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Cloud of Virtual Photons Surrounding a Nonrelativistic Electron

100%

Compagno G., Passante R., Persico F., Salamone G.

Acta Physica Polonica A

1994

vol. 85

issue 4

667-676

A review is presented of the virtual cloud of photons surrounding a nonrelativistic electron. Two cases are considered. In the first, the electron is taken as bound to a proton to form a is hydrogen atom. In the second case the electron is considered as free. It is shown that the virtual cloud, as measured by the transverse electromagnetic energy density, in the near region of the ground-state hydrogen is not influenced by the dynamic properties of the atom and in practice it coincides with that of the free electron. The influence of the atomic eigenvalue spectrum is evident in the far region of the atom where retardation effects play an important role. These results are discussed from a physical point of view.

Field Theoretic Models of the Dispersive Dielectric Medium

63%

Artyszuk Ź., Bechler A.

Acta Physica Polonica A

2003

vol. 103

issue 2-3

263-273

The purpose of this paper is a description of the dispersive dielectric medium, both linear and nonlinear, from first principles using the field theoretic methods based on the Feynman path integrals over classical trajectories. The main idea is to use notion of effective fields, in the present case the electromagnetic field modified by presence of a polarizable medium. Interaction of the field with the medium on the microscopic level is described by a modified Hopfield Lagrangian containing terms corresponding to the electromagnetic field, the matter polarization field modelled by harmonic oscillators with some resonance frequency and other matter fields describing the degrees of freedom responsible for absorption in the medium (reservoir fields). The polarization field is coupled both to the electric field and the reservoir fields. Effective theory is obtained by elimination of the matter degrees of freedom which is achieved by functional integration over all matter fields. For a linear medium all calculations can be done exactly leading to the effective Lagrangian from which, among others, an expression for frequency dependent dielectric constant can be extracted. Explicit form of the dielectric constant depends on the way by which the polarization field couples to the reservoir fields. In particular, uniform coupling to all reservoir modes gives the standard Lorentz oscillator model, and for any type of coupling the Lorentz form of dielectric constant is retrieved for frequencies close to the resonance. For weak damping the dispersion ω(k) is little sensitive to the form of coupling leading to polariton modes not different from those of the Lorentz model. It is also outlined briefly how the functional integration method could be used to description of nonlinear effects in the medium.

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2 Acta Physica Polonica A

1 2003

1 1994

1 Artyszuk Ź.

1 Bechler A.

1 Compagno G.

1 Passante R.

1 Persico F.

1 Salamone G.

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Cloud of Virtual Photons Surrounding a Nonrelativistic Electron

Field Theoretic Models of the Dispersive Dielectric Medium