Many body satellite in the photoemission spectra of the heavy rare earths

A narrow feature is reported in the photoemission spectra of the heavy rare earths, Gd, Tb, and Dy on a variety of substrates. This feature is not expected from the initial densities of states. This feature appears to require a density of states at the Fermi energy to exist. We propose that the feature is due to a many electron shakeup process to the unoccupied 4f levels.     

On the formalism of relativistic many body theory

The thermodynamic potential is constructed as an effective action functional of the various n point amplitudes (n ? 4). One of the functionals is used to obtain the equations of state as simple, convergent expressions involving the conventionally renormalized charges and masses.     

Many body theory of the coster-kronig satellite spectrum

It is shown that the formula used by Nyholm et al. to obtain the L₂ linewidths of the elements Ti(Z = 22) to Zn(Z = 30) from the L₃ linewidths is valid only when the L₃ linewidth is dominated by the L₃-M₄₅M₄₅ Auger decay process.     

Many body shake up in X-ray photoemission from bundles of lithium-intercalated single-walled carbon nanotubes

We present a model to describe the asymmetric features of X-ray photoemission spectra from bundles of clean and Li-intercalated single-walled carbon nanotubes due to shake up processes in both metallic and semiconducting bands, with energy gaps below ∼1 eV. Using the tight binding method, we determine the effect of the suddenly created core hole - in the 1s-state of a carbon atom - on the many electron states of π and π^∗ bands. We compute the energy distributions of many body excitations created at the expense of the photoelectron energy in (10, 10) and (16, 0) tubes, thus, obtaining an merit function for the X-ray photo-peak, resulting from the superposition of a symmetric and an asymmetric components. The latter describes to the average behavior of shake up electrons in tubes of different chirality and changes with the concentration of dopants.     

Many body theory of THz intervalence gain in quantum wells

This paper presents calculations of THz gain in III–V quantum wells based on transitions between the valence bands. The system is out of equilibrium and the optical susceptibility leading to absorption and gain is calculated after a Keldysh nonequilibrium Greens’ functions approach. The relevance of many body and nonresonant contribution to the spectrum is discussed as a function of local population inversion in k-space for a system where the injected holes are distributed within the two lowest subbands without global population inversion.     

Many body theory of magnetic susceptibility of bloch electrons

We present a theory of the total susceptibility (χ) of solids using a finite temperature Green's function formalism. The many body effects on orbital (χ_o), spin (χ_s) and spin-orbit (χ_s-o) contributions to χ are calculated. Our expression for χ_s is equivalent to the earlier results but with the g-factor replaced by the effective g-factor. An important aspect of our work is the analysis of many body effects on χ_s?o.     

Renormalization of a quadratic interaction in the Hamiltonian formalism

The method of the dressing transformation is used to perform a mass renormalization of a neutral scalar free field in the Hamiltonian formalism, for arbitrary space dimension. The resulting situation is analyzed by means of a Bogoliubov transformation, and seen to yield the expected results.Laboratoire associé au C.N.R.S.     

Measurement theory in the Lax-Phillips formalism

It is shown that the application of the Lax-Phillips scattering theory to quantum mechanics provides a natural framework for the realization of the ideas of the Many-Hilbert-Space theory of Machida and Namiki to describe the development of decoherence in the process of measurement. We show that if the quantum mechanical evolution is pointwise in time, then decoherence occurs only if the Hamiltonian is time-dependent. If the evolution is not pointwise in time (as in Liouville space), then the decoherence may occur even for closed systems. These conclusions apply as well to the general problem of mixing of states.     

Quantization of Podolsky theory in the BFV formalism

We quantize the Podolsky electromagnetic theory by using the BFV formalism. We consider the Lorentz gauge and since the theory exhibits higher derivatives it is possible to have two kinds of such gauge. The quantization is carried out in both of them.     

On the theory of internal photoemission in heterojunctions

The theory of internal photoemission in semiconductor heterojunctions has been reviewed and the existing model has been extended by incorporating the effects of the difference in the effective masses in the active region and the substrate, nonspherical-nonparabolic bands, and the energy loss per collisions. This complete model has been applied to describe the experimental results obtained from Si_1−xGe_x/Si heterojunction infrared photodetectors. The barrier heights (correspondingly the cut-off wavelengths) of SiGe/Si samples have been determined from their internal photoemission spectra by using the extended model which has the wavelength and doping concentration dependent free carrier absorption parameters. Fowler analysis showed that the model is in good agreement with the experiments for the entire spectrum.     

Reparametrization-invariant Hamiltonian formalism in the general theory of relativity

A method is proposed that is appropriate for resolving the Hamiltonian constraint and which leads to a reparametrization-invariant reduced theory specified by a well-defined nonzero local Hamiltonian. This method is based on introducing a global (dependent only on time) conformal variable. The physical and geometric meaning of the variables in the reduced action functional is investigated. It is shown that, within the theory, the method of small perturbations is self-consistent. It is demonstrated that, in the theory of gravity, there are no wavelike excitations that make a negative contribution to the Hamiltonian. From an analysis of the reduced classical theory in the linear approximation, it follows that, at the first instants from the birth of the Universe, the extremely rigid equation of state appeared to be the effective equation of the state of gravity matter.     

S-matrix theory and the density matrix formalism

A general equation governing the time development of the diagonal part of the density matrix is proposed for weakly interacting systems possessing no off-diagonal long range order. This equation, which involves generalized Møller operators of the type employed in S-matrix theory, is solved for two cases and leads to the generalized Pauli and Boltzmann equations.     

Many body generalization of the Landau-Zener problem

We formulate and approximately solve a specific many body generalization of the Landau-Zener problem. Unlike with the single particle Landau-Zener problem, our system does not abide in the adiabatic ground state, even at very slow driving rates. The structure of the theory suggests that this finding reflects a more general phenomenon in the physics of adiabatically driven many particle systems. Our solution can be used to understand, for example, the behavior of two-level systems coupled to an electromagnetic field, as realized in cavity QED experiments.     

A finite-dimensional canonical formalism in the classical field theory

A canonical formalism based on the geometrical approach to the calculus of variations is given. The notion of multi-phase space is introduced which enables to define whole the canonical structure (physical quantities, Poisson bracket, canonical fields) without use of functional derivatives. All definitions are of pure geometrical (finite dimensional) character.The observable algebra (physical quantities algebra) obtained here is much smaller then the algebra of all (sufficiently smooth) functionals on the space of states, derived from the standard infinite-dimensional formulation. As it is known, the latter is much too large for purposes of quantization. As the examples prove, our algebra could be an adequate start-point for quantization.For simplifying the language the notion of observable-valued distribution is introduced. Many concrete physical examples are given. E.g. it is shown that some problems connected with gauge in electrodynamics are automatically solved in this approach. The introduced language allows to obtain the Noether theorem in a most natural way.     

Gauge-invariant bilocal formalism in quantum field theory

A gauge-invariant continuation of the S-matrix generating functional outside the mass shell is proposed. A generating functional of gauge-invariant Green functions is obtained. Using the path integral formalism, collective gauge-invariant bilocal field variables are introduced. With the aid of the bilocal formalism, an integral equation is obtained for the gauge-invariant spinor propagator. It is shown that the propagator of the bilocal field corresponds to the gauge-invariant wave function of a two-particle system in ladder approximation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 105–111, April, 1990.The authors thank A. N. Sisakyan, N. B. Skachkov, and O. Yu. Shevchenko for their interest to this work and useful discussions of the obtained results.