Stochastic aspects of large amplitude collective motion

Bulgac, Aurel; Dang, G. Do; Kusnezov, Dimitri

doi:10.1016/0370-1573(95)00028-3

Cited by 7 publications

(3 citation statements)

References 40 publications

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“…In nuclei the level density increases with the excitation energy quite fast, practically exponentially at energies of the order of the neutron separation energy, when ρ(E * ) ∝ exp √ 2aE * [54,55], and it reaches values of O(10 5 ) MeV −1 and various potential energy surfaces, corresponding to different "molecular terms" display a large number of avoided level crossings, see Ref. [56]. analysis strongly violated.…”

Section: The Presentmentioning

confidence: 99%

Nuclear Fission Dynamics: Past, Present, Needs, and Future

2020

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Recent developments in theoretical modeling and in computational power have allowed us to make significant progress on a goal not achieved yet in nuclear theory: a fully microscopic theory of nuclear fission. The complete microscopic description remains a computationally demanding task, but the information that can be provided by current calculations can be extremely useful to guide and constrain phenomenological approaches. First, a truly microscopic framework that can describe the real-time dynamics of the fissioning system can justify or rule out assumptions and approximations incompatible with an accurate quantum treatment or with our understanding of the inter nucleon interactions. Second, the microscopic approach can be used to obtain trends such as: the excitation energy sharing mechanism between fission fragments (FFs) with increasing excitation energy of the fissioning system, the angular momentum content of the FFs, or even to compute observables that cannot be otherwise calculated in phenomenological approaches or even measured, as in the case of astronomical environments. Merely the characterization of the trends would be of great importance for various application. We present here arguments that a truly microscopic approach to fission does not support the assumption of adiabaticity of the large amplitude collective motion in fission, particularly starting from the outer saddle down to the scission configuration. Such an assumption legitimize the introduction of a collective potential energy surface and inertia tensor, which are the essential elements of many simpler theoretical approaches. The nuclear shape evolution it is paradoxically 3...4 times slower than it would have been in the case of a pure adiabatic motion, and it is strongly overdamped. We demonstrate that the FFs properties are defined only after the FFs become separated significantly from each other. I. THE PASTIn a matter of days after Hahn and Strassmann [1] communicated their yet unpublished results to Lise Meitner, she and her nephew Otto Frisch [2] understood that an unexpected and qualitatively new type of nuclear reaction has been put in evidence and they dubbed it nuclear fission, in analogy to cell divisions in biology. Until that moment in time nuclear fission was considered a totally unthinkable process [3,4], "as excluded by the small penetrability of the Coulomb barrier [5], indicated by the Gamov's theory of alpha-decay" [2]. Meitner and Frisch [2] also gave the correct physical interpretation of the nuclear fission mechanism. They understood that Bohr's compound nucleus [6] is formed after the absorption of a neutron, which eventually slowly evolves in shape, while the volume remains constant, and that the competition between the surface energy of a nucleus and its Coulomb energy leads to the eventual scission. Meitner and Frisch [2] also correctly estimated the total energy released in this process to be about 200 MeV. A few months later Bohr and Wheeler [7] filled in all the technical details and the long road to develo...

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Section: The Presentmentioning

confidence: 99%

Nuclear Fission Dynamics: Past, Present, Needs, and Future

2020

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“…The giant dipole resonance, for example, constitutes a regular oscillation of the protons against the neutrons albeit it is excited at energies where the spectrum displays fluctuations which are typical for chaotic systems [3]. This interesting interplay of collective and chaotic motion and the effects of chaotic dynamics on the damping and dissipation of nuclear excitations is a matter of intense research [4][5][6][7][8][9][10][11][12][13][14] but still not fully understood.…”

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confidence: 99%

Collective and chaotic motion in self-bound many-body systems

Papenbrock

2000

Phys. Rev. C

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We investigate the interplay of collective and chaotic motion in a classical self-bound N-body system with two-body interactions. This system displays a hierarchy of three well separated time scales that govern the onset of chaos, damping of collective motion and equilibration. Comparison with a mean-field problem shows that damping is mainly due to dephasing. The Lyapunov exponent, damping and equilibration rates depend mildly on the system size N.Comment: 5 pages, 4 EPS-figures, uses psfig.sty, revised versio

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“…In the last decades several papers have been published on the subject, see for example refs. [4][5][6][7][8][9]11,10,[13][14][15][16]. The most studied case is the extreme adiabatic limit, namely when the ratio between the characteristic times of the fast degrees of freedom and of the slow one is considered arbitrary small.…”

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confidence: 99%

One-body dissipation and chaotic dynamics in a classical simulation of a nuclear gas

et al. 1998

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In order to understand the origin of one-body dissipation in nuclei, we analyze the behavior of a gas of classical particles moving in a two-dimensional cavity with nuclear dimensions. This “nuclear” billiard has multipole-deformed walls which undergo periodic shape oscillations. We demonstrate that a single-particle Hamiltonian containing coupling terms between the particle motion and the collective coordinate induces a chaotic dynamics for any multipolarity, independently of the geometry of the billiard. If the coupling terms are switched off, the “wall formula” predictions are recovered. We discuss the dissipative behavior of the wall motion and its relation to the order-to-chaos transition in the dynamics of the microscopic degrees of freedom

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Stochastic aspects of large amplitude collective motion

Cited by 7 publications

References 40 publications

Nuclear Fission Dynamics: Past, Present, Needs, and Future

Nuclear Fission Dynamics: Past, Present, Needs, and Future

Collective and chaotic motion in self-bound many-body systems

One-body dissipation and chaotic dynamics in a classical simulation of a nuclear gas

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