Reducibility and thermal scaling in nuclear multifragmentation

Moretto, L.G.; Ghetti, R.; Phair, L.; Tso, K.; Wozniak, G.J.

doi:10.1016/s0370-1573(97)00007-0

Cited by 78 publications

(107 citation statements)

References 88 publications

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“…could be extended by using a minimal, but crucial modification in their schemes to account for the existence of an anomalous regime with negative heat capacities C < 0 [1,2,3,4,5,6]. This fact avoids the incidence of the so-called super-critical slowing down, a dynamical anomaly that significantly affects the efficiency of large-scale canonical MC simulations [7].…”

Section: Introductionmentioning

confidence: 99%

Extending canonical Monte Carlo methods

Velázquez

Curilef

2010

J. Stat. Mech.

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In this work, we discuss the implications of a recently obtained equilibrium fluctuation-dissipation relation on the extension of the available Monte Carlo methods based on the consideration of the Gibbs canonical ensemble to account for the existence of an anomalous regime with negative heat capacities C < 0. The resulting framework appears as a suitable generalization of the methodology associated with the so-called dynamical ensemble, which is applied to the extension of two well-known Monte Carlo methods: the Metropolis importance sample and the Swendsen-Wang clusters algorithm. These Monte Carlo algorithms are employed to study the anomalous thermodynamic behavior of the Potts models with many spin states q defined on a d-dimensional hypercubic lattice with periodic boundary conditions, which successfully reduce the exponential divergence of decorrelation time τ with the increase of the system size N to a weak power-law divergence τ ∝ N α with α ≈ 0.2 for the particular case of the 2D 10-state Potts model.

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Section: Introductionmentioning

confidence: 99%

Extending canonical Monte Carlo methods

Velázquez

Curilef

2010

J. Stat. Mech.

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“…Powerlaw fragment-mass distributions have also been obtained from dynamical nucleation in a thermodynamically unstable nucleonic system [13]. However, as indicated by the great success of statistical models [14,15,16,17], the observables in multifragmentation seem to be mainly determined by the available phase space at the point of freeze out [18]. This conclusion remains valid even if the time evolution (expansion) of the statistically emitting source is taken into account [19].…”

Section: Introductionmentioning

confidence: 99%

Stability and instability of a hot and dilute nuclear droplet

2000

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Abstract. The diabatic approach to collective nuclear motion is reformulated in the local-density approximation in order to treat the normal modes of a spherical nuclear droplet analytically. In a first application the adiabatic isoscalar modes are studied and results for the eigenvalues of compressional (bulk) and pure surface modes are presented as function of density and temperature inside the droplet, as well as for different mass numbers and for soft and stiff equations of state. We find that the region of bulk instabilities (spinodal regime) is substantially smaller for nuclear droplets than for infinite nuclear matter. For small densities below 30% of normal nuclear matter density and for temperatures below 5 MeV all relevant bulk modes become unstable with the same growth rates. The surface modes have a larger spinodal region, reaching out to densities and temperatures way beyond the spinodal line for bulk instabilities. Essential experimental features of multifragmentation, like fragmentation temperatures and fragmentmass distributions (in particular the power-law behavior) are consistent with the instability properties of an expanding nuclear droplet, and hence with a dynamical fragmentation process within the spinodal regime of bulk and surface modes (spinodal decomposition).PACS. 21.60. Ev, 21.65.+f, 25.70.Mn

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“…Nuclear multifragmentation is one of the most interesting phenomena in nuclear physics as it holds promise for understanding nuclear matter properties at the extreme conditions of high excitation energy and large isospin (N/Z) asymmetry [1,2,3,4,5]. The latter, in particular, plays a profound role in the dynamics of various astrophysical environments [6,7,8,9].…”

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Tracing the evolution of the symmetry energy of hot nuclear fragments from the compound nucleus towards multifragmentation

et al. 2007

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The evolution of the symmetry energy coefficient of the binding energy of hot fragments with increasing excitation is explored in multifragmentation processes following heavy-ion collisions below the Fermi energy. In this work, high-resolution mass spectrometric data on isotopic distributions of projectile-like fragments are systematically compared to calculations involving the Statistical Multifragmentation Model (SMM). Within the SMM picture, the present study suggests a gradual decrease of the symmetry energy coefficient of the hot primary fragments from 25 MeV at the compound nucleus regime towards 15 MeV in the multifragmentation regime. The isotopic distributions of the hot primary fragments are found to be very wide and extend towards the neutron drip-line. These findings are expected to have important implications to the modeling of the composition and the evolution of hot and dense astrophysical environments, such as those of core-collapse supernova.PACS numbers: 25.70.Hi,25.70.Lm,26.30.+k Nuclear multifragmentation is one of the most interesting phenomena in nuclear physics as it holds promise for understanding nuclear matter properties at the extreme conditions of high excitation energy and large isospin (N/Z) asymmetry [1,2,3,4,5]. The latter, in particular, plays a profound role in the dynamics of various astrophysical environments [6,7,8,9]. It is well established (e.g. [4]) that nuclear systems with relatively low excitation energy (E * /A ≤ 2 MeV) form the traditional compound nucleus, whereas at higher excitation energy, the hot nuclear system expands and, subsequently, disassembles into an ensemble of hot primary fragments. This extremely complicated process, namely the multifragmentation, occurs on a timescale of 100 fm/c (3.3×10 −22 sec) during which the system can sample a large number of configurations. For this reason, statistical calculations (e.g., [10,11]) have been very successful in describing this process.Recently, a remarkable similarity has been pointed out between the thermodynamic conditions (temperature, density, isospin asymmetry N/Z) reached in nuclear multifragmentation and the collapse/explosion of massive stars [12,13,14]. This observation opens up the possibility of applying well-established models of nuclear reactions to describe matter distribution and evolution during supernova explosions [12]. In addition, statistical calculations suggest that in multifragmentation [12,15] and in hot astrophysical environments (e.g. supernova) [12,16], the ensemble of primary fragments includes neutron-rich nuclei towards or beyond the neutron drip-line.The primary fragments are expected to be hot (with excitation energies approaching 2-3 MeV/nucleon [17]) and, initially, in close proximity to neighboring fragments or nucleons. These conditions render their properties, e.g. binding energy, different from those of cold (ground state) isolated nuclei. In particular, recent studies [18,19,20,21] give evidence for a significant decrease of the symmetry energy of hot primary fragments. ...

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Reducibility and thermal scaling in nuclear multifragmentation

Cited by 78 publications

References 88 publications

Extending canonical Monte Carlo methods

Extending canonical Monte Carlo methods

Stability and instability of a hot and dilute nuclear droplet

Tracing the evolution of the symmetry energy of hot nuclear fragments from the compound nucleus towards multifragmentation

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