Einstein's theory of quantum radiation

The stationary probability distribution of the one-step process corresponding to Einstein's theory of absorption and emission of radiation is derived. Gauss' principle is used to identify the entropy, and the second law gives the dynamical equilibrium condition or Planck's radiation law. This condition is in disagreement with Einstein's criterion of dynamical equilibrium. The physical consequences of the new condition are investigated.     

Possible generation of electric multipole radiation from solid state quantum rings

The self-organized crystal growth of semiconductor quantum rings has opened a new possibility to study and exploit optical transitions between ring-shaped quantum states. In such states, orbital angular momenta of particle envelope functions are well-defined. We investigate theoretically the intraband interlevel transitions between such states and examine the possibility of electrical multipole radiations (EMRs). Selections rules due to envelope function quantum numbers are deduced. To enhance the EMR efficiency, we propose a novel coupled dot–ring structure, by which the lowest allowed EMR can be selected and manipulated, allowing the efficient radiation of multipole photons.     

Spontaneous multipole radiation in a condensed medium

The probability of the spontaneous emission of electromagnetic radiation of an arbitrary multipolarity in an infinite homogeneous isotropic nonabsorbent condensed medium with constant permittivity and permeability is determined using the perturbation theory for quantum electrodynamics. The local field inside a sphere is calculated for fields of arbitrary configuration in the medium with the help of the real and virtual cavity models.     

Parametric generation of multipole radiation in a gas laser

The conditions are investigated for the resonant parametric generation of coherent electromagnetic multipole radiation in a gas laser amplifier by two light waves which interact with two coupled atomic transitions. Cross susceptibility tensors are derived within a semiclassical model taking the polarization of light and atoms into account. Doppler broadening restricts the generation to a difference frequency in a “folded” array of levels. In a specific example an intensity of 10^?10 W/mm² is estimated.     

A quantum correction to radiation theory for a short-magnet system

The radiation pattern is considered for an ultrarelativistic spinless charged particle deflected through a small angle by an external magnetic field. The radiation characteristics are determined up to the first order in the Plank constant. The quantum parameter in the expansion differs substantially from the corresponding quantum parameter in synchrotron radiation theory.Tomsk Polytechnical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 61–65, November, 1993.     

The quantum theory of an ideal superlattice responding to far-infrared laser radiation

Minibands of quasienergies can be defined for a superlattice interacting with far-infrared laser radiation. It is demonstrated that the width of these quasienergy minibands depends not only on the parameters of the superlattice, but also on strength and frequency of the driving laser field. In particular, the width approaches zero at certain values of these parameters. A strong coupling ansatz, combined with perturbation theory for degenerate quasienergy states, leads to a detailed understanding of these results.     

On the quantum theory of radiation by channeling particles

On the basis of the Dirac equation the intensity of the spontaneous γ-radiation by relativistic channeling particles has been calculated. In the ultrarelativistic limit the quantum treatment gives a result close to that of the classic calculation.     

Nonlinear quantum theory of interaction of charged particles and monochromatic radiation in a medium

We study the quantum theory of nonlinear interaction of charged particles and a given field of plane-transverse electromagnetic radiation in a medium. Using the exact solution of the generalized Lamé equation, we find the nonlinear solution of the Mathieu equation to which the relativistic quantum equation of particle motion in the field of a monochromatic wave in the medium reduces if one ignores the spin-spin interaction (the Klein-Gordon equation).We study the stability of solutions of the generalized Lamé equation and find a class of bounded solutions corresponding to the wave function of the particle. On the basis of this solution we establish that the particle states in a stimulated Cherenkov process form bands. Depending on the wave intensity and polarization, such a band structure describes both bound particle-wave states (capture) and states in the continuous spectrum. It is obvious that in a plasma there can be no such bands, since bound states of a particle with a transverse wave whose phase velocity v _ph is higher than c are impossible in this case. The method developed in the paper can be applied to a broad class of problems reducible to the solution of the Mathieu equation. Zh. éksp. Teor. Fiz. 113, 43–57 (January 1998)     

The quantum theory of the radiation from charged polarized fermions moving in crossed fields

The radiation of a charged Dirac particle, moving at relativistic velocity in orthogonal electric and magnetic fields (E H), is examined here. The formulas obtained are applicable for arbitrary orientation of the particle spin.     

Selective switching of individual multipole resonances in single dielectric nanoparticles

Following Mie theory, nanoparticles made of a high‐refractive‐index dielectric, such as silicon, exhibit a resonator‐like behavior and very rich resonance spectra. Which electric or magnetic particle mode is excited depends on the wavelength, the refractive‐index contrast relative to the environment, and the geometry of the nanoparticle itself. In addition, the spatial structure of the impinging light field plays a major role in the excitation of the nanoparticle resonances. Here, it is shown that, by tailoring the excitation field, individual multipole resonances can be selectively addressed while suppressing the excitation of other particle modes. This enables a detailed study of selected individual resonances without interference by the other modes.

     

Čerenkov radiation in a dielectric layer

The present paper is devoted to the investigation of the erenkov radiation field generated in an infinite plane-parallel layer by a sinusoidally bunched beam of electric charges moving with constant velocity along its surface.     

Classical and quantum theory of synergic synchrotron-Čerenkov radiation

The power spectra of ?erenkov, synchrotron, and synchrotron-?erenkov radiation are calculated both classically (by source methods) and quantum mechanically (by mass operator methods). The synergic features of the synchrotron-?erenkov radiation are pointed out. The existence of a transition region near nβ = 1 [n(ω, H) = index of refraction of the medium; $\text{β =}\text{v}\text{c}$, v - velocity of the charged particle] coupled with the intrinsic dispersion of the medium is then applied to the discussion of the suppression of X-ray radiation, the construction of X-ray counters, the detection of the quantum corrections, and the modification of the synchrotron radiation from pulsars.     

Non-relativistic quantum theory of stimulated Cherenkov radiation and Compton scattering in plasma

The stimulated processes in electron plasma, i.e., Cherenkov radiation by a nonrelativistic electron beam of longitudinal oscillations and Compton scattering of a transverse electromagnetic wave in plasma with quantum mode excitation (de Broglie wave), are considered in the three-wave approximation. The possibility of the occurrence of quantum oscillations is discussed.     

The effect of a magnetic flux line in quantum theory

The nonlocal exchange of the conserved, gauge invariant quantity e (i/variant Planck's) (p(k)-(e/cA(k))L(k)), L(k)=const, k=1,2 between the charged particle and the magnetic flux line (in the k=3 direction) is responsible for the Aharonov-Bohm effect. This exchange occurs at a definite time, before the wave packets are brought together to interfere, and can be verified experimentally.     

The development of quantum theory

During the last decade an acceptable explanation of superconductivity at the atomic level has been developed. In this article the physical principles underlying the electron pair theory are described. Experimental verification of the theory and its application to real superconductors are examined.     

Spontaneous radiation of a two-level atom into multipole modes of a plasmonic nanoparticle

We consider the relaxation of an excited two-level system (TLS) positioned near a spherical plasmonic nanoparticle (NP). The transition frequency of the TLS is assumed to coincide with the frequency of the condensation point of NP plasmonic resonances. We show that the relaxation of the TLS excitation is a two-step process. Following an initial exponential decay, the TLS breaks in to Rabi oscillations. Depending upon the distance between the TLS and NP, the probability of the TLS being in the excited state exhibits either chaotic or nearly regular oscillations. In the latter case, the eigenfrequency of the TLS-NP system coincides with one of NP multipole modes.     

The Heisenberg ferromagnet as a quantum field theory

We consider a lattice of spin 1/2 ions, described by the discrete form of the current commutation relationsJ _i J _(i) =1/2, [J _i ,J _i ]=i _ij J _i where =1, 2, 3 andi label the lattice sites. The algebra is realized as the Clifford algebra over a Hilbert space. The equations of motion are specified by a formal Hamiltonian of the Heisenberg form: , wheref _ij 0 and only a finite numberQ of ions are linked to any given lattice site. We prove that the Hamiltonian is non-negative in a representation of , and has a ground state exhibiting ferromagnetism. The time displacement group acts continuously on , inducing automorphisms. is asymptotically abelian with respect to the space translations of the lattice.The model is an example of an algebraic quantum field theory and possesses a broken symmetry, the rotation group 0(3). The consequent Goldstone theorem is proved, namely, there is no energy gap in the spectrum ofH.     

The principles of a stochastic formulation of quantum theory

Nelson's stochastic formulation of quantum theory is briefly surveyed and put in relation to the classical stochastic formalisms. The approach is investigated comparatively with the Bohm-Vigier model of stochastic fluctuations. Parallels to the causal interpretation of de Broglie-Bohm are drawn.