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Equations of nuclear motion are derived from a time-dependent variational principle. They have the same form as the equations of classical hydrodynamics for irrotational flow, and can described motions with arbitrary amplitudes. The theory also gives an equation of state for the nuclear medium. 相似文献
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The effect of intrinsic degrees of freedom on tunneling through a potential barrier is discussed using a BKW-like approximation. In the present work intrinsic degrees of freedom are represented by a single harmonic oscillator. The theory leads to a formula for the effect of the coupling on the decay width Γ of a metastable state. When the frequency ω of the intrinsic degree of freedom is large, then Γ → Γad where Γad is the decay width calculated with the adiabatic barrier. An inequality Γ ≤ Γad is proved for any form of the coupling hamitonian. Corrections are discussed and are shown to be of order where M is the mass of the tunneling coordinate. An application to fission is considered. The generalization of our formula for Γ to the case of many intrinsic degrees of freedom is given explicitly. 相似文献
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By expanding the overlap and the hamiltonian kervels in the Hill-Wheeler equation into a series of hermitian differential operators, expressions for the collective potential and mass parameter are derived. 相似文献
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Green functions techniques at finite temperature are used to calculate nuclear partition functions in the random phase approximation. The theory is shown to yield corrections to the results of functional methods neglecting exchange terms. We discuss the special case of a schematic model for which the level density and the temperature dependence of collective states can be worked out explicitly. 相似文献
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Using a microscopic formalism and taking fully nto account the Pauli principle, we compute the interaction potential between two 40Ca nuclei as a function of their interdistance and their deformation. We attempt an analysis of our results within the proximity formalism and we point out some difficulties. We also extract the coupling parameter between the radial motion of the ions and the excitations of their giant quadrupole modes. 相似文献
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G. Baym J.-P. Blaizot M. Holzmann F. Laloë D. Vautherin 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(1):107-124
We study the effects of repulsive interactions on the critical density for the Bose-Einstein transition in a homogeneous dilute
gas of bosons. First, we point out that the simple mean field approximation produces no change in the critical density, or
critical temperature, and discuss the inadequacies of various contradictory results in the literature. Then, both within the
frameworks of Ursell operators and of Green's functions, we derive self-consistent equations that include correlations in
the system and predict the change of the critical density. We argue that the dominant contribution to this change can be obtained
within classical field theory and show that the lowest order correction introduced by interactions is linear in the scattering
length, a, with a positive coefficient. Finally, we calculate this coefficient within various approximations, and compare with various
recent numerical estimates.
Received 15 July 2001 相似文献
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J.Rayford Nix Arnold J. Sierk Helmut Hofmann Franz Scheuter Dominique Vautherin 《Nuclear Physics A》1984,424(2):239-261
By use of both analytical and numerical techniques, we study the relaxation of time-dependent solutions of the Fokker-Planck equation for an inverted oscillator to Kramers' stationary solution. This is done by integrating over all time the time-dependent solutions for given initial conditions at the saddle point to obtain stationary solutions, whose densities and higher velocity moments are compared as functions of the coordinate with the corresponding quantities calculated from Kramers' stationary solution. For large values of the coordinate an a symptotic expansion of the density is obtained, but for general values of the coordinate and for higher velocity moments the time integration must be done numerically. With increasing dissipation the relaxation to Kramers' stationary solution occurs at successively smaller values of the coordinate. By use of Kramers' stationary solution, we derive analytical expressions as functions of nuclear temperature and dissipation strength for several quantities of interest in fission dynamics, including the mean time from the saddle point to scission, the mean fission-fragment kinetic energy at the scission point and the contribution to the variance in the fission-fragment kinetic energy resulting from fluctuations in the fission degree of freedom. We apply these results to some examples that have been studied experimentally, including the mean saddle-to-scission time for the heavy-ion-induced fission of the compound nucleus 168Yb and the mean fission-fragment kinetic energy at scission and the contribution to its variance for the α-particle-induced fission of the compound nucleus 213At. 相似文献