Search results for " ELECTRODYNAMICS"
showing 10 items of 813 documents
Path Integral Formulation of Quantum Electrodynamics
2020
Let us consider a pure Abelian gauge theory given by the Lagrangian $$\displaystyle\begin{array}{rcl} \mathcal{L}_{\text{photon}}& =& -\frac{1} {4}F_{\mu \nu }F^{\mu \nu } \\ & =& -\frac{1} {4}\left (\partial _{\mu }A_{\nu } - \partial _{\nu }A_{\mu }\right )\left (\partial ^{\mu }A^{\nu } - \partial ^{\nu }A^{\mu }\right ){}\end{array}$$ (36.1) or, after integration by parts, $$\displaystyle\begin{array}{rcl} \mathcal{L}_{\text{photon}}& =& -\frac{1} {2}\left [-\left (\partial _{\mu }\partial ^{\mu }A_{\nu }\right )A^{\nu } + \left (\partial ^{\mu }\partial ^{\nu }A_{\mu }\right )A_{\nu }\right ] \\ & =& \frac{1} {2}A_{\mu }\left [g^{\mu \nu }\square - \partial ^{\mu }\partial ^{\nu }\righ…
Rotational Three-Body Resonances: A New Adiabatic Approach
2001
In the standard adiabatic approach the motion of the fast, light particle (electron) is treated so as to produce an effective potential that governs the motion of the heavy particles (nuclei). The rotational degrees of freedom are then taken into account by adding the centrifugal J(J + 1)-term to the channel potentials and introducing rotational (Coriolis) couplings into conventional close-coupling calculations. Of course, a perturbative treatment of the rotational motion is justified only provided the rotational energy is sufficiently small. If, however, the rotation is as energetic as the motion of the fast particle, both motions should be treated on the same footing in order to produce s…
Multidimensional Skyrme-density-functional Study of the Spontaneous Fission of 238U
2015
We determined the spontaneous fission lifetime of 238U by a minimization of the action integral in a three-dimensional space of collective variables. Apart from the mass-distribution multipole moments Q20 (elongation) and Q30 (left–right asymmetry), we also considered the pairing- fluctuation parameter λ2 as a collective coordinate. The collective potential was obtained self-consistently using the Skyrme energy density functional SkM∗ . The inertia tensor was obtained within the nonperturbative cranking approximation to the adiabatic time-dependent Hartree–Fock– Bogoliubov approach. The pairing-fluctuation parameter λ2 allowed us to control the pairing gap along the fission path, which sign…
Mean-Field Calculation Based on Proton-Neutron Mixed Energy Density Functionals
2015
We have performed calculations based on the Skyrme energy density functional (EDF) that includes arbitrary mixing between protons and neutrons. In this framework, single-particle states are generalized as mixtures of proton and neutron components. The model assumes that the Skyrme EDF is invariant under the rotation in isospin space and the Coulomb force is the only source of the isospin symmetry breaking. To control the isospin of the system, we employ the isocranking method, which is analogous to the standard cranking approach used for describing high-spin states. Here, we present results of the isocranking calculations performed for the isobaric analog states in A = 40 and A = 54 nuclei.
Detuning-induced robustness of a three-state Landau-Zener model against dissipation
2019
A three-state system subjected to a time-dependent Hamiltonian whose bare energies undergo one or more crossings, depending on the relevant parameters, is considered, also taking into account the role of dissipation in the adiabatic following of the Hamiltonian eigenstates. Depending on the fact that the bare energies are equidistant or not, the relevant population transfer turns out to be very sensitive to the environmental interaction or relatively robust. The physical mechanisms on the basis of this behavior are discussed in detail.
Particle in Harmonic E-Field E ( t ) = E sin ω 0 t $$E(t)= E \sin \omega _0 t$$ ; Schwinger–Fock Proper-Time Method
2020
Since the Green’s function of a Dirac particle in an external field, which is described by a potential Aμ(x), is given by
Analytic behavior of the QED polarizability function at finite temperature
2012
We revisit the analytical properties of the static quasi-photon polarizability function for an electron gas at finite temperature, in connection with the existence of Friedel oscillations in the potential created by an impurity. In contrast with the zero temperature case, where the polarizability is an analytical function, except for the two branch cuts which are responsible for Friedel oscillations, at finite temperature the corresponding function is not analytical, in spite of becoming continuous everywhere on the complex plane. This effect produces, as a result, the survival of the oscillatory behavior of the potential. We calculate the potential at large distances, and relate the calcul…
Symmetry-based canonical dressing of a bidimensionally trapped and laser-driven ion
2001
Abstract We present a detailed and exact construction of a unitary operator accomplishing the diagonalization of an effective quadratic radiation-matter interaction model describing a bidimensionally trapped and appropriately laser-driven ion. The possibility of applying the same mathematical method to other effective radiation-matter interaction model is briefly put into evidence.
Unitary decoupling treatment of a quadratic bimodal cavity quantum electrodynamics model
2013
We consider a two-photon quantum model of radiation–matter interaction between a single two-level atom and a degenerate bimodal high-Q cavity field. Within this tripartite system, the explicit construction of two collective radiation modes, one of which is freely evolving and the other one quadratically coupled to the matter subsystem, is reported. The meaning and advantages of such a decoupling treatment are carefully discussed.
The Modelling of Cell Membrane Electrodynamics
2013
Main electrical processes in cells are defined by membranes. The membrane maintains a biochemical environment inside the cell that differs from the outside one, keeping the electrical potential negative inside the cell and organizing the selective transport across the surface. In the paper, it is attempted to explain the cell membrane electrodynamics using modelling experiments with magnetic dipoles. It is shown that the membrane has a definite symmetry or handenness. In addition, a characteristic mechanism of the excited state physics is given. The modelling experiments have also shown that a membrane with different symmetry can exist. Since the electrical processes in these cases are diff…