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The article presents a study that examines the nonlinear Breit-Wheeler process of the pair production of electron and positron off a probe photon that collides with two electromagnetic waves that propagate in the same direction. The researchers also investigate the probability of the electron-positron pair production for the process. They observe that the contributions of the low-frequency electromagnetic wave to such probability can be enhanced through the presence of a high-frequency wave.

Taking into account the Euler-Heisenberg effective Lagrangian of one-loop nonperturbative quantum electrodynamics (QED) contributions, we formulate the Einstein-Euler-Heisenberg theory and study the solutions of nonrotating black holes with electric and magnetic charges in spherical geometry. In the limit of strong and weak electromagnetic fields of black holes, we calculate the black hole horizon radius, area, and total energy up to the leading order of QED corrections and discuss the black hole irreducible mass, entropy, and maximally extractable energy as well as the Christodoulou-Ruffini mass formula. We find that these black hole quantities receive the QED corrections, in comparison with their counterparts in the Reissner-Nordström solution. The QED corrections show the screening effect on black hole electric charges and the paramagnetic effect on black hole magnetic charges. As a result, the black hole horizon area, irreducible mass, and entropy increase; however, the black hole total energy and maximally extractable energy decrease compared with the Reissner-Nordström solution. In addition, we show that the condition for extremely charged black holes is modified due to the QED correction. [ABSTRACT FROM AUTHOR]

Dissociative electron attachment to carbon monoxide, e- + CO → C + O-, at 9.5, 10.0, and 10.6 eV is investigated by using the anion velocity time-sliced map imaging technique. The completely backward scattering distributions of the fast O- fragment are observed at 10.0 and 10.6 eV. The single electron-molecule resonance model fails in interpretation to these unusual angular distributions, while a quantum interference model including two (at 10.0 eV) or three (at 10.6 eV) dissociative outgoing waves is consequently proposed and provides the satisfying results about the experimental data fittings. Moreover, coherent interference among the ²Π, ²Δ, and ²ɸ resonant states of CO- at 10.6 eV could be further established, based on the fact that the sum of the phase-shift fitting values equals π rad. [ABSTRACT FROM AUTHOR]

Stereodynamics of dissociative electron attachment to CO2 is investigated using O- anion velocity imaging experiments. Here 2&Pgr;g as a Feshbach resonant state of C02- is confirmed to play a role in the dissociation CO2- → CO(1&Sgr;+) + 0-(2P) around 8.0 eV. At the lower energy, 7.7 eV, two split states of 2Ilg due to the Renner-Teller effect are found to couple with the dissociation path; while above this energy, at 8.2 and 8.7 eV, the coupling between the dissociation and the C-O bond stretching becomes predominant. The evolutions of the potential energy surface around this Feshbach resonant state result in the dramatically different angular distributions of the O- momentum. [ABSTRACT FROM AUTHOR]

Abstract: For ultrasonic non-destructive inspection of spherical curved plates, which is used in the fields of pressure vessels, spherical domes of power plants, and so on, characteristics of guided waves in spherical curved plates must be understood. Based on linear three-dimensional elasticity, an orthogonal polynomial series expansion approach is used for determining the guided wave dispersion curves and the displacements distributions in homogeneous anisotropic spherical curved plates. When the material is orthotropic or has fewer independent constants in the wave propagation direction, the coupled propagating waves can be decomposed of Lamb-like waves and SH wave. The independent SH wave is solved analytically by Bessel function. In order to test the accuracy and range of applicability of this polynomial approach, the two results of the SH wave is compared, the exact results by Bessel function and the results by the polynomial method. Guided wave dispersion curves for unidirectional composite spherical curved plates with different fiber intensity are calculated to show the effect of the fiber intensity on dispersion curves. Finally, the guided wave dispersion curves for orthotropic spherical curved plates at different radius of curvature are calculated and the inherited influences of the radius of curvature on the wave characteristics are discussed. [Copyright &y& Elsevier]

Due to the nonindependence of entropy and thermodynamic volume for spherically symmetric black holes in the anti-de Sitter (AdS) spacetime, when applying the Ruppeiner thermodynamic geometry theory to these black holes, we often encounter an unavoidable problem of the singularity about the line element of thermodynamic geometry. In this paper, we propose a basic and natural scheme for dealing with the thermodynamic geometry of spherically symmetric AdS black holes. We point out that enthalpy, not internal energy, is the fundamental thermodynamic characteristic function for the Ruppeiner thermodynamic geometry. Based on this fact, we give the specific forms of the line element of thermodynamic geometry for the Schwarzschild AdS (SAdS) black hole in different phase spaces, and the results show that the thermodynamic curvatures obtained in different phase spaces are equivalent. It is shown that the thermodynamic curvature is negative which may be related to the information of attractive interaction between black hole molecules for the SAdS black hole. Meanwhile we also give an approximate expression of the thermodynamic curvature of the Schwarzschild black hole which shows that the black hole may be dominated by repulsion on the low temperature region and by attraction on the high temperature region phenomenologically or qualitatively. [ABSTRACT FROM AUTHOR]

A time evolving fluid system is constructed on a timelike boundary hypersurface at finite cutoff in Vaidya spacetime. The approach used to construct the fluid equations is a direct extension of the ordinary gravity/fluid correspondence under the constrained fluctuation obeying Petrov type I conditions. The explicit relationships between the time dependent fluctuation modes and the fluid quantities such as density, velocity field and kinematic viscosity parameters are established, and the resulting fluid system is governed by a system of a sourced continuity equation and a compressible Navier-Stokes equation with nontrivial time evolution. [ABSTRACT FROM AUTHOR]

Using deep inelastic scattering on a large nucleus as an example, we consider the transverse momentum broadening of partons in hard processes in the presence of medium. We find that one can factorize the vacuum radiation contribution and medium related PT broadening effects into the Sudakov factor and medium dependent distributions, respectively. Our derivations can be generalized to other hard processes, such as dijet productions, which can be used as a probe to measure the medium PT broadening effects in heavy ion collisions when Sudakov effects are not overwhelming. [ABSTRACT FROM AUTHOR]

The article focuses on issues related to Chinese students in Great Britain. It mentions the problems that arise from the lack of integration between home and international students including the negative effects on learning, well-being and even mental health of students. It discusses the results of a survey of Chinese students living in Nottingham, England.

Taking into account the Euler-Heisenberg effective Lagrangian of one-loop nonperturbative quantum electrodynamics (QED) contributions, we formulate the Einstein-Euler-Heisenberg theory and study the solutions of nonrotating black holes with electric and magnetic charges in spherical geometry. In the limit of strong and weak electromagnetic fields of black holes, we calculate the black hole horizon radius, area, and total energy up to the leading order of QED corrections and discuss the black hole irreducible mass, entropy, and maximally extractable energy as well as the Christodoulou-Ruffini mass formula. We find that these black hole quantities receive the QED corrections, in comparison with their counterparts in the Reissner-Nordström solution. The QED corrections show the screening effect on black hole electric charges and the paramagnetic effect on black hole magnetic charges. As a result, the black hole horizon area, irreducible mass, and entropy increase; however, the black hole total energy and maximally extractable energy decrease compared with the Reissner-Nordström solution. In addition, we show that the condition for extremely charged black holes is modified due to the QED correction. [ABSTRACT FROM AUTHOR]

Abstract A new method based on Legendre orthogonal polynomials method (LOPM) is proposed to calculate the acoustic reflection and transmission coefficients at liquid/solid interfaces. The displacement solutions of each layer in a multilayer plate are fitted approximately by multiple groups of Legendre orthogonal polynomials. The stress components and the governing wave equations in the plate are derived. Reassembling the boundary conditions of liquid/solid interfaces, solid/solid interfaces and governing wave equations, the linear independent equations are established to calculate the reflection and transmission coefficients and the expansion coefficients of Legendre polynomials in displacement solutions. The transfer matrix method (TMM) is used to verify the accuracy of this proposed method. The relationship between reflection and transmission coefficients with oblique incident angles and frequencies is discussed. The influence of the polynomial cut-off order on the calculation results is analyzed, and the displacement and stress profiles in multilayer plate are reconstructed. The research extends the applicable range of LOPM, moreover, lays the foundation of non-destructive testing and inversion of mechanical properties and bonding quality of the multilayer structures by acoustic waves. Highlights • A new method for calculating the reflection and transmission coefficients was proposed. • Application range of Legendre orthogonal polynomials has been extended. • The relationship between reflection coefficients and dispersion curves was obtained. • The displacement and stress profiles versus different cut-off order were reconstructed. [ABSTRACT FROM AUTHOR]

We study the Boltzmann equation with elastic pointlike scalar interactions in two different versions of the classical approximation. Although solving numerically the Boltzmann equation with the unapproximated collision term poses no problem, this allows one to study the effect of the ultraviolet cutoff in these approximations. This cutoff dependence in the classical approximations of the Boltzmann equation is closely related to the nonrenormalizability of the classical statistical approximation of the underlying quantum field theory. The kinetic theory setup that we consider here allows one to study in a much simpler way the dependence on the ultraviolet cutoff, since one also has access to the nonapproximated result for comparison. [ABSTRACT FROM AUTHOR]

Atom cooling and trapping by partially spatially coherent lasers is investigated both experimentally and theoretically. The degree of spatial coherence of the laser beams is controlled by the electro-optic crystal. The characteristics of the trapped atomic cloud are studied. The experimental results indicate that the atom number and atomic Gaussian density distribution stay unchanged due to the fact that the average photon scattering rate is independent of the spatial coherence of the laser beams. However, the measured temperature of the atomic cloud increases as the degree of spatial coherence of the laser beams decreases. The reason is that the scattering force of the partially spatially coherent lasers acting on the atoms fluctuates temporally and spatially, which broadens the velocity distribution of the atoms. [ABSTRACT FROM AUTHOR]