Unitary evolution with fluctuations and dissipation

Bulgac, Aurel; Jin, Shi; Stetcu, Ionel

doi:10.1103/physrevc.100.014615

Cited by 41 publications

(36 citation statements)

References 78 publications

(109 reference statements)

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“…As we have established in Ref. [78] the fluctuations, or equivalently the role of two-body collisions, does not affect this conclusion.…”

Section: What Lessons Have We Learned So Far and What Is The Mostsupporting

confidence: 52%

“…In particular, the excitation energy sharing mechanism between FFs and its evolution with the initial excitation energy of the compound nucleus was not accessible until now within a dynamic approach. Fluctuations, which are essential in order to reproduce mass and charge yields for example, can be now incorporated into a pure quantum framework [78].…”

Section: What Lessons Have We Learned So Far and What Is The Mostmentioning

confidence: 99%

“…7 and Ref. [78], the inclusion of which likely is going to influence the angular momentum distributions of the FFs [82].…”

Section: What Lessons Have We Learned So Far and What Is The Mostmentioning

confidence: 99%

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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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“…As we have established in Ref. [78] the fluctuations, or equivalently the role of two-body collisions, does not affect this conclusion.…”

Section: What Lessons Have We Learned So Far and What Is The Mostsupporting

confidence: 52%

Section: What Lessons Have We Learned So Far and What Is The Mostmentioning

confidence: 99%

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

2020

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“…R defines the transformation between the original basis and the rotated basis in gauge-space. In the specific case considered here, we have [13,16,17]:…”

Section: A Generating Functions For Quasi-particle Vacuummentioning

confidence: 99%

“…The generating function is intimately connected to the projection operator approach [10,11] that is standardly used nowadays in the nuclear many-body context. The problem of selecting a finite volume turns out to be rather similar to the problem addressed recently in nuclear reactions where the projection operator technique has been used [12][13][14][15][16][17]. We will use here this technique as a starting point focusing on the static properties of a single Fermi system.…”

Section: Introductionmentioning

confidence: 99%

Counting statistics in finite Fermi systems: Illustrations with the atomic nucleus

Lacroix

Ayık

2020

Phys. Rev. C

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We analyze here in details the probability to find a given number of particles in a finite volume inside a normal or superfluid finite system. This probability, also known as counting statistics, is obtained using projection operator techniques directly linked to the characteristic function of the probability distribution. The method is illustrated in atomic nuclei. The nature of the particle number fluctuations from small to large volumes compared to the system size are carefully analyzed in three cases: normal systems, superfluid systems and superfluid systems with total particle number restoration. The transition from Poissonian distribution in the small volume limit to Gaussian fluctuations as the number of particles participating to the fluctuations increases, is analyzed both in the interior and at the surface of the system. While the restoration of total number of particles is not necessary for small volume, we show that it affects the counting statistics as soon as more than very few particles are involved.

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Time‐Dependent Density Functional Theory for Fermionic Superfluids: From Cold Atomic Gases − To Nuclei and Neutron Stars Crust

Bulgac

2019

Physica Status Solidi (b)

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In cold atoms and in the crust of neutron stars, the pairing gap can reach values comparable with the Fermi energy. While in nuclei the neutron gap is smaller, it is still of the order of a few percent of the Fermi energy. The pairing mechanism in these systems is due to short range attractive interactions between fermions and the size of the Cooper pair is either comparable to the inter-particle separation or it can be as big as a nucleus, which is still relatively small in size. Such a strong pairing gap is the result of the superposition of a very large number of particle-particle configurations, which contribute to the formation of the Cooper pairs. These systems have been shown to be the host of a large number of remarkable phenomena, in which the large magnitude of the pairing gap plays an essential role: quantum shock waves, quantum turbulence, Anderson-Bogoliubov-Higgs mode, vortex rings, domain walls, soliton vortices, vortex pinning in neutron star crust, unexpected dynamics of fragmented condensates and role of pairing correlations in collisions on heavy-ions, Larkin-Ovchinnikov phase as an example of a Fermi supersolid, role of pairing correlations in controlling the dynamics of fissioning nuclei.Two prevailing theoretical models are used to describe the dynamics of superfluids. The oldest is the Landau two-fluid hydrodynamics, [9,10] which at zero-temperature reduces to the hydrodynamics of a single perfect classical fluid, [11,12] namely of the superfluid component alone. Naturally, in such a formalism Planck's constant is absent and the two-fluid hydrodynamics is unable to describe the formation of quantized vortices, [13] their dynamics, their crossing, and recombination, which is at the

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Unitary evolution with fluctuations and dissipation

Cited by 41 publications

References 78 publications

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

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

Counting statistics in finite Fermi systems: Illustrations with the atomic nucleus

Time‐Dependent Density Functional Theory for Fermionic Superfluids: From Cold Atomic Gases − To Nuclei and Neutron Stars Crust

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