Entropy in the nuclear caloric curve

Barrañón, Armando; Roa, Jesus Escamilla; López, Jörge A.

doi:10.1103/physrevc.69.014601

Cited by 23 publications

(21 citation statements)

References 33 publications

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“…The M D simulations presented provide further support to the scenario collision -isentropic expansion -spinodal decomposition put forward in [14]. The main results of this study is that the entropy produced in the initial stage of the reaction defines the trajectory that is followed by the compound nucleus in its expansion into the spinodal line where it disassembles.…”

Section: Discussionmentioning

confidence: 56%

“…S o is then set to the value needed to have equation (1) yield the appropriate value of S at point D (see [14] for details).…”

Section: Molecular Dynamics Simulationsmentioning

confidence: 99%

“…Using theoretical analysis and molecular dynamics simulations, a more recent study [14] investigated the question of what really determines the transition temperature in nuclear reactions. This article submits more supporting evidence to the premise advanced in that previous study.…”

Section: Introductionmentioning

confidence: 99%

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The transition temperature of the nuclear caloric curve

Barrañón¹,

Roa²,

López³

2004

Braz. J. Phys.

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Experimental studies have obtained the caloric curve of nuclear matter from heavy ion collisions as well as its dependence on the size of the fragmenting source. In particular it has been determined that smaller systems have caloric curves with higher plateau temperatures than larger systems. This work uses molecular dynamics simulations to study the thermodynamics of heavy ion collisions and to identify the main factors that determine the caloric curve. The simulations indicate that the reaction is composed of three stages: 1) an initial collision that transforms the nuclei from normal density and zero temperature and entropy, to a hot and dense blob of matter with higher values of density, temperature and entropy; 2) this is followed by a constant-entropy expansion that takes the system to the spinodal of the phase diagram; 3) where the system rapidly disassembles into fragments by the process of spinodal decomposition, and not by nucleation. These findings indicate that the plateau temperature of the caloric curve is nothing more than the temperature of the phase change and it is set by the intersection of the isentropic expansion and the spinodal. In other words, the plateau temperature is simply the temperature at which the system breaks as it enters the spinodal. This transition temperature is thus set by the entropy generated during the initial part of the collision.

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Section: Discussionmentioning

confidence: 56%

“…S o is then set to the value needed to have equation (1) yield the appropriate value of S at point D (see [14] for details).…”

Section: Molecular Dynamics Simulationsmentioning

confidence: 99%

See 1 more Smart Citation

The transition temperature of the nuclear caloric curve

Barrañón¹,

Roa²,

López³

2004

Braz. J. Phys.

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“…In the present work, we use a molecular dynamics (M D) model that can describe non-equilibrium dynamics, hydrodynamic flow and changes of phase without adjustable parameters. The combination of this M D code with a fragment-recognition algorithm, has been dubbed "Latino" [15], and in recent years it has been applied successfully to study, among other things, neck fragmentation [16], phase transitions [17], critical phenomena [18,19] and the caloric curve [20,21] in nuclear reactions.…”

Section: Molecular Dynamicsmentioning

confidence: 99%

Dynamical aspects of isoscaling

et al. 2006

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The origin and dynamical evolution of isoscaling was studied using classical molecular dynamics simulations of ${}^{40}$Ca + ${}^{40}$Ca, ${}^{48}$Ca + ${}^{48}$Ca, and ${}^{52}$Ca + ${}^{52}$Ca, at beam energies ranging from $20 \ MeV/A$ to $85 MeV/A$. The analysis included a study of the time evolution of this effect. Isoscaling was observed to exist in these reactions from the very early primary isotope distributions (produced by highly {\it non-equilibrated} systems) all the way to asymptotic times. This indicates that isoscaling is independent of quantum effects and thermodynamical equilibrium. In summary, collision-produced isoscaling appears to be due more to the mere partitioning of the proton-neutron content of the participant nuclei, than to specific details of the reaction dynamics

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“…The thermodynamics of the multifragment emission in nuclear reactions has been intensively investigated both experimentally [1,2,3,4,5] and theoretically [6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]. Particularly, the qualitative aspects of the nuclear caloric curve, such as the existence of a plateau, has been strongly debated [1,4,5,22,23,24,25,26,27,28,29,30,31,32,33].…”

Section: Introductionmentioning

confidence: 99%

Nuclear multifragmentation within the framework of different statistical ensembles

2006

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The sensitivity of the Statistical Multifragmentation Model to the underlying statistical assumptions is investigated. We concentrate on its micro-canonical, canonical, and isobaric formulations.As far as average values are concerned, our results reveal that all the ensembles make very similar predictions, as long as the relevant macroscopic variables (such as temperature, excitation energy and breakup volume) are the same in all statistical ensembles. It also turns out that the multiplicity dependence of the breakup volume in the micro-canonical version of the model mimics a system at (approximately) constant pressure, at least in the plateau region of the caloric curve. However, in contrast to average values, our results suggest that the distributions of physical observables are quite sensitive to the statistical assumptions. This finding may help deciding which hypothesis corresponds to the best picture for the freeze-out stage.

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Entropy in the nuclear caloric curve

Cited by 23 publications

References 33 publications

The transition temperature of the nuclear caloric curve

The transition temperature of the nuclear caloric curve

Dynamical aspects of isoscaling

Nuclear multifragmentation within the framework of different statistical ensembles

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