Search

Scattering properties and time delays for general (nonsymmetric) potentials in terms of the respective S-matrices are discussed paradigmatically in one dimension and in comparison to symmetric potentials. Only for the latter the Wigner and Smith time delays coincide. Considering asymmetric potentials also reveals that only one version of S-matrices used in the literature (the one with reflection coefficients on the diagonal) generalizes to the asymmetric case. Finally, we give a criterion how to identify a potential with intrinsic symmetry that behaves like an asymmetric one if it is merely offset from the scattering center. [ABSTRACT FROM AUTHOR]

The elastic cross-section is calculated for the elements 12C, 40Ca and 4He at high energies using the radial Klein–Gordon equation. These calculations were made for the case of pions using the Yukawa potential. To this end, the coupling constant of the Yukawa potential for the elements 12C, 40Ca and 4He was calculated first by fitting the numerical solutions to the experimental data. Our results are in agreement with the experimental data at low angular distribution. Finally, we calculate the bounds for the parameter of the model. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new numerical method to simulate acoustic scattering problems in two‐dimensional periodic structures with non‐periodic incident fields. Applying the Floquet‐Bloch transform to the scattering problem yields a family of quasi‐periodic boundary value problems dependent on the Floquet‐Bloch parameter. Consequently, the solution of the original scattering problem is written as the inverse Floquet‐Bloch transform of the solutions to these boundary value problems. The key step in our method is the numerical approximation of this integral transform by a quadrature rule with a nonuniform choice of quadrature points adapted to the regularity of the family of quasi‐periodic solutions. This achieved by a graded subdivision of the full interval for the Floquet‐Bloch parameter and applying a Gauss‐Legrendre quadrature rule on each subinterval. We prove that the numerical method converges exponentially with respect to both the number of subintervals and the number of Gaussian quadrature points. Some numerical experiments are provided to illustrate the results. [ABSTRACT FROM AUTHOR]

The scattering problem of elastic waves impinging on periodic single and double arrays of parallel cylindrical defects is considered for isotropic materials. An analytic expression for the scattering matrix is obtained by means of the Lippmann–Schwinger formalism and analyzed in the long-wavelength approximation. It is proved that, for a specific curve in the space of physical and geometrical parameters, the scattering is dominated by resonances. The shear mode polarized parallel to the cylinders is decoupled from the other two polarization modes due to the translational symmetry along the cylinders. It is found that a relative mass density and relative Lamé coefficients of the scatterers give opposite contributions to the width of resonances in this mode. A relation between the Bloch phase and material parameters is found to obtain a global minimum of the width. The minimal width is shown to vanish in the leading order of the long wavelength limit for the single array. This new effect is not present in similar acoustic and photonic systems. The shear and compression modes in a plane perpendicular to the cylinders are coupled due to the normal traction boundary condition and have different group velocities. For the double array, it is proved that, under certain conditions on physical and geometrical parameters, there exist resonances with the vanishing width, known as Bound States in the Continuum (BSC). Necessary and sufficient conditions for the existence of BSC are found for any number of open diffraction channels. Analytic BSC solutions are obtained. Spectral parameters of BSC are given in terms of the Bloch phase and group velocities of the shear and compression modes. [ABSTRACT FROM AUTHOR]

In this paper, we consider the fourth-order Schrödinger equations with focusing, $ L^2 $-supercritical nonlinearity in one dimension. We prove the global existence and scattering of even solutions below the ground state threshold, under the assumption that the threshold for even solutions is less than a certain constant times the threshold for general solutions. [ABSTRACT FROM AUTHOR]

In this paper we show how to measure in the setting of digital quantum simulations the reflection and transmission amplitudes of the one-dimensional scattering of a particle with a short-ranged potential. The main feature of the protocol is the coupling between the particle and an ancillary spin-1/2 degree of freedom. This allows us to reconstruct tomographically the scattering amplitudes, which are in general complex numbers, from the readout of one qubit. Applications of our results are discussed. [ABSTRACT FROM AUTHOR]

We will explore, in any space dimension d ≥ 4 , the decay in the energy space for the damped magnetic Schrödinger equation with non-local nonlinearity and radial initial data in H 1 (R d) . We will also display new Morawetz identities and corresponding localized Morawetz estimates. [ABSTRACT FROM AUTHOR]

The low-lying eigenvalues of the generator of a Langevin process are known to satisfy the Eyring--Kramers law in the low temperature regime under suitable assumptions. These eigenvalues are generically real. We construct generators whose spectral gap is given by nonreal eigenvalues or by a real eigenvalue having a Jordan block. [ABSTRACT FROM AUTHOR]

This paper proves new results on spectral and scattering theory for matrix-valued Schrödinger operators on the discrete line with non-compactly supported perturbations whose first moments are assumed to exist. In particular, a Levinson theorem is proved, in which a relation between scattering data and spectral properties (bound and half-bound states) of the corresponding Hamiltonians is derived. The proof is based on stationary scattering theory with prominent use of Jost solutions at complex energies that are controlled by Volterra-type integral equations. [ABSTRACT FROM AUTHOR]

In this paper, we consider the inhomogeneous nonlinear Schrödinger equation i ∂ t u + Δ u = K (x) | u | α u , u (0) = u 0 ∈ H 1 (R N) , N ≥ 3 , | K (x) | + | x | | ∇ K (x) | ≲ | x | - b , 0 < b < min (2 , N - 2) , 0 < α < (4 - 2 b) / (N - 2) . We obtain novel results of global existence for oscillating initial data and scattering theory in a weighted L 2 -space for a new range α 0 (b) < α < (4 - 2 b) / N . The value α 0 (b) is the positive root of N α 2 + (N - 2 + 2 b) α - 4 + 2 b = 0 , which extends the Strauss exponent known for b = 0 . Our results improve the known ones for K (x) = μ | x | - b , μ ∈ C . For general potentials, we highlight the impact of the behavior at the origin and infinity on the allowed range of α . In the defocusing case, we prove decay estimates provided that the potential satisfies some rigidity-type condition which leads to a scattering result. We give also a new scattering criterion taking into account the potential K. [ABSTRACT FROM AUTHOR]

The irregular solutions of the stationary Schrodinger equation are important for the fundamental formal development of scattering theory. They are also necessary for the analytical properties of the Green function, which in practice can greatly speed up calculations. Nevertheless, they are seldom considered in numerical treatments because of their divergent behavior at origin. This divergence demands high numerical precision that is difficult to achieve, particularly for non-spherical potentials which lead to different divergence rates in the coupled angular momentum channels. Based on an unconventional treatment of boundary conditions, an integral-equation method is here developed which is capable of dealing with this problem. The available precision is illustrated by electron-density calculations for NiTi in its monoclinic B19' structure. [ABSTRACT FROM AUTHOR]

The Ablowitz–Ladik (AL) chain is an integrable discretized version of the nonlinear Schrödinger equation. We report on a novel underlying Hamiltonian particle system with properties similar to the ones known for the classical Toda chain and Calogero fluid with 1 / sinh 2 pair interaction. Boundary conditions are imposed such that, both in the distant past and future, particles have a constant velocity. We establish the many-particle scattering for the AL chain and obtain properties known for generic integrable many-body systems. For a specific choice of the chain, real initial data remain real in the course of time. Then, asymptotically, particles move in pairs with a velocity-dependent size and scattering shifts are governed by the fusion rule. [ABSTRACT FROM AUTHOR]

We give a short description of the proof of asymptotic-completeness for NLS-type equations with radial data in three dimensions. We also show some aspects of the method by giving a new proof of Asymptotic Completeness for the two-body Quantum Scattering case. [ABSTRACT FROM AUTHOR]

In this paper, based on the first-order Born approximation, the scope of scattering theory was broadened by analyzing the scattering of generalized multi-Gaussian correlated Schell-model (GMGCSM) beam upon a deterministic medium with semi-hard boundary. It was revealed that the scattering spectral density and degree of coherence (DOC) are affected by several parameters, covered semi-hard boundary medium’s summation index L and effective radius σR, and GMGCSM beam’s coherence length δ, index M and transverse width σ0. The valuable and meaningful results obtained here could contribute to the expansion of the application range of scattering theory, making it applicable in various fields such as optical communication, remote sensing, and medicine.

Abstract The advancement of imaging systems has significantly ameliorated various technologies, including Intelligence Surveillance Reconnaissance Systems and Guidance Systems, by enhancing target detection, recognition, identification, positioning, and tracking capabilities. These systems can be countered by deploying obscurants like smoke, dust, or fog to hinder visibility and communication. However, these counter-systems affect the visibility of both sides of the cloud. In this sense, this manuscript introduces a new concept of a smoke cloud composed of engineered Janus particles to conceal the target image on one side while providing clear vision from the other. The proposed method exploits the unique scattering properties of Janus particles, which selectively interact with photons from different directions to open up the possibility of asymmetric imaging. This approach employs a model that combines a genetic algorithm with Discrete Dipole Approximation to optimize the Janus particles' geometrical parameters for the desired scattering properties. Moreover, we propose a Monte Carlo-based approach to calculate the image formed as photons pass through the cloud, considering highly asymmetric particles, such as Janus particles. The effectiveness of the cloud in disguising a target is evaluated by calculating the Probability of Detection (PD) and the Probability of Identification (PID) based on the constructed image. The optimized Janus particles can produce a cloud where it is possible to identify a target more than 50% of the time from one side (PID > 50%) while the target is not detected more than 50% of the time from the other side (PD

We consider the nonlinear Schrödinger equation with a defocusing nonlinearity which is mass-(super)critical and energy-subcritical. We prove uniform in time error estimates for the Lie–Trotter time splitting discretization. This uniformity in time is obtained thanks to a vectorfield which provides time decay estimates for the exact and numerical solutions. This vectorfield is classical in scattering theory and requires several technical modifications compared to previous error estimates for splitting methods. [ABSTRACT FROM AUTHOR]

In this paper, we show the scattering of the radial solution for the nonlinear Schrödinger equation with combined power-type and Choquard-type nonlinearities i u t + Δ u = λ 1 ∣ u ∣ p 1 − 1 u + λ 2 (I α ∗ ∣ u ∣ p 2 ) ∣ u ∣ p 2 − 2 u. in the energy space H1(ℝN) for λ1λ2 = −1. We establish a scattering criterion for radial solution together with Morawetz estimate which implies the scattering theory. Results show that the defocusing perturbation terms does not determine the scattering solution in energy space. [ABSTRACT FROM AUTHOR]

This paper is about two important trends of scattering theory in general relativity: time-dependent spectral analytic scattering and conformal scattering. The former was initiated by Jonathan Dimock and Bernard Kay in the mid-1980s and is based on spectral and functional analysis. The latter was proposed by Roger Penrose in 1965 and then constructed for the first time by Gerard Friedlander in 1980 by putting together Penrose's conformal method and another analytic approach to scattering: the Lax–Phillips theory due to Peter Lax and Ralph Phillips. We shall review the history of the two approaches and explain their general principles. We shall also explore an important question: 'can the tools of one approach be used to obtain a complete construction in the other?' This article is part of a discussion meeting issue 'At the interface of asymptotics, conformal methods and analysis in general relativity'. [ABSTRACT FROM AUTHOR]

Scattering of time-harmonic electromagnetic waves by penetrable obstacles admits an equivalent formulation in terms of a strongly singular volume integral equation (VIE). For the case of piecewise-constant physical parameters and Lipschitz interfaces, we give a characterization of the essential spectrum of the magnetic and the electromagnetic operators which describe the VIE, based on the spectral properties of the normal derivative of the Laplace single-layer potential 1 2 I + K 0 ′ . This extends the results obtained in a previous paper (Costabel et al., 2012) which were available only for smooth domains. The results on the spectrum will then be used to derive necessary and sufficient conditions to ensure that the diffraction problem is well-posed in the Fredholm sense. Also, we use the employed spectral methods to show that the construction of regularizers for the operators which appear in the VIE needs only the determination of a regularizer for the operator λ I + K 0 ′ . [ABSTRACT FROM AUTHOR]

The irregular solutions of the stationary Schrödinger equation are important for the fundamental formal development of scattering theory. They are also necessary for the analytical properties of the Green function, which in practice can greatly speed up calculations. Nevertheless, they are seldom considered in numerical treatments because of their divergent behavior at origin. This divergence demands high numerical precision that is difficult to achieve, particularly for non-spherical potentials which lead to different divergence rates in the coupled angular momentum channels. Based on an unconventional treatment of boundary conditions, an integral-equation method is here developed which is capable of dealing with this problem. The available precision is illustrated by electron-density calculations for NiTi in its monoclinic B19’ structure.

The scattering problem of elastic waves impinging on periodic single and double arrays of parallel cylindrical defects is considered for isotropic materials. An analytic expression for the scattering matrix is obtained by means of the Lippmann–Schwinger formalism and analyzed in the long-wavelength approximation. It is proved that, for a specific curve in the space of physical and geometrical parameters, the scattering is dominated by resonances. The shear mode polarized parallel to the cylinders is decoupled from the other two polarization modes due to the translational symmetry along the cylinders. It is found that a relative mass density and relative Lamé coefficients of the scatterers give opposite contributions to the width of resonances in this mode. A relation between the Bloch phase and material parameters is found to obtain a global minimum of the width. The minimal width is shown to vanish in the leading order of the long wavelength limit for the single array. This new effect is not present in similar acoustic and photonic systems. The shear and compression modes in a plane perpendicular to the cylinders are coupled due to the normal traction boundary condition and have different group velocities. For the double array, it is proved that, under certain conditions on physical and geometrical parameters, there exist resonances with the vanishing width, known as Bound States in the Continuum (BSC). Necessary and sufficient conditions for the existence of BSC are found for any number of open diffraction channels. Analytic BSC solutions are obtained. Spectral parameters of BSC are given in terms of the Bloch phase and group velocities of the shear and compression modes.

We will explore, in any space dimension d≥4, the decay in the energy space for the damped magnetic Schrödinger equation with non-local nonlinearity and radial initial data in H1(Rd). We will also display new Morawetz identities and corresponding localized Morawetz estimates.

We provide a new construction of infraparticle states in the massless Nelson model. The approximating sequence of our infraparticle state does not involve any infrared cut-offs. Its derivative w.r.t. the time parameter t is given by a simple explicit formula. The convergence of this sequence as t → ∞ to a nonzero limit is then obtained by the Cook method combined with stationary phase estimates. To apply the latter technique, we exploit recent results on regularity of ground states in the massless Nelson model, which hold in the low coupling regime. [ABSTRACT FROM AUTHOR]

In this study, we review some topics on spectral and scattering theory for Schrödinger operators or time-independent wave equations and inverse scattering problems. First, we consider an example of an inverse problem for a one-dimensional wave equation with a piecewise constant coefficient. Nonscattering energy naturally appears in the process of reconstruction of the coefficient. A similar problem is known in multidimensional cases. This problem can be reduced to an interior transmission eigenvalue problem. Furthermore, herein, we refer to the shape resonance model for the Schrödinger equation as a related topic. [ABSTRACT FROM AUTHOR]

The lattice thermal conductivity of graphene is evaluated using a microscopic model that takes into account the lattice's discrete nature and the phonon dispersion relation within the Brillouin zone. The Boltzmann transport equation is solved iteratively within the framework of three-phonon interactions without taking into account the four-phonon scattering process. The Umklapp and normal collisions are treated rigorously, thereby avoiding relaxation-time and long-wavelength approximations. The mechanisms of the failures of these approximations in predicting the thermal transport properties are discussed. Evaluation of the thermal conductivity is performed at different temperatures and frequencies and in different crystallite sizes. Reasonably good agreement with the experimental data is obtained. The calculation reveals a critical role of out-of-plane acoustic phonons in determining the thermal conductivity. The out-of-plane acoustic phonons contribute greatly and the longitudinal and transverse acoustic phonons make small contributions over a wide range of temperatures and frequencies. The out-of-plane acoustic phonons dominate the thermal conductivity due to their high density of states and restrictions governing the anharmonic phonon scattering. The selection rule severely restricts the phase space for out-of-plane phonon scattering due to reflection symmetry. The optical phonon contribution cannot be neglected at higher temperatures. Both Umklapp and normal processes must be taken into account in order to predict the phonon transport properties accurately. [ABSTRACT FROM AUTHOR]

We study the stationary elastic wave equation with free boundary condition in a locally perturbed half‐space in ℝ3$$ {\mathrm{\mathbb{R}}}&#x0005E;3 $$. Using the stationary phase method, we derive an asymptotic behavior at infinity of the resolvent of the elastic operator uniformly with respect to the direction in 핊+2. Consequently, the body waves and the Rayleigh surface waves appear simultaneously in the expansion. From the far‐field pattern of the expansion, we obtain the scattering amplitude. We also characterize the space of generalized eigenfunctions in terms of Agmon–Hörmander space B∗$$ {\mathcal{B}}&#x0005E;{\ast } $$ and derive their spatial asymptotics. [ABSTRACT FROM AUTHOR]

We consider the large time asymptotics of solutions to the Cauchy problem for the nonlinear nonlocal Schrödinger equation with critical nonlinearity$ \begin{equation*} \left\{ \begin{array}{c} i\partial _{t}u-\mathbf{\Lambda }u = \lambda \left\vert u\right\vert u,\text{ } t>0,{\ }x\in \mathbb{R}^{2}\mathbf{,} \\ u\left(0,x\right) = u_{0}\left(x\right) ,{\ }x\in \mathbb{R}^{2} \mathbf{,} \end{array} \right. \end{equation*} $where the linear pseudodifferential operator $ \mathbf{\Lambda }u = \left(1-\Delta \right) ^{-1}\left(-\Delta +a\Delta ^{2}\right) u $ is characterized by its symbol $ \Lambda \left(\xi \right) = \frac{\left\vert\xi \right\vert ^{2}+a\left\vert \xi \right\vert ^{4}}{1+\left\vert \xi\right\vert ^{2}}. $ We will show below the modified scattering for solutions of equation (1). We continue to develop the factorization techniques which was started in our previous papers. The crucial points of our approach presented here are the $ \mathbf{L}^{2} $ - boundedness of the pseudodifferential operators. [ABSTRACT FROM AUTHOR]

We study the stationary elastic wave equation with free boundary condition in a locally perturbed half‐space in ℝ3$$ {\mathrm{\mathbb{R}}}&#x0005E;3 $$. Using the stationary phase method, we derive an asymptotic behavior at infinity of the resolvent of the elastic operator uniformly with respect to the direction in 핊+2. Consequently, the body waves and the Rayleigh surface waves appear simultaneously in the expansion. From the far‐field pattern of the expansion, we obtain the scattering amplitude. We also characterize the space of generalized eigenfunctions in terms of Agmon–Hörmander space B∗$$ {\mathcal{B}}&#x0005E;{\ast } $$ and derive their spatial asymptotics. [ABSTRACT FROM AUTHOR]

The spectrum of bound and scattering states of the one dimensional Dirac Hamiltonian describing fermions distorted by a static background built from two Dirac delta potentials is studied. A distinction will be made between 'mass-spike' and 'electrostatic' δ -potentials. The second quantisation is then performed to promote the relativistic quantum mechanical problem to a relativistic quantum field theory and study the quantum vacuum interaction energy for fermions confined between opaque plates. The work presented here is a continuation of (Guilarte et al 2019 Front. Phys. 7 109). [ABSTRACT FROM AUTHOR]

In this article, we focus on the scattering analysis of Sturm-Liouville type singular operator including an impulsive condition and turning point. In the classical literature, there are plenty of papers considering the positive values of the weight function in both continuous and discontinuous cases. However, this article differs from the others in terms of the impulsive condition appearing at the turning point. We generate the scattering function, resolvent operator, and discrete spectrum of the operator using the hyperbolic representations of the fundamental solutions. Finally, we create an example to show the article’s primary conclusions.

We review mathematical models describing how Optical Coherence Tomography works. Hereby, we focus on models based on Maxwell's equations and their simplifications. We highlight especially the effects of different modeling assumptions for the incident illumination, the medium, the light propagation, and the measurement setup and illustrate the qualitatively differing behavior in numerical simulations of the OCT data and compare them with real data from OCT measurements.

Frequency selectivity of routing signals in quantum channels is of great significance for a quantum optical network. We have proposed a novel tunable bandpass router constructed by two waveguides linked mediately via a driven three-level emitter. The routing properties in the output port are investigated theoretically by using the real-space Hamiltonian. Numerical results show that the continuous central frequencies on demand of routing photons can be manipulated almost linearly by tuning the driving field, and high routing efficiencies of resonance transmission can be achieved via reflection feedback. The proposed routing system could be exploited potentially in designing other quantum optical devices and quantum information processing. [ABSTRACT FROM AUTHOR]

We provide an asymptotic completeness criterion and a representation formula for the scattering matrix of the scattering couple. AB; A/, where both A and AB are self-adjoint operator and AB formally corresponds to adding to A two terms, one regular and the other singular. In particular, our abstract results apply to the couple. B; /, where  is the free selfadjoint Laplacian in L2.R3/and B is a self-adjoint operator in a class of Laplacians with both a regular perturbation, given by a short-range potential, and a singular one describing boundary conditions (like Dirichlet, Neumann and semi-transparent ı and ı0 ones) at the boundary of an open, bounded Lipschitz domain. The results hinge upon a limiting absorption principle for AB and a Kre˘ın-like formula for the resolvent difference. 􀀀AB C z/􀀀1 􀀀. 􀀀A C z/􀀀1 which puts on an equal footing the regular (here, in the case of the Laplacian, a Kato-Rellich potential suffices) and the singular perturbations. [ABSTRACT FROM AUTHOR]

Massive Klein–Gordon theory is quantized on the timelike hypercylinder in Minkowski space. Crucially, not only the propagating, but also the evanescent sector of phase space is included, laying in this way foundations for a quantum scattering theory of fields at finite distance. To achieve this, the novel α -Kähler quantization scheme is employed in the framework of general boundary quantum field theory. A potential quantization ambiguity is fixed by stringent requirements, leading to a unitary radial evolution. Formulas for building scattering amplitudes and correlation functions are exhibited. A novel LSZ formula is derived, applicable to scattering at finite distance. [ABSTRACT FROM AUTHOR]

In this article, we study the asymptotic fields of the Yukawa particle-field model of quantum physics in the semiclassical regime ℏ → 0 , with an interaction subject to an ultraviolet cutoff. We show that the transition amplitudes between final (respectively initial) states converge towards explicit quantities involving the outgoing (respectively incoming) wave operators of the nonlinear Schrödinger–Klein–Gordon (S-KG) equation. Thus, we rigorously link the scattering theory of the Yukawa model to that of the Schrödinger–Klein–Gordon equation. Moreover, we prove that the asymptotic vacuum states of the Yukawa model have a phase space concentration property around classical radiationless solutions. Under further assumptions, we show that the S-KG energy admits a unique minimizer modulo symmetries and we identify exactly the semiclassical measure of Yukawa ground states. Some additional consequences of asymptotic completeness are also discussed, and some further open questions are raised. [ABSTRACT FROM AUTHOR]

In this paper, scattering medium with a semi-hard boundary is extended to the case of a quasi-homogeneous random medium for the first time. Applying the first-order Born approximation, far-field distribution of radially polarized partially coherent vortex beams scattered upon the random medium with semi-hard boundary is studied. Spectral density distribution, degree of spectral polarization, polarization angle, and degree of ellipticity of the scattering field in the far zone are investigated. Influence of characteristics of the incident beam and scattering medium on the far-zone scattering field are discussed. In addition, phase singularity of the scattering field’s center is also described. It is interesting to find that the far-field scattering field is circularly polarized with a Gaussian distribution, though the incident field is radially polarized with a dark-hollow distribution. The center of the scattering field is completely polarized, while on the edge of the scattering field, degree of polarization shows obvious fluctuations with the change of parameters of the incident beam and medium. Results obtained here could find application in the acquisition of medium structure information.

Scattering of time-harmonic electromagnetic waves by penetrable, anisotropic dielectric obstacles admits an equivalent formulation in terms of a strongly singular volume integral equation (VIE). The aim of this study is to analyse the essential spectrum of the integral operator that describes this equation in the case where the dielectric permittivity is a piecewise constant symmetric 3 × 3 matrix with some bounds on the eigenvalues. For Lipschitz interfaces, we show that the spectrum is contained in some finite interval which depends on the spectral properties of the above matrix. The results on the spectrum will then be used to derive sufficient conditions to ensure that the integral operator of the VIE is Fredholm of index zero. [ABSTRACT FROM AUTHOR]

Optical filtering with low crosstalk effect and high drop efficiency is of great importance in multi-channel filter structures. We propose a dual-channel drop filter of single photons with high drop efficiency in a configuration with a bus waveguide and two drop waveguides, where these waveguides are mediately coupled by two single-mode whispering gallery resonators with a qubit. By adjusting the waveguide-resonator and qubit-resonator couplings, the crosstalk effects between different peak wavelengths are suppressed, and multi-wavelength filtering with high drop efficiency is availably performed. Therefore, the proposed two-channel filter can provide potential applications in optical communication, such as multiplexers, routers, etc. [ABSTRACT FROM AUTHOR]

The recent results in the description of elastic and inelastic nucleon-nucleon scattering within the dibaryon model of nuclear forces are reviewed. This original model taking into account non-nucleonic degrees of freedom is based on the special mechanism including an exchange by an intermediate six-quark state. A good description of the partial phase shifts and inelasticities is found for the main lowest partial NN configurations in a wide energy range from zero up to 0.6–1 GeV. The model gives the resonances in each NN configuration as well, the parameters of which are compared with the data found from recent experiments on single- and double-pion production and partial wave analysis. [ABSTRACT FROM AUTHOR]

We review mathematical models describing how Optical Coherence Tomography works. Hereby, we focus on models based on Maxwell's equations and their simplifications. We highlight especially the effects of different modeling assumptions for the incident illumination, the medium, the light propagation, and the measurement setup and illustrate the qualitatively differing behavior in numerical simulations of the OCT data and compare them with real data from OCT measurements. [ABSTRACT FROM AUTHOR]

The lattice thermal conductivity of graphene is evaluated using a microscopic model that takes into account the lattice's discrete nature and the phonon dispersion relation within the Brillouin zone. The Boltzmann transport equation is solved iteratively within the framework of three-phonon interactions without taking into account the four-phonon scattering process. The Umklapp and normal collisions are treated rigorously, thereby avoiding relaxation-time and long-wavelength approximations. The mechanisms of the failures of these approximations in predicting the thermal transport properties are discussed. Evaluation of the thermal conductivity is performed at different temperatures and frequencies and in different crystallite sizes. Reasonably good agreement with the experimental data is obtained. The calculation reveals a critical role of out-of-plane acoustic phonons in determining the thermal conductivity. The out-of-plane acoustic phonons contribute greatly and the longitudinal and transverse acoustic phonons make small contributions over a wide range of temperatures and frequencies. The out-of-plane acoustic phonons dominate the thermal conductivity due to their high density of states and restrictions governing the anharmonic phonon scattering. The selection rule severely restricts the phase space for out-of-plane phonon scattering due to reflection symmetry. The optical phonon contribution cannot be neglected at higher temperatures. Both Umklapp and normal processes must be taken into account in order to predict the phonon transport properties accurately.

Due to the nonlinear vibration of ultrasound contrast agent bubbles, a nonlinear scattered sound field will be generated when bubbles are driven by ultrasound. A bubble cluster consists of numerous bubbles gathering in a spherical space. It has been noted that the forward scattering of a bubble cluster is larger than its backscattering, and some studies have experimentally found the angular dependence of a bubble cluster’s scattering signal. In this paper, a theory is proposed to explain the difference of acoustic scattering at different directions of a bubble cluster when it is driven by ultrasound, and predicts the angular distribution of scattered acoustic pressure under different parameters. The theory is proved to be correct under circumstances of small clusters and weak interactions by comparing theoretical results with numerical simulations. This theory not only sheds light on the physics of bubble cluster scattering, but also may contribute to the improvement of ultrasound imaging technology, including ultrasonic harmonic imaging and contrast-enhanced ultrasonography.