Multifragmentation of hot and compressed nuclei within a time dependent thomas fermi and percolation model

Németh, J.; Barranco, M.; Desbois, J.; Ngo, Cheryl

doi:10.1007/bf01294619

Cited by 8 publications

(10 citation statements)

References 25 publications

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“…Similar results have been observed before in proton induced reactions between ~ 2 and 350 GeV [1,2]. 3. Emulsion experiments directly show events where the system breaks up into several pieces.…”

Section: Introductionsupporting

confidence: 84%

Multifragmentation of excited nuclei within a schematic hydrodynamical and percolation picture

Desbois

Boisgard

Ngô

et al. 1987

Z. Physik A - Atomic Nuclei

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We present a simple model to describe the evolution of hot and compressed nuclei. It is based on irrotational hydrodynamics and a 3-dimensional site-bond percolation model. Hydrodynamics is used if the evolution of the system is dominated by the mean field. This situation occurs when the fluctuations of the mean field are small. These latter are evaluated using the percolation model. In some cases it turns out that these fluctuations become very large and the system breaks up into several pieces (multifragmentation). The results of this process are described by the percolation model. We have obtained analytical or fitted expressions for all the results which compare well with those obtained in a previous and more involved model based on the same physical ideas. In particular we found that a noncompressed nucleus undergoes multifragmentation if the thermal excitation energy is larger than 70% of its binding energy. If the nucleus is compressed this value is notably decreased.

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Section: Introductionsupporting

confidence: 84%

Multifragmentation of excited nuclei within a schematic hydrodynamical and percolation picture

Desbois

Boisgard

Ngô

et al. 1987

Z. Physik A - Atomic Nuclei

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“…Lattice percolation has been extensively used to describe multifragmentation of nuclei [10,11,17,18]. In the first approaches [10,11] it is supposed that multifragmentation is a critical phenomenon which can be described by lattice percolation.…”

Section: Percolation Models a Lattice Percolationmentioning

confidence: 99%

“…Three kinds of percolation approaches have been used, all based on a cubic lattice: bond percolation [10], site percolation [10] and sitebond percolation [11]. Phenomenological attempts have been done in [17,18] using site-bond lattice percolation on a cubic lattice coupled to a mean field calculation (time dependent Thomas Fermi calculation [17] or expanding liquid drop model [18]). In these first approaches there was no connection between the percolation parameters and the physical quantities of the nuclear physics problem but just an analogy that, in both cases, a critical phenomenon takes place.…”

Section: Percolation Models a Lattice Percolationmentioning

confidence: 99%

“…At the critical point these models give an inclusive mass distribution following a power law, a characteristic in good agreement with the experimental observations although one is not sure that the whole measured mass distribution comes fi'om multifragmentation. We shall not describe the principle of lattice percolation simulations since this subject is treated in a large number of papers [10,11] and has been extensively used in nuclear physics to understand multifragmentation [ 10,11,17,18]. Phenomenological attempts have been done in [17,18] using site-bond lattice percolation on a cubic lattice coupled to a mean field calculation (time dependent Thomas Fermi calculation [17] or expanding liquid drop model [18]).…”

Section: Percolation Models a Lattice Percolationmentioning

confidence: 99%

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Scaling properties of percolation models for multifragmentation

Ngô

Ighezou

et al. 1990

Z. Physik A - Atomic Nuclei

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We have used scaling properties of nuclear multifragmentation, which have been observed with emulsion data, to investigate the properties of some approaches based on percolation. We have studied different percolation models on a cubic lattice and shown that they can rather well reproduce the data except for binary break up. We have described what the mean field approximation would give in this context and showed that it cannot reproduce the experimental results. Most of the paper is focused on the restructured aggregation model introduced earlier which allows to well reproduce the scaling properties observed experimentally. This model has been studied in details and extended to take account of bonds breaking. It is shown that, in some cases, a nucleus can break up in two pieces. This process cannot be obtained in conventional percolation or aggregation but is observed experimentally in the emulsion data. Other features like the dimensionality of the aggregation model, the restructuration of the clusters and a schematic constraint in momentum space have also been investigated. 25.70.Np It is now well established that a lot of intermediate mass fragments can be produced in central heavy ion collisions at intermediate and high bombarding energies [-1]. One possible mechanism is that the interacting system breaks up into several pieces. This process is called multifragmentation. It was first observed in proton induced reactions at bombarding energies larger than a few GeV [2]. How and why nuclei break up is an open problem which has received a considerable theoretical attention within the last few years [1].Several models based, at first sight, on different grounds have been proposed to explain nuclear multifragmentation. A major problem in this field is a lack * Unit6 de Recherche des Universit6s de Paris XI et Paris VI asso-ci6e au CNRS of exclusive experiments which prevents any serious comparison between experiment and theory. In line measurements, using detectors and electronic devices, have only shown that three or four intermediate mass fragments can be produced in heavy ion collisions [3] but we are far from a complete identification of the fragments emitted during the break up of the system. We also do not know experimentally which part of the total reaction cross section is associated to multifragmentation for a given system and bombarding energy. Some phenomenological models predict .these quantities [4] but experimental results are still missing. One quantitative information of in line experiments is the inclusive mass distribution of the intermediate mass fragments which follows, in most of the cases, a power law A-~, where A is the fragment mass and ~ an exponent which takes values between 2 and 4 depending on the system [5]. This behaviour was taken as an evidence of a gas-liquid phase transition near the critical point. Nevertheless, it should be noted that exponential distributions have also been observed at ultrarelativistic energies [5]. Since other theoretical models predict also a power law f...

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“…[22][23][24][25][26][27] The work of Runge and Gross on time-dependent DFT (TDDFT) lays the formal foundations for TDOF, 28 and there have been practical simulations which use the static OFDFT potential in studying metal and fullerene clusters. 29 Formally it is possible to relate the TDDFT and TDOF potentials; this can be done directly, as shown in Appendix.…”

Section: Introductionmentioning

confidence: 99%

Dynamic kinetic energy potential for orbital-free density functional theory

Neuhauser

Pistinner

Coomar

et al. 2011

The Journal of Chemical Physics

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A dynamic kinetic energy potential (DKEP) is developed for time-dependent orbital-free (TDOF) density function theory applications. This potential is constructed to affect only the dynamical (ω ≠ 0) response of an orbital-free electronic system. It aims at making the orbital-free simulation respond in the same way as that of a noninteracting homogenous electron gas (HEG), as required by a correct kinetic energy, therefore enabling extension of the success of orbital-free density functional theory in the static case (e.g., for embedding and description of processes in bulk materials) to dynamic processes. The potential is constructed by expansions of terms, each of which necessitates only simple time evolution (concurrent with the TDOF evolution) and a spatial convolution at each time-step. With 14 such terms a good fit is obtained to the response of the HEG at a large range of frequencies, wavevectors, and densities. The method is demonstrated for simple jellium spheres, approximating Na(9)(+) and Na(65)(+) clusters. It is applicable both to small and large (even ultralarge) excitations and the results converge (i.e., do not blow up) as a function of time. An extension to iterative frequency-resolved extraction is briefly outlined, as well as possibly numerically simpler expansions. The approach could also be extended to fit, instead of the HEG susceptibility, either an experimental susceptibility or a theoretically derived one for a non-HEG system. The DKEP potential should be a powerful tool for embedding a dynamical system described by a more accurate method (such as time-dependent density functional theory, TDDFT) in a large background described by TDOF with a DKEP potential. The type of expansions used and envisioned should be useful for other approaches, such as memory functionals in TDDFT. Finally, an appendix details the formal connection between TDOF and TDDFT.

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Multifragmentation of hot and compressed nuclei within a time dependent thomas fermi and percolation model

Cited by 8 publications

References 25 publications

Multifragmentation of excited nuclei within a schematic hydrodynamical and percolation picture

Multifragmentation of excited nuclei within a schematic hydrodynamical and percolation picture

Scaling properties of percolation models for multifragmentation

Dynamic kinetic energy potential for orbital-free density functional theory

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