scholarly journals Renormalization of the 2PI-Hartree approximation in a broken phase with nonzero superflow

2014 ◽  
Vol 90 (11) ◽  
Author(s):  
G. Fejős

Leaving out of consideration those nuclei of small atomic number it is possible to develop a statistical theory of nuclei. Bethe and Bacher (1936, p. 149), as well as many other writers, have treated this subject in great detail starting from the Hartree approximation. All these investigations were mainly concerned with the binding energy, and not much attention has been paid so far to the stability of nuclei according to the statistical theory, except the determination of the most stable nucleus with a given atomic number: this is due to the fact that previous investigators have always neglected to distinguish between quantum states with opposite spin, thereby losing the distinction between “odd” and “even” nuclei, which is essential for stability considerations.


2005 ◽  
Vol 15 (08) ◽  
pp. 1253-1272 ◽  
Author(s):  
L. L. BONILLA ◽  
R. ESCOBEDO

A Wigner–Poisson kinetic equation describing charge transport in doped semiconductor superlattices is proposed. Electrons are assumed to occupy the lowest miniband, exchange of lateral momentum is ignored and the electron–electron interaction is treated in the Hartree approximation. There are elastic collisions with impurities and inelastic collisions with phonons, imperfections, etc. The latter are described by a modified BGK (Bhatnagar–Gross–Krook) collision model that allows for energy dissipation while yielding charge continuity. In the hyperbolic limit, nonlocal drift-diffusion equations are derived systematically from the kinetic Wigner–Poisson–BGK system by means of the Chapman–Enskog method. The nonlocality of the original quantum kinetic model equations implies that the derived drift-diffusion equations contain spatial averages over one or more superlattice periods. Numerical solutions of the latter equations show self-sustained oscillations of the current through a voltage biased superlattice, in agreement with known experiments.


1987 ◽  
Vol 36 (6) ◽  
pp. 1922-1928 ◽  
Author(s):  
M. Schaden ◽  
St. Glazek ◽  
E. Werner

Author(s):  
Marek S. Wartak ◽  
Ching-Yao Fong

We have used the quantum theory of radiation, within the time-dependent Hartree approximation, to study exciton states of a van der Waals molecular crystal. The radiation variables are eliminated to give a semi-classical picture of molecular dipoles interacting through a retarded potential, and the solutions of the Hartree equations are closely connected with the quasi-particle excited states in Agranovich’s theory. In the Lorentz-Lorenz approximation the crystal has excited states which correspond to both longitudinal and transverse exciton weaves, and the refractive index behaves classically. The paper concludes with a brief discussion of metallic reflexion by dye crystals.


1998 ◽  
Vol 57 (3) ◽  
pp. 1458-1463 ◽  
Author(s):  
Amand Faessler ◽  
A. J. Buchmann ◽  
M. I. Krivoruchenko

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