bifurcates out in a SSB way. For the focusing regime, as the power exceeds a critical value, the asymmetric soliton bifurcates from fundamental symmetric solitons, and when it turns to the defocusing regime, the symmetry breaking phenomenon is found in the branch of the first excited state. The symmetric solitons (including fundamental one and first excited state) are destabilized at this point. Intriguingly, the branches of asymmetry solitons are existing with complex conjugate propagation constants (alias ghost states), which is solely in fractional media. Moreover, we investigate the dependence of fractional Lévy index (α) on the symmetry breaking of solitons in detail. And the stabilities of fundamental symmetric soliton, asymmetric solitons, as well as the first excited states are explored. Moreover, The management of optical field propagation is achieved by modulation of the external potential. Meanwhile, we find the stable excitations of solitons via adiabatic excitations of system parameters. These results will provide some theoretical basis for the study of SSB phenomena and related physical experiments in the 2D fractional media with {{{{{mathcal{PT}}}}}}-symmetric potentials.

Evolution of eccentricities induced by geometrical and quantum fluctuations in proton-nucleus collisions

We compute the azimuthal eccentricities arising from initial stage fluctuations in high energy proton-nucleus collisions at proper times $\tau \geq 0^+$. We consider two sources of fluctuations, namely the geometrical structure of the proton and the fluctuation of color fields carried by both proton and nucleus. Describing these effects with Gaussian models allows us to analytically calculate the one- and two-point correlators of energy density, from which the eccentricities are obtained. We compute the proper time evolution of these quantities by approximating the Glasma dynamics in terms of linearized Yang-Mills equations, which we solve by assuming free field propagation and adopting the dilute-dense limit.

On causality conditions in de Sitter spacetime

We carefully consider the Shapiro time delay due to black holes and shockwaves in de Sitter spacetime and study the implications for causality. We discuss how causality conditions of AdS and flat spacetime can be applied in de Sitter spacetime, using spatial shifts measured on the boundary to define ‘fastest null geodesics’ and taking into account the ‘stretching’ of the de Sitter Penrose diagram. We consider the propagation of a massless spin-1 field with a non-minimal coupling in a de Sitter shockwave background as an illustrative example. We also briefly discuss connections to the average null energy condition.

COVARIANT REPRESENTATION OF MAXWELL’S EQUATIONS IN A MEDIUM WITH SOURCES

A geometric approach to describing an electromagnetic field in a medium with sources as a single field object is proposed. The description is based on the coordinate-free covariant approach adopted in the present-day geometrized field theories. Maxwell’s equations in a medium with sources are presented in terms of differential 2-forms for electric and magnetic fields in a four-dimensional space-time continuum. The generalequations include special cases of propagation, scattering, and emission of an electromagnetic field in media with different properties.

Solar energetic particle event onsets at different heliolongitudes: The effect of turbulence in Parker spiral geometry

Context. Solar energetic particles (SEPs), accelerated during solar eruptions, are observed to rapidly reach a wide heliolongitudinal range in the interplanetary space. Turbulence-associated SEP propagation across the mean Parker spiral direction has been suggested to contribute to this phenomenon. Aims. We study SEP propagation in turbulent magnetic fields to evaluate SEP spatial distribution in the heliosphere, their path lengths, and the overall evolution of SEP intensities at 1 au. Methods. We use full-orbit test particle simulations of 100-MeV protons in a novel analytic model of the turbulent heliospheric magnetic field, where the turbulence is dominated by modes that are transverse and 2D with respect to the Parker spiral direction. Results. We find that by propagating along meandering field lines, SEPs reach a 60°-wide heliolongitudinal range at 1 au within an hour of their injection for the turbulence parameters considered. The SEP onset times are asymmetric with respect to the location connected to the source along the Parker spiral, with the earliest arrival times being 15° westwards from the well-connected Parker spiral longitude. The inferred path length of the first arriving particles is 1.5−1.8 au within 30° of the well-connected longitude; 20−30% longer than the length of the random-walking field lines, increasing monotonously at longitudes further away; and 30−50% longer than the Parker spiral. The global maximum intensity is reached 15° west from the well-connected longitude an hour after the SEP injection. Subsequently, the SEP distribution broadens, consistent with diffusive spreading of SEPs across the field lines. Conclusions. Our results indicate that magnetic field line meandering can explain rapid access of SEPs to wide longitudinal ranges, as well as several other features of SEP event intensity evolution.

Deep-sea explosion sound signal propagation loss measurement and model verification

This paper researched the low-frequency sound field propagation characteristics in the continental slope sea area, the sound field propagation loss is calculated by using the radiated sound field data of the deep-fixed explosive sound sources with 50 m and 200 m depth in the continental slope sea area, and the experimental results are verified by combining with the Kraken normal wave model. The model verification results are in good agreement with the experimental measurement data.

Soliton Solutions of Fractional Stochastic Kraenkel–Manna–Merle Equations in Ferromagnetic Materials

In this study, we take into account the fractional stochastic Kraenkel–Manna–Merle system (FSKMMS). The mapping approach may be used to produce various type of stochastic fractional solutions, such as elliptic, hyperbolic, and trigonometric functions. Solutions to the Kraenkel–Manna–Merle system equation, which explains the propagation of a magnetic field in a zero-conductivity ferromagnet, may provide insight into a variety of fascinating scientific phenomena. Moreover, we construct a variety of 3D and 2D graphics in MATLAB to illustrate the influence of the stochastic term and the conformable derivative on the exact solutions of the FSKMMS.

Prediction of combustion promotion effect of high/low-frequency AC electric fields based on machine learning method

Electric field-assisted combustion has become a trend in the past several decades. The effects of low-frequency and high-frequency AC electric fields on the flame propagation and combustion process of CH4-N2-O2 lean burning flame are compared experimentally, and different machine learning methods are applied to predict the flame propagation and combustion characteristics in this research. The experimental results show that both the fields can affect the flame significantly in the electric field direction, while the flame front under a low-frequency field is more stable. The promotion effect of the fields on the average flame propagation speed is in the same order, and the high-frequency fields increase the combustion pressure and pressure rise rate more than the low-frequency one. Support vector machine and artificial neural network are used to establish the correlation model of the average flame propagation and combustion pressure, respectively. It is found that the generation ability and the prediction performance of the models are very impressive and reliable. The correlation coefficient of each model established by SVM method is over 0.998, and the values of MAPE and Theil IC are below 1.093% and 0.007, respectively. The calculation speed of the ANN model is much higher than that of the SVM one. Besides, the results of the SVM method are more deterministic than that of the ANN method. Present work illustrates that machine learning methods provide time-saving research approaches for the forecasting of the flame propagation and combustion characteristic parameters in the electric field-assisted combustion field.

Numerical solution for a nonlinear diffusion model with source terms

Abstract The nonlinear diffusion system with source terms is studied. This model is derived via Maxwell equations describing electromagnetic field propagation in media. The uniqueness of the solution and its behavior as t → ∞ t\to\infty are proved. We also prove that the finite difference approximation converges in space and time. Numerical implementation with various experiments for different values of the input parameters is performed to validate the theoretical conclusions.

Numerical simulation of fracture propagation in child wells considering dual-stress field

Shale gas can easily generate interwell fracture hits during fracturing and stimulation, which might significantly interfere with the production of parent wells. Therefore, it is crucial to clarify the mechanism of fracture hits between wells to advance the technology for controlling fracture hits. In this study, considering the nonuniform stress field after parent well production, a numerical model of fracture propagation in a dual-stress field was established using the extended finite element method, and the fracture propagation behaviour of interwell fracturing was analysed. The results show that when the hydraulic fractures of the child well reach the low-stress zone generated during the parent well production, the fracture propagation accelerates, and the fracture propagation on both sides of the child well is nonuniform. The fracture length is mainly influenced by the minimum horizontal principal stress. The more significant the difference in the in situ stress of the reservoir and the more developed the natural fractures, the more prone the child well becomes to fracture hits. Controlling the operation scale and optimising well spacing patterns can effectively prevent or minimise the influence of fracture hits.

Classical double copy of spinning worldline quantum field theory

We study the classical double copy of massive spinning objects in the worldline quantum field theories (WQFT) formalism. We couple the mathcal{N} = 1 supersymmetric model to a Yang-Mills background to describe the propagation of a spin-half particle interacting with gluons. At the classical level, this model captures physical effects up to linear order in spin. We propose a double copy relation to map the spin tensors to the gravitation side. Enforcing R-symmetry and supersymmetry (SUSY) on the double copy integrands, we find that the gravitational theory is the mathcal{N} = 2 particle coupled to dilaton-gravity (DG). We check the double copy prescription for the eikonal phase up to next-to-leading order and for radiation at leading order in coupling constants, finding that the Grassmann nature of the spin tensor in WQFT plays a crucial role in finding full agreement with direct calculation in the mathcal{N} = 2 model. We show how to deform the SUSY charges of the free theory to include DG. Since the constraints algebra is first class, the worldline model can be quantized, describing the propagation of a massive vector field coupled to DG, in agreement with the literature. In addition, we investigate the double copy without preserving SUSY and R-symmetry, finding that the B-field also couples to the worldline.

Study on flow noise characteristic of transonic deep buffeting over an airfoil

Transonic buffeting can induce strong noise and reduce aircraft lifespan. In view of the complexity of the transonic buffeting flow, this study combines the highly accurate Delayed-Detached Eddy Simulation and Discrete Frequency Response method to analyze the flow field and sound propagation law in different buffeting states and also investigates its noise-generating characteristics by Dynamic Mode Decomposition and Pearson correlation. It is found that the low-frequency and small-amplitude shock oscillation of the light buffeting state is insufficient to trigger large separated flow. Besides, the reattachment phenomenon occurs in the trailing edge, which is the second mode of boundary layer separation, corresponding to the lower Sound Pressure Levels (SPL). In the deep buffeting state, however, the shock oscillates with high frequency and large amplitude, producing large separated bubbles without the reattachment phenomenon, which is the first mode of boundary layer separation. Moreover, there is a large-scale vortex structure with high energy content in the recirculation zone, which develops toward the trailing edge under the action of convection and produces strong Upstream Traveling Waves (UTWs). The collision occurs between UTWs and the shock wave oscillation. In this process, they promote each other, which increases the shock wave oscillation frequency and SPL. This state is not the superposition effect of buffeting and stall. And its main sound sources are shock oscillation and the von Kármán mode.

Microelongated Thermo-Elastodiffusive Waves of Excited Semiconductor Material under Laser Pulses Impact

The current study focuses on one-dimensional (1D) deformation in an excited microelongated semiconductor medium impacted by optoelectronics with exponential laser-pulsed heat. Diffusion effect is considered in a photothermal problem of a semiconducting media. Microelongated optoelectronics and a broad variety of concepts have been introduced. Appropriate solutions to a set of microelongated photothermal diffusion differential equations have been found. The homogeneous (thermal and mechanical) and isotropic characteristics of the medium are thought to be in the x-direction, including coupled diffusion equations. The linear photo-thermoelasticity (PTE) theory of semiconductors is used to describe thermo-elastodiffusive waves. As a case study, the developed theoretical framework may be used to explore the microelongation-photo-thermoelastic problem in a semiconductor medium caused by the laser pulse. The analytical linear solutions for the main quantities during thermoelastic (TD) and electronic (ED) deformation are obtained using Laplace transforms for dimensionless quantities. To obtain exact expressions of the important physical variables according to certain boundary surface conditions, numerical approximations solutions of the fundamental relevant relations are performed in the Laplace inverse time domain. To describe the wave propagation of the physical fields graphically, the computational results for silicon (Si) semiconductor material are derived using several cases of thermal memory and microelongation factors.

Saturated absorption spectrum of cesium micrometric-thin cell with suppressed crossover spectral lines

Micrometric-thin cells (MCs) with alkali vapor atoms have been valuable for research and applications of hyperfine Zeeman splitting and atomic magnetometers under strong magnetic fields. We theoretically and experimentally study the saturated absorption spectra using a 100-μm cesium MC, where the pump and probe beams are linearly polarized with mutually perpendicular polarizations, and the magnetic field is along the pump beam. Because of the distinctive thin chamber of the MC, crossover spectral lines in saturated absorption spectra are largely suppressed leading to clear splittings of hyperfine Zeeman transitions in experiments, and the effect of spatial magnetic field gradient is expected to be reduced. A calculation method is proposed to achieve good agreements between theoretical calculations and experimental results. This method successfully explains the suppression of crossover lines in MCs, as well as the effects of magnetic field direction, propagation and polarization directions of the pump/probe beam on saturated absorption spectrum. The saturated absorption spectrum with suppressed crossover lines is used for laser frequency stabilization, which may provide the potential value of MCs for high spatial resolution strong-field magnetometry with high sensitivity.

Spin-3/2 and spin-2 charged massive states in a constant electromagnetic background

We develop in components the superspace action obtained in [1] describing the first massive level of the open charged superstring in a flat four-dimensional spacetime. In the absence of an electromagnetic background, we show how the Rarita-Schwinger and Fierz-Pauli Lagrangians are retrieved for spin-3/2 and 2, respectively. We then write different forms of the action in the presence of the electromagnetic background. The resulting equations of motion describe the propagation of fields of charged spin-3/2 and spin-1/2 on the one hand, and spin-2, 1 and 0 on the other.

Simulation on a new reverse circulation fishing tool: Design and evaluation of the salvage capacity and efficiency

AbstractTo solve the insufficient energy for reverse circulation fishing tools in complex structure wells, it is necessary to further optimize the design of the tools to improve the impurity salvage efficiency. In this work, a three‐dimensional (3D) flow field simulation model of reverse circulation fishing tool with venturi negative pressure is employed to identify the vortex zone of circulation channel and to investigate the negative pressure and jet velocity distribution around the spray nozzle based on the ANSYS‐CFX. The effects of the spray angle, diameter of the suction nozzle, and the nonstructural parameters on negative pressure and jet velocity are investigated through sensitivity analysis. As revealed from the results, there may be an optimum value for the spray angle, and the nozzle jet direction can indeed affect the propagation and attenuation of the bottom hole flow field greatly. The combination of the inner diameter of the nozzle outlet and that of the nozzle inlet (Φ + Φ′ = 3 mm + 6 mm) is the best design solution when the negative pressure at the nozzle outlet can be the highest. The negative pressure and jet velocity increase with the increasement of the inlet flow rate. The comparative analysis of different bottom hole impurity mass in the cases of the borehole inner diameter 5′ and 8.5″ on the salvage efficiency are conducted numerically. It is observed that the impurity mass salvaged and salvage time are not directly related to its total amount, but only related to the flow rate of the sucked fluid flow. The impurity salvage efficiency can be as high as 95.4%, which meets the engineering requirements in the field. This work improves the working performance of the reverse circulation fishing tool and provides theoretical guidance for well washing.

High-efficiency broadband polarisation converter via patterned multilayer twisted liquid crystal polymer

ABSTRACT We propose an ultra-compact polarisation converter based on liquid crystal (LC) material for effectively converting the obliquely incident unpolarised light into horizontal linearly polarised beam within the visible frequency range. Multilayer twisted configuration is introduced here to tackle the inherent dispersion issue from the LC itself and extended Jones matrix is employed to analyse the propagation of the electric field inside the LC medium under possible oblique illumination. Spatial angular separation of orthogonal polarised lights and polarisation conversion into the same polarisation direction are realised through specific patterned structure design, which effectively reduce the thickness of the device without sacrificing performance. Experimental results demonstrated that our fabricated LC-based device can deliver >80% polarisation conversion efficiency at normal illumination and 59%–80.5% efficiency for ±10° oblique incidence over the visible spectrum. Therefore, we envision that our presented device might find numerous potential applications associated with polarisation regulation such as vortex beam generator, augmented reality and optical computing.