“…This invariant is an ingenious way to deal with the oscillator with a time-dependent frequency, but it works for particular time dependencies. For other approaches to the problem discussed here see [7], [9], [? ].…”
Here we prove that the classical (respectively, quantum) system, consisting of a particle moving in a static electromagnetic field, is canonically (respectively, unitarily) equivalent to a harmonic oscillator perturbed by a spatially homogeneous force field. This system is canonically and unitarily equivalent to a standard oscillator. Therefore, by composing the two transformations we can integrate the initial problem. Actually, the eigenstates of the initial problem turn out to be entangled states of the harmonic oscillator.When the magnetic field is spatially homogeneous but time-dependent, the equivalent harmonic oscillator has a time-varying frequency. This system can be exactly integrated only for some particular cases of the time dependence of the magnetic field.The unitary transformations between the quantum systems are a representation of the canonical transformations by unitary transformations of the corresponding Hilbert spaces.
“…This invariant is an ingenious way to deal with the oscillator with a time-dependent frequency, but it works for particular time dependencies. For other approaches to the problem discussed here see [7], [9], [? ].…”
Here we prove that the classical (respectively, quantum) system, consisting of a particle moving in a static electromagnetic field, is canonically (respectively, unitarily) equivalent to a harmonic oscillator perturbed by a spatially homogeneous force field. This system is canonically and unitarily equivalent to a standard oscillator. Therefore, by composing the two transformations we can integrate the initial problem. Actually, the eigenstates of the initial problem turn out to be entangled states of the harmonic oscillator.When the magnetic field is spatially homogeneous but time-dependent, the equivalent harmonic oscillator has a time-varying frequency. This system can be exactly integrated only for some particular cases of the time dependence of the magnetic field.The unitary transformations between the quantum systems are a representation of the canonical transformations by unitary transformations of the corresponding Hilbert spaces.
“…Under a helical wiggler field, the particles experience the transverse magnetic field revolving around the propagation direction of the beam. The gyrating motion of electrons has already been investigated in this kind of configuration for free electron lasers [28]. The helical wiggler field extends the time duration of laser-particle interaction, due to which the particles can not only gain but also retain the significant amount of energy that results in intense radiations.…”
Polarization-tunable terahertz (THz) radiation in pair plasma has been generated under the combined configuration of a helical wiggler and solenoidal magnetic fields. The control over the electromagnetic vector of the emitted field (i.e. polarization) furnishes the knob of another degree of freedom which is very useful in numerous applications. With the optimization of wiggler period and frequency, the total angular spread of the field has been reduced which provides a narrow-band THz spectrum. Additionally, the solenoidal field not only prevents the escape of particles during laser-matter interaction but also enhances the magnitude of emitted field. Along with the external magnetic field, collisions among the particles and ripples in plasma density have also been considered to fine-tune the radiation.
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