Search results for "Quantum electrodynamics."

Self-dressing and radiation reaction in classical electrodynamics

2002

A canonical approach to self-dressing in classical electrodynamics is presented. A slowly moving, rigid charge distribution is assumed to be completely deprived of the transverse electric E⊥ at an initial time t1' and the development of this component of the field is studied for t > t1' by solving the coupled charge-field Hamilton equations of motion. The theory is specialized to charge distributions of spherical symmetry, and in particular the point-charge, the spherical shell of charge and the spherical volume of charge are considered. As for the dynamics of the charge, the radiation-reaction force during self-dressing is obtained and it is shown to be substantially different at short tim…

Universal correction for the Becke-Johnson exchange potential

2010

The Becke-Johnson exchange potential [A. D. Becke and E. R. Johnson, J. Chem. Phys. 124, 221101 (2006)] has been successfully used in electronic structure calculations within density-functional theory. However, in its original form, the potential may dramatically fail in systems with non-Coulombic external potentials, or in the presence of external magnetic or electric fields. Here, we provide a system-independent correction to the Becke-Johnson approximation by (i) enforcing its gauge-invariance and (ii) making it exact for any single-electron system. The resulting approximation is then better designed to deal with current-carrying states and recovers the correct asymptotic behavior for sy…

Antikaons in the medium within a chiral non-perturbative approach

2000

Improved unitarized heavy baryon chiral perturbation theory for πN scattering to fourth order

2004

We extend our previous analysis of the unitarized pion-nucleon scattering amplitude including up to fourth order terms in heavy baryon chiral perturbation theory. We pay special attention to the stability of the generated Delta(1232) resonance, the convergence problems, and the power counting of the chiral parameters.

Finite volume corrections to forward Compton scattering off the nucleon

2021

We calculate the spin-averaged amplitude for doubly virtual forward Compton scattering off nucleons in the framework of manifestly Lorentz invariant baryon chiral perturbation theory at complete one-loop order $O(p^4)$. The calculations are carried out both in the infinite and in a finite volume. The obtained results allow for a detailed estimation the finite-volume corrections to the amplitude which can be extracted on the lattice using the background field technique.

Three-nucleon forces and the three-nucleon systems

1993

The basic principles and philosophy which have guided the area of few-nucleon physics are motivated and discussed. Recent advances have made it possible to solve accurately the Schrodinger (or Faddeev) equation for many of the configurations of the few-nucleon systems, A brief review is given of some of the results of these calculations, which also Indicate that one-pion exchange plays roughly the same role in binding these systems that it plays in electromagnetic meson-exchange currents. Finally, a qualitative discussion of chiral perturbation theory is presented, which highlights the role that chiral symmetry plays in the nuclear force. Three-body forces from different areas of physics ar…

The <FONT FACE=Symbol>d</font> Expansion and the Principle of Minimal Sensitivity

1998

The d-expansion is a nonperturbative approach for field theoretic models wich combines the techniques of perturbation theory and the variational principle. Different ways of implemeting the principle of minimal sensitivity to the d-expansion produce in general different results for observables. For illustration we use the Nambu- Jona-Lasinio model for chiral symmetry restoration at finite density and compare results with those obtained with the Hartree-Fock approximation.

Inelastic scattering and interactions of three-wave parametric solitons.

2006

We study the interactions of velocity-locked three-wave parametric solitons in a medium with quadratic nonlinearity and dispersion. We reveal that the inelastic scattering between three-wave solitons and linear waves may be described in terms of analytical solutions with dynamically varying group velocity, or boomerons. Moreover, we demonstrate the elastic nature of three-wave soliton-soliton collisions and interactions.

Influence of dispersion on the resonant interaction between three incoherent waves

2005

We study the influence of group-velocity dispersion (or diffraction) on the coherence properties of the parametric three-wave interaction driven from an incoherent pump wave. We show that, under certain conditions, the incoherent pump may efficiently amplify a signal wave with a high degree of coherence, in contrast with the usual kinetic description of the incoherent three-wave interaction. The group-velocity dispersion is shown to be responsible for a spectral filtering process, in which the coherence of the generated signal increases, as the coherence of the pump wave decreases. As a result, the coherence acquired by the signal in the presence of an incoherent pump, is higher than that a…

Computation of Amplitudes in the Discretized Approach to String Field Theory

1988

An approach to Witten string field theory based on the discretization of the world sheet is adopted. We use it to calculate tree amplitudes with the formulation of the theory based on string functionals. The results are evaluated numerically and turn out to be very accurate, giving, for a string approximated by 600 points, values within 0.02% of the prediction of the dual model. The method opens a way to calculate amplitudes in string field theory using nonflat backgrounds as well as compactified dimensions.