Symmetry breaking and fluctuations within stochastic mean-field dynamics: Importance of initial quantum fluctuations

Lacroix, Denis; Ayık, S.; Yilmaz, B.

doi:10.1103/physrevc.85.041602

Cited by 30 publications

(53 citation statements)

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“…In nuclear physics this approach, called stochastic mean field [36], has been originally introduced such that initial fluctuations in collective space are reproduced through arXiv:1609.01424v2 [nucl-th] 21 Mar 2017 fluctuations of the initial one-body density. In a series of works, it was shown that it surprisingly well accounts for correlations beyond mean-field [37][38][39] while treating properly the dynamic close to a spontaneous symmetry breaking [38]. It is also able to include approximately many-body correlation to all orders by connecting the evolution to the BBGKY hierarchy [40].…”

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confidence: 99%

Microscopic Phase-Space Exploration Modeling ofFm258Spontaneous Fission

2017

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We show that the total kinetic energy (TKE) of nuclei after the spontaneous fission of 258 Fm can be well reproduced using simple assumptions on the quantum collective phase-space explored by the nucleus after passing the fission barrier. Assuming energy conservation and phase-space exploration according to the stochastic mean-field approach, a set of initial densities is generated. Each density is then evolved in time using the nuclear time-dependent density-functional theory with pairing. This approach goes beyond mean-field by allowing spontaneous symmetry breaking as well as a wider dynamical phase-space exploration leading to larger fluctuations in collective space. The total kinetic energy and mass distributions are calculated. New information on the fission process: fluctuations in scission time, strong correlation between TKE and collective deformation as well as pre-scission particle emission, are obtained. We conclude that fluctuations of TKE and mass are triggered by quantum fluctuations.PACS numbers: 21.60. Jz, 24.75.+i, 25.85.Ca, 27.90.+b The dynamical modeling of a nuclear Fermi quantum droplet that spontaneously breaks into two pieces represents one of the most exciting challenges of nuclear physics today. Beside its description, a deeper microscopic understanding of spontaneous fission (SF) is of great importance to form the heaviest elements at the frontier of the nuclear chart [1][2][3] or to further improve our knowledge about the competition between the r-process and fission during the primordial nucleosynthesis [4]. Motivated also by its importance in nuclear energy production, intensive experimental efforts have been made to accumulate precise measurements [5][6][7][8][9]. In recent years, an increasing effort was made to remove empirical ingredients that are employed in macroscopic modeling of fission and use microscopic theories [10,11]. The nuclear Density Functional Theory (DFT) is a suitable starting point to describe some aspects related to the large amplitude collective motion (LACM). A minimal information obtained from DFT is the adiabatic collective energy landscape [11]. One challenge to describe spontaneous fission (SF) is the necessity to explicitly treat the evolution as a quantum dynamic in collective space. Progresses have been made with the Time-Dependent Generator Coordinate Method (TDGCM) [12][13][14]. This theory by treating quantally collective degrees of freedom (DOF) is promising. However, the adiabatic assumption often made becomes critical especially close to scission [15]. Dissipation of the collective motion into internal excitations also plays a key role to understand the excitation energy and kinetic energy sharing during fragments separation [16]. Understanding this dissipation requires to include many-body states beyond the adiabatic limit [17]. It is yet unclear how the pre-scission neutron and proton emissions can be incorporated in the TDGCM.The nuclear time-dependent DFT (TDDFT) overcomes some of these limitations. With recently developed symmetry unrest...

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Microscopic Phase-Space Exploration Modeling ofFm258Spontaneous Fission

2017

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“…These transport coefficients have similar form with those that are familiar from phenomenological nucleon exchange model [16], but provide a more refined description for transport mechanism. In a recent application, the SMF approach is tested with Lipkin-Meshkov-Glick model, and it is found that the gross properties of the model are well produced in the SMF approach [17]. The SMF approach was also extended by including pairing interaction [18].…”

Section: Introductionmentioning

confidence: 99%

Nucleon exchange in heavy-ion collisions within a stochastic mean-field approach

et al. 2014

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Nucleon exchange mechanism is investigated in deep-inelastic symmetric heavy-ion collisions in the basis of the Stochastic Mean-Field approach. By extending the previous work to off-central collisions, analytical expression is deduced for diffusion coefficient of nucleon exchange mechanism. Numerical calculations are carried out for 40 Ca + 40 Ca and 90 Zr + 90 Zr systems and the results are compared with the phenomenological nucleon exchange model. Also, calculations are compared with the available experimental results of deep-inelastic collisions between calcium nuclei.

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“…x (t), σ 2 y (t) and ∆ 2 z (t), respectively. In each case, results of the SMF simulations are shown with triangles (σ 2 x ), squares (σ 2 y ) and circles (σ 2 z ) (taken from [3]). …”

Section: Many-body Dynamics Near a Saddle Pointmentioning

confidence: 99%

“…Starting from the statistical properties (6) and (7), it could be shown that the quasi-spins should be initially sampled according to Gaussian probabilities with first moments given by [3] …”

Section: Many-body Dynamics Near a Saddle Pointmentioning

confidence: 99%

“…We have recently shown that a stochastic mean-field (SMF) approach [1,2] where the TDHF evolution is replaced by a set of mean-field evolution with properly chosen initial conditions. It will be shown that this approach can be a suitable tool to go beyond mean-field and describe the evolution of a system close to a quantum phase-transition [3]. In a series of article, we applied the SMF approach to describe transport properties in fusion reaction.…”

Section: Introductionmentioning

confidence: 99%

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Large amplitude motion with a stochastic mean-field approach

Lacroix

Ayık

Yilmaz

et al. 2012

EPJ Web of Conferences

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Abstract. In the stochastic mean-field approach, an ensemble of initial conditions is considered to incorporate correlations beyond the mean-field. Then each starting point is propagated separately using the Time-Dependent Hartree-Fock equation of motion. This approach provides a rather simple tool to better describe fluctuations compared to the standard TDHF. Several illustrations are presented showing that this theory can be rather effective to treat the dynamics close to a quantum phase transition. Applications to fusion and transfer reactions demonstrate the great improvement in the description of mass dispersion.

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Symmetry breaking and fluctuations within stochastic mean-field dynamics: Importance of initial quantum fluctuations

Cited by 30 publications

References 31 publications

Microscopic Phase-Space Exploration Modeling ofFm258Spontaneous Fission

Microscopic Phase-Space Exploration Modeling ofFm258Spontaneous Fission

Nucleon exchange in heavy-ion collisions within a stochastic mean-field approach

Large amplitude motion with a stochastic mean-field approach

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