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Showing 1 to 20 of 33 for “"scattering amplitude"”.
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Approximation of the Scattering Amplitude using Nonsymmetric Saddle Point Matrices
… systems of linear equations to approximate the scattering amplitude defined by g<em><sup><strong>T</strong></sup></em>x =y<em><sup><strong>T</strong></sup></em>b. We use a conjugate gradient-like iteration for a unsymmetric saddle point matrix that is contructed so as to have a real positive …
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A Modified Preconditioned Conjugate Gradient Method for Approximating the Scattering Amplitude
… at an iterative method for approximating the scattering amplitude that involves solving two linear systems: a forward system A<strong>x</strong>=<strong>b</strong> and an adjoint system A<sup>T</sup><strong>y</strong>=<strong>g</strong>. Once these two systems are solved, the scattering …
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Semiclassical asymptotics for the scattering amplitude in the presence of focal points at infinity
We consider scattering in $\R^n$, $n\ge 2$, described by the Schr\"odinger operator $P(h)=-h^2\Delta+V$, where $V$ is a short-range potential. With the aid of Maslov theory, we give a geometrical formula for the semiclassical asymptotics as $h\to 0$ of the scattering amplitude …
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Some aspects of non-Abelian gauge theories
… the first part,we calculate the fermion-fermion scattering amplitude for a non-Abelian gauge theory with SU(N) gauge symmetry in the limit of high energy with fixed momentum transfer through sixth order in the coupling constant. We keep only the leading logarithmic terms in each order of …
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Finite system size effects on the effective coupling in scalar quantum field theory
… We first recount the infinite volume NLO 2 → 2 scattering amplitude calculation using dimensional regularisation, and then introduce and employ denominator regularisation. We then perform the non-trivial calculation of the NLO 2 → 2 scattering amplitude in our compactified spacetime. This …
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Rigorous Bounds on Strong Interaction Coupling Constants
… problem of deriving bounds on strong interaction scattering amplitudes from the results of axiomatic field theory. The bounds on the π-π scattering amplitude at points within its analyticity domain which have been obtained by Łukaszuk and Martin are especially interesting because they contain no …
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A study of Mac Dowell symmetry, conspiracy, and fermion Regge trajectories
"Non-dynamical constraints on the scattering amplitude are derived and applied to the Regge pole model. In particular, the effects of Mac- Dowell symmetry and the conspiracy constraints are derived for fermion Regge trajectory and residue functions. It is shown that two solutions of the constraints …
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Optimal Control for an Impedance Boundary Value Problem
We consider the analysis of the scattering problem. Assume that an incoming time harmonic wave is scattered by a surface of an impenetrable obstacle. The reflected wave is determined by the surface impedance of the obstacle. In this paper we will investigate the problem of choosing the surface …
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Investigating on elastic and inelastic nuclear scattering and polarisation
Elastic and inelastic scattering of nuclear particles are treated in a partial wave formalism. It is assumed that only a few partial waves having large angular momenta contribute significantly to the scattering amplitude. Parameterised elastic S-matrix elements are used in the Austern-Blair theory …
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High-energy approximations to nuclear scattering
We study high-energy approximations to nuclear scattering. These are based on expansions of the free-particle propagator. We distinguish the eikonal expansion and the Fresnel expansion and interpret their physical meaning in optical terms. A "Fresnel approximation" is defined as a partial sum of …
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Beam spin asymmetry measurements in deeply virtual Compton scattering
… (BSA) is studied in the Deeply Virtual Compton Scattering (DVCS) using CLAS detector at Jefferson Lab and longitudinally polarized electron beam with 4.8 GeV energy. This asymmetry is directly proportional to the imaginary part of the scattering amplitude, which relates it to the Generalized …
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Perturbative QCD in exclusive processes
… and evaluates all Feynman diagrams required for scattering amplitude for exclusive processes is tested, corrected, extended, and brought to operational status. The sensitivity of perturbative QCD predictions for the nucleon form factors, ψ → pp̅, and 𝛾𝛾 → pp̅, to the theoretical uncertainties of …
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Extremal effects in rotationally inelastic diffraction
The scattering of the hydrogenic molecules H2, D2, and HD from vacuum cleaved MgO (001) along the [110] azimuth has been studied. A thermal beam at 300 K and 80 K was used. Particular emphasis has been placed on the rotational inelastic processes which accompany diffraction of RD. Singularities in …
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Quantum electrodynamic model for production amplitudes at infinite momentum
"The scattering amplitude for the production of an arbitrary number of electron"" positron pairs in electron-electron collisions is calculated in a infinite momentum field theory model. More precisely, the model considers only events where"" the center of momentum energy is, much larger, than …
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Studies of Light Scalar Particles and Dressed Gauge Propagators in QCD
… Theory and carefully considering the poles in a scattering amplitude. In chapters 2 and 3 we apply these methods to determine the composition of the sigma(600) and f0(980) scalar resonances observed in scattering. In chapter 4 we turn to make the connection between the fundamental Lagrangian and …
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Aspects of amplitudes, gravity & complexity
… two aspects of modern theoretical physics: scattering amplitudes in gravitational theories and entanglement entropy & complexity in quantum field theory. In part one, we utilise modern scattering amplitude techniques to efficiently calculate the deflection angle of both light and gravity due …
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Scattering theory approach to electrodynamic Casimir forces
… combines each object's classical electromagnetic scattering amplitude with universal translation matrices, which convert between the bases used to calculate scattering for each object, but are otherwise independent of the details of the individual objects. The method is illustrated by rederiving …
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Time-frequency domain modelling for ultrasonic nondestructive testing
… uses the mathematics of inverse problems and scattering theory to extract information about such defects and puts forward an objective approach which employs a mathematical model. A relationship between the pulse-echo response curve of a scattering matrix and the size and orientation of a flaw …
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Subordinacy and spectral analysis of Schrödinger operators
… central potentials, and some related aspects of scattering theory. After an introductory discussion on the aims of the thesis and its relation to existing work, the background mathematical material required for subsequent developments is presented in Chapter II. The theory of subordinacy, which …
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Understanding and Improving Moment Method Scattering Solutions
… of moment method solutions to electromagnetic scattering problems has been studied by many researchers. Error bounds for the moment method have been obtained in terms of Sobolev norms of the current solution. Motivated by the historical origins of Sobolev spaces as energy spaces, it is shown …
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