1,593 research outputs found
Dynamic structure factor and collective excitations of neutral and Coulomb fluids
The dynamic sructure factor as the basic quantity describing the collective
excitations in a fluid is considered. We consider the cases of neutral and
Coulombic fluids. The classical method of moments is applied to construct the
dynamic structure factor satisfying all known sum rules. An interpolational
formula is found which expresses the dynamic characteristics of a classical or
quantum fluid system in terms of its static correlation parameters. The
analytical results based on the theory of moments are compared with Molecular
dynamics data for various model systems.Comment: 20 pages, 4 figures, to be published in Physica Script
Ground-state energy of a high-density electron gas in a strong magnetic field
The high-density electron gas in a strong magnetic field B and at zero
temperature is investigated. The quantum strong-field limit is considered in
which only the lowest Landau level is occupied. It is shown that the
perturbation series of the ground-state energy can be represented in analogy to
the Gell-Mann Brueckner expression of the ground-state energy of the field-free
electron gas. The role of the expansion parameter is taken by instead of the field-free Gell-Mann Brueckner
parameter r_s.Comment: 4 pages, 2 figures, to appear in the proceedings of the 1999
International Conference on Strongly Coupled Coulomb Systems (St.Malo
The use of relativistic action in strong-field nonlinear photoionization
Nonlinear relativistic ionization phenomena induced by a strong linearly
polarized laser field are considered. The starting point is the classical
relativistic action for a free electron moving in the electromagnetic field
created by a strong laser beam. This action has been used to calculate
semiclassical transition rates. Simple analytical expressions for the
ionization rate, the photoelectron emission velocity and for the drift momentum
distribution of the photoelectron have been found. The analytical formulas
apply to nonrelativistic bound systems as well as to initial states with an
energy corresponding to the upper boundary of the lower continuum and to the
tunnel as well as the multiphoton regime. In the case of a nonrelativistic
bound system we recover the Keldysh formula for the ionization rate.
Relativistic effects in the initial state lead to a weak enhancement of the
rate of sub-barrier ionization and to the appearance of a nonzero photoelectron
leaving velocity.Comment: 6 pages, 2 figure
Development of protective coatings for tantalum T-22 alloy Final summary report
Oxidation resistance tests of protective coatings for tantalum allo
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